InstCombineCompares.cpp revision 39a7de72c8b5013f32802ceacefaaf6697726c28
1//===- InstCombineCompares.cpp --------------------------------------------===// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file is distributed under the University of Illinois Open Source 6// License. See LICENSE.TXT for details. 7// 8//===----------------------------------------------------------------------===// 9// 10// This file implements the visitICmp and visitFCmp functions. 11// 12//===----------------------------------------------------------------------===// 13 14#include "InstCombine.h" 15#include "llvm/IntrinsicInst.h" 16#include "llvm/Analysis/InstructionSimplify.h" 17#include "llvm/Analysis/MemoryBuiltins.h" 18#include "llvm/Target/TargetData.h" 19#include "llvm/Support/ConstantRange.h" 20#include "llvm/Support/GetElementPtrTypeIterator.h" 21#include "llvm/Support/PatternMatch.h" 22using namespace llvm; 23using namespace PatternMatch; 24 25static ConstantInt *getOne(Constant *C) { 26 return ConstantInt::get(cast<IntegerType>(C->getType()), 1); 27} 28 29/// AddOne - Add one to a ConstantInt 30static Constant *AddOne(Constant *C) { 31 return ConstantExpr::getAdd(C, ConstantInt::get(C->getType(), 1)); 32} 33/// SubOne - Subtract one from a ConstantInt 34static Constant *SubOne(Constant *C) { 35 return ConstantExpr::getSub(C, ConstantInt::get(C->getType(), 1)); 36} 37 38static ConstantInt *ExtractElement(Constant *V, Constant *Idx) { 39 return cast<ConstantInt>(ConstantExpr::getExtractElement(V, Idx)); 40} 41 42static bool HasAddOverflow(ConstantInt *Result, 43 ConstantInt *In1, ConstantInt *In2, 44 bool IsSigned) { 45 if (IsSigned) 46 if (In2->getValue().isNegative()) 47 return Result->getValue().sgt(In1->getValue()); 48 else 49 return Result->getValue().slt(In1->getValue()); 50 else 51 return Result->getValue().ult(In1->getValue()); 52} 53 54/// AddWithOverflow - Compute Result = In1+In2, returning true if the result 55/// overflowed for this type. 56static bool AddWithOverflow(Constant *&Result, Constant *In1, 57 Constant *In2, bool IsSigned = false) { 58 Result = ConstantExpr::getAdd(In1, In2); 59 60 if (const VectorType *VTy = dyn_cast<VectorType>(In1->getType())) { 61 for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) { 62 Constant *Idx = ConstantInt::get(Type::getInt32Ty(In1->getContext()), i); 63 if (HasAddOverflow(ExtractElement(Result, Idx), 64 ExtractElement(In1, Idx), 65 ExtractElement(In2, Idx), 66 IsSigned)) 67 return true; 68 } 69 return false; 70 } 71 72 return HasAddOverflow(cast<ConstantInt>(Result), 73 cast<ConstantInt>(In1), cast<ConstantInt>(In2), 74 IsSigned); 75} 76 77static bool HasSubOverflow(ConstantInt *Result, 78 ConstantInt *In1, ConstantInt *In2, 79 bool IsSigned) { 80 if (IsSigned) 81 if (In2->getValue().isNegative()) 82 return Result->getValue().slt(In1->getValue()); 83 else 84 return Result->getValue().sgt(In1->getValue()); 85 else 86 return Result->getValue().ugt(In1->getValue()); 87} 88 89/// SubWithOverflow - Compute Result = In1-In2, returning true if the result 90/// overflowed for this type. 91static bool SubWithOverflow(Constant *&Result, Constant *In1, 92 Constant *In2, bool IsSigned = false) { 93 Result = ConstantExpr::getSub(In1, In2); 94 95 if (const VectorType *VTy = dyn_cast<VectorType>(In1->getType())) { 96 for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) { 97 Constant *Idx = ConstantInt::get(Type::getInt32Ty(In1->getContext()), i); 98 if (HasSubOverflow(ExtractElement(Result, Idx), 99 ExtractElement(In1, Idx), 100 ExtractElement(In2, Idx), 101 IsSigned)) 102 return true; 103 } 104 return false; 105 } 106 107 return HasSubOverflow(cast<ConstantInt>(Result), 108 cast<ConstantInt>(In1), cast<ConstantInt>(In2), 109 IsSigned); 110} 111 112/// isSignBitCheck - Given an exploded icmp instruction, return true if the 113/// comparison only checks the sign bit. If it only checks the sign bit, set 114/// TrueIfSigned if the result of the comparison is true when the input value is 115/// signed. 116static bool isSignBitCheck(ICmpInst::Predicate pred, ConstantInt *RHS, 117 bool &TrueIfSigned) { 118 switch (pred) { 119 case ICmpInst::ICMP_SLT: // True if LHS s< 0 120 TrueIfSigned = true; 121 return RHS->isZero(); 122 case ICmpInst::ICMP_SLE: // True if LHS s<= RHS and RHS == -1 123 TrueIfSigned = true; 124 return RHS->isAllOnesValue(); 125 case ICmpInst::ICMP_SGT: // True if LHS s> -1 126 TrueIfSigned = false; 127 return RHS->isAllOnesValue(); 128 case ICmpInst::ICMP_UGT: 129 // True if LHS u> RHS and RHS == high-bit-mask - 1 130 TrueIfSigned = true; 131 return RHS->getValue() == 132 APInt::getSignedMaxValue(RHS->getType()->getPrimitiveSizeInBits()); 133 case ICmpInst::ICMP_UGE: 134 // True if LHS u>= RHS and RHS == high-bit-mask (2^7, 2^15, 2^31, etc) 135 TrueIfSigned = true; 136 return RHS->getValue().isSignBit(); 137 default: 138 return false; 139 } 140} 141 142// isHighOnes - Return true if the constant is of the form 1+0+. 143// This is the same as lowones(~X). 144static bool isHighOnes(const ConstantInt *CI) { 145 return (~CI->getValue() + 1).isPowerOf2(); 146} 147 148/// ComputeSignedMinMaxValuesFromKnownBits - Given a signed integer type and a 149/// set of known zero and one bits, compute the maximum and minimum values that 150/// could have the specified known zero and known one bits, returning them in 151/// min/max. 152static void ComputeSignedMinMaxValuesFromKnownBits(const APInt& KnownZero, 153 const APInt& KnownOne, 154 APInt& Min, APInt& Max) { 155 assert(KnownZero.getBitWidth() == KnownOne.getBitWidth() && 156 KnownZero.getBitWidth() == Min.getBitWidth() && 157 KnownZero.getBitWidth() == Max.getBitWidth() && 158 "KnownZero, KnownOne and Min, Max must have equal bitwidth."); 159 APInt UnknownBits = ~(KnownZero|KnownOne); 160 161 // The minimum value is when all unknown bits are zeros, EXCEPT for the sign 162 // bit if it is unknown. 163 Min = KnownOne; 164 Max = KnownOne|UnknownBits; 165 166 if (UnknownBits.isNegative()) { // Sign bit is unknown 167 Min.setBit(Min.getBitWidth()-1); 168 Max.clearBit(Max.getBitWidth()-1); 169 } 170} 171 172// ComputeUnsignedMinMaxValuesFromKnownBits - Given an unsigned integer type and 173// a set of known zero and one bits, compute the maximum and minimum values that 174// could have the specified known zero and known one bits, returning them in 175// min/max. 176static void ComputeUnsignedMinMaxValuesFromKnownBits(const APInt &KnownZero, 177 const APInt &KnownOne, 178 APInt &Min, APInt &Max) { 179 assert(KnownZero.getBitWidth() == KnownOne.getBitWidth() && 180 KnownZero.getBitWidth() == Min.getBitWidth() && 181 KnownZero.getBitWidth() == Max.getBitWidth() && 182 "Ty, KnownZero, KnownOne and Min, Max must have equal bitwidth."); 183 APInt UnknownBits = ~(KnownZero|KnownOne); 184 185 // The minimum value is when the unknown bits are all zeros. 186 Min = KnownOne; 187 // The maximum value is when the unknown bits are all ones. 188 Max = KnownOne|UnknownBits; 189} 190 191 192 193/// FoldCmpLoadFromIndexedGlobal - Called we see this pattern: 194/// cmp pred (load (gep GV, ...)), cmpcst 195/// where GV is a global variable with a constant initializer. Try to simplify 196/// this into some simple computation that does not need the load. For example 197/// we can optimize "icmp eq (load (gep "foo", 0, i)), 0" into "icmp eq i, 3". 198/// 199/// If AndCst is non-null, then the loaded value is masked with that constant 200/// before doing the comparison. This handles cases like "A[i]&4 == 0". 201Instruction *InstCombiner:: 202FoldCmpLoadFromIndexedGlobal(GetElementPtrInst *GEP, GlobalVariable *GV, 203 CmpInst &ICI, ConstantInt *AndCst) { 204 // We need TD information to know the pointer size unless this is inbounds. 205 if (!GEP->isInBounds() && TD == 0) return 0; 206 207 ConstantArray *Init = dyn_cast<ConstantArray>(GV->getInitializer()); 208 if (Init == 0 || Init->getNumOperands() > 1024) return 0; 209 210 // There are many forms of this optimization we can handle, for now, just do 211 // the simple index into a single-dimensional array. 212 // 213 // Require: GEP GV, 0, i {{, constant indices}} 214 if (GEP->getNumOperands() < 3 || 215 !isa<ConstantInt>(GEP->getOperand(1)) || 216 !cast<ConstantInt>(GEP->getOperand(1))->isZero() || 217 isa<Constant>(GEP->getOperand(2))) 218 return 0; 219 220 // Check that indices after the variable are constants and in-range for the 221 // type they index. Collect the indices. This is typically for arrays of 222 // structs. 223 SmallVector<unsigned, 4> LaterIndices; 224 225 const Type *EltTy = cast<ArrayType>(Init->getType())->getElementType(); 226 for (unsigned i = 3, e = GEP->getNumOperands(); i != e; ++i) { 227 ConstantInt *Idx = dyn_cast<ConstantInt>(GEP->getOperand(i)); 228 if (Idx == 0) return 0; // Variable index. 229 230 uint64_t IdxVal = Idx->getZExtValue(); 231 if ((unsigned)IdxVal != IdxVal) return 0; // Too large array index. 232 233 if (const StructType *STy = dyn_cast<StructType>(EltTy)) 234 EltTy = STy->getElementType(IdxVal); 235 else if (const ArrayType *ATy = dyn_cast<ArrayType>(EltTy)) { 236 if (IdxVal >= ATy->getNumElements()) return 0; 237 EltTy = ATy->getElementType(); 238 } else { 239 return 0; // Unknown type. 240 } 241 242 LaterIndices.push_back(IdxVal); 243 } 244 245 enum { Overdefined = -3, Undefined = -2 }; 246 247 // Variables for our state machines. 248 249 // FirstTrueElement/SecondTrueElement - Used to emit a comparison of the form 250 // "i == 47 | i == 87", where 47 is the first index the condition is true for, 251 // and 87 is the second (and last) index. FirstTrueElement is -2 when 252 // undefined, otherwise set to the first true element. SecondTrueElement is 253 // -2 when undefined, -3 when overdefined and >= 0 when that index is true. 254 int FirstTrueElement = Undefined, SecondTrueElement = Undefined; 255 256 // FirstFalseElement/SecondFalseElement - Used to emit a comparison of the 257 // form "i != 47 & i != 87". Same state transitions as for true elements. 258 int FirstFalseElement = Undefined, SecondFalseElement = Undefined; 259 260 /// TrueRangeEnd/FalseRangeEnd - In conjunction with First*Element, these 261 /// define a state machine that triggers for ranges of values that the index 262 /// is true or false for. This triggers on things like "abbbbc"[i] == 'b'. 263 /// This is -2 when undefined, -3 when overdefined, and otherwise the last 264 /// index in the range (inclusive). We use -2 for undefined here because we 265 /// use relative comparisons and don't want 0-1 to match -1. 266 int TrueRangeEnd = Undefined, FalseRangeEnd = Undefined; 267 268 // MagicBitvector - This is a magic bitvector where we set a bit if the 269 // comparison is true for element 'i'. If there are 64 elements or less in 270 // the array, this will fully represent all the comparison results. 271 uint64_t MagicBitvector = 0; 272 273 274 // Scan the array and see if one of our patterns matches. 275 Constant *CompareRHS = cast<Constant>(ICI.getOperand(1)); 276 for (unsigned i = 0, e = Init->getNumOperands(); i != e; ++i) { 277 Constant *Elt = Init->getOperand(i); 278 279 // If this is indexing an array of structures, get the structure element. 280 if (!LaterIndices.empty()) 281 Elt = ConstantExpr::getExtractValue(Elt, LaterIndices.data(), 282 LaterIndices.size()); 283 284 // If the element is masked, handle it. 285 if (AndCst) Elt = ConstantExpr::getAnd(Elt, AndCst); 286 287 // Find out if the comparison would be true or false for the i'th element. 288 Constant *C = ConstantFoldCompareInstOperands(ICI.getPredicate(), Elt, 289 CompareRHS, TD); 290 // If the result is undef for this element, ignore it. 291 if (isa<UndefValue>(C)) { 292 // Extend range state machines to cover this element in case there is an 293 // undef in the middle of the range. 294 if (TrueRangeEnd == (int)i-1) 295 TrueRangeEnd = i; 296 if (FalseRangeEnd == (int)i-1) 297 FalseRangeEnd = i; 298 continue; 299 } 300 301 // If we can't compute the result for any of the elements, we have to give 302 // up evaluating the entire conditional. 303 if (!isa<ConstantInt>(C)) return 0; 304 305 // Otherwise, we know if the comparison is true or false for this element, 306 // update our state machines. 307 bool IsTrueForElt = !cast<ConstantInt>(C)->isZero(); 308 309 // State machine for single/double/range index comparison. 310 if (IsTrueForElt) { 311 // Update the TrueElement state machine. 312 if (FirstTrueElement == Undefined) 313 FirstTrueElement = TrueRangeEnd = i; // First true element. 314 else { 315 // Update double-compare state machine. 316 if (SecondTrueElement == Undefined) 317 SecondTrueElement = i; 318 else 319 SecondTrueElement = Overdefined; 320 321 // Update range state machine. 322 if (TrueRangeEnd == (int)i-1) 323 TrueRangeEnd = i; 324 else 325 TrueRangeEnd = Overdefined; 326 } 327 } else { 328 // Update the FalseElement state machine. 329 if (FirstFalseElement == Undefined) 330 FirstFalseElement = FalseRangeEnd = i; // First false element. 331 else { 332 // Update double-compare state machine. 333 if (SecondFalseElement == Undefined) 334 SecondFalseElement = i; 335 else 336 SecondFalseElement = Overdefined; 337 338 // Update range state machine. 339 if (FalseRangeEnd == (int)i-1) 340 FalseRangeEnd = i; 341 else 342 FalseRangeEnd = Overdefined; 343 } 344 } 345 346 347 // If this element is in range, update our magic bitvector. 348 if (i < 64 && IsTrueForElt) 349 MagicBitvector |= 1ULL << i; 350 351 // If all of our states become overdefined, bail out early. Since the 352 // predicate is expensive, only check it every 8 elements. This is only 353 // really useful for really huge arrays. 354 if ((i & 8) == 0 && i >= 64 && SecondTrueElement == Overdefined && 355 SecondFalseElement == Overdefined && TrueRangeEnd == Overdefined && 356 FalseRangeEnd == Overdefined) 357 return 0; 358 } 359 360 // Now that we've scanned the entire array, emit our new comparison(s). We 361 // order the state machines in complexity of the generated code. 362 Value *Idx = GEP->getOperand(2); 363 364 // If the index is larger than the pointer size of the target, truncate the 365 // index down like the GEP would do implicitly. We don't have to do this for 366 // an inbounds GEP because the index can't be out of range. 