InstCombineCompares.cpp revision 3472766f9eb7d66f234c390ce1b3a8b76f0ee9ce
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 25/// AddOne - Add one to a ConstantInt 26static Constant *AddOne(Constant *C) { 27 return ConstantExpr::getAdd(C, ConstantInt::get(C->getType(), 1)); 28} 29/// SubOne - Subtract one from a ConstantInt 30static Constant *SubOne(ConstantInt *C) { 31 return ConstantExpr::getSub(C, ConstantInt::get(C->getType(), 1)); 32} 33 34static ConstantInt *ExtractElement(Constant *V, Constant *Idx) { 35 return cast<ConstantInt>(ConstantExpr::getExtractElement(V, Idx)); 36} 37 38static bool HasAddOverflow(ConstantInt *Result, 39 ConstantInt *In1, ConstantInt *In2, 40 bool IsSigned) { 41 if (IsSigned) 42 if (In2->getValue().isNegative()) 43 return Result->getValue().sgt(In1->getValue()); 44 else 45 return Result->getValue().slt(In1->getValue()); 46 else 47 return Result->getValue().ult(In1->getValue()); 48} 49 50/// AddWithOverflow - Compute Result = In1+In2, returning true if the result 51/// overflowed for this type. 52static bool AddWithOverflow(Constant *&Result, Constant *In1, 53 Constant *In2, bool IsSigned = false) { 54 Result = ConstantExpr::getAdd(In1, In2); 55 56 if (const VectorType *VTy = dyn_cast<VectorType>(In1->getType())) { 57 for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) { 58 Constant *Idx = ConstantInt::get(Type::getInt32Ty(In1->getContext()), i); 59 if (HasAddOverflow(ExtractElement(Result, Idx), 60 ExtractElement(In1, Idx), 61 ExtractElement(In2, Idx), 62 IsSigned)) 63 return true; 64 } 65 return false; 66 } 67 68 return HasAddOverflow(cast<ConstantInt>(Result), 69 cast<ConstantInt>(In1), cast<ConstantInt>(In2), 70 IsSigned); 71} 72 73static bool HasSubOverflow(ConstantInt *Result, 74 ConstantInt *In1, ConstantInt *In2, 75 bool IsSigned) { 76 if (IsSigned) 77 if (In2->getValue().isNegative()) 78 return Result->getValue().slt(In1->getValue()); 79 else 80 return Result->getValue().sgt(In1->getValue()); 81 else 82 return Result->getValue().ugt(In1->getValue()); 83} 84 85/// SubWithOverflow - Compute Result = In1-In2, returning true if the result 86/// overflowed for this type. 87static bool SubWithOverflow(Constant *&Result, Constant *In1, 88 Constant *In2, bool IsSigned = false) { 89 Result = ConstantExpr::getSub(In1, In2); 90 91 if (const VectorType *VTy = dyn_cast<VectorType>(In1->getType())) { 92 for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) { 93 Constant *Idx = ConstantInt::get(Type::getInt32Ty(In1->getContext()), i); 94 if (HasSubOverflow(ExtractElement(Result, Idx), 95 ExtractElement(In1, Idx), 96 ExtractElement(In2, Idx), 97 IsSigned)) 98 return true; 99 } 100 return false; 101 } 102 103 return HasSubOverflow(cast<ConstantInt>(Result), 104 cast<ConstantInt>(In1), cast<ConstantInt>(In2), 105 IsSigned); 106} 107 108/// isSignBitCheck - Given an exploded icmp instruction, return true if the 109/// comparison only checks the sign bit. If it only checks the sign bit, set 110/// TrueIfSigned if the result of the comparison is true when the input value is 111/// signed. 112static bool isSignBitCheck(ICmpInst::Predicate pred, ConstantInt *RHS, 113 bool &TrueIfSigned) { 114 switch (pred) { 115 case ICmpInst::ICMP_SLT: // True if LHS s< 0 116 TrueIfSigned = true; 117 return RHS->isZero(); 118 case ICmpInst::ICMP_SLE: // True if LHS s<= RHS and RHS == -1 119 TrueIfSigned = true; 120 return RHS->isAllOnesValue(); 121 case ICmpInst::ICMP_SGT: // True if LHS s> -1 122 TrueIfSigned = false; 123 return RHS->isAllOnesValue(); 124 case ICmpInst::ICMP_UGT: 125 // True if LHS u> RHS and RHS == high-bit-mask - 1 126 TrueIfSigned = true; 127 return RHS->getValue() == 128 APInt::getSignedMaxValue(RHS->getType()->getPrimitiveSizeInBits()); 129 case ICmpInst::ICMP_UGE: 130 // True if LHS u>= RHS and RHS == high-bit-mask (2^7, 2^15, 2^31, etc) 131 TrueIfSigned = true; 132 return RHS->getValue().isSignBit(); 133 default: 134 return false; 135 } 136} 137 138// isHighOnes - Return true if the constant is of the form 1+0+. 139// This is the same as lowones(~X). 