367 if (!GEP->isInBounds() && 368 Idx->getType()->getPrimitiveSizeInBits() > TD->getPointerSizeInBits()) 369 Idx = Builder->CreateTrunc(Idx, TD->getIntPtrType(Idx->getContext())); 370 371 // If the comparison is only true for one or two elements, emit direct 372 // comparisons. 373 if (SecondTrueElement != Overdefined) { 374 // None true -> false. 375 if (FirstTrueElement == Undefined) 376 return ReplaceInstUsesWith(ICI, ConstantInt::getFalse(GEP->getContext())); 377 378 Value *FirstTrueIdx = ConstantInt::get(Idx->getType(), FirstTrueElement); 379 380 // True for one element -> 'i == 47'. 381 if (SecondTrueElement == Undefined) 382 return new ICmpInst(ICmpInst::ICMP_EQ, Idx, FirstTrueIdx); 383 384 // True for two elements -> 'i == 47 | i == 72'. 385 Value *C1 = Builder->CreateICmpEQ(Idx, FirstTrueIdx); 386 Value *SecondTrueIdx = ConstantInt::get(Idx->getType(), SecondTrueElement); 387 Value *C2 = Builder->CreateICmpEQ(Idx, SecondTrueIdx); 388 return BinaryOperator::CreateOr(C1, C2); 389 } 390 391 // If the comparison is only false for one or two elements, emit direct 392 // comparisons. 393 if (SecondFalseElement != Overdefined) { 394 // None false -> true. 395 if (FirstFalseElement == Undefined) 396 return ReplaceInstUsesWith(ICI, ConstantInt::getTrue(GEP->getContext())); 397 398 Value *FirstFalseIdx = ConstantInt::get(Idx->getType(), FirstFalseElement); 399 400 // False for one element -> 'i != 47'. 401 if (SecondFalseElement == Undefined) 402 return new ICmpInst(ICmpInst::ICMP_NE, Idx, FirstFalseIdx); 403 404 // False for two elements -> 'i != 47 & i != 72'. 405 Value *C1 = Builder->CreateICmpNE(Idx, FirstFalseIdx); 406 Value *SecondFalseIdx = ConstantInt::get(Idx->getType(),SecondFalseElement); 407 Value *C2 = Builder->CreateICmpNE(Idx, SecondFalseIdx); 408 return BinaryOperator::CreateAnd(C1, C2); 409 } 410 411 // If the comparison can be replaced with a range comparison for the elements 412 // where it is true, emit the range check. 413 if (TrueRangeEnd != Overdefined) { 414 assert(TrueRangeEnd != FirstTrueElement && "Should emit single compare"); 415 416 // Generate (i-FirstTrue) <u (TrueRangeEnd-FirstTrue+1). 417 if (FirstTrueElement) { 418 Value *Offs = ConstantInt::get(Idx->getType(), -FirstTrueElement); 419 Idx = Builder->CreateAdd(Idx, Offs); 420 } 421 422 Value *End = ConstantInt::get(Idx->getType(), 423 TrueRangeEnd-FirstTrueElement+1); 424 return new ICmpInst(ICmpInst::ICMP_ULT, Idx, End); 425 } 426 427 // False range check. 428 if (FalseRangeEnd != Overdefined) { 429 assert(FalseRangeEnd != FirstFalseElement && "Should emit single compare"); 430 // Generate (i-FirstFalse) >u (FalseRangeEnd-FirstFalse). 431 if (FirstFalseElement) { 432 Value *Offs = ConstantInt::get(Idx->getType(), -FirstFalseElement); 433 Idx = Builder->CreateAdd(Idx, Offs); 434 } 435 436 Value *End = ConstantInt::get(Idx->getType(), 437 FalseRangeEnd-FirstFalseElement); 438 return new ICmpInst(ICmpInst::ICMP_UGT, Idx, End); 439 } 440 441 442 // If a 32-bit or 64-bit magic bitvector captures the entire comparison state 443 // of this load, replace it with computation that does: 444 // ((magic_cst >> i) & 1) != 0 445 if (Init->getNumOperands() <= 32 || 446 (TD && Init->getNumOperands() <= 64 && TD->isLegalInteger(64))) { 447 const Type *Ty; 448 if (Init->getNumOperands() <= 32) 449 Ty = Type::getInt32Ty(Init->getContext()); 450 else 451 Ty = Type::getInt64Ty(Init->getContext()); 452 Value *V = Builder->CreateIntCast(Idx, Ty, false); 453 V = Builder->CreateLShr(ConstantInt::get(Ty, MagicBitvector), V); 454 V = Builder->CreateAnd(ConstantInt::get(Ty, 1), V); 455 return new ICmpInst(ICmpInst::ICMP_NE, V, ConstantInt::get(Ty, 0)); 456 } 457 458 return 0; 459} 460 461 462/// EvaluateGEPOffsetExpression - Return a value that can be used to compare 463/// the *offset* implied by a GEP to zero. For example, if we have &A[i], we 464/// want to return 'i' for "icmp ne i, 0". Note that, in general, indices can 465/// be complex, and scales are involved. The above expression would also be 466/// legal to codegen as "icmp ne (i*4), 0" (assuming A is a pointer to i32). 467/// This later form is less amenable to optimization though, and we are allowed 468/// to generate the first by knowing that pointer arithmetic doesn't overflow. 469/// 470/// If we can't emit an optimized form for this expression, this returns null. 471/// 472static Value *EvaluateGEPOffsetExpression(User *GEP, Instruction &I, 473 InstCombiner &IC) { 474 TargetData &TD = *IC.getTargetData(); 475 gep_type_iterator GTI = gep_type_begin(GEP); 476 477 // Check to see if this gep only has a single variable index. If so, and if 478 // any constant indices are a multiple of its scale, then we can compute this 479 // in terms of the scale of the variable index. For example, if the GEP 480 // implies an offset of "12 + i*4", then we can codegen this as "3 + i", 481 // because the expression will cross zero at the same point. 482 unsigned i, e = GEP->getNumOperands(); 483 int64_t Offset = 0; 484 for (i = 1; i != e; ++i, ++GTI) { 485 if (ConstantInt *CI = dyn_cast<ConstantInt>(GEP->getOperand(i))) { 486 // Compute the aggregate offset of constant indices. 487 if (CI->isZero()) continue; 488 489 // Handle a struct index, which adds its field offset to the pointer. 490 if (const StructType *STy = dyn_cast<StructType>(*GTI)) { 491 Offset += TD.getStructLayout(STy)->getElementOffset(CI->getZExtValue()); 492 } else { 493 uint64_t Size = TD.getTypeAllocSize(GTI.getIndexedType()); 494 Offset += Size*CI->getSExtValue(); 495 } 496 } else { 497 // Found our variable index. 498 break; 499 } 500 } 501 502 // If there are no variable indices, we must have a constant offset, just 503 // evaluate it the general way. 504 if (i == e) return 0; 505 506 Value *VariableIdx = GEP->getOperand(i); 507 // Determine the scale factor of the variable element. For example, this is 508 // 4 if the variable index is into an array of i32. 509 uint64_t VariableScale = TD.getTypeAllocSize(GTI.getIndexedType()); 510 511 // Verify that there are no other variable indices. If so, emit the hard way. 512 for (++i, ++GTI; i != e; ++i, ++GTI) { 513 ConstantInt *CI = dyn_cast<ConstantInt>(GEP->getOperand(i)); 514 if (!CI) return 0; 515 516 // Compute the aggregate offset of constant indices. 517 if (CI->isZero()) continue; 518 519 // Handle a struct index, which adds its field offset to the pointer. 520 if (const StructType *STy = dyn_cast<StructType>(*GTI)) { 521 Offset += TD.getStructLayout(STy)->getElementOffset(CI->getZExtValue()); 522 } else { 523 uint64_t Size = TD.getTypeAllocSize(GTI.getIndexedType()); 524 Offset += Size*CI->getSExtValue(); 525 } 526 } 527 528 // Okay, we know we have a single variable index, which must be a 529 // pointer/array/vector index. If there is no offset, life is simple, return 530 // the index. 531 unsigned IntPtrWidth = TD.getPointerSizeInBits(); 532 if (Offset == 0) { 533 // Cast to intptrty in case a truncation occurs. If an extension is needed, 534 // we don't need to bother extending: the extension won't affect where the 535 // computation crosses zero. 536 if (VariableIdx->getType()->getPrimitiveSizeInBits() > IntPtrWidth) 537 VariableIdx = new TruncInst(VariableIdx, 538 TD.getIntPtrType(VariableIdx->getContext()), 539 VariableIdx->getName(), &I); 540 return VariableIdx; 541 } 542 543 // Otherwise, there is an index. The computation we will do will be modulo 544 // the pointer size, so get it. 545 uint64_t PtrSizeMask = ~0ULL >> (64-IntPtrWidth); 546 547 Offset &= PtrSizeMask; 548 VariableScale &= PtrSizeMask; 549 550 // To do this transformation, any constant index must be a multiple of the 551 // variable scale factor. For example, we can evaluate "12 + 4*i" as "3 + i", 552 // but we can't evaluate "10 + 3*i" in terms of i. Check that the offset is a 553 // multiple of the variable scale. 554 int64_t NewOffs = Offset / (int64_t)VariableScale; 555 if (Offset != NewOffs*(int64_t)VariableScale) 556 return 0; 557 558 // Okay, we can do this evaluation. Start by converting the index to intptr. 559 const Type *IntPtrTy = TD.getIntPtrType(VariableIdx->getContext()); 560 if (VariableIdx->getType() != IntPtrTy) 561 VariableIdx = CastInst::CreateIntegerCast(VariableIdx, IntPtrTy, 562 true /*SExt*/, 563 VariableIdx->getName(), &I); 564 Constant *OffsetVal = ConstantInt::get(IntPtrTy, NewOffs); 565 return BinaryOperator::CreateAdd(VariableIdx, OffsetVal, "offset", &I); 566} 567 568/// FoldGEPICmp - Fold comparisons between a GEP instruction and something 569/// else. At this point we know that the GEP is on the LHS of the comparison. 570Instruction *InstCombiner::FoldGEPICmp(GEPOperator *GEPLHS, Value *RHS, 571 ICmpInst::Predicate Cond, 572 Instruction &I) { 573 // Look through bitcasts. 574 if (BitCastInst *BCI = dyn_cast<BitCastInst>(RHS)) 575 RHS = BCI->getOperand(0); 576 577 Value *PtrBase = GEPLHS->getOperand(0); 578 if (TD && PtrBase == RHS && GEPLHS->isInBounds()) { 579 // ((gep Ptr, OFFSET) cmp Ptr) ---> (OFFSET cmp 0). 580 // This transformation (ignoring the base and scales) is valid because we 581 // know pointers can't overflow since the gep is inbounds. See if we can 582 // output an optimized form. 583 Value *Offset = EvaluateGEPOffsetExpression(GEPLHS, I, *this); 584 585 // If not, synthesize the offset the hard way. 586 if (Offset == 0) 587 Offset = EmitGEPOffset(GEPLHS); 588 return new ICmpInst(ICmpInst::getSignedPredicate(Cond), Offset, 589 Constant::getNullValue(Offset->getType())); 590 } else if (GEPOperator *GEPRHS = dyn_cast<GEPOperator>(RHS)) { 591 // If the base pointers are different, but the indices are the same, just 592 // compare the base pointer. 593 if (PtrBase != GEPRHS->getOperand(0)) { 594 bool IndicesTheSame = GEPLHS->getNumOperands()==GEPRHS->getNumOperands(); 595 IndicesTheSame &= GEPLHS->getOperand(0)->getType() == 596 GEPRHS->getOperand(0)->getType(); 597 if (IndicesTheSame) 598 for (unsigned i = 1, e = GEPLHS->getNumOperands(); i != e; ++i) 599 if (GEPLHS->getOperand(i) != GEPRHS->getOperand(i)) { 600 IndicesTheSame = false; 601 break; 602 } 603 604 // If all indices are the same, just compare the base pointers. 605 if (IndicesTheSame) 606 return new ICmpInst(ICmpInst::getSignedPredicate(Cond), 607 GEPLHS->getOperand(0), GEPRHS->getOperand(0)); 608 609 // Otherwise, the base pointers are different and the indices are 610 // different, bail out. 611 return 0; 612 } 613 614 // If one of the GEPs has all zero indices, recurse. 615 bool AllZeros = true; 616 for (unsigned i = 1, e = GEPLHS->getNumOperands(); i != e; ++i) 617 if (!isa<Constant>(GEPLHS->getOperand(i)) || 618 !cast<Constant>(GEPLHS->getOperand(i))->isNullValue()) { 619 AllZeros = false; 620 break; 621 } 622 if (AllZeros) 623 return FoldGEPICmp(GEPRHS, GEPLHS->getOperand(0), 624 ICmpInst::getSwappedPredicate(Cond), I); 625 626 // If the other GEP has all zero indices, recurse. 627 AllZeros = true; 628 for (unsigned i = 1, e = GEPRHS->getNumOperands(); i != e; ++i) 629 if (!isa<Constant>(GEPRHS->getOperand(i)) || 630 !cast<Constant>(GEPRHS->getOperand(i))->isNullValue()) { 631 AllZeros = false; 632 break; 633 } 634 if (AllZeros) 635 return FoldGEPICmp(GEPLHS, GEPRHS->getOperand(0), Cond, I); 636 637 if (GEPLHS->getNumOperands() == GEPRHS->getNumOperands()) { 638 // If the GEPs only differ by one index, compare it. 639 unsigned NumDifferences = 0; // Keep track of # differences. 640 unsigned DiffOperand = 0; // The operand that differs. 641 for (unsigned i = 1, e = GEPRHS->getNumOperands(); i != e; ++i) 642 if (GEPLHS->getOperand(i) != GEPRHS->getOperand(i)) { 643 if (GEPLHS->getOperand(i)->getType()->getPrimitiveSizeInBits() != 644 GEPRHS->getOperand(i)->getType()->getPrimitiveSizeInBits()) { 645 // Irreconcilable differences. 646 NumDifferences = 2; 647 break; 648 } else { 649 if (NumDifferences++) break; 650 DiffOperand = i; 651 } 652 } 653 654 if (NumDifferences == 0) // SAME GEP? 655 return ReplaceInstUsesWith(I, // No comparison is needed here. 656 ConstantInt::get(Type::getInt1Ty(I.getContext()), 657 ICmpInst::isTrueWhenEqual(Cond))); 658 659 else if (NumDifferences == 1) { 660 Value *LHSV = GEPLHS->getOperand(DiffOperand); 661 Value *RHSV = GEPRHS->getOperand(DiffOperand); 662 // Make sure we do a signed comparison here. 663 return new ICmpInst(ICmpInst::getSignedPredicate(Cond), LHSV, RHSV); 664 } 665 } 666 667 // Only lower this if the icmp is the only user of the GEP or if we expect 668 // the result to fold to a constant! 669 if (TD && 670 (isa<ConstantExpr>(GEPLHS) || GEPLHS->hasOneUse()) && 671 (isa<ConstantExpr>(GEPRHS) || GEPRHS->hasOneUse())) { 672 // ((gep Ptr, OFFSET1) cmp (gep Ptr, OFFSET2) ---> (OFFSET1 cmp OFFSET2) 673 Value *L = EmitGEPOffset(GEPLHS); 674 Value *R = EmitGEPOffset(GEPRHS); 675 return new ICmpInst(ICmpInst::getSignedPredicate(Cond), L, R); 676 } 677 } 678 return 0; 679} 680 681/// FoldICmpAddOpCst - Fold "icmp pred (X+CI), X". 682Instruction *InstCombiner::FoldICmpAddOpCst(ICmpInst &ICI, 683 Value *X, ConstantInt *CI, 684 ICmpInst::Predicate Pred, 685 Value *TheAdd) { 686 // If we have X+0, exit early (simplifying logic below) and let it get folded 687 // elsewhere. icmp X+0, X -> icmp X, X 688 if (CI->isZero()) { 689 bool isTrue = ICmpInst::isTrueWhenEqual(Pred); 690 return ReplaceInstUsesWith(ICI, ConstantInt::get(ICI.getType(), isTrue)); 691 } 692 693 // (X+4) == X -> false. 694 if (Pred == ICmpInst::ICMP_EQ) 695 return ReplaceInstUsesWith(ICI, ConstantInt::getFalse(X->getContext())); 696 697 // (X+4) != X -> true. 698 if (Pred == ICmpInst::ICMP_NE) 699 return ReplaceInstUsesWith(ICI, ConstantInt::getTrue(X->getContext())); 700 701 // From this point on, we know that (X+C <= X) --> (X+C < X) because C != 0, 702 // so the values can never be equal. Similiarly for all other "or equals" 703 // operators. 