140static bool isHighOnes(const ConstantInt *CI) { 141 return (~CI->getValue() + 1).isPowerOf2(); 142} 143 144/// ComputeSignedMinMaxValuesFromKnownBits - Given a signed integer type and a 145/// set of known zero and one bits, compute the maximum and minimum values that 146/// could have the specified known zero and known one bits, returning them in 147/// min/max. 148static void ComputeSignedMinMaxValuesFromKnownBits(const APInt& KnownZero, 149 const APInt& KnownOne, 150 APInt& Min, APInt& Max) { 151 assert(KnownZero.getBitWidth() == KnownOne.getBitWidth() && 152 KnownZero.getBitWidth() == Min.getBitWidth() && 153 KnownZero.getBitWidth() == Max.getBitWidth() && 154 "KnownZero, KnownOne and Min, Max must have equal bitwidth."); 155 APInt UnknownBits = ~(KnownZero|KnownOne); 156 157 // The minimum value is when all unknown bits are zeros, EXCEPT for the sign 158 // bit if it is unknown. 159 Min = KnownOne; 160 Max = KnownOne|UnknownBits; 161 162 if (UnknownBits.isNegative()) { // Sign bit is unknown 163 Min.set(Min.getBitWidth()-1); 164 Max.clear(Max.getBitWidth()-1); 165 } 166} 167 168// ComputeUnsignedMinMaxValuesFromKnownBits - Given an unsigned integer type and 169// a set of known zero and one bits, compute the maximum and minimum values that 170// could have the specified known zero and known one bits, returning them in 171// min/max. 172static void ComputeUnsignedMinMaxValuesFromKnownBits(const APInt &KnownZero, 173 const APInt &KnownOne, 174 APInt &Min, APInt &Max) { 175 assert(KnownZero.getBitWidth() == KnownOne.getBitWidth() && 176 KnownZero.getBitWidth() == Min.getBitWidth() && 177 KnownZero.getBitWidth() == Max.getBitWidth() && 178 "Ty, KnownZero, KnownOne and Min, Max must have equal bitwidth."); 179 APInt UnknownBits = ~(KnownZero|KnownOne); 180 181 // The minimum value is when the unknown bits are all zeros. 182 Min = KnownOne; 183 // The maximum value is when the unknown bits are all ones. 184 Max = KnownOne|UnknownBits; 185} 186 187 188 189/// FoldCmpLoadFromIndexedGlobal - Called we see this pattern: 190/// cmp pred (load (gep GV, ...)), cmpcst 191/// where GV is a global variable with a constant initializer. Try to simplify 192/// this into some simple computation that does not need the load. For example 193/// we can optimize "icmp eq (load (gep "foo", 0, i)), 0" into "icmp eq i, 3". 194/// 195/// If AndCst is non-null, then the loaded value is masked with that constant 196/// before doing the comparison. This handles cases like "A[i]&4 == 0". 197Instruction *InstCombiner:: 198FoldCmpLoadFromIndexedGlobal(GetElementPtrInst *GEP, GlobalVariable *GV, 199 CmpInst &ICI, ConstantInt *AndCst) { 200 // We need TD information to know the pointer size unless this is inbounds. 201 if (!GEP->isInBounds() && TD == 0) return 0; 202 203 ConstantArray *Init = dyn_cast<ConstantArray>(GV->getInitializer()); 204 if (Init == 0 || Init->getNumOperands() > 1024) return 0; 205 206 // There are many forms of this optimization we can handle, for now, just do 207 // the simple index into a single-dimensional array. 208 // 209 // Require: GEP GV, 0, i {{, constant indices}} 210 if (GEP->getNumOperands() < 3 || 211 !isa<ConstantInt>(GEP->getOperand(1)) || 212 !cast<ConstantInt>(GEP->getOperand(1))->isZero() || 213 isa<Constant>(GEP->getOperand(2))) 214 return 0; 215 216 // Check that indices after the variable are constants and in-range for the 217 // type they index. Collect the indices. This is typically for arrays of 218 // structs. 219 SmallVector<unsigned, 4> LaterIndices; 220 221 const Type *EltTy = cast<ArrayType>(Init->getType())->getElementType(); 222 for (unsigned i = 3, e = GEP->getNumOperands(); i != e; ++i) { 223 ConstantInt *Idx = dyn_cast<ConstantInt>(GEP->getOperand(i)); 224 if (Idx == 0) return 0; // Variable index. 225 226 uint64_t IdxVal = Idx->getZExtValue(); 227 if ((unsigned)IdxVal != IdxVal) return 0; // Too large array index. 228 229 if (const StructType *STy = dyn_cast<StructType>(EltTy)) 230 EltTy = STy->getElementType(IdxVal); 231 else if (const ArrayType *ATy = dyn_cast<ArrayType>(EltTy)) { 232 if (IdxVal >= ATy->getNumElements()) return 0; 233 EltTy = ATy->getElementType(); 234 } else { 235 return 0; // Unknown type. 236 } 237 238 LaterIndices.push_back(IdxVal); 239 } 240 241 enum { Overdefined = -3, Undefined = -2 }; 242 243 // Variables for our state machines. 244 245 // FirstTrueElement/SecondTrueElement - Used to emit a comparison of the form 246 // "i == 47 | i == 87", where 47 is the first index the condition is true for, 247 // and 87 is the second (and last) index. FirstTrueElement is -2 when 248 // undefined, otherwise set to the first true element. SecondTrueElement is 249 // -2 when undefined, -3 when overdefined and >= 0 when that index is true. 250 int FirstTrueElement = Undefined, SecondTrueElement = Undefined; 251 252 // FirstFalseElement/SecondFalseElement - Used to emit a comparison of the 253 // form "i != 47 & i != 87". Same state transitions as for true elements. 254 int FirstFalseElement = Undefined, SecondFalseElement = Undefined; 255 256 /// TrueRangeEnd/FalseRangeEnd - In conjunction with First*Element, these 257 /// define a state machine that triggers for ranges of values that the index 258 /// is true or false for. This triggers on things like "abbbbc"[i] == 'b'. 259 /// This is -2 when undefined, -3 when overdefined, and otherwise the last 260 /// index in the range (inclusive). We use -2 for undefined here because we 261 /// use relative comparisons and don't want 0-1 to match -1. 262 int TrueRangeEnd = Undefined, FalseRangeEnd = Undefined; 263 264 // MagicBitvector - This is a magic bitvector where we set a bit if the 265 // comparison is true for element 'i'. If there are 64 elements or less in 266 // the array, this will fully represent all the comparison results. 267 uint64_t MagicBitvector = 0; 268 269 270 // Scan the array and see if one of our patterns matches. 271 Constant *CompareRHS = cast<Constant>(ICI.getOperand(1)); 272 for (unsigned i = 0, e = Init->getNumOperands(); i != e; ++i) { 273 Constant *Elt = Init->getOperand(i); 274 275 // If this is indexing an array of structures, get the structure element. 276 if (!LaterIndices.empty()) 277 Elt = ConstantExpr::getExtractValue(Elt, LaterIndices.data(), 278 LaterIndices.size()); 279 280 // If the element is masked, handle it. 281 if (AndCst) Elt = ConstantExpr::getAnd(Elt, AndCst); 282 283 // Find out if the comparison would be true or false for the i'th element. 284 Constant *C = ConstantFoldCompareInstOperands(ICI.getPredicate(), Elt, 285 CompareRHS, TD); 286 // If the result is undef for this element, ignore it. 287 if (isa<UndefValue>(C)) { 288 // Extend range state machines to cover this element in case there is an 289 // undef in the middle of the range. 290 if (TrueRangeEnd == (int)i-1) 291 TrueRangeEnd = i; 292 if (FalseRangeEnd == (int)i-1) 293 FalseRangeEnd = i; 294 continue; 295 } 296 297 // If we can't compute the result for any of the elements, we have to give 298 // up evaluating the entire conditional. 299 if (!isa<ConstantInt>(C)) return 0; 300 301 // Otherwise, we know if the comparison is true or false for this element, 302 // update our state machines. 303 bool IsTrueForElt = !cast<ConstantInt>(C)->isZero(); 304 305 // State machine for single/double/range index comparison. 306 if (IsTrueForElt) { 307 // Update the TrueElement state machine. 308 if (FirstTrueElement == Undefined) 309 FirstTrueElement = TrueRangeEnd = i; // First true element. 310 else { 311 // Update double-compare state machine. 312 if (SecondTrueElement == Undefined) 313 SecondTrueElement = i; 314 else 315 SecondTrueElement = Overdefined; 316 317 // Update range state machine. 318 if (TrueRangeEnd == (int)i-1) 319 TrueRangeEnd = i; 320 else 321 TrueRangeEnd = Overdefined; 322 } 323 } else { 324 // Update the FalseElement state machine. 325 if (FirstFalseElement == Undefined) 326 FirstFalseElement = FalseRangeEnd = i; // First false element. 327 else { 328 // Update double-compare state machine. 329 if (SecondFalseElement == Undefined) 330 SecondFalseElement = i; 331 else 332 SecondFalseElement = Overdefined; 333 334 // Update range state machine. 335 if (FalseRangeEnd == (int)i-1) 336 FalseRangeEnd = i; 337 else 338 FalseRangeEnd = Overdefined; 339 } 340 } 341 342 343 // If this element is in range, update our magic bitvector. 344 if (i < 64 && IsTrueForElt) 345 MagicBitvector |= 1ULL << i; 346 347 // If all of our states become overdefined, bail out early. Since the 348 // predicate is expensive, only check it every 8 elements. This is only 349 // really useful for really huge arrays. 