704 705 // (X+1) <u X --> X >u (MAXUINT-1) --> X == 255 706 // (X+2) <u X --> X >u (MAXUINT-2) --> X > 253 707 // (X+MAXUINT) <u X --> X >u (MAXUINT-MAXUINT) --> X != 0 708 if (Pred == ICmpInst::ICMP_ULT || Pred == ICmpInst::ICMP_ULE) { 709 Value *R = 710 ConstantExpr::getSub(ConstantInt::getAllOnesValue(CI->getType()), CI); 711 return new ICmpInst(ICmpInst::ICMP_UGT, X, R); 712 } 713 714 // (X+1) >u X --> X <u (0-1) --> X != 255 715 // (X+2) >u X --> X <u (0-2) --> X <u 254 716 // (X+MAXUINT) >u X --> X <u (0-MAXUINT) --> X <u 1 --> X == 0 717 if (Pred == ICmpInst::ICMP_UGT || Pred == ICmpInst::ICMP_UGE) 718 return new ICmpInst(ICmpInst::ICMP_ULT, X, ConstantExpr::getNeg(CI)); 719 720 unsigned BitWidth = CI->getType()->getPrimitiveSizeInBits(); 721 ConstantInt *SMax = ConstantInt::get(X->getContext(), 722 APInt::getSignedMaxValue(BitWidth)); 723 724 // (X+ 1) <s X --> X >s (MAXSINT-1) --> X == 127 725 // (X+ 2) <s X --> X >s (MAXSINT-2) --> X >s 125 726 // (X+MAXSINT) <s X --> X >s (MAXSINT-MAXSINT) --> X >s 0 727 // (X+MINSINT) <s X --> X >s (MAXSINT-MINSINT) --> X >s -1 728 // (X+ -2) <s X --> X >s (MAXSINT- -2) --> X >s 126 729 // (X+ -1) <s X --> X >s (MAXSINT- -1) --> X != 127 730 if (Pred == ICmpInst::ICMP_SLT || Pred == ICmpInst::ICMP_SLE) 731 return new ICmpInst(ICmpInst::ICMP_SGT, X, ConstantExpr::getSub(SMax, CI)); 732 733 // (X+ 1) >s X --> X <s (MAXSINT-(1-1)) --> X != 127 734 // (X+ 2) >s X --> X <s (MAXSINT-(2-1)) --> X <s 126 735 // (X+MAXSINT) >s X --> X <s (MAXSINT-(MAXSINT-1)) --> X <s 1 736 // (X+MINSINT) >s X --> X <s (MAXSINT-(MINSINT-1)) --> X <s -2 737 // (X+ -2) >s X --> X <s (MAXSINT-(-2-1)) --> X <s -126 738 // (X+ -1) >s X --> X <s (MAXSINT-(-1-1)) --> X == -128 739 740 assert(Pred == ICmpInst::ICMP_SGT || Pred == ICmpInst::ICMP_SGE); 741 Constant *C = ConstantInt::get(X->getContext(), CI->getValue()-1); 742 return new ICmpInst(ICmpInst::ICMP_SLT, X, ConstantExpr::getSub(SMax, C)); 743} 744 745/// FoldICmpDivCst - Fold "icmp pred, ([su]div X, DivRHS), CmpRHS" where DivRHS 746/// and CmpRHS are both known to be integer constants. 747Instruction *InstCombiner::FoldICmpDivCst(ICmpInst &ICI, BinaryOperator *DivI, 748 ConstantInt *DivRHS) { 749 ConstantInt *CmpRHS = cast<ConstantInt>(ICI.getOperand(1)); 750 const APInt &CmpRHSV = CmpRHS->getValue(); 751 752 // FIXME: If the operand types don't match the type of the divide 753 // then don't attempt this transform. The code below doesn't have the 754 // logic to deal with a signed divide and an unsigned compare (and 755 // vice versa). This is because (x /s C1) <s C2 produces different 756 // results than (x /s C1) <u C2 or (x /u C1) <s C2 or even 757 // (x /u C1) <u C2. Simply casting the operands and result won't 758 // work. :( The if statement below tests that condition and bails 759 // if it finds it. 760 bool DivIsSigned = DivI->getOpcode() == Instruction::SDiv; 761 if (!ICI.isEquality() && DivIsSigned != ICI.isSigned()) 762 return 0; 763 if (DivRHS->isZero()) 764 return 0; // The ProdOV computation fails on divide by zero. 765 if (DivIsSigned && DivRHS->isAllOnesValue()) 766 return 0; // The overflow computation also screws up here 767 if (DivRHS->isOne()) { 768 // This eliminates some funny cases with INT_MIN. 769 ICI.setOperand(0, DivI->getOperand(0)); // X/1 == X. 770 return &ICI; 771 } 772 773 // Compute Prod = CI * DivRHS. We are essentially solving an equation 774 // of form X/C1=C2. We solve for X by multiplying C1 (DivRHS) and 775 // C2 (CI). By solving for X we can turn this into a range check 776 // instead of computing a divide. 777 Constant *Prod = ConstantExpr::getMul(CmpRHS, DivRHS); 778 779 // Determine if the product overflows by seeing if the product is 780 // not equal to the divide. Make sure we do the same kind of divide 781 // as in the LHS instruction that we're folding. 782 bool ProdOV = (DivIsSigned ? ConstantExpr::getSDiv(Prod, DivRHS) : 783 ConstantExpr::getUDiv(Prod, DivRHS)) != CmpRHS; 784 785 // Get the ICmp opcode 786 ICmpInst::Predicate Pred = ICI.getPredicate(); 787 788 /// If the division is known to be exact, then there is no remainder from the 789 /// divide, so the covered range size is unit, otherwise it is the divisor. 790 ConstantInt *RangeSize = DivI->isExact() ? getOne(Prod) : DivRHS; 791 792 // Figure out the interval that is being checked. For example, a comparison 793 // like "X /u 5 == 0" is really checking that X is in the interval [0, 5). 794 // Compute this interval based on the constants involved and the signedness of 795 // the compare/divide. This computes a half-open interval, keeping track of 796 // whether either value in the interval overflows. After analysis each 797 // overflow variable is set to 0 if it's corresponding bound variable is valid 798 // -1 if overflowed off the bottom end, or +1 if overflowed off the top end. 799 int LoOverflow = 0, HiOverflow = 0; 800 Constant *LoBound = 0, *HiBound = 0; 801 802 if (!DivIsSigned) { // udiv 803 // e.g. X/5 op 3 --> [15, 20) 804 LoBound = Prod; 805 HiOverflow = LoOverflow = ProdOV; 806 if (!HiOverflow) { 807 // If this is not an exact divide, then many values in the range collapse 808 // to the same result value. 809 HiOverflow = AddWithOverflow(HiBound, LoBound, RangeSize, false); 810 } 811 812 } else if (DivRHS->getValue().isStrictlyPositive()) { // Divisor is > 0. 813 if (CmpRHSV == 0) { // (X / pos) op 0 814 // Can't overflow. e.g. X/2 op 0 --> [-1, 2) 815 LoBound = ConstantExpr::getNeg(SubOne(RangeSize)); 816 HiBound = RangeSize; 817 } else if (CmpRHSV.isStrictlyPositive()) { // (X / pos) op pos 818 LoBound = Prod; // e.g. X/5 op 3 --> [15, 20) 819 HiOverflow = LoOverflow = ProdOV; 820 if (!HiOverflow) 821 HiOverflow = AddWithOverflow(HiBound, Prod, RangeSize, true); 822 } else { // (X / pos) op neg 823 // e.g. X/5 op -3 --> [-15-4, -15+1) --> [-19, -14) 824 HiBound = AddOne(Prod); 825 LoOverflow = HiOverflow = ProdOV ? -1 : 0; 826 if (!LoOverflow) { 827 ConstantInt *DivNeg =cast<ConstantInt>(ConstantExpr::getNeg(RangeSize)); 828 LoOverflow = AddWithOverflow(LoBound, HiBound, DivNeg, true) ? -1 : 0; 829 } 830 } 831 } else if (DivRHS->getValue().isNegative()) { // Divisor is < 0. 832 if (DivI->isExact()) 833 RangeSize = cast<ConstantInt>(ConstantExpr::getNeg(RangeSize)); 834 if (CmpRHSV == 0) { // (X / neg) op 0 835 // e.g. X/-5 op 0 --> [-4, 5) 836 LoBound = AddOne(RangeSize); 837 HiBound = cast<ConstantInt>(ConstantExpr::getNeg(RangeSize)); 838 if (HiBound == DivRHS) { // -INTMIN = INTMIN 839 HiOverflow = 1; // [INTMIN+1, overflow) 840 HiBound = 0; // e.g. X/INTMIN = 0 --> X > INTMIN 841 } 842 } else if (CmpRHSV.isStrictlyPositive()) { // (X / neg) op pos 843 // e.g. X/-5 op 3 --> [-19, -14) 844 HiBound = AddOne(Prod); 845 HiOverflow = LoOverflow = ProdOV ? -1 : 0; 846 if (!LoOverflow) 847 LoOverflow = AddWithOverflow(LoBound, HiBound, RangeSize, true) ? -1:0; 848 } else { // (X / neg) op neg 849 LoBound = Prod; // e.g. X/-5 op -3 --> [15, 20) 850 LoOverflow = HiOverflow = ProdOV; 851 if (!HiOverflow) 852 HiOverflow = SubWithOverflow(HiBound, Prod, RangeSize, true); 853 } 854 855 // Dividing by a negative swaps the condition. LT <-> GT 856 Pred = ICmpInst::getSwappedPredicate(Pred); 857 } 858 859 Value *X = DivI->getOperand(0); 860 switch (Pred) { 861 default: llvm_unreachable("Unhandled icmp opcode!"); 862 case ICmpInst::ICMP_EQ: 863 if (LoOverflow && HiOverflow) 864 return ReplaceInstUsesWith(ICI, ConstantInt::getFalse(ICI.getContext())); 865 if (HiOverflow) 866 return new ICmpInst(DivIsSigned ? ICmpInst::ICMP_SGE : 867 ICmpInst::ICMP_UGE, X, LoBound); 868 if (LoOverflow) 869 return new ICmpInst(DivIsSigned ? ICmpInst::ICMP_SLT : 870 ICmpInst::ICMP_ULT, X, HiBound); 871 return ReplaceInstUsesWith(ICI, InsertRangeTest(X, LoBound, HiBound, 872 DivIsSigned, true)); 873 case ICmpInst::ICMP_NE: 874 if (LoOverflow && HiOverflow) 875 return ReplaceInstUsesWith(ICI, ConstantInt::getTrue(ICI.getContext())); 876 if (HiOverflow) 877 return new ICmpInst(DivIsSigned ? ICmpInst::ICMP_SLT : 878 ICmpInst::ICMP_ULT, X, LoBound); 879 if (LoOverflow) 880 return new ICmpInst(DivIsSigned ? ICmpInst::ICMP_SGE : 881 ICmpInst::ICMP_UGE, X, HiBound); 882 return ReplaceInstUsesWith(ICI, InsertRangeTest(X, LoBound, HiBound, 883 DivIsSigned, false)); 884 case ICmpInst::ICMP_ULT: 885 case ICmpInst::ICMP_SLT: 886 if (LoOverflow == +1) // Low bound is greater than input range. 887 return ReplaceInstUsesWith(ICI, ConstantInt::getTrue(ICI.getContext())); 888 if (LoOverflow == -1) // Low bound is less than input range. 889 return ReplaceInstUsesWith(ICI, ConstantInt::getFalse(ICI.getContext())); 890 return new ICmpInst(Pred, X, LoBound); 891 case ICmpInst::ICMP_UGT: 892 case ICmpInst::ICMP_SGT: 893 if (HiOverflow == +1) // High bound greater than input range. 894 return ReplaceInstUsesWith(ICI, ConstantInt::getFalse(ICI.getContext())); 895 if (HiOverflow == -1) // High bound less than input range. 896 return ReplaceInstUsesWith(ICI, ConstantInt::getTrue(ICI.getContext())); 897 if (Pred == ICmpInst::ICMP_UGT) 898 return new ICmpInst(ICmpInst::ICMP_UGE, X, HiBound); 899 return new ICmpInst(ICmpInst::ICMP_SGE, X, HiBound); 900 } 901} 902 903/// FoldICmpShrCst - Handle "icmp(([al]shr X, cst1), cst2)". 904Instruction *InstCombiner::FoldICmpShrCst(ICmpInst &ICI, BinaryOperator *Shr, 905 ConstantInt *ShAmt) { 906 const APInt &CmpRHSV = cast<ConstantInt>(ICI.getOperand(1))->getValue(); 907 908 // Check that the shift amount is in range. If not, don't perform 909 // undefined shifts. When the shift is visited it will be 910 // simplified. 911 uint32_t TypeBits = CmpRHSV.getBitWidth(); 912 uint32_t ShAmtVal = (uint32_t)ShAmt->getLimitedValue(TypeBits); 913 if (ShAmtVal >= TypeBits || ShAmtVal == 0) 914 return 0; 915 916 if (!ICI.isEquality()) { 917 // If we have an unsigned comparison and an ashr, we can't simplify this. 918 // Similarly for signed comparisons with lshr. 919 if (ICI.isSigned() != (Shr->getOpcode() == Instruction::AShr)) 920 return 0; 921 922 // Otherwise, all lshr and all exact ashr's are equivalent to a udiv/sdiv by 923 // a power of 2. Since we already have logic to simplify these, transform 924 // to div and then simplify the resultant comparison. 925 if (Shr->getOpcode() == Instruction::AShr && 926 !Shr->isExact()) 927 return 0; 928 929 // Revisit the shift (to delete it). 930 Worklist.Add(Shr); 931 932 Constant *DivCst = 933 ConstantInt::get(Shr->getType(), APInt::getOneBitSet(TypeBits, ShAmtVal)); 934 935 Value *Tmp = 936 Shr->getOpcode() == Instruction::AShr ? 937 Builder->CreateSDiv(Shr->getOperand(0), DivCst, "", Shr->isExact()) : 938 Builder->CreateUDiv(Shr->getOperand(0), DivCst, "", Shr->isExact()); 939 940 ICI.setOperand(0, Tmp); 941 942 // If the builder folded the binop, just return it. 943 BinaryOperator *TheDiv = dyn_cast<BinaryOperator>(Tmp); 944 if (TheDiv == 0) 945 return &ICI; 946 947 // Otherwise, fold this div/compare. 948 assert(TheDiv->getOpcode() == Instruction::SDiv || 949 TheDiv->getOpcode() == Instruction::UDiv); 950 951 Instruction *Res = FoldICmpDivCst(ICI, TheDiv, cast<ConstantInt>(DivCst)); 952 assert(Res && "This div/cst should have folded!"); 953 return Res; 954 } 955 956 957 // If we are comparing against bits always shifted out, the 958 // comparison cannot succeed. 959 APInt Comp = CmpRHSV << ShAmtVal; 960 ConstantInt *ShiftedCmpRHS = ConstantInt::get(ICI.getContext(), Comp); 961 if (Shr->getOpcode() == Instruction::LShr) 962 Comp = Comp.lshr(ShAmtVal); 963 else 964 Comp = Comp.ashr(ShAmtVal); 965 966 if (Comp != CmpRHSV) { // Comparing against a bit that we know is zero. 967 bool IsICMP_NE = ICI.getPredicate() == ICmpInst::ICMP_NE; 968 Constant *Cst = ConstantInt::get(Type::getInt1Ty(ICI.getContext()), 969 IsICMP_NE); 970 return ReplaceInstUsesWith(ICI, Cst); 971 } 972 973 // Otherwise, check to see if the bits shifted out are known to be zero. 974 // If so, we can compare against the unshifted value: 975 // (X & 4) >> 1 == 2 --> (X & 4) == 4. 976 if (Shr->hasOneUse() && Shr->isExact()) 977 return new ICmpInst(ICI.getPredicate(), Shr->getOperand(0), ShiftedCmpRHS); 978 979 if (Shr->hasOneUse()) { 980 // Otherwise strength reduce the shift into an and. 981 APInt Val(APInt::getHighBitsSet(TypeBits, TypeBits - ShAmtVal)); 982 Constant *Mask = ConstantInt::get(ICI.getContext(), Val); 983 984 Value *And = Builder->CreateAnd(Shr->getOperand(0), 985 Mask, Shr->getName()+".mask"); 986 return new ICmpInst(ICI.getPredicate(), And, ShiftedCmpRHS); 987 } 988 return 0; 989} 990 991 992/// visitICmpInstWithInstAndIntCst - Handle "icmp (instr, intcst)". 993/// 994Instruction *InstCombiner::visitICmpInstWithInstAndIntCst(ICmpInst &ICI, 995 Instruction *LHSI, 996 ConstantInt *RHS) { 997 const APInt &RHSV = RHS->getValue(); 998 999 switch (LHSI->getOpcode()) { 1000 case Instruction::Trunc: 1001 if (ICI.isEquality() && LHSI->hasOneUse()) { 1002 // Simplify icmp eq (trunc x to i8), 42 -> icmp eq x, 42|highbits if all 1003 // of the high bits truncated out of x are known. 1004 unsigned DstBits = LHSI->getType()->getPrimitiveSizeInBits(), 1005 SrcBits = LHSI->getOperand(0)->getType()->getPrimitiveSizeInBits(); 1006 APInt Mask(APInt::getHighBitsSet(SrcBits, SrcBits-DstBits)); 1007 APInt KnownZero(SrcBits, 0), KnownOne(SrcBits, 0); 1008 ComputeMaskedBits(LHSI->getOperand(0), Mask, KnownZero, KnownOne); 1009 1010 // If all the high bits are known, we can do this xform. 1011 if ((KnownZero|KnownOne).countLeadingOnes() >= SrcBits-DstBits) { 1012 // Pull in the high bits from known-ones set. 1013 APInt NewRHS = RHS->getValue().zext(SrcBits); 1014 NewRHS |= KnownOne; 1015 return new ICmpInst(ICI.getPredicate(), LHSI->getOperand(0), 1016 ConstantInt::get(ICI.getContext(), NewRHS)); 1017 } 1018 } 1019 break; 1020 1021 case Instruction::Xor: // (icmp pred (xor X, XorCST), CI) 1022 if (ConstantInt *XorCST = dyn_cast<ConstantInt>(LHSI->getOperand(1))) { 1023 // If this is a comparison that tests the signbit (X < 0) or (x > -1), 1024 // fold the xor. 1025 if ((ICI.getPredicate() == ICmpInst::ICMP_SLT && RHSV == 0) || 1026 (ICI.getPredicate() == ICmpInst::ICMP_SGT && RHSV.isAllOnesValue())) { 1027 Value *CompareVal = LHSI->getOperand(0); 1028 1029 // If the sign bit of the XorCST is not set, there is no change to 1030 // the operation, just stop using the Xor. 1031 if (!XorCST->getValue().isNegative()) { 1032 ICI.setOperand(0, CompareVal); 1033 Worklist.Add(LHSI); 1034 return &ICI; 1035 } 1036 1037 // Was the old condition true if the operand is positive? 1038 bool isTrueIfPositive = ICI.getPredicate() == ICmpInst::ICMP_SGT; 1039 1040 // If so, the new one isn't. 1041 isTrueIfPositive ^= true; 1042 1043 if (isTrueIfPositive) 1044 return new ICmpInst(ICmpInst::ICMP_SGT, CompareVal, 1045 SubOne(RHS)); 1046 else 1047 return new ICmpInst(ICmpInst::ICMP_SLT, CompareVal, 1048 AddOne(RHS)); 1049 } 1050 1051 if (LHSI->hasOneUse()) { 1052 // (icmp u/s (xor A SignBit), C) -> (icmp s/u A, (xor C SignBit)) 1053 if (!ICI.isEquality() && XorCST->getValue().isSignBit()) { 1054 const APInt &SignBit = XorCST->getValue(); 1055 ICmpInst::Predicate Pred = ICI.isSigned() 1056 ? ICI.getUnsignedPredicate() 1057 : ICI.getSignedPredicate(); 1058 return new ICmpInst(Pred, LHSI->getOperand(0), 1059 ConstantInt::get(ICI.getContext(), 1060 RHSV ^ SignBit)); 1061 } 1062 1063 // (icmp u/s (xor A ~SignBit), C) -> (icmp s/u (xor C ~SignBit), A) 1064 if (!ICI.isEquality() && XorCST->getValue().isMaxSignedValue()) { 1065 const APInt &NotSignBit = XorCST->getValue(); 1066 ICmpInst::Predicate Pred = ICI.isSigned() 1067 ? ICI.getUnsignedPredicate() 1068 : ICI.getSignedPredicate(); 1069 Pred = ICI.getSwappedPredicate(Pred); 1070 return new ICmpInst(Pred, LHSI->getOperand(0), 1071 ConstantInt::get(ICI.getContext(), 1072 RHSV ^ NotSignBit)); 1073 } 1074 } 1075 } 1076 break; 1077 case Instruction::And: // (icmp pred (and X, AndCST), RHS) 1078 if (LHSI->hasOneUse() && isa<ConstantInt>(LHSI->getOperand(1)) && 1079 LHSI->getOperand(0)->hasOneUse()) { 1080 ConstantInt *AndCST = cast<ConstantInt>(LHSI->getOperand(1)); 1081 1082 // If the LHS is an AND of a truncating cast, we can widen the 1083 // and/compare to be the input width without changing the value 1084 // produced, eliminating a cast. 1085 if (TruncInst *Cast = dyn_cast<TruncInst>(LHSI->getOperand(0))) { 1086 // We can do this transformation if either the AND constant does not 1087 // have its sign bit set or if it is an equality comparison. 1088 // Extending a relational comparison when we're checking the sign 1089 // bit would not work. 1090 if (Cast->hasOneUse() && 1091 (ICI.isEquality() || 1092 (AndCST->getValue().isNonNegative() && RHSV.isNonNegative()))) { 1093 uint32_t BitWidth = 1094 cast<IntegerType>(Cast->getOperand(0)->getType())->getBitWidth(); 1095 APInt NewCST = AndCST->getValue().zext(BitWidth); 1096 APInt NewCI = RHSV.zext(BitWidth); 1097 Value *NewAnd = 1098 Builder->CreateAnd(Cast->getOperand(0), 1099 ConstantInt::get(ICI.getContext(), NewCST), 1100 LHSI->getName()); 1101 return new ICmpInst(ICI.getPredicate(), NewAnd, 1102 ConstantInt::get(ICI.getContext(), NewCI)); 1103 } 1104 } 1105 1106 // If this is: (X >> C1) & C2 != C3 (where any shift and any compare 1107 // could exist), turn it into (X & (C2 << C1)) != (C3 << C1). This 1108 // happens a LOT in code produced by the C front-end, for bitfield 1109 // access. 1110 BinaryOperator *Shift = dyn_cast<BinaryOperator>(LHSI->getOperand(0)); 1111 if (Shift && !Shift->isShift()) 1112 Shift = 0; 1113 1114 ConstantInt *ShAmt; 1115 ShAmt = Shift ? dyn_cast<ConstantInt>(Shift->getOperand(1)) : 0; 1116 const Type *Ty = Shift ? Shift->getType() : 0; // Type of the shift. 1117 const Type *AndTy = AndCST->getType(); // Type of the and. 1118 1119 // We can fold this as long as we can't shift unknown bits 1120 // into the mask. This can only happen with signed shift 1121 // rights, as they sign-extend. 1122 if (ShAmt) { 1123 bool CanFold = Shift->isLogicalShift(); 1124 if (!CanFold) { 1125 // To test for the bad case of the signed shr, see if any 1126 // of the bits shifted in could be tested after the mask. 1127 uint32_t TyBits = Ty->getPrimitiveSizeInBits(); 1128 int ShAmtVal = TyBits - ShAmt->getLimitedValue(TyBits); 1129 1130 uint32_t BitWidth = AndTy->getPrimitiveSizeInBits(); 1131 if ((APInt::getHighBitsSet(BitWidth, BitWidth-ShAmtVal) & 1132 AndCST->getValue()) == 0) 1133 CanFold = true; 1134 } 1135 1136 if (CanFold) { 1137 Constant *NewCst; 1138 if (Shift->getOpcode() == Instruction::Shl) 1139 NewCst = ConstantExpr::getLShr(RHS, ShAmt); 1140 else 1141 NewCst = ConstantExpr::getShl(RHS, ShAmt); 1142 1143 // Check to see if we are shifting out any of the bits being 1144 // compared. 1145 if (ConstantExpr::get(Shift->getOpcode(), 1146 NewCst, ShAmt) != RHS) { 1147 // If we shifted bits out, the fold is not going to work out. 1148 // As a special case, check to see if this means that the 1149 // result is always true or false now. 1150 if (ICI.getPredicate() == ICmpInst::ICMP_EQ) 1151 return ReplaceInstUsesWith(ICI, 1152 ConstantInt::getFalse(ICI.getContext())); 1153 if (ICI.getPredicate() == ICmpInst::ICMP_NE) 1154 return ReplaceInstUsesWith(ICI, 1155 ConstantInt::getTrue(ICI.getContext())); 1156 } else { 1157 ICI.setOperand(1, NewCst); 1158 Constant *NewAndCST; 1159 if (Shift->getOpcode() == Instruction::Shl) 1160 NewAndCST = ConstantExpr::getLShr(AndCST, ShAmt); 1161 else 1162 NewAndCST = ConstantExpr::getShl(AndCST, ShAmt); 1163 LHSI->setOperand(1, NewAndCST); 1164 LHSI->setOperand(0, Shift->getOperand(0)); 1165 Worklist.Add(Shift); // Shift is dead. 1166 return &ICI; 1167 } 1168 } 1169 } 1170 1171 // Turn ((X >> Y) & C) == 0 into (X & (C << Y)) == 0. The later is 1172 // preferable because it allows the C<<Y expression to be hoisted out 1173 // of a loop if Y is invariant and X is not. 1174 if (Shift && Shift->hasOneUse() && RHSV == 0 && 1175 ICI.isEquality() && !Shift->isArithmeticShift() && 1176 !isa<Constant>(Shift->getOperand(0))) { 1177 // Compute C << Y. 1178 Value *NS; 1179 if (Shift->getOpcode() == Instruction::LShr) { 1180 NS = Builder->CreateShl(AndCST, Shift->getOperand(1), "tmp"); 1181 } else { 1182 // Insert a logical shift. 1183 NS = Builder->CreateLShr(AndCST, Shift->getOperand(1), "tmp"); 1184 } 1185 1186 // Compute X & (C << Y). 1187 Value *NewAnd = 1188 Builder->CreateAnd(Shift->getOperand(0), NS, LHSI->getName()); 1189 1190 ICI.setOperand(0, NewAnd); 1191 return &ICI; 1192 } 1193 } 1194 1195 // Try to optimize things like "A[i]&42 == 0" to index computations. 1196 if (LoadInst *LI = dyn_cast<LoadInst>(LHSI->getOperand(0))) { 1197 if (GetElementPtrInst *GEP = 1198 dyn_cast<GetElementPtrInst>(LI->getOperand(0))) 1199 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(GEP->getOperand(0))) 1200 if (GV->isConstant() && GV->hasDefinitiveInitializer() && 1201 !LI->isVolatile() && isa<ConstantInt>(LHSI->getOperand(1))) { 1202 ConstantInt *C = cast<ConstantInt>(LHSI->getOperand(1)); 1203 if (Instruction *Res = FoldCmpLoadFromIndexedGlobal(GEP, GV,ICI, C)) 1204 return Res; 1205 } 1206 } 1207 break; 1208 1209 case Instruction::Or: { 1210 if (!ICI.isEquality() || !RHS->isNullValue() || !LHSI->hasOneUse()) 1211 break; 1212 Value *P, *Q; 1213 if (match(LHSI, m_Or(m_PtrToInt(m_Value(P)), m_PtrToInt(m_Value(Q))))) { 1214 // Simplify icmp eq (or (ptrtoint P), (ptrtoint Q)), 0 1215 // -> and (icmp eq P, null), (icmp eq Q, null). 1216 Value *ICIP = Builder->CreateICmp(ICI.getPredicate(), P, 1217 Constant::getNullValue(P->getType())); 1218 Value *ICIQ = Builder->CreateICmp(ICI.getPredicate(), Q, 1219 Constant::getNullValue(Q->getType())); 1220 Instruction *Op; 1221 if (ICI.getPredicate() == ICmpInst::ICMP_EQ) 1222 Op = BinaryOperator::CreateAnd(ICIP, ICIQ); 1223 else 1224 Op = BinaryOperator::CreateOr(ICIP, ICIQ); 1225 return Op; 1226 } 1227 break; 1228 } 1229 1230 case Instruction::Shl: { // (icmp pred (shl X, ShAmt), CI) 1231 ConstantInt *ShAmt = dyn_cast<ConstantInt>(LHSI->getOperand(1)); 1232 if (!ShAmt) break; 1233 1234 uint32_t TypeBits = RHSV.getBitWidth(); 1235 1236 // Check that the shift amount is in range. If not, don't perform 1237 // undefined shifts. When the shift is visited it will be 1238 // simplified. 1239 if (ShAmt->uge(TypeBits)) 1240 break; 1241 1242 if (ICI.isEquality()) { 1243 // If we are comparing against bits always shifted out, the 1244 // comparison cannot succeed. 1245 Constant *Comp = 1246 ConstantExpr::getShl(ConstantExpr::getLShr(RHS, ShAmt), 1247 ShAmt); 1248 if (Comp != RHS) {// Comparing against a bit that we know is zero. 1249 bool IsICMP_NE = ICI.getPredicate() == ICmpInst::ICMP_NE; 1250 Constant *Cst = 1251 ConstantInt::get(Type::getInt1Ty(ICI.getContext()), IsICMP_NE); 1252 return ReplaceInstUsesWith(ICI, Cst); 1253 } 1254 1255 // If the shift is NUW, then it is just shifting out zeros, no need for an 1256 // AND. 1257 if (cast<BinaryOperator>(LHSI)->hasNoUnsignedWrap()) 1258 return new ICmpInst(ICI.getPredicate(), LHSI->getOperand(0), 1259 ConstantExpr::getLShr(RHS, ShAmt)); 1260 1261 if (LHSI->hasOneUse()) { 1262 // Otherwise strength reduce the shift into an and. 1263 uint32_t ShAmtVal = (uint32_t)ShAmt->getLimitedValue(TypeBits); 1264 Constant *Mask = 1265 ConstantInt::get(ICI.getContext(), APInt::getLowBitsSet(TypeBits, 1266 TypeBits-ShAmtVal)); 1267 1268 Value *And = 1269 Builder->CreateAnd(LHSI->getOperand(0),Mask, LHSI->getName()+".mask"); 1270 return new ICmpInst(ICI.getPredicate(), And, 1271 ConstantExpr::getLShr(RHS, ShAmt)); 1272 } 1273 } 1274 1275 // Otherwise, if this is a comparison of the sign bit, simplify to and/test. 1276 bool TrueIfSigned = false; 1277 if (LHSI->hasOneUse() && 1278 isSignBitCheck(ICI.getPredicate(), RHS, TrueIfSigned)) { 1279 // (X << 31) <s 0 --> (X&1) != 0 1280 Constant *Mask = ConstantInt::get(LHSI->getOperand(0)->getType(), 1281 APInt::getOneBitSet(TypeBits, 1282 TypeBits-ShAmt->getZExtValue()-1)); 1283 Value *And = 1284 Builder->CreateAnd(LHSI->getOperand(0), Mask, LHSI->getName()+".mask"); 1285 return new ICmpInst(TrueIfSigned ? ICmpInst::ICMP_NE : ICmpInst::ICMP_EQ, 1286 And, Constant::getNullValue(And->getType())); 1287 } 1288 break; 1289 } 1290 1291 case Instruction::LShr: // (icmp pred (shr X, ShAmt), CI) 1292 case Instruction::AShr: 1293 // Only handle equality comparisons of shift-by-constant. 1294 if (ConstantInt *ShAmt = dyn_cast<ConstantInt>(LHSI->getOperand(1))) 1295 if (Instruction *Res = FoldICmpShrCst(ICI, cast<BinaryOperator>(LHSI), 1296 ShAmt)) 1297 return Res; 1298 break; 1299 1300 case Instruction::SDiv: 1301 case Instruction::UDiv: 1302 // Fold: icmp pred ([us]div X, C1), C2 -> range test 1303 // Fold this div into the comparison, producing a range check. 1304 // Determine, based on the divide type, what the range is being 1305 // checked. If there is an overflow on the low or high side, remember 1306 // it, otherwise compute the range [low, hi) bounding the new value. 1307 // See: InsertRangeTest above for the kinds of replacements possible. 1308 if (ConstantInt *DivRHS = dyn_cast<ConstantInt>(LHSI->getOperand(1))) 1309 if (Instruction *R = FoldICmpDivCst(ICI, cast<BinaryOperator>(LHSI), 1310 DivRHS)) 1311 return R; 1312 break; 1313 1314 case Instruction::Add: 1315 // Fold: icmp pred (add X, C1), C2 1316 if (!ICI.isEquality()) { 1317 ConstantInt *LHSC = dyn_cast<ConstantInt>(LHSI->getOperand(1)); 1318 if (!LHSC) break; 1319 const APInt &LHSV = LHSC->getValue(); 1320 1321 ConstantRange CR = ICI.makeConstantRange(ICI.getPredicate(), RHSV) 1322 .subtract(LHSV); 1323 1324 if (ICI.isSigned()) { 1325 if (CR.getLower().isSignBit()) { 1326 return new ICmpInst(ICmpInst::ICMP_SLT, LHSI->getOperand(0), 1327 ConstantInt::get(ICI.getContext(),CR.getUpper())); 1328 } else if (CR.getUpper().isSignBit()) { 1329 return new ICmpInst(ICmpInst::ICMP_SGE, LHSI->getOperand(0), 1330 ConstantInt::get(ICI.getContext(),CR.getLower())); 1331 } 1332 } else { 1333 if (CR.getLower().isMinValue()) { 1334 return new ICmpInst(ICmpInst::ICMP_ULT, LHSI->getOperand(0), 1335 ConstantInt::get(ICI.getContext(),CR.getUpper())); 1336 } else if (CR.getUpper().isMinValue()) { 1337 return new ICmpInst(ICmpInst::ICMP_UGE, LHSI->getOperand(0), 1338 ConstantInt::get(ICI.getContext(),CR.getLower())); 1339 } 1340 } 1341 } 1342 break; 1343 } 1344 1345 // Simplify icmp_eq and icmp_ne instructions with integer constant RHS. 1346 if (ICI.isEquality()) { 1347 bool isICMP_NE = ICI.getPredicate() == ICmpInst::ICMP_NE; 1348 1349 // If the first operand is (add|sub|and|or|xor|rem) with a constant, and 1350 // the second operand is a constant, simplify a bit. 1351 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(LHSI)) { 1352 switch (BO->getOpcode()) { 1353 case Instruction::SRem: 1354 // If we have a signed (X % (2^c)) == 0, turn it into an unsigned one. 1355 if (RHSV == 0 && isa<ConstantInt>(BO->getOperand(1)) &&BO->hasOneUse()){ 1356 const APInt &V = cast<ConstantInt>(BO->getOperand(1))->getValue(); 1357 if (V.sgt(1) && V.isPowerOf2()) { 1358 Value *NewRem = 1359 Builder->CreateURem(BO->getOperand(0), BO->getOperand(1), 1360 BO->getName()); 1361 return new ICmpInst(ICI.getPredicate(), NewRem, 1362 Constant::getNullValue(BO->getType())); 1363 } 1364 } 1365 break; 1366 case Instruction::Add: 1367 // Replace ((add A, B) != C) with (A != C-B) if B & C are constants. 1368 if (ConstantInt *BOp1C = dyn_cast<ConstantInt>(BO->getOperand(1))) { 1369 if (BO->hasOneUse()) 1370 return new ICmpInst(ICI.getPredicate(), BO->getOperand(0), 1371 ConstantExpr::getSub(RHS, BOp1C)); 1372 } else if (RHSV == 0) { 1373 // Replace ((add A, B) != 0) with (A != -B) if A or B is 1374 // efficiently invertible, or if the add has just this one use. 1375 Value *BOp0 = BO->getOperand(0), *BOp1 = BO->getOperand(1); 1376 1377 if (Value *NegVal = dyn_castNegVal(BOp1)) 1378 return new ICmpInst(ICI.getPredicate(), BOp0, NegVal); 1379 else if (Value *NegVal = dyn_castNegVal(BOp0)) 1380 return new ICmpInst(ICI.getPredicate(), NegVal, BOp1); 1381 else if (BO->hasOneUse()) { 1382 Value *Neg = Builder->CreateNeg(BOp1); 1383 Neg->takeName(BO); 1384 return new ICmpInst(ICI.getPredicate(), BOp0, Neg); 1385 } 1386 } 1387 break; 1388 case Instruction::Xor: 1389 // For the xor case, we can xor two constants together, eliminating 1390 // the explicit xor. 1391 if (Constant *BOC = dyn_cast<Constant>(BO->getOperand(1))) 1392 return new ICmpInst(ICI.getPredicate(), BO->getOperand(0), 1393 ConstantExpr::getXor(RHS, BOC)); 1394 1395 // FALLTHROUGH 1396 case Instruction::Sub: 1397 // Replace (([sub|xor] A, B) != 0) with (A != B) 1398 if (RHSV == 0) 1399 return new ICmpInst(ICI.getPredicate(), BO->getOperand(0), 1400 BO->getOperand(1)); 1401 break; 1402 1403 case Instruction::Or: 1404 // If bits are being or'd in that are not present in the constant we 1405 // are comparing against, then the comparison could never succeed! 