350 if ((i & 8) == 0 && i >= 64 && SecondTrueElement == Overdefined && 351 SecondFalseElement == Overdefined && TrueRangeEnd == Overdefined && 352 FalseRangeEnd == Overdefined) 353 return 0; 354 } 355 356 // Now that we've scanned the entire array, emit our new comparison(s). We 357 // order the state machines in complexity of the generated code. 358 Value *Idx = GEP->getOperand(2); 359 360 // If the index is larger than the pointer size of the target, truncate the 361 // index down like the GEP would do implicitly. We don't have to do this for 362 // an inbounds GEP because the index can't be out of range. 363 if (!GEP->isInBounds() && 364 Idx->getType()->getPrimitiveSizeInBits() > TD->getPointerSizeInBits()) 365 Idx = Builder->CreateTrunc(Idx, TD->getIntPtrType(Idx->getContext())); 366 367 // If the comparison is only true for one or two elements, emit direct 368 // comparisons. 369 if (SecondTrueElement != Overdefined) { 370 // None true -> false. 371 if (FirstTrueElement == Undefined) 372 return ReplaceInstUsesWith(ICI, ConstantInt::getFalse(GEP->getContext())); 373 374 Value *FirstTrueIdx = ConstantInt::get(Idx->getType(), FirstTrueElement); 375 376 // True for one element -> 'i == 47'. 377 if (SecondTrueElement == Undefined) 378 return new ICmpInst(ICmpInst::ICMP_EQ, Idx, FirstTrueIdx); 379 380 // True for two elements -> 'i == 47 | i == 72'. 381 Value *C1 = Builder->CreateICmpEQ(Idx, FirstTrueIdx); 382 Value *SecondTrueIdx = ConstantInt::get(Idx->getType(), SecondTrueElement); 383 Value *C2 = Builder->CreateICmpEQ(Idx, SecondTrueIdx); 384 return BinaryOperator::CreateOr(C1, C2); 385 } 386 387 // If the comparison is only false for one or two elements, emit direct 388 // comparisons. 389 if (SecondFalseElement != Overdefined) { 390 // None false -> true. 391 if (FirstFalseElement == Undefined) 392 return ReplaceInstUsesWith(ICI, ConstantInt::getTrue(GEP->getContext())); 393 394 Value *FirstFalseIdx = ConstantInt::get(Idx->getType(), FirstFalseElement); 395 396 // False for one element -> 'i != 47'. 397 if (SecondFalseElement == Undefined) 398 return new ICmpInst(ICmpInst::ICMP_NE, Idx, FirstFalseIdx); 399 400 // False for two elements -> 'i != 47 & i != 72'. 401 Value *C1 = Builder->CreateICmpNE(Idx, FirstFalseIdx); 402 Value *SecondFalseIdx = ConstantInt::get(Idx->getType(),SecondFalseElement); 403 Value *C2 = Builder->CreateICmpNE(Idx, SecondFalseIdx); 404 return BinaryOperator::CreateAnd(C1, C2); 405 } 406 407 // If the comparison can be replaced with a range comparison for the elements 408 // where it is true, emit the range check. 409 if (TrueRangeEnd != Overdefined) { 410 assert(TrueRangeEnd != FirstTrueElement && "Should emit single compare"); 411 412 // Generate (i-FirstTrue) <u (TrueRangeEnd-FirstTrue+1). 413 if (FirstTrueElement) { 414 Value *Offs = ConstantInt::get(Idx->getType(), -FirstTrueElement); 415 Idx = Builder->CreateAdd(Idx, Offs); 416 } 417 418 Value *End = ConstantInt::get(Idx->getType(), 419 TrueRangeEnd-FirstTrueElement+1); 420 return new ICmpInst(ICmpInst::ICMP_ULT, Idx, End); 421 } 422 423 // False range check. 424 if (FalseRangeEnd != Overdefined) { 425 assert(FalseRangeEnd != FirstFalseElement && "Should emit single compare"); 426 // Generate (i-FirstFalse) >u (FalseRangeEnd-FirstFalse). 427 if (FirstFalseElement) { 428 Value *Offs = ConstantInt::get(Idx->getType(), -FirstFalseElement); 429 Idx = Builder->CreateAdd(Idx, Offs); 430 } 431 432 Value *End = ConstantInt::get(Idx->getType(), 433 FalseRangeEnd-FirstFalseElement); 434 return new ICmpInst(ICmpInst::ICMP_UGT, Idx, End); 435 } 436 437 438 // If a 32-bit or 64-bit magic bitvector captures the entire comparison state 439 // of this load, replace it with computation that does: 440 // ((magic_cst >> i) & 1) != 0 441 if (Init->getNumOperands() <= 32 || 442 (TD && Init->getNumOperands() <= 64 && TD->isLegalInteger(64))) { 443 const Type *Ty; 444 if (Init->getNumOperands() <= 32) 445 Ty = Type::getInt32Ty(Init->getContext()); 446 else 447 Ty = Type::getInt64Ty(Init->getContext()); 448 Value *V = Builder->CreateIntCast(Idx, Ty, false); 449 V = Builder->CreateLShr(ConstantInt::get(Ty, MagicBitvector), V); 450 V = Builder->CreateAnd(ConstantInt::get(Ty, 1), V); 451 return new ICmpInst(ICmpInst::ICMP_NE, V, ConstantInt::get(Ty, 0)); 452 } 453 454 return 0; 455} 456 457 458/// EvaluateGEPOffsetExpression - Return a value that can be used to compare 459/// the *offset* implied by a GEP to zero. For example, if we have &A[i], we 460/// want to return 'i' for "icmp ne i, 0". Note that, in general, indices can 461/// be complex, and scales are involved. The above expression would also be 462/// legal to codegen as "icmp ne (i*4), 0" (assuming A is a pointer to i32). 463/// This later form is less amenable to optimization though, and we are allowed 464/// to generate the first by knowing that pointer arithmetic doesn't overflow. 465/// 466/// If we can't emit an optimized form for this expression, this returns null. 467/// 468static Value *EvaluateGEPOffsetExpression(User *GEP, Instruction &I, 469 InstCombiner &IC) { 470 TargetData &TD = *IC.getTargetData(); 471 gep_type_iterator GTI = gep_type_begin(GEP); 472 473 // Check to see if this gep only has a single variable index. If so, and if 474 // any constant indices are a multiple of its scale, then we can compute this 475 // in terms of the scale of the variable index. For example, if the GEP 476 // implies an offset of "12 + i*4", then we can codegen this as "3 + i", 477 // because the expression will cross zero at the same point. 478 unsigned i, e = GEP->getNumOperands(); 479 int64_t Offset = 0; 480 for (i = 1; i != e; ++i, ++GTI) { 481 if (ConstantInt *CI = dyn_cast<ConstantInt>(GEP->getOperand(i))) { 482 // Compute the aggregate offset of constant indices. 483 if (CI->isZero()) continue; 484 485 // Handle a struct index, which adds its field offset to the pointer. 486 if (const StructType *STy = dyn_cast<StructType>(*GTI)) { 487 Offset += TD.getStructLayout(STy)->getElementOffset(CI->getZExtValue()); 488 } else { 489 uint64_t Size = TD.getTypeAllocSize(GTI.getIndexedType()); 490 Offset += Size*CI->getSExtValue(); 491 } 492 } else { 493 // Found our variable index. 494 break; 495 } 496 } 497 498 // If there are no variable indices, we must have a constant offset, just 499 // evaluate it the general way. 500 if (i == e) return 0; 501 502 Value *VariableIdx = GEP->getOperand(i); 503 // Determine the scale factor of the variable element. For example, this is 504 // 4 if the variable index is into an array of i32. 505 uint64_t VariableScale = TD.getTypeAllocSize(GTI.getIndexedType()); 506 507 // Verify that there are no other variable indices. If so, emit the hard way. 508 for (++i, ++GTI; i != e; ++i, ++GTI) { 509 ConstantInt *CI = dyn_cast<ConstantInt>(GEP->getOperand(i)); 510 if (!CI) return 0; 511 512 // Compute the aggregate offset of constant indices. 513 if (CI->isZero()) continue; 514 515 // Handle a struct index, which adds its field offset to the pointer. 516 if (const StructType *STy = dyn_cast<StructType>(*GTI)) { 517 Offset += TD.getStructLayout(STy)->getElementOffset(CI->getZExtValue()); 518 } else { 519 uint64_t Size = TD.getTypeAllocSize(GTI.getIndexedType()); 520 Offset += Size*CI->getSExtValue(); 521 } 522 } 523 524 // Okay, we know we have a single variable index, which must be a 525 // pointer/array/vector index. If there is no offset, life is simple, return 526 // the index. 527 unsigned IntPtrWidth = TD.getPointerSizeInBits(); 528 if (Offset == 0) { 529 // Cast to intptrty in case a truncation occurs. If an extension is needed, 530 // we don't need to bother extending: the extension won't affect where the 531 // computation crosses zero. 532 if (VariableIdx->getType()->getPrimitiveSizeInBits() > IntPtrWidth) 533 VariableIdx = new TruncInst(VariableIdx, 534 TD.getIntPtrType(VariableIdx->getContext()), 535 VariableIdx->getName(), &I); 536 return VariableIdx; 537 } 538 539 // Otherwise, there is an index. The computation we will do will be modulo 540 // the pointer size, so get it. 541 uint64_t PtrSizeMask = ~0ULL >> (64-IntPtrWidth); 542 543 Offset &= PtrSizeMask; 544 VariableScale &= PtrSizeMask; 545 546 // To do this transformation, any constant index must be a multiple of the 547 // variable scale factor. For example, we can evaluate "12 + 4*i" as "3 + i", 548 // but we can't evaluate "10 + 3*i" in terms of i. Check that the offset is a 549 // multiple of the variable scale. 550 int64_t NewOffs = Offset / (int64_t)VariableScale; 551 if (Offset != NewOffs*(int64_t)VariableScale) 552 return 0; 553 554 // Okay, we can do this evaluation. Start by converting the index to intptr. 