1406 if (ConstantInt *BOC = dyn_cast<ConstantInt>(BO->getOperand(1))) { 1407 Constant *NotCI = ConstantExpr::getNot(RHS); 1408 if (!ConstantExpr::getAnd(BOC, NotCI)->isNullValue()) 1409 return ReplaceInstUsesWith(ICI, 1410 ConstantInt::get(Type::getInt1Ty(ICI.getContext()), 1411 isICMP_NE)); 1412 } 1413 break; 1414 1415 case Instruction::And: 1416 if (ConstantInt *BOC = dyn_cast<ConstantInt>(BO->getOperand(1))) { 1417 // If bits are being compared against that are and'd out, then the 1418 // comparison can never succeed! 1419 if ((RHSV & ~BOC->getValue()) != 0) 1420 return ReplaceInstUsesWith(ICI, 1421 ConstantInt::get(Type::getInt1Ty(ICI.getContext()), 1422 isICMP_NE)); 1423 1424 // If we have ((X & C) == C), turn it into ((X & C) != 0). 1425 if (RHS == BOC && RHSV.isPowerOf2()) 1426 return new ICmpInst(isICMP_NE ? ICmpInst::ICMP_EQ : 1427 ICmpInst::ICMP_NE, LHSI, 1428 Constant::getNullValue(RHS->getType())); 1429 1430 // Replace (and X, (1 << size(X)-1) != 0) with x s< 0 1431 if (BOC->getValue().isSignBit()) { 1432 Value *X = BO->getOperand(0); 1433 Constant *Zero = Constant::getNullValue(X->getType()); 1434 ICmpInst::Predicate pred = isICMP_NE ? 1435 ICmpInst::ICMP_SLT : ICmpInst::ICMP_SGE; 1436 return new ICmpInst(pred, X, Zero); 1437 } 1438 1439 // ((X & ~7) == 0) --> X < 8 1440 if (RHSV == 0 && isHighOnes(BOC)) { 1441 Value *X = BO->getOperand(0); 1442 Constant *NegX = ConstantExpr::getNeg(BOC); 1443 ICmpInst::Predicate pred = isICMP_NE ? 1444 ICmpInst::ICMP_UGE : ICmpInst::ICMP_ULT; 1445 return new ICmpInst(pred, X, NegX); 1446 } 1447 } 1448 default: break; 1449 } 1450 } else if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(LHSI)) { 1451 // Handle icmp {eq|ne} <intrinsic>, intcst. 1452 switch (II->getIntrinsicID()) { 1453 case Intrinsic::bswap: 1454 Worklist.Add(II); 1455 ICI.setOperand(0, II->getArgOperand(0)); 1456 ICI.setOperand(1, ConstantInt::get(II->getContext(), RHSV.byteSwap())); 1457 return &ICI; 1458 case Intrinsic::ctlz: 1459 case Intrinsic::cttz: 1460 // ctz(A) == bitwidth(a) -> A == 0 and likewise for != 1461 if (RHSV == RHS->getType()->getBitWidth()) { 1462 Worklist.Add(II); 1463 ICI.setOperand(0, II->getArgOperand(0)); 1464 ICI.setOperand(1, ConstantInt::get(RHS->getType(), 0)); 1465 return &ICI; 1466 } 1467 break; 1468 case Intrinsic::ctpop: 1469 // popcount(A) == 0 -> A == 0 and likewise for != 1470 if (RHS->isZero()) { 1471 Worklist.Add(II); 1472 ICI.setOperand(0, II->getArgOperand(0)); 1473 ICI.setOperand(1, RHS); 1474 return &ICI; 1475 } 1476 break; 1477 default: 1478 break; 1479 } 1480 } 1481 } 1482 return 0; 1483} 1484 1485/// visitICmpInstWithCastAndCast - Handle icmp (cast x to y), (cast/cst). 1486/// We only handle extending casts so far. 1487/// 1488Instruction *InstCombiner::visitICmpInstWithCastAndCast(ICmpInst &ICI) { 1489 const CastInst *LHSCI = cast<CastInst>(ICI.getOperand(0)); 1490 Value *LHSCIOp = LHSCI->getOperand(0); 1491 const Type *SrcTy = LHSCIOp->getType(); 1492 const Type *DestTy = LHSCI->getType(); 1493 Value *RHSCIOp; 1494 1495 // Turn icmp (ptrtoint x), (ptrtoint/c) into a compare of the input if the 1496 // integer type is the same size as the pointer type. 1497 if (TD && LHSCI->getOpcode() == Instruction::PtrToInt && 1498 TD->getPointerSizeInBits() == 1499 cast<IntegerType>(DestTy)->getBitWidth()) { 1500 Value *RHSOp = 0; 1501 if (Constant *RHSC = dyn_cast<Constant>(ICI.getOperand(1))) { 1502 RHSOp = ConstantExpr::getIntToPtr(RHSC, SrcTy); 1503 } else if (PtrToIntInst *RHSC = dyn_cast<PtrToIntInst>(ICI.getOperand(1))) { 1504 RHSOp = RHSC->getOperand(0); 1505 // If the pointer types don't match, insert a bitcast. 1506 if (LHSCIOp->getType() != RHSOp->getType()) 1507 RHSOp = Builder->CreateBitCast(RHSOp, LHSCIOp->getType()); 1508 } 1509 1510 if (RHSOp) 1511 return new ICmpInst(ICI.getPredicate(), LHSCIOp, RHSOp); 1512 } 1513 1514 // The code below only handles extension cast instructions, so far. 1515 // Enforce this. 1516 if (LHSCI->getOpcode() != Instruction::ZExt && 1517 LHSCI->getOpcode() != Instruction::SExt) 1518 return 0; 1519 1520 bool isSignedExt = LHSCI->getOpcode() == Instruction::SExt; 1521 bool isSignedCmp = ICI.isSigned(); 1522 1523 if (CastInst *CI = dyn_cast<CastInst>(ICI.getOperand(1))) { 1524 // Not an extension from the same type? 1525 RHSCIOp = CI->getOperand(0); 1526 if (RHSCIOp->getType() != LHSCIOp->getType()) 1527 return 0; 1528 1529 // If the signedness of the two casts doesn't agree (i.e. one is a sext 1530 // and the other is a zext), then we can't handle this. 1531 if (CI->getOpcode() != LHSCI->getOpcode()) 1532 return 0; 1533 1534 // Deal with equality cases early. 1535 if (ICI.isEquality()) 1536 return new ICmpInst(ICI.getPredicate(), LHSCIOp, RHSCIOp); 1537 1538 // A signed comparison of sign extended values simplifies into a 1539 // signed comparison. 1540 if (isSignedCmp && isSignedExt) 1541 return new ICmpInst(ICI.getPredicate(), LHSCIOp, RHSCIOp); 1542 1543 // The other three cases all fold into an unsigned comparison. 1544 return new ICmpInst(ICI.getUnsignedPredicate(), LHSCIOp, RHSCIOp); 1545 } 1546 1547 // If we aren't dealing with a constant on the RHS, exit early 1548 ConstantInt *CI = dyn_cast<ConstantInt>(ICI.getOperand(1)); 1549 if (!CI) 1550 return 0; 1551 1552 // Compute the constant that would happen if we truncated to SrcTy then 1553 // reextended to DestTy. 1554 Constant *Res1 = ConstantExpr::getTrunc(CI, SrcTy); 1555 Constant *Res2 = ConstantExpr::getCast(LHSCI->getOpcode(), 1556 Res1, DestTy); 1557 1558 // If the re-extended constant didn't change... 1559 if (Res2 == CI) { 1560 // Deal with equality cases early. 1561 if (ICI.isEquality()) 1562 return new ICmpInst(ICI.getPredicate(), LHSCIOp, Res1); 1563 1564 // A signed comparison of sign extended values simplifies into a 1565 // signed comparison. 1566 if (isSignedExt && isSignedCmp) 1567 return new ICmpInst(ICI.getPredicate(), LHSCIOp, Res1); 1568 1569 // The other three cases all fold into an unsigned comparison. 1570 return new ICmpInst(ICI.getUnsignedPredicate(), LHSCIOp, Res1); 1571 } 1572 1573 // The re-extended constant changed so the constant cannot be represented 1574 // in the shorter type. Consequently, we cannot emit a simple comparison. 1575 // All the cases that fold to true or false will have already been handled 1576 // by SimplifyICmpInst, so only deal with the tricky case. 1577 1578 if (isSignedCmp || !isSignedExt) 1579 return 0; 1580 1581 // Evaluate the comparison for LT (we invert for GT below). LE and GE cases 1582 // should have been folded away previously and not enter in here. 1583 1584 // We're performing an unsigned comp with a sign extended value. 1585 // This is true if the input is >= 0. [aka >s -1] 1586 Constant *NegOne = Constant::getAllOnesValue(SrcTy); 1587 Value *Result = Builder->CreateICmpSGT(LHSCIOp, NegOne, ICI.getName()); 1588 1589 // Finally, return the value computed. 1590 if (ICI.getPredicate() == ICmpInst::ICMP_ULT) 1591 return ReplaceInstUsesWith(ICI, Result); 1592 1593 assert(ICI.getPredicate() == ICmpInst::ICMP_UGT && "ICmp should be folded!"); 1594 return BinaryOperator::CreateNot(Result); 1595} 1596 1597/// ProcessUGT_ADDCST_ADD - The caller has matched a pattern of the form: 1598/// I = icmp ugt (add (add A, B), CI2), CI1 1599/// If this is of the form: 1600/// sum = a + b 1601/// if (sum+128 >u 255) 1602/// Then replace it with llvm.sadd.with.overflow.i8. 1603/// 1604static Instruction *ProcessUGT_ADDCST_ADD(ICmpInst &I, Value *A, Value *B, 1605 ConstantInt *CI2, ConstantInt *CI1, 1606 InstCombiner &IC) { 1607 // The transformation we're trying to do here is to transform this into an 1608 // llvm.sadd.with.overflow. To do this, we have to replace the original add 1609 // with a narrower add, and discard the add-with-constant that is part of the 1610 // range check (if we can't eliminate it, this isn't profitable). 1611 1612 // In order to eliminate the add-with-constant, the compare can be its only 1613 // use. 1614 Instruction *AddWithCst = cast<Instruction>(I.getOperand(0)); 1615 if (!AddWithCst->hasOneUse()) return 0; 1616 1617 // If CI2 is 2^7, 2^15, 2^31, then it might be an sadd.with.overflow. 1618 if (!CI2->getValue().isPowerOf2()) return 0; 1619 unsigned NewWidth = CI2->getValue().countTrailingZeros(); 1620 if (NewWidth != 7 && NewWidth != 15 && NewWidth != 31) return 0; 1621 1622 // The width of the new add formed is 1 more than the bias. 1623 ++NewWidth; 1624 1625 // Check to see that CI1 is an all-ones value with NewWidth bits. 1626 if (CI1->getBitWidth() == NewWidth || 1627 CI1->getValue() != APInt::getLowBitsSet(CI1->getBitWidth(), NewWidth)) 1628 return 0; 1629 1630 // In order to replace the original add with a narrower 1631 // llvm.sadd.with.overflow, the only uses allowed are the add-with-constant 1632 // and truncates that discard the high bits of the add. Verify that this is 1633 // the case. 1634 Instruction *OrigAdd = cast<Instruction>(AddWithCst->getOperand(0)); 1635 for (Value::use_iterator UI = OrigAdd->use_begin(), E = OrigAdd->use_end(); 1636 UI != E; ++UI) { 1637 if (*UI == AddWithCst) continue; 1638 1639 // Only accept truncates for now. We would really like a nice recursive 1640 // predicate like SimplifyDemandedBits, but which goes downwards the use-def 1641 // chain to see which bits of a value are actually demanded. If the 1642 // original add had another add which was then immediately truncated, we 1643 // could still do the transformation. 1644 TruncInst *TI = dyn_cast<TruncInst>(*UI); 1645 if (TI == 0 || 1646 TI->getType()->getPrimitiveSizeInBits() > NewWidth) return 0; 1647 } 1648 1649 // If the pattern matches, truncate the inputs to the narrower type and 1650 // use the sadd_with_overflow intrinsic to efficiently compute both the 1651 // result and the overflow bit. 1652 Module *M = I.getParent()->getParent()->getParent(); 1653 1654 const Type *NewType = IntegerType::get(OrigAdd->getContext(), NewWidth); 1655 Value *F = Intrinsic::getDeclaration(M, Intrinsic::sadd_with_overflow, 1656 &NewType, 1); 1657 1658 InstCombiner::BuilderTy *Builder = IC.Builder; 1659 1660 // Put the new code above the original add, in case there are any uses of the 1661 // add between the add and the compare. 1662 Builder->SetInsertPoint(OrigAdd); 1663 1664 Value *TruncA = Builder->CreateTrunc(A, NewType, A->getName()+".trunc"); 1665 Value *TruncB = Builder->CreateTrunc(B, NewType, B->getName()+".trunc"); 1666 CallInst *Call = Builder->CreateCall2(F, TruncA, TruncB, "sadd"); 1667 Value *Add = Builder->CreateExtractValue(Call, 0, "sadd.result"); 1668 Value *ZExt = Builder->CreateZExt(Add, OrigAdd->getType()); 1669 1670 // The inner add was the result of the narrow add, zero extended to the 1671 // wider type. Replace it with the result computed by the intrinsic. 1672 IC.ReplaceInstUsesWith(*OrigAdd, ZExt); 1673 1674 // The original icmp gets replaced with the overflow value. 1675 return ExtractValueInst::Create(Call, 1, "sadd.overflow"); 1676} 1677 1678static Instruction *ProcessUAddIdiom(Instruction &I, Value *OrigAddV, 1679 InstCombiner &IC) { 1680 // Don't bother doing this transformation for pointers, don't do it for 1681 // vectors. 1682 if (!isa<IntegerType>(OrigAddV->getType())) return 0; 1683 1684 // If the add is a constant expr, then we don't bother transforming it. 1685 Instruction *OrigAdd = dyn_cast<Instruction>(OrigAddV); 1686 if (OrigAdd == 0) return 0; 1687 1688 Value *LHS = OrigAdd->getOperand(0), *RHS = OrigAdd->getOperand(1); 1689 1690 // Put the new code above the original add, in case there are any uses of the 1691 // add between the add and the compare. 1692 InstCombiner::BuilderTy *Builder = IC.Builder; 1693 Builder->SetInsertPoint(OrigAdd); 1694 1695 Module *M = I.getParent()->getParent()->getParent(); 1696 const Type *Ty = LHS->getType(); 1697 Value *F = Intrinsic::getDeclaration(M, Intrinsic::uadd_with_overflow, &Ty,1); 1698 CallInst *Call = Builder->CreateCall2(F, LHS, RHS, "uadd"); 1699 Value *Add = Builder->CreateExtractValue(Call, 0); 1700 1701 IC.ReplaceInstUsesWith(*OrigAdd, Add); 1702 1703 // The original icmp gets replaced with the overflow value. 1704 return ExtractValueInst::Create(Call, 1, "uadd.overflow"); 1705} 1706 1707// DemandedBitsLHSMask - When performing a comparison against a constant, 1708// it is possible that not all the bits in the LHS are demanded. This helper 1709// method computes the mask that IS demanded. 1710static APInt DemandedBitsLHSMask(ICmpInst &I, 1711 unsigned BitWidth, bool isSignCheck) { 1712 if (isSignCheck) 1713 return APInt::getSignBit(BitWidth); 1714 1715 ConstantInt *CI = dyn_cast<ConstantInt>(I.getOperand(1)); 1716 if (!CI) return APInt::getAllOnesValue(BitWidth); 1717 const APInt &RHS = CI->getValue(); 1718 1719 switch (I.getPredicate()) { 1720 // For a UGT comparison, we don't care about any bits that 1721 // correspond to the trailing ones of the comparand. The value of these 1722 // bits doesn't impact the outcome of the comparison, because any value 1723 // greater than the RHS must differ in a bit higher than these due to carry. 1724 case ICmpInst::ICMP_UGT: { 1725 unsigned trailingOnes = RHS.countTrailingOnes(); 1726 APInt lowBitsSet = APInt::getLowBitsSet(BitWidth, trailingOnes); 1727 return ~lowBitsSet; 1728 } 1729 1730 // Similarly, for a ULT comparison, we don't care about the trailing zeros. 1731 // Any value less than the RHS must differ in a higher bit because of carries. 1732 case ICmpInst::ICMP_ULT: { 1733 unsigned trailingZeros = RHS.countTrailingZeros(); 1734 APInt lowBitsSet = APInt::getLowBitsSet(BitWidth, trailingZeros); 1735 return ~lowBitsSet; 1736 } 1737 1738 default: 1739 return APInt::getAllOnesValue(BitWidth); 1740 } 1741 1742} 1743 1744Instruction *InstCombiner::visitICmpInst(ICmpInst &I) { 1745 bool Changed = false; 1746 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1); 1747 1748 /// Orders the operands of the compare so that they are listed from most 1749 /// complex to least complex. This puts constants before unary operators, 1750 /// before binary operators. 1751 if (getComplexity(Op0) < getComplexity(Op1)) { 1752 I.swapOperands(); 1753 std::swap(Op0, Op1); 1754 Changed = true; 1755 } 1756 1757 if (Value *V = SimplifyICmpInst(I.getPredicate(), Op0, Op1, TD)) 1758 return ReplaceInstUsesWith(I, V); 1759 1760 const Type *Ty = Op0->getType(); 1761 1762 // icmp's with boolean values can always be turned into bitwise operations 1763 if (Ty->isIntegerTy(1)) { 1764 switch (I.getPredicate()) { 1765 default: llvm_unreachable("Invalid icmp instruction!"); 1766 case ICmpInst::ICMP_EQ: { // icmp eq i1 A, B -> ~(A^B) 1767 Value *Xor = Builder->CreateXor(Op0, Op1, I.getName()+"tmp"); 1768 return BinaryOperator::CreateNot(Xor); 1769 } 1770 case ICmpInst::ICMP_NE: // icmp eq i1 A, B -> A^B 1771 return BinaryOperator::CreateXor(Op0, Op1); 1772 1773 case ICmpInst::ICMP_UGT: 1774 std::swap(Op0, Op1); // Change icmp ugt -> icmp ult 1775 // FALL THROUGH 1776 case ICmpInst::ICMP_ULT:{ // icmp ult i1 A, B -> ~A & B 1777 Value *Not = Builder->CreateNot(Op0, I.getName()+"tmp"); 1778 return BinaryOperator::CreateAnd(Not, Op1); 1779 } 1780 case ICmpInst::ICMP_SGT: 1781 std::swap(Op0, Op1); // Change icmp sgt -> icmp slt 1782 // FALL THROUGH 1783 case ICmpInst::ICMP_SLT: { // icmp slt i1 A, B -> A & ~B 1784 Value *Not = Builder->CreateNot(Op1, I.getName()+"tmp"); 1785 return BinaryOperator::CreateAnd(Not, Op0); 1786 } 1787 case ICmpInst::ICMP_UGE: 1788 std::swap(Op0, Op1); // Change icmp uge -> icmp ule 1789 // FALL THROUGH 1790 case ICmpInst::ICMP_ULE: { // icmp ule i1 A, B -> ~A | B 1791 Value *Not = Builder->CreateNot(Op0, I.getName()+"tmp"); 1792 return BinaryOperator::CreateOr(Not, Op1); 1793 } 1794 case ICmpInst::ICMP_SGE: 1795 std::swap(Op0, Op1); // Change icmp sge -> icmp sle 1796 // FALL THROUGH 1797 case ICmpInst::ICMP_SLE: { // icmp sle i1 A, B -> A | ~B 1798 Value *Not = Builder->CreateNot(Op1, I.getName()+"tmp"); 1799 return BinaryOperator::CreateOr(Not, Op0); 1800 } 1801 } 1802 } 1803 1804 unsigned BitWidth = 0; 1805 if (Ty->isIntOrIntVectorTy()) 1806 BitWidth = Ty->getScalarSizeInBits(); 1807 else if (TD) // Pointers require TD info to get their size. 1808 BitWidth = TD->getTypeSizeInBits(Ty->getScalarType()); 1809 1810 bool isSignBit = false; 1811 1812 // See if we are doing a comparison with a constant. 1813 if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) { 1814 Value *A = 0, *B = 0; 1815 1816 // Match the following pattern, which is a common idiom when writing 1817 // overflow-safe integer arithmetic function. The source performs an 1818 // addition in wider type, and explicitly checks for overflow using 1819 // comparisons against INT_MIN and INT_MAX. Simplify this by using the 1820 // sadd_with_overflow intrinsic. 1821 // 1822 // TODO: This could probably be generalized to handle other overflow-safe 1823 // operations if we worked out the formulas to compute the appropriate 1824 // magic constants. 1825 // 1826 // sum = a + b 1827 // if (sum+128 >u 255) ... -> llvm.sadd.with.overflow.i8 1828 { 1829 ConstantInt *CI2; // I = icmp ugt (add (add A, B), CI2), CI 1830 if (I.getPredicate() == ICmpInst::ICMP_UGT && 1831 match(Op0, m_Add(m_Add(m_Value(A), m_Value(B)), m_ConstantInt(CI2)))) 1832 if (Instruction *Res = ProcessUGT_ADDCST_ADD(I, A, B, CI2, CI, *this)) 1833 return Res; 1834 } 1835 1836 // (icmp ne/eq (sub A B) 0) -> (icmp ne/eq A, B) 1837 if (I.isEquality() && CI->isZero() && 1838 match(Op0, m_Sub(m_Value(A), m_Value(B)))) { 1839 // (icmp cond A B) if cond is equality 1840 return new ICmpInst(I.getPredicate(), A, B); 1841 } 1842 1843 // If we have an icmp le or icmp ge instruction, turn it into the 1844 // appropriate icmp lt or icmp gt instruction. This allows us to rely on 1845 // them being folded in the code below. The SimplifyICmpInst code has 1846 // already handled the edge cases for us, so we just assert on them. 1847 switch (I.getPredicate()) { 1848 default: break; 1849 case ICmpInst::ICMP_ULE: 1850 assert(!CI->isMaxValue(false)); // A <=u MAX -> TRUE 1851 return new ICmpInst(ICmpInst::ICMP_ULT, Op0, 1852 ConstantInt::get(CI->getContext(), CI->getValue()+1)); 1853 case ICmpInst::ICMP_SLE: 1854 assert(!CI->isMaxValue(true)); // A <=s MAX -> TRUE 1855 return new ICmpInst(ICmpInst::ICMP_SLT, Op0, 1856 ConstantInt::get(CI->getContext(), CI->getValue()+1)); 1857 case ICmpInst::ICMP_UGE: 1858 assert(!CI->isMinValue(false)); // A >=u MIN -> TRUE 1859 return new ICmpInst(ICmpInst::ICMP_UGT, Op0, 1860 ConstantInt::get(CI->getContext(), CI->getValue()-1)); 1861 case ICmpInst::ICMP_SGE: 1862 assert(!CI->isMinValue(true)); // A >=s MIN -> TRUE 1863 return new ICmpInst(ICmpInst::ICMP_SGT, Op0, 1864 ConstantInt::get(CI->getContext(), CI->getValue()-1)); 1865 } 1866 1867 // If this comparison is a normal comparison, it demands all 1868 // bits, if it is a sign bit comparison, it only demands the sign bit. 1869 bool UnusedBit; 1870 isSignBit = isSignBitCheck(I.getPredicate(), CI, UnusedBit); 1871 } 1872 1873 // See if we can fold the comparison based on range information we can get 1874 // by checking whether bits are known to be zero or one in the input. 1875 if (BitWidth != 0) { 1876 APInt Op0KnownZero(BitWidth, 0), Op0KnownOne(BitWidth, 0); 1877 APInt Op1KnownZero(BitWidth, 0), Op1KnownOne(BitWidth, 0); 1878 1879 if (SimplifyDemandedBits(I.getOperandUse(0), 1880 DemandedBitsLHSMask(I, BitWidth, isSignBit), 1881 Op0KnownZero, Op0KnownOne, 0)) 1882 return &I; 1883 if (SimplifyDemandedBits(I.getOperandUse(1), 1884 APInt::getAllOnesValue(BitWidth), 1885 Op1KnownZero, Op1KnownOne, 0)) 1886 return &I; 1887 1888 // Given the known and unknown bits, compute a range that the LHS could be 1889 // in. Compute the Min, Max and RHS values based on the known bits. For the 1890 // EQ and NE we use unsigned values. 1891 APInt Op0Min(BitWidth, 0), Op0Max(BitWidth, 0); 1892 APInt Op1Min(BitWidth, 0), Op1Max(BitWidth, 0); 1893 if (I.isSigned()) { 1894 ComputeSignedMinMaxValuesFromKnownBits(Op0KnownZero, Op0KnownOne, 1895 Op0Min, Op0Max); 1896 ComputeSignedMinMaxValuesFromKnownBits(Op1KnownZero, Op1KnownOne, 1897 Op1Min, Op1Max); 1898 } else { 1899 ComputeUnsignedMinMaxValuesFromKnownBits(Op0KnownZero, Op0KnownOne, 1900 Op0Min, Op0Max); 1901 ComputeUnsignedMinMaxValuesFromKnownBits(Op1KnownZero, Op1KnownOne, 1902 Op1Min, Op1Max); 1903 } 1904 1905 // If Min and Max are known to be the same, then SimplifyDemandedBits 1906 // figured out that the LHS is a constant. Just constant fold this now so 1907 // that code below can assume that Min != Max. 1908 if (!isa<Constant>(Op0) && Op0Min == Op0Max) 1909 return new ICmpInst(I.getPredicate(), 1910 ConstantInt::get(I.getContext(), Op0Min), Op1); 1911 if (!isa<Constant>(Op1) && Op1Min == Op1Max) 1912 return new ICmpInst(I.getPredicate(), Op0, 1913 ConstantInt::get(I.getContext(), Op1Min)); 1914 1915 // Based on the range information we know about the LHS, see if we can 1916 // simplify this comparison. For example, (x&4) < 8 is always true. 1917 switch (I.getPredicate()) { 1918 default: llvm_unreachable("Unknown icmp opcode!"); 1919 case ICmpInst::ICMP_EQ: { 1920 if (Op0Max.ult(Op1Min) || Op0Min.ugt(Op1Max)) 1921 return ReplaceInstUsesWith(I, ConstantInt::getFalse(I.getContext())); 1922 1923 // If all bits are known zero except for one, then we know at most one 1924 // bit is set. If the comparison is against zero, then this is a check 1925 // to see if *that* bit is set. 1926 APInt Op0KnownZeroInverted = ~Op0KnownZero; 1927 if (~Op1KnownZero == 0 && Op0KnownZeroInverted.isPowerOf2()) { 1928 // If the LHS is an AND with the same constant, look through it. 1929 Value *LHS = 0; 1930 ConstantInt *LHSC = 0; 1931 if (!match(Op0, m_And(m_Value(LHS), m_ConstantInt(LHSC))) || 1932 LHSC->getValue() != Op0KnownZeroInverted) 1933 LHS = Op0; 1934 1935 // If the LHS is 1 << x, and we know the result is a power of 2 like 8, 1936 // then turn "((1 << x)&8) == 0" into "x != 3". 1937 Value *X = 0; 1938 if (match(LHS, m_Shl(m_One(), m_Value(X)))) { 1939 unsigned CmpVal = Op0KnownZeroInverted.countTrailingZeros(); 1940 return new ICmpInst(ICmpInst::ICMP_NE, X, 1941 ConstantInt::get(X->getType(), CmpVal)); 1942 } 1943 1944 // If the LHS is 8 >>u x, and we know the result is a power of 2 like 1, 1945 // then turn "((8 >>u x)&1) == 0" into "x != 3". 1946 const APInt *CI; 1947 if (Op0KnownZeroInverted == 1 && 1948 match(LHS, m_LShr(m_Power2(CI), m_Value(X)))) 1949 return new ICmpInst(ICmpInst::ICMP_NE, X, 1950 ConstantInt::get(X->getType(), 1951 CI->countTrailingZeros())); 1952 } 1953 1954 break; 1955 } 1956 case ICmpInst::ICMP_NE: { 1957 if (Op0Max.ult(Op1Min) || Op0Min.ugt(Op1Max)) 1958 return ReplaceInstUsesWith(I, ConstantInt::getTrue(I.getContext())); 1959 1960 // If all bits are known zero except for one, then we know at most one 1961 // bit is set. If the comparison is against zero, then this is a check 1962 // to see if *that* bit is set. 1963 APInt Op0KnownZeroInverted = ~Op0KnownZero; 1964 if (~Op1KnownZero == 0 && Op0KnownZeroInverted.isPowerOf2()) { 1965 // If the LHS is an AND with the same constant, look through it. 1966 Value *LHS = 0; 1967 ConstantInt *LHSC = 0; 1968 if (!match(Op0, m_And(m_Value(LHS), m_ConstantInt(LHSC))) || 1969 LHSC->getValue() != Op0KnownZeroInverted) 1970 LHS = Op0; 1971 1972 // If the LHS is 1 << x, and we know the result is a power of 2 like 8, 1973 // then turn "((1 << x)&8) != 0" into "x == 3". 1974 Value *X = 0; 1975 if (match(LHS, m_Shl(m_One(), m_Value(X)))) { 1976 unsigned CmpVal = Op0KnownZeroInverted.countTrailingZeros(); 1977 return new ICmpInst(ICmpInst::ICMP_EQ, X, 1978 ConstantInt::get(X->getType(), CmpVal)); 1979 } 1980 1981 // If the LHS is 8 >>u x, and we know the result is a power of 2 like 1, 1982 // then turn "((8 >>u x)&1) != 0" into "x == 3". 1983 const APInt *CI; 1984 if (Op0KnownZeroInverted == 1 && 1985 match(LHS, m_LShr(m_Power2(CI), m_Value(X)))) 1986 return new ICmpInst(ICmpInst::ICMP_EQ, X, 1987 ConstantInt::get(X->getType(), 1988 CI->countTrailingZeros())); 1989 } 1990 1991 break; 1992 } 1993 case ICmpInst::ICMP_ULT: 1994 if (Op0Max.ult(Op1Min)) // A <u B -> true if max(A) < min(B) 1995 return ReplaceInstUsesWith(I, ConstantInt::getTrue(I.getContext())); 1996 if (Op0Min.uge(Op1Max)) // A <u B -> false if min(A) >= max(B) 1997 return ReplaceInstUsesWith(I, ConstantInt::getFalse(I.getContext())); 1998 if (Op1Min == Op0Max) // A <u B -> A != B if max(A) == min(B) 1999 return new ICmpInst(ICmpInst::ICMP_NE, Op0, Op1); 2000 if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) { 2001 if (Op1Max == Op0Min+1) // A <u C -> A == C-1 if min(A)+1 == C 2002 return new ICmpInst(ICmpInst::ICMP_EQ, Op0, 2003 ConstantInt::get(CI->getContext(), CI->getValue()-1)); 2004 2005 // (x <u 2147483648) -> (x >s -1) -> true if sign bit clear 2006 if (CI->isMinValue(true)) 2007 return new ICmpInst(ICmpInst::ICMP_SGT, Op0, 2008 Constant::getAllOnesValue(Op0->getType())); 2009 } 2010 break; 2011 case ICmpInst::ICMP_UGT: 2012 if (Op0Min.ugt(Op1Max)) // A >u B -> true if min(A) > max(B) 2013 return ReplaceInstUsesWith(I, ConstantInt::getTrue(I.getContext())); 2014 if (Op0Max.ule(Op1Min)) // A >u B -> false if max(A) <= max(B) 2015 return ReplaceInstUsesWith(I, ConstantInt::getFalse(I.getContext())); 2016 2017 if (Op1Max == Op0Min) // A >u B -> A != B if min(A) == max(B) 2018 return new ICmpInst(ICmpInst::ICMP_NE, Op0, Op1); 2019 if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) { 2020 if (Op1Min == Op0Max-1) // A >u C -> A == C+1 if max(a)-1 == C 2021 return new ICmpInst(ICmpInst::ICMP_EQ, Op0, 2022 ConstantInt::get(CI->getContext(), CI->getValue()+1)); 2023 2024 // (x >u 2147483647) -> (x <s 0) -> true if sign bit set 2025 if (CI->isMaxValue(true)) 2026 return new ICmpInst(ICmpInst::ICMP_SLT, Op0, 2027 Constant::getNullValue(Op0->getType())); 2028 } 2029 break; 2030 case ICmpInst::ICMP_SLT: 2031 if (Op0Max.slt(Op1Min)) // A <s B -> true if max(A) < min(C) 2032 return ReplaceInstUsesWith(I, ConstantInt::getTrue(I.getContext())); 2033 if (Op0Min.sge(Op1Max)) // A <s B -> false if min(A) >= max(C) 2034 return ReplaceInstUsesWith(I, ConstantInt::getFalse(I.getContext())); 2035 if (Op1Min == Op0Max) // A <s B -> A != B if max(A) == min(B) 2036 return new ICmpInst(ICmpInst::ICMP_NE, Op0, Op1); 2037 if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) { 2038 if (Op1Max == Op0Min+1) // A <s C -> A == C-1 if min(A)+1 == C 2039 return new ICmpInst(ICmpInst::ICMP_EQ, Op0, 2040 ConstantInt::get(CI->getContext(), CI->getValue()-1)); 2041 } 2042 break; 2043 case ICmpInst::ICMP_SGT: 2044 if (Op0Min.sgt(Op1Max)) // A >s B -> true if min(A) > max(B) 2045 return ReplaceInstUsesWith(I, ConstantInt::getTrue(I.getContext())); 2046 if (Op0Max.sle(Op1Min)) // A >s B -> false if max(A) <= min(B) 2047 return ReplaceInstUsesWith(I, ConstantInt::getFalse(I.getContext())); 2048 2049 if (Op1Max == Op0Min) // A >s B -> A != B if min(A) == max(B) 2050 return new ICmpInst(ICmpInst::ICMP_NE, Op0, Op1); 2051 if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) { 2052 if (Op1Min == Op0Max-1) // A >s C -> A == C+1 if max(A)-1 == C 2053 return new ICmpInst(ICmpInst::ICMP_EQ, Op0, 2054 ConstantInt::get(CI->getContext(), CI->getValue()+1)); 2055 } 2056 break; 2057 case ICmpInst::ICMP_SGE: 2058 assert(!isa<ConstantInt>(Op1) && "ICMP_SGE with ConstantInt not folded!"); 2059 if (Op0Min.sge(Op1Max)) // A >=s B -> true if min(A) >= max(B) 2060 return ReplaceInstUsesWith(I, ConstantInt::getTrue(I.getContext())); 2061 if (Op0Max.slt(Op1Min)) // A >=s B -> false if max(A) < min(B) 2062 return ReplaceInstUsesWith(I, ConstantInt::getFalse(I.getContext())); 2063 break; 2064 case ICmpInst::ICMP_SLE: 2065 assert(!isa<ConstantInt>(Op1) && "ICMP_SLE with ConstantInt not folded!"); 2066 if (Op0Max.sle(Op1Min)) // A <=s B -> true if max(A) <= min(B) 2067 return ReplaceInstUsesWith(I, ConstantInt::getTrue(I.getContext())); 2068 if (Op0Min.sgt(Op1Max)) // A <=s B -> false if min(A) > max(B) 2069 return ReplaceInstUsesWith(I, ConstantInt::getFalse(I.getContext())); 2070 break; 2071 case ICmpInst::ICMP_UGE: 2072 assert(!isa<ConstantInt>(Op1) && "ICMP_UGE with ConstantInt not folded!"); 2073 if (Op0Min.uge(Op1Max)) // A >=u B -> true if min(A) >= max(B) 2074 return ReplaceInstUsesWith(I, ConstantInt::getTrue(I.getContext())); 2075 if (Op0Max.ult(Op1Min)) // A >=u B -> false if max(A) < min(B) 2076 return ReplaceInstUsesWith(I, ConstantInt::getFalse(I.getContext())); 2077 break; 2078 case ICmpInst::ICMP_ULE: 2079 assert(!isa<ConstantInt>(Op1) && "ICMP_ULE with ConstantInt not folded!"); 2080 if (Op0Max.ule(Op1Min)) // A <=u B -> true if max(A) <= min(B) 2081 return ReplaceInstUsesWith(I, ConstantInt::getTrue(I.getContext())); 2082 if (Op0Min.ugt(Op1Max)) // A <=u B -> false if min(A) > max(B) 2083 return ReplaceInstUsesWith(I, ConstantInt::getFalse(I.getContext())); 2084 break; 2085 } 2086 2087 // Turn a signed comparison into an unsigned one if both operands 2088 // are known to have the same sign. 2089 if (I.isSigned() && 2090 ((Op0KnownZero.isNegative() && Op1KnownZero.isNegative()) || 2091 (Op0KnownOne.isNegative() && Op1KnownOne.isNegative()))) 2092 return new ICmpInst(I.getUnsignedPredicate(), Op0, Op1); 2093 } 2094 2095 // Test if the ICmpInst instruction is used exclusively by a select as 2096 // part of a minimum or maximum operation. If so, refrain from doing 2097 // any other folding. This helps out other analyses which understand 2098 // non-obfuscated minimum and maximum idioms, such as ScalarEvolution 2099 // and CodeGen. And in this case, at least one of the comparison 2100 // operands has at least one user besides the compare (the select), 2101 // which would often largely negate the benefit of folding anyway. 