555 const Type *IntPtrTy = TD.getIntPtrType(VariableIdx->getContext()); 556 if (VariableIdx->getType() != IntPtrTy) 557 VariableIdx = CastInst::CreateIntegerCast(VariableIdx, IntPtrTy, 558 true /*SExt*/, 559 VariableIdx->getName(), &I); 560 Constant *OffsetVal = ConstantInt::get(IntPtrTy, NewOffs); 561 return BinaryOperator::CreateAdd(VariableIdx, OffsetVal, "offset", &I); 562} 563 564/// FoldGEPICmp - Fold comparisons between a GEP instruction and something 565/// else. At this point we know that the GEP is on the LHS of the comparison. 566Instruction *InstCombiner::FoldGEPICmp(GEPOperator *GEPLHS, Value *RHS, 567 ICmpInst::Predicate Cond, 568 Instruction &I) { 569 // Look through bitcasts. 570 if (BitCastInst *BCI = dyn_cast<BitCastInst>(RHS)) 571 RHS = BCI->getOperand(0); 572 573 Value *PtrBase = GEPLHS->getOperand(0); 574 if (TD && PtrBase == RHS && GEPLHS->isInBounds()) { 575 // ((gep Ptr, OFFSET) cmp Ptr) ---> (OFFSET cmp 0). 576 // This transformation (ignoring the base and scales) is valid because we 577 // know pointers can't overflow since the gep is inbounds. See if we can 578 // output an optimized form. 579 Value *Offset = EvaluateGEPOffsetExpression(GEPLHS, I, *this); 580 581 // If not, synthesize the offset the hard way. 582 if (Offset == 0) 583 Offset = EmitGEPOffset(GEPLHS); 584 return new ICmpInst(ICmpInst::getSignedPredicate(Cond), Offset, 585 Constant::getNullValue(Offset->getType())); 586 } else if (GEPOperator *GEPRHS = dyn_cast<GEPOperator>(RHS)) { 587 // If the base pointers are different, but the indices are the same, just 588 // compare the base pointer. 589 if (PtrBase != GEPRHS->getOperand(0)) { 590 bool IndicesTheSame = GEPLHS->getNumOperands()==GEPRHS->getNumOperands(); 591 IndicesTheSame &= GEPLHS->getOperand(0)->getType() == 592 GEPRHS->getOperand(0)->getType(); 593 if (IndicesTheSame) 594 for (unsigned i = 1, e = GEPLHS->getNumOperands(); i != e; ++i) 595 if (GEPLHS->getOperand(i) != GEPRHS->getOperand(i)) { 596 IndicesTheSame = false; 597 break; 598 } 599 600 // If all indices are the same, just compare the base pointers. 601 if (IndicesTheSame) 602 return new ICmpInst(ICmpInst::getSignedPredicate(Cond), 603 GEPLHS->getOperand(0), GEPRHS->getOperand(0)); 604 605 // Otherwise, the base pointers are different and the indices are 606 // different, bail out. 607 return 0; 608 } 609 610 // If one of the GEPs has all zero indices, recurse. 611 bool AllZeros = true; 612 for (unsigned i = 1, e = GEPLHS->getNumOperands(); i != e; ++i) 613 if (!isa<Constant>(GEPLHS->getOperand(i)) || 614 !cast<Constant>(GEPLHS->getOperand(i))->isNullValue()) { 615 AllZeros = false; 616 break; 617 } 618 if (AllZeros) 619 return FoldGEPICmp(GEPRHS, GEPLHS->getOperand(0), 620 ICmpInst::getSwappedPredicate(Cond), I); 621 622 // If the other GEP has all zero indices, recurse. 623 AllZeros = true; 624 for (unsigned i = 1, e = GEPRHS->getNumOperands(); i != e; ++i) 625 if (!isa<Constant>(GEPRHS->getOperand(i)) || 626 !cast<Constant>(GEPRHS->getOperand(i))->isNullValue()) { 627 AllZeros = false; 628 break; 629 } 630 if (AllZeros) 631 return FoldGEPICmp(GEPLHS, GEPRHS->getOperand(0), Cond, I); 632 633 if (GEPLHS->getNumOperands() == GEPRHS->getNumOperands()) { 634 // If the GEPs only differ by one index, compare it. 635 unsigned NumDifferences = 0; // Keep track of # differences. 636 unsigned DiffOperand = 0; // The operand that differs. 637 for (unsigned i = 1, e = GEPRHS->getNumOperands(); i != e; ++i) 638 if (GEPLHS->getOperand(i) != GEPRHS->getOperand(i)) { 639 if (GEPLHS->getOperand(i)->getType()->getPrimitiveSizeInBits() != 640 GEPRHS->getOperand(i)->getType()->getPrimitiveSizeInBits()) { 641 // Irreconcilable differences. 642 NumDifferences = 2; 643 break; 644 } else { 645 if (NumDifferences++) break; 646 DiffOperand = i; 647 } 648 } 649 650 if (NumDifferences == 0) // SAME GEP? 651 return ReplaceInstUsesWith(I, // No comparison is needed here. 652 ConstantInt::get(Type::getInt1Ty(I.getContext()), 653 ICmpInst::isTrueWhenEqual(Cond))); 654 655 else if (NumDifferences == 1) { 656 Value *LHSV = GEPLHS->getOperand(DiffOperand); 657 Value *RHSV = GEPRHS->getOperand(DiffOperand); 658 // Make sure we do a signed comparison here. 659 return new ICmpInst(ICmpInst::getSignedPredicate(Cond), LHSV, RHSV); 660 } 661 } 662 663 // Only lower this if the icmp is the only user of the GEP or if we expect 664 // the result to fold to a constant! 665 if (TD && 666 (isa<ConstantExpr>(GEPLHS) || GEPLHS->hasOneUse()) && 667 (isa<ConstantExpr>(GEPRHS) || GEPRHS->hasOneUse())) { 668 // ((gep Ptr, OFFSET1) cmp (gep Ptr, OFFSET2) ---> (OFFSET1 cmp OFFSET2) 669 Value *L = EmitGEPOffset(GEPLHS); 670 Value *R = EmitGEPOffset(GEPRHS); 671 return new ICmpInst(ICmpInst::getSignedPredicate(Cond), L, R); 672 } 673 } 674 return 0; 675} 676 677/// FoldICmpAddOpCst - Fold "icmp pred (X+CI), X". 678Instruction *InstCombiner::FoldICmpAddOpCst(ICmpInst &ICI, 679 Value *X, ConstantInt *CI, 680 ICmpInst::Predicate Pred, 681 Value *TheAdd) { 682 // If we have X+0, exit early (simplifying logic below) and let it get folded 683 // elsewhere. icmp X+0, X -> icmp X, X 684 if (CI->isZero()) { 685 bool isTrue = ICmpInst::isTrueWhenEqual(Pred); 686 return ReplaceInstUsesWith(ICI, ConstantInt::get(ICI.getType(), isTrue)); 687 } 688 689 // (X+4) == X -> false. 690 if (Pred == ICmpInst::ICMP_EQ) 691 return ReplaceInstUsesWith(ICI, ConstantInt::getFalse(X->getContext())); 692 693 // (X+4) != X -> true. 694 if (Pred == ICmpInst::ICMP_NE) 695 return ReplaceInstUsesWith(ICI, ConstantInt::getTrue(X->getContext())); 696 697 // If this is an instruction (as opposed to constantexpr) get NUW/NSW info. 698 bool isNUW = false, isNSW = false; 699 if (BinaryOperator *Add = dyn_cast<BinaryOperator>(TheAdd)) { 700 isNUW = Add->hasNoUnsignedWrap(); 701 isNSW = Add->hasNoSignedWrap(); 702 } 703 704 // From this point on, we know that (X+C <= X) --> (X+C < X) because C != 0, 705 // so the values can never be equal. Similiarly for all other "or equals" 706 // operators. 707 708 // (X+1) <u X --> X >u (MAXUINT-1) --> X == 255 709 // (X+2) <u X --> X >u (MAXUINT-2) --> X > 253 710 // (X+MAXUINT) <u X --> X >u (MAXUINT-MAXUINT) --> X != 0 711 if (Pred == ICmpInst::ICMP_ULT || Pred == ICmpInst::ICMP_ULE) { 712 // If this is an NUW add, then this is always false. 713 if (isNUW) 714 return ReplaceInstUsesWith(ICI, ConstantInt::getFalse(X->getContext())); 715 716 Value *R = 717 ConstantExpr::getSub(ConstantInt::getAllOnesValue(CI->getType()), CI); 718 return new ICmpInst(ICmpInst::ICMP_UGT, X, R); 719 } 720 721 // (X+1) >u X --> X <u (0-1) --> X != 255 722 // (X+2) >u X --> X <u (0-2) --> X <u 254 723 // (X+MAXUINT) >u X --> X <u (0-MAXUINT) --> X <u 1 --> X == 0 724 if (Pred == ICmpInst::ICMP_UGT || Pred == ICmpInst::ICMP_UGE) { 725 // If this is an NUW add, then this is always true. 726 if (isNUW) 727 return ReplaceInstUsesWith(ICI, ConstantInt::getTrue(X->getContext())); 728 return new ICmpInst(ICmpInst::ICMP_ULT, X, ConstantExpr::getNeg(CI)); 729 } 730 731 unsigned BitWidth = CI->getType()->getPrimitiveSizeInBits(); 732 ConstantInt *SMax = ConstantInt::get(X->getContext(), 733 APInt::getSignedMaxValue(BitWidth)); 734 735 // (X+ 1) <s X --> X >s (MAXSINT-1) --> X == 127 736 // (X+ 2) <s X --> X >s (MAXSINT-2) --> X >s 125 737 // (X+MAXSINT) <s X --> X >s (MAXSINT-MAXSINT) --> X >s 0 738 // (X+MINSINT) <s X --> X >s (MAXSINT-MINSINT) --> X >s -1 739 // (X+ -2) <s X --> X >s (MAXSINT- -2) --> X >s 126 740 // (X+ -1) <s X --> X >s (MAXSINT- -1) --> X != 127 741 if (Pred == ICmpInst::ICMP_SLT || Pred == ICmpInst::ICMP_SLE) { 742 // If this is an NSW add, then we have two cases: if the constant is 743 // positive, then this is always false, if negative, this is always true. 744 if (isNSW) { 745 bool isTrue = CI->getValue().isNegative(); 746 return ReplaceInstUsesWith(ICI, ConstantInt::get(ICI.getType(), isTrue)); 747 } 748 749 return new ICmpInst(ICmpInst::ICMP_SGT, X, ConstantExpr::getSub(SMax, CI)); 750 } 751 752 // (X+ 1) >s X --> X <s (MAXSINT-(1-1)) --> X != 127 753 // (X+ 2) >s X --> X <s (MAXSINT-(2-1)) --> X <s 126 754 // (X+MAXSINT) >s X --> X <s (MAXSINT-(MAXSINT-1)) --> X <s 1 755 // (X+MINSINT) >s X --> X <s (MAXSINT-(MINSINT-1)) --> X <s -2 756 // (X+ -2) >s X --> X <s (MAXSINT-(-2-1)) --> X <s -126 757 // (X+ -1) >s X --> X <s (MAXSINT-(-1-1)) --> X == -128 758 759 // If this is an NSW add, then we have two cases: if the constant is 760 // positive, then this is always true, if negative, this is always false. 