2102 if (I.hasOneUse()) 2103 if (SelectInst *SI = dyn_cast<SelectInst>(*I.use_begin())) 2104 if ((SI->getOperand(1) == Op0 && SI->getOperand(2) == Op1) || 2105 (SI->getOperand(2) == Op0 && SI->getOperand(1) == Op1)) 2106 return 0; 2107 2108 // See if we are doing a comparison between a constant and an instruction that 2109 // can be folded into the comparison. 2110 if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) { 2111 // Since the RHS is a ConstantInt (CI), if the left hand side is an 2112 // instruction, see if that instruction also has constants so that the 2113 // instruction can be folded into the icmp 2114 if (Instruction *LHSI = dyn_cast<Instruction>(Op0)) 2115 if (Instruction *Res = visitICmpInstWithInstAndIntCst(I, LHSI, CI)) 2116 return Res; 2117 } 2118 2119 // Handle icmp with constant (but not simple integer constant) RHS 2120 if (Constant *RHSC = dyn_cast<Constant>(Op1)) { 2121 if (Instruction *LHSI = dyn_cast<Instruction>(Op0)) 2122 switch (LHSI->getOpcode()) { 2123 case Instruction::GetElementPtr: 2124 // icmp pred GEP (P, int 0, int 0, int 0), null -> icmp pred P, null 2125 if (RHSC->isNullValue() && 2126 cast<GetElementPtrInst>(LHSI)->hasAllZeroIndices()) 2127 return new ICmpInst(I.getPredicate(), LHSI->getOperand(0), 2128 Constant::getNullValue(LHSI->getOperand(0)->getType())); 2129 break; 2130 case Instruction::PHI: 2131 // Only fold icmp into the PHI if the phi and icmp are in the same 2132 // block. If in the same block, we're encouraging jump threading. If 2133 // not, we are just pessimizing the code by making an i1 phi. 2134 if (LHSI->getParent() == I.getParent()) 2135 if (Instruction *NV = FoldOpIntoPhi(I)) 2136 return NV; 2137 break; 2138 case Instruction::Select: { 2139 // If either operand of the select is a constant, we can fold the 2140 // comparison into the select arms, which will cause one to be 2141 // constant folded and the select turned into a bitwise or. 2142 Value *Op1 = 0, *Op2 = 0; 2143 if (Constant *C = dyn_cast<Constant>(LHSI->getOperand(1))) 2144 Op1 = ConstantExpr::getICmp(I.getPredicate(), C, RHSC); 2145 if (Constant *C = dyn_cast<Constant>(LHSI->getOperand(2))) 2146 Op2 = ConstantExpr::getICmp(I.getPredicate(), C, RHSC); 2147 2148 // We only want to perform this transformation if it will not lead to 2149 // additional code. This is true if either both sides of the select 2150 // fold to a constant (in which case the icmp is replaced with a select 2151 // which will usually simplify) or this is the only user of the 2152 // select (in which case we are trading a select+icmp for a simpler 2153 // select+icmp). 2154 if ((Op1 && Op2) || (LHSI->hasOneUse() && (Op1 || Op2))) { 2155 if (!Op1) 2156 Op1 = Builder->CreateICmp(I.getPredicate(), LHSI->getOperand(1), 2157 RHSC, I.getName()); 2158 if (!Op2) 2159 Op2 = Builder->CreateICmp(I.getPredicate(), LHSI->getOperand(2), 2160 RHSC, I.getName()); 2161 return SelectInst::Create(LHSI->getOperand(0), Op1, Op2); 2162 } 2163 break; 2164 } 2165 case Instruction::IntToPtr: 2166 // icmp pred inttoptr(X), null -> icmp pred X, 0 2167 if (RHSC->isNullValue() && TD && 2168 TD->getIntPtrType(RHSC->getContext()) == 2169 LHSI->getOperand(0)->getType()) 2170 return new ICmpInst(I.getPredicate(), LHSI->getOperand(0), 2171 Constant::getNullValue(LHSI->getOperand(0)->getType())); 2172 break; 2173 2174 case Instruction::Load: 2175 // Try to optimize things like "A[i] > 4" to index computations. 2176 if (GetElementPtrInst *GEP = 2177 dyn_cast<GetElementPtrInst>(LHSI->getOperand(0))) { 2178 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(GEP->getOperand(0))) 2179 if (GV->isConstant() && GV->hasDefinitiveInitializer() && 2180 !cast<LoadInst>(LHSI)->isVolatile()) 2181 if (Instruction *Res = FoldCmpLoadFromIndexedGlobal(GEP, GV, I)) 2182 return Res; 2183 } 2184 break; 2185 } 2186 } 2187 2188 // If we can optimize a 'icmp GEP, P' or 'icmp P, GEP', do so now. 2189 if (GEPOperator *GEP = dyn_cast<GEPOperator>(Op0)) 2190 if (Instruction *NI = FoldGEPICmp(GEP, Op1, I.getPredicate(), I)) 2191 return NI; 2192 if (GEPOperator *GEP = dyn_cast<GEPOperator>(Op1)) 2193 if (Instruction *NI = FoldGEPICmp(GEP, Op0, 2194 ICmpInst::getSwappedPredicate(I.getPredicate()), I)) 2195 return NI; 2196 2197 // Test to see if the operands of the icmp are casted versions of other 2198 // values. If the ptr->ptr cast can be stripped off both arguments, we do so 2199 // now. 2200 if (BitCastInst *CI = dyn_cast<BitCastInst>(Op0)) { 2201 if (Op0->getType()->isPointerTy() && 2202 (isa<Constant>(Op1) || isa<BitCastInst>(Op1))) { 2203 // We keep moving the cast from the left operand over to the right 2204 // operand, where it can often be eliminated completely. 2205 Op0 = CI->getOperand(0); 2206 2207 // If operand #1 is a bitcast instruction, it must also be a ptr->ptr cast 2208 // so eliminate it as well. 2209 if (BitCastInst *CI2 = dyn_cast<BitCastInst>(Op1)) 2210 Op1 = CI2->getOperand(0); 2211 2212 // If Op1 is a constant, we can fold the cast into the constant. 2213 if (Op0->getType() != Op1->getType()) { 2214 if (Constant *Op1C = dyn_cast<Constant>(Op1)) { 2215 Op1 = ConstantExpr::getBitCast(Op1C, Op0->getType()); 2216 } else { 2217 // Otherwise, cast the RHS right before the icmp 2218 Op1 = Builder->CreateBitCast(Op1, Op0->getType()); 2219 } 2220 } 2221 return new ICmpInst(I.getPredicate(), Op0, Op1); 2222 } 2223 } 2224 2225 if (isa<CastInst>(Op0)) { 2226 // Handle the special case of: icmp (cast bool to X), <cst> 2227 // This comes up when you have code like 2228 // int X = A < B; 2229 // if (X) ... 2230 // For generality, we handle any zero-extension of any operand comparison 2231 // with a constant or another cast from the same type. 2232 if (isa<Constant>(Op1) || isa<CastInst>(Op1)) 2233 if (Instruction *R = visitICmpInstWithCastAndCast(I)) 2234 return R; 2235 } 2236 2237 // Special logic for binary operators. 2238 BinaryOperator *BO0 = dyn_cast<BinaryOperator>(Op0); 2239 BinaryOperator *BO1 = dyn_cast<BinaryOperator>(Op1); 2240 if (BO0 || BO1) { 2241 CmpInst::Predicate Pred = I.getPredicate(); 2242 bool NoOp0WrapProblem = false, NoOp1WrapProblem = false; 2243 if (BO0 && isa<OverflowingBinaryOperator>(BO0)) 2244 NoOp0WrapProblem = ICmpInst::isEquality(Pred) || 2245 (CmpInst::isUnsigned(Pred) && BO0->hasNoUnsignedWrap()) || 2246 (CmpInst::isSigned(Pred) && BO0->hasNoSignedWrap()); 2247 if (BO1 && isa<OverflowingBinaryOperator>(BO1)) 2248 NoOp1WrapProblem = ICmpInst::isEquality(Pred) || 2249 (CmpInst::isUnsigned(Pred) && BO1->hasNoUnsignedWrap()) || 2250 (CmpInst::isSigned(Pred) && BO1->hasNoSignedWrap()); 2251 2252 // Analyze the case when either Op0 or Op1 is an add instruction. 2253 // Op0 = A + B (or A and B are null); Op1 = C + D (or C and D are null). 2254 Value *A = 0, *B = 0, *C = 0, *D = 0; 2255 if (BO0 && BO0->getOpcode() == Instruction::Add) 2256 A = BO0->getOperand(0), B = BO0->getOperand(1); 2257 if (BO1 && BO1->getOpcode() == Instruction::Add) 2258 C = BO1->getOperand(0), D = BO1->getOperand(1); 2259 2260 // icmp (X+Y), X -> icmp Y, 0 for equalities or if there is no overflow. 2261 if ((A == Op1 || B == Op1) && NoOp0WrapProblem) 2262 return new ICmpInst(Pred, A == Op1 ? B : A, 2263 Constant::getNullValue(Op1->getType())); 2264 2265 // icmp X, (X+Y) -> icmp 0, Y for equalities or if there is no overflow. 2266 if ((C == Op0 || D == Op0) && NoOp1WrapProblem) 2267 return new ICmpInst(Pred, Constant::getNullValue(Op0->getType()), 2268 C == Op0 ? D : C); 2269 2270 // icmp (X+Y), (X+Z) -> icmp Y, Z for equalities or if there is no overflow. 2271 if (A && C && (A == C || A == D || B == C || B == D) && 2272 NoOp0WrapProblem && NoOp1WrapProblem && 2273 // Try not to increase register pressure. 2274 BO0->hasOneUse() && BO1->hasOneUse()) { 2275 // Determine Y and Z in the form icmp (X+Y), (X+Z). 2276 Value *Y = (A == C || A == D) ? B : A; 2277 Value *Z = (C == A || C == B) ? D : C; 2278 return new ICmpInst(Pred, Y, Z); 2279 } 2280 2281 // Analyze the case when either Op0 or Op1 is a sub instruction. 2282 // Op0 = A - B (or A and B are null); Op1 = C - D (or C and D are null). 2283 A = 0; B = 0; C = 0; D = 0; 2284 if (BO0 && BO0->getOpcode() == Instruction::Sub) 2285 A = BO0->getOperand(0), B = BO0->getOperand(1); 2286 if (BO1 && BO1->getOpcode() == Instruction::Sub) 2287 C = BO1->getOperand(0), D = BO1->getOperand(1); 2288 2289 // icmp (X-Y), X -> icmp 0, Y for equalities or if there is no overflow. 2290 if (A == Op1 && NoOp0WrapProblem) 2291 return new ICmpInst(Pred, Constant::getNullValue(Op1->getType()), B); 2292 2293 // icmp X, (X-Y) -> icmp Y, 0 for equalities or if there is no overflow. 2294 if (C == Op0 && NoOp1WrapProblem) 2295 return new ICmpInst(Pred, D, Constant::getNullValue(Op0->getType())); 2296 2297 // icmp (Y-X), (Z-X) -> icmp Y, Z for equalities or if there is no overflow. 2298 if (B && D && B == D && NoOp0WrapProblem && NoOp1WrapProblem && 2299 // Try not to increase register pressure. 2300 BO0->hasOneUse() && BO1->hasOneUse()) 2301 return new ICmpInst(Pred, A, C); 2302 2303 // icmp (X-Y), (X-Z) -> icmp Z, Y for equalities or if there is no overflow. 2304 if (A && C && A == C && NoOp0WrapProblem && NoOp1WrapProblem && 2305 // Try not to increase register pressure. 2306 BO0->hasOneUse() && BO1->hasOneUse()) 2307 return new ICmpInst(Pred, D, B); 2308 2309 if (BO0 && BO1 && BO0->getOpcode() == BO1->getOpcode() && 2310 BO0->hasOneUse() && BO1->hasOneUse() && 2311 BO0->getOperand(1) == BO1->getOperand(1)) { 2312 switch (BO0->getOpcode()) { 2313 default: break; 2314 case Instruction::Add: 2315 case Instruction::Sub: 2316 case Instruction::Xor: 2317 if (I.isEquality()) // a+x icmp eq/ne b+x --> a icmp b 2318 return new ICmpInst(I.getPredicate(), BO0->getOperand(0), 2319 BO1->getOperand(0)); 2320 // icmp u/s (a ^ signbit), (b ^ signbit) --> icmp s/u a, b 2321 if (ConstantInt *CI = dyn_cast<ConstantInt>(BO0->getOperand(1))) { 2322 if (CI->getValue().isSignBit()) { 2323 ICmpInst::Predicate Pred = I.isSigned() 2324 ? I.getUnsignedPredicate() 2325 : I.getSignedPredicate(); 2326 return new ICmpInst(Pred, BO0->getOperand(0), 2327 BO1->getOperand(0)); 2328 } 2329 2330 if (CI->getValue().isMaxSignedValue()) { 2331 ICmpInst::Predicate Pred = I.isSigned() 2332 ? I.getUnsignedPredicate() 2333 : I.getSignedPredicate(); 2334 Pred = I.getSwappedPredicate(Pred); 2335 return new ICmpInst(Pred, BO0->getOperand(0), 2336 BO1->getOperand(0)); 2337 } 2338 } 2339 break; 2340 case Instruction::Mul: 2341 if (!I.isEquality()) 2342 break; 2343 2344 if (ConstantInt *CI = dyn_cast<ConstantInt>(BO0->getOperand(1))) { 2345 // a * Cst icmp eq/ne b * Cst --> a & Mask icmp b & Mask 2346 // Mask = -1 >> count-trailing-zeros(Cst). 2347 if (!CI->isZero() && !CI->isOne()) { 2348 const APInt &AP = CI->getValue(); 2349 ConstantInt *Mask = ConstantInt::get(I.getContext(), 2350 APInt::getLowBitsSet(AP.getBitWidth(), 2351 AP.getBitWidth() - 2352 AP.countTrailingZeros())); 2353 Value *And1 = Builder->CreateAnd(BO0->getOperand(0), Mask); 2354 Value *And2 = Builder->CreateAnd(BO1->getOperand(0), Mask); 2355 return new ICmpInst(I.getPredicate(), And1, And2); 2356 } 2357 } 2358 break; 2359 } 2360 } 2361 } 2362 2363 { Value *A, *B; 2364 // ~x < ~y --> y < x 2365 // ~x < cst --> ~cst < x 2366 if (match(Op0, m_Not(m_Value(A)))) { 2367 if (match(Op1, m_Not(m_Value(B)))) 2368 return new ICmpInst(I.getPredicate(), B, A); 2369 if (ConstantInt *RHSC = dyn_cast<ConstantInt>(Op1)) 2370 return new ICmpInst(I.getPredicate(), ConstantExpr::getNot(RHSC), A); 2371 } 2372 2373 // (a+b) <u a --> llvm.uadd.with.overflow. 2374 // (a+b) <u b --> llvm.uadd.with.overflow. 2375 if (I.getPredicate() == ICmpInst::ICMP_ULT && 2376 match(Op0, m_Add(m_Value(A), m_Value(B))) && 2377 (Op1 == A || Op1 == B)) 2378 if (Instruction *R = ProcessUAddIdiom(I, Op0, *this)) 2379 return R; 2380 2381 // a >u (a+b) --> llvm.uadd.with.overflow. 2382 // b >u (a+b) --> llvm.uadd.with.overflow. 2383 if (I.getPredicate() == ICmpInst::ICMP_UGT && 2384 match(Op1, m_Add(m_Value(A), m_Value(B))) && 2385 (Op0 == A || Op0 == B)) 2386 if (Instruction *R = ProcessUAddIdiom(I, Op1, *this)) 2387 return R; 2388 } 2389 2390 if (I.isEquality()) { 2391 Value *A, *B, *C, *D; 2392 2393 if (match(Op0, m_Xor(m_Value(A), m_Value(B)))) { 2394 if (A == Op1 || B == Op1) { // (A^B) == A -> B == 0 2395 Value *OtherVal = A == Op1 ? B : A; 2396 return new ICmpInst(I.getPredicate(), OtherVal, 2397 Constant::getNullValue(A->getType())); 2398 } 2399 2400 if (match(Op1, m_Xor(m_Value(C), m_Value(D)))) { 2401 // A^c1 == C^c2 --> A == C^(c1^c2) 2402 ConstantInt *C1, *C2; 2403 if (match(B, m_ConstantInt(C1)) && 2404 match(D, m_ConstantInt(C2)) && Op1->hasOneUse()) { 2405 Constant *NC = ConstantInt::get(I.getContext(), 2406 C1->getValue() ^ C2->getValue()); 2407 Value *Xor = Builder->CreateXor(C, NC, "tmp"); 2408 return new ICmpInst(I.getPredicate(), A, Xor); 2409 } 2410 2411 // A^B == A^D -> B == D 2412 if (A == C) return new ICmpInst(I.getPredicate(), B, D); 2413 if (A == D) return new ICmpInst(I.getPredicate(), B, C); 2414 if (B == C) return new ICmpInst(I.getPredicate(), A, D); 2415 if (B == D) return new ICmpInst(I.getPredicate(), A, C); 2416 } 2417 } 2418 2419 if (match(Op1, m_Xor(m_Value(A), m_Value(B))) && 2420 (A == Op0 || B == Op0)) { 2421 // A == (A^B) -> B == 0 2422 Value *OtherVal = A == Op0 ? B : A; 2423 return new ICmpInst(I.getPredicate(), OtherVal, 2424 Constant::getNullValue(A->getType())); 2425 } 2426 2427 // (X&Z) == (Y&Z) -> (X^Y) & Z == 0 2428 if (Op0->hasOneUse() && Op1->hasOneUse() && 2429 match(Op0, m_And(m_Value(A), m_Value(B))) && 2430 match(Op1, m_And(m_Value(C), m_Value(D)))) { 2431 Value *X = 0, *Y = 0, *Z = 0; 2432 2433 if (A == C) { 2434 X = B; Y = D; Z = A; 2435 } else if (A == D) { 2436 X = B; Y = C; Z = A; 2437 } else if (B == C) { 2438 X = A; Y = D; Z = B; 2439 } else if (B == D) { 2440 X = A; Y = C; Z = B; 2441 } 2442 2443 if (X) { // Build (X^Y) & Z 2444 Op1 = Builder->CreateXor(X, Y, "tmp"); 2445 Op1 = Builder->CreateAnd(Op1, Z, "tmp"); 2446 I.setOperand(0, Op1); 2447 I.setOperand(1, Constant::getNullValue(Op1->getType())); 2448 return &I; 2449 } 2450 } 2451 } 2452 2453 { 2454 Value *X; ConstantInt *Cst; 2455 // icmp X+Cst, X 2456 if (match(Op0, m_Add(m_Value(X), m_ConstantInt(Cst))) && Op1 == X) 2457 return FoldICmpAddOpCst(I, X, Cst, I.getPredicate(), Op0); 2458 2459 // icmp X, X+Cst 2460 if (match(Op1, m_Add(m_Value(X), m_ConstantInt(Cst))) && Op0 == X) 2461 return FoldICmpAddOpCst(I, X, Cst, I.getSwappedPredicate(), Op1); 2462 } 2463 return Changed ? &I : 0; 2464} 2465 2466 2467 2468 2469 2470 2471/// FoldFCmp_IntToFP_Cst - Fold fcmp ([us]itofp x, cst) if possible. 2472/// 2473Instruction *InstCombiner::FoldFCmp_IntToFP_Cst(FCmpInst &I, 2474 Instruction *LHSI, 2475 Constant *RHSC) { 2476 if (!isa<ConstantFP>(RHSC)) return 0; 2477 const APFloat &RHS = cast<ConstantFP>(RHSC)->getValueAPF(); 2478 2479 // Get the width of the mantissa. We don't want to hack on conversions that 2480 // might lose information from the integer, e.g. "i64 -> float" 2481 int MantissaWidth = LHSI->getType()->getFPMantissaWidth(); 2482 if (MantissaWidth == -1) return 0; // Unknown. 2483 2484 // Check to see that the input is converted from an integer type that is small 2485 // enough that preserves all bits. TODO: check here for "known" sign bits. 2486 // This would allow us to handle (fptosi (x >>s 62) to float) if x is i64 f.e. 2487 unsigned InputSize = LHSI->getOperand(0)->getType()->getScalarSizeInBits(); 2488 2489 // If this is a uitofp instruction, we need an extra bit to hold the sign. 2490 bool LHSUnsigned = isa<UIToFPInst>(LHSI); 2491 if (LHSUnsigned) 2492 ++InputSize; 2493 2494 // If the conversion would lose info, don't hack on this. 2495 if ((int)InputSize > MantissaWidth) 2496 return 0; 2497 2498 // Otherwise, we can potentially simplify the comparison. We know that it 2499 // will always come through as an integer value and we know the constant is 2500 // not a NAN (it would have been previously simplified). 2501 assert(!RHS.isNaN() && "NaN comparison not already folded!"); 2502 2503 ICmpInst::Predicate Pred; 2504 switch (I.getPredicate()) { 2505 default: llvm_unreachable("Unexpected predicate!"); 2506 case FCmpInst::FCMP_UEQ: 2507 case FCmpInst::FCMP_OEQ: 2508 Pred = ICmpInst::ICMP_EQ; 2509 break; 2510 case FCmpInst::FCMP_UGT: 2511 case FCmpInst::FCMP_OGT: 2512 Pred = LHSUnsigned ? ICmpInst::ICMP_UGT : ICmpInst::ICMP_SGT; 2513 break; 2514 case FCmpInst::FCMP_UGE: 2515 case FCmpInst::FCMP_OGE: 2516 Pred = LHSUnsigned ? ICmpInst::ICMP_UGE : ICmpInst::ICMP_SGE; 2517 break; 2518 case FCmpInst::FCMP_ULT: 2519 case FCmpInst::FCMP_OLT: 2520 Pred = LHSUnsigned ? ICmpInst::ICMP_ULT : ICmpInst::ICMP_SLT; 2521 break; 2522 case FCmpInst::FCMP_ULE: 2523 case FCmpInst::FCMP_OLE: 2524 Pred = LHSUnsigned ? ICmpInst::ICMP_ULE : ICmpInst::ICMP_SLE; 2525 break; 2526 case FCmpInst::FCMP_UNE: 2527 case FCmpInst::FCMP_ONE: 2528 Pred = ICmpInst::ICMP_NE; 2529 break; 2530 case FCmpInst::FCMP_ORD: 2531 return ReplaceInstUsesWith(I, ConstantInt::getTrue(I.getContext())); 2532 case FCmpInst::FCMP_UNO: 2533 return ReplaceInstUsesWith(I, ConstantInt::getFalse(I.getContext())); 2534 } 2535 2536 const IntegerType *IntTy = cast<IntegerType>(LHSI->getOperand(0)->getType()); 2537 2538 // Now we know that the APFloat is a normal number, zero or inf. 2539 2540 // See if the FP constant is too large for the integer. For example, 2541 // comparing an i8 to 300.0. 2542 unsigned IntWidth = IntTy->getScalarSizeInBits(); 2543 2544 if (!LHSUnsigned) { 2545 // If the RHS value is > SignedMax, fold the comparison. This handles +INF 2546 // and large values. 2547 APFloat SMax(RHS.getSemantics(), APFloat::fcZero, false); 2548 SMax.convertFromAPInt(APInt::getSignedMaxValue(IntWidth), true, 2549 APFloat::rmNearestTiesToEven); 2550 if (SMax.compare(RHS) == APFloat::cmpLessThan) { // smax < 13123.0 2551 if (Pred == ICmpInst::ICMP_NE || Pred == ICmpInst::ICMP_SLT || 2552 Pred == ICmpInst::ICMP_SLE) 2553 return ReplaceInstUsesWith(I, ConstantInt::getTrue(I.getContext())); 2554 return ReplaceInstUsesWith(I, ConstantInt::getFalse(I.getContext())); 2555 } 2556 } else { 2557 // If the RHS value is > UnsignedMax, fold the comparison. This handles 2558 // +INF and large values. 2559 APFloat UMax(RHS.getSemantics(), APFloat::fcZero, false); 2560 UMax.convertFromAPInt(APInt::getMaxValue(IntWidth), false, 2561 APFloat::rmNearestTiesToEven); 2562 if (UMax.compare(RHS) == APFloat::cmpLessThan) { // umax < 13123.0 2563 if (Pred == ICmpInst::ICMP_NE || Pred == ICmpInst::ICMP_ULT || 2564 Pred == ICmpInst::ICMP_ULE) 2565 return ReplaceInstUsesWith(I, ConstantInt::getTrue(I.getContext())); 2566 return ReplaceInstUsesWith(I, ConstantInt::getFalse(I.getContext())); 2567 } 2568 } 2569 2570 if (!LHSUnsigned) { 2571 // See if the RHS value is < SignedMin. 2572 APFloat SMin(RHS.getSemantics(), APFloat::fcZero, false); 2573 SMin.convertFromAPInt(APInt::getSignedMinValue(IntWidth), true, 2574 APFloat::rmNearestTiesToEven); 2575 if (SMin.compare(RHS) == APFloat::cmpGreaterThan) { // smin > 12312.0 2576 if (Pred == ICmpInst::ICMP_NE || Pred == ICmpInst::ICMP_SGT || 2577 Pred == ICmpInst::ICMP_SGE) 2578 return ReplaceInstUsesWith(I, ConstantInt::getTrue(I.getContext())); 2579 return ReplaceInstUsesWith(I, ConstantInt::getFalse(I.getContext())); 2580 } 2581 } 2582 2583 // Okay, now we know that the FP constant fits in the range [SMIN, SMAX] or 2584 // [0, UMAX], but it may still be fractional. See if it is fractional by 2585 // casting the FP value to the integer value and back, checking for equality. 2586 // Don't do this for zero, because -0.0 is not fractional. 2587 Constant *RHSInt = LHSUnsigned 2588 ? ConstantExpr::getFPToUI(RHSC, IntTy) 2589 : ConstantExpr::getFPToSI(RHSC, IntTy); 2590 if (!RHS.isZero()) { 2591 bool Equal = LHSUnsigned 2592 ? ConstantExpr::getUIToFP(RHSInt, RHSC->getType()) == RHSC 2593 : ConstantExpr::getSIToFP(RHSInt, RHSC->getType()) == RHSC; 2594 if (!Equal) { 2595 // If we had a comparison against a fractional value, we have to adjust 2596 // the compare predicate and sometimes the value. RHSC is rounded towards 2597 // zero at this point. 2598 switch (Pred) { 2599 default: llvm_unreachable("Unexpected integer comparison!"); 2600 case ICmpInst::ICMP_NE: // (float)int != 4.4 --> true 2601 return ReplaceInstUsesWith(I, ConstantInt::getTrue(I.getContext())); 2602 case ICmpInst::ICMP_EQ: // (float)int == 4.4 --> false 2603 return ReplaceInstUsesWith(I, ConstantInt::getFalse(I.getContext())); 2604 case ICmpInst::ICMP_ULE: 2605 // (float)int <= 4.4 --> int <= 4 2606 // (float)int <= -4.4 --> false 2607 if (RHS.isNegative()) 2608 return ReplaceInstUsesWith(I, ConstantInt::getFalse(I.getContext())); 2609 break; 2610 case ICmpInst::ICMP_SLE: 2611 // (float)int <= 4.4 --> int <= 4 2612 // (float)int <= -4.4 --> int < -4 2613 if (RHS.isNegative()) 2614 Pred = ICmpInst::ICMP_SLT; 2615 break; 2616 case ICmpInst::ICMP_ULT: 2617 // (float)int < -4.4 --> false 2618 // (float)int < 4.4 --> int <= 4 2619 if (RHS.isNegative()) 2620 return ReplaceInstUsesWith(I, ConstantInt::getFalse(I.getContext())); 2621 Pred = ICmpInst::ICMP_ULE; 2622 break; 2623 case ICmpInst::ICMP_SLT: 2624 // (float)int < -4.4 --> int < -4 2625 // (float)int < 4.4 --> int <= 4 2626 if (!RHS.isNegative()) 2627 Pred = ICmpInst::ICMP_SLE; 2628 break; 2629 case ICmpInst::ICMP_UGT: 2630 // (float)int > 4.4 --> int > 4 2631 // (float)int > -4.4 --> true 2632 if (RHS.isNegative()) 2633 return ReplaceInstUsesWith(I, ConstantInt::getTrue(I.getContext())); 2634 break; 2635 case ICmpInst::ICMP_SGT: 2636 // (float)int > 4.4 --> int > 4 2637 // (float)int > -4.4 --> int >= -4 2638 if (RHS.isNegative()) 2639 Pred = ICmpInst::ICMP_SGE; 2640 break; 2641 case ICmpInst::ICMP_UGE: 2642 // (float)int >= -4.4 --> true 2643 // (float)int >= 4.4 --> int > 4 2644 if (!RHS.isNegative()) 2645 return ReplaceInstUsesWith(I, ConstantInt::getTrue(I.getContext())); 2646 Pred = ICmpInst::ICMP_UGT; 2647 break; 2648 case ICmpInst::ICMP_SGE: 2649 // (float)int >= -4.4 --> int >= -4 2650 // (float)int >= 4.4 --> int > 4 2651 if (!RHS.isNegative()) 2652 Pred = ICmpInst::ICMP_SGT; 2653 break; 2654 } 2655 } 2656 } 2657 2658 // Lower this FP comparison into an appropriate integer version of the 2659 // comparison. 2660 return new ICmpInst(Pred, LHSI->getOperand(0), RHSInt); 2661} 2662 2663Instruction *InstCombiner::visitFCmpInst(FCmpInst &I) { 2664 bool Changed = false; 2665 2666 /// Orders the operands of the compare so that they are listed from most 2667 /// complex to least complex. This puts constants before unary operators, 2668 /// before binary operators. 2669 if (getComplexity(I.getOperand(0)) < getComplexity(I.getOperand(1))) { 2670 I.swapOperands(); 2671 Changed = true; 2672 } 2673 2674 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1); 2675 2676 if (Value *V = SimplifyFCmpInst(I.getPredicate(), Op0, Op1, TD)) 2677 return ReplaceInstUsesWith(I, V); 2678 2679 // Simplify 'fcmp pred X, X' 2680 if (Op0 == Op1) { 2681 switch (I.getPredicate()) { 2682 default: llvm_unreachable("Unknown predicate!"); 2683 case FCmpInst::FCMP_UNO: // True if unordered: isnan(X) | isnan(Y) 2684 case FCmpInst::FCMP_ULT: // True if unordered or less than 2685 case FCmpInst::FCMP_UGT: // True if unordered or greater than 2686 case FCmpInst::FCMP_UNE: // True if unordered or not equal 2687 // Canonicalize these to be 'fcmp uno %X, 0.0'. 2688 I.setPredicate(FCmpInst::FCMP_UNO); 2689 I.setOperand(1, Constant::getNullValue(Op0->getType())); 2690 return &I; 2691 2692 case FCmpInst::FCMP_ORD: // True if ordered (no nans) 2693 case FCmpInst::FCMP_OEQ: // True if ordered and equal 2694 case FCmpInst::FCMP_OGE: // True if ordered and greater than or equal 2695 case FCmpInst::FCMP_OLE: // True if ordered and less than or equal 2696 // Canonicalize these to be 'fcmp ord %X, 0.0'. 2697 I.setPredicate(FCmpInst::FCMP_ORD); 2698 I.setOperand(1, Constant::getNullValue(Op0->getType())); 2699 return &I; 2700 } 2701 } 2702 2703 // Handle fcmp with constant RHS 2704 if (Constant *RHSC = dyn_cast<Constant>(Op1)) { 2705 if (Instruction *LHSI = dyn_cast<Instruction>(Op0)) 2706 switch (LHSI->getOpcode()) { 2707 case Instruction::PHI: 2708 // Only fold fcmp into the PHI if the phi and fcmp are in the same 2709 // block. If in the same block, we're encouraging jump threading. If 2710 // not, we are just pessimizing the code by making an i1 phi. 2711 if (LHSI->getParent() == I.getParent()) 2712 if (Instruction *NV = FoldOpIntoPhi(I)) 2713 return NV; 2714 break; 2715 case Instruction::SIToFP: 2716 case Instruction::UIToFP: 2717 if (Instruction *NV = FoldFCmp_IntToFP_Cst(I, LHSI, RHSC)) 2718 return NV; 2719 break; 2720 case Instruction::Select: { 2721 // If either operand of the select is a constant, we can fold the 2722 // comparison into the select arms, which will cause one to be 2723 // constant folded and the select turned into a bitwise or. 2724 Value *Op1 = 0, *Op2 = 0; 2725 if (LHSI->hasOneUse()) { 2726 if (Constant *C = dyn_cast<Constant>(LHSI->getOperand(1))) { 2727 // Fold the known value into the constant operand. 2728 Op1 = ConstantExpr::getCompare(I.getPredicate(), C, RHSC); 2729 // Insert a new FCmp of the other select operand. 2730 Op2 = Builder->CreateFCmp(I.getPredicate(), 2731 LHSI->getOperand(2), RHSC, I.getName()); 2732 } else if (Constant *C = dyn_cast<Constant>(LHSI->getOperand(2))) { 2733 // Fold the known value into the constant operand. 2734 Op2 = ConstantExpr::getCompare(I.getPredicate(), C, RHSC); 2735 // Insert a new FCmp of the other select operand. 2736 Op1 = Builder->CreateFCmp(I.getPredicate(), LHSI->getOperand(1), 2737 RHSC, I.getName()); 2738 } 2739 } 2740 2741 if (Op1) 2742 return SelectInst::Create(LHSI->getOperand(0), Op1, Op2); 2743 break; 2744 } 2745 case Instruction::Load: 2746 if (GetElementPtrInst *GEP = 2747 dyn_cast<GetElementPtrInst>(LHSI->getOperand(0))) { 2748 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(GEP->getOperand(0))) 2749 if (GV->isConstant() && GV->hasDefinitiveInitializer() && 2750 !cast<LoadInst>(LHSI)->isVolatile()) 2751 if (Instruction *Res = FoldCmpLoadFromIndexedGlobal(GEP, GV, I)) 2752 return Res; 2753 } 2754 break; 2755 } 2756 } 2757 2758 return Changed ? &I : 0; 2759} 2760