761 if (isNSW) { 762 bool isTrue = !CI->getValue().isNegative(); 763 return ReplaceInstUsesWith(ICI, ConstantInt::get(ICI.getType(), isTrue)); 764 } 765 766 assert(Pred == ICmpInst::ICMP_SGT || Pred == ICmpInst::ICMP_SGE); 767 Constant *C = ConstantInt::get(X->getContext(), CI->getValue()-1); 768 return new ICmpInst(ICmpInst::ICMP_SLT, X, ConstantExpr::getSub(SMax, C)); 769} 770 771/// FoldICmpDivCst - Fold "icmp pred, ([su]div X, DivRHS), CmpRHS" where DivRHS 772/// and CmpRHS are both known to be integer constants. 773Instruction *InstCombiner::FoldICmpDivCst(ICmpInst &ICI, BinaryOperator *DivI, 774 ConstantInt *DivRHS) { 775 ConstantInt *CmpRHS = cast<ConstantInt>(ICI.getOperand(1)); 776 const APInt &CmpRHSV = CmpRHS->getValue(); 777 778 // FIXME: If the operand types don't match the type of the divide 779 // then don't attempt this transform. The code below doesn't have the 780 // logic to deal with a signed divide and an unsigned compare (and 781 // vice versa). This is because (x /s C1) <s C2 produces different 782 // results than (x /s C1) <u C2 or (x /u C1) <s C2 or even 783 // (x /u C1) <u C2. Simply casting the operands and result won't 784 // work. :( The if statement below tests that condition and bails 785 // if it finds it. 786 bool DivIsSigned = DivI->getOpcode() == Instruction::SDiv; 787 if (!ICI.isEquality() && DivIsSigned != ICI.isSigned()) 788 return 0; 789 if (DivRHS->isZero()) 790 return 0; // The ProdOV computation fails on divide by zero. 791 if (DivIsSigned && DivRHS->isAllOnesValue()) 792 return 0; // The overflow computation also screws up here 793 if (DivRHS->isOne()) 794 return 0; // Not worth bothering, and eliminates some funny cases 795 // with INT_MIN. 796 797 // Compute Prod = CI * DivRHS. We are essentially solving an equation 798 // of form X/C1=C2. We solve for X by multiplying C1 (DivRHS) and 799 // C2 (CI). By solving for X we can turn this into a range check 800 // instead of computing a divide. 801 Constant *Prod = ConstantExpr::getMul(CmpRHS, DivRHS); 802 803 // Determine if the product overflows by seeing if the product is 804 // not equal to the divide. Make sure we do the same kind of divide 805 // as in the LHS instruction that we're folding. 806 bool ProdOV = (DivIsSigned ? ConstantExpr::getSDiv(Prod, DivRHS) : 807 ConstantExpr::getUDiv(Prod, DivRHS)) != CmpRHS; 808 809 // Get the ICmp opcode 810 ICmpInst::Predicate Pred = ICI.getPredicate(); 811 812 // Figure out the interval that is being checked. For example, a comparison 813 // like "X /u 5 == 0" is really checking that X is in the interval [0, 5). 814 // Compute this interval based on the constants involved and the signedness of 815 // the compare/divide. This computes a half-open interval, keeping track of 816 // whether either value in the interval overflows. After analysis each 817 // overflow variable is set to 0 if it's corresponding bound variable is valid 818 // -1 if overflowed off the bottom end, or +1 if overflowed off the top end. 819 int LoOverflow = 0, HiOverflow = 0; 820 Constant *LoBound = 0, *HiBound = 0; 821 822 if (!DivIsSigned) { // udiv 823 // e.g. X/5 op 3 --> [15, 20) 824 LoBound = Prod; 825 HiOverflow = LoOverflow = ProdOV; 826 if (!HiOverflow) 827 HiOverflow = AddWithOverflow(HiBound, LoBound, DivRHS, false); 828 } else if (DivRHS->getValue().isStrictlyPositive()) { // Divisor is > 0. 829 if (CmpRHSV == 0) { // (X / pos) op 0 830 // Can't overflow. e.g. X/2 op 0 --> [-1, 2) 831 LoBound = cast<ConstantInt>(ConstantExpr::getNeg(SubOne(DivRHS))); 832 HiBound = DivRHS; 833 } else if (CmpRHSV.isStrictlyPositive()) { // (X / pos) op pos 834 LoBound = Prod; // e.g. X/5 op 3 --> [15, 20) 835 HiOverflow = LoOverflow = ProdOV; 836 if (!HiOverflow) 837 HiOverflow = AddWithOverflow(HiBound, Prod, DivRHS, true); 838 } else { // (X / pos) op neg 839 // e.g. X/5 op -3 --> [-15-4, -15+1) --> [-19, -14) 840 HiBound = AddOne(Prod); 841 LoOverflow = HiOverflow = ProdOV ? -1 : 0; 842 if (!LoOverflow) { 843 ConstantInt* DivNeg = 844 cast<ConstantInt>(ConstantExpr::getNeg(DivRHS)); 845 LoOverflow = AddWithOverflow(LoBound, HiBound, DivNeg, true) ? -1 : 0; 846 } 847 } 848 } else if (DivRHS->getValue().isNegative()) { // Divisor is < 0. 849 if (CmpRHSV == 0) { // (X / neg) op 0 850 // e.g. X/-5 op 0 --> [-4, 5) 851 LoBound = AddOne(DivRHS); 852 HiBound = cast<ConstantInt>(ConstantExpr::getNeg(DivRHS)); 853 if (HiBound == DivRHS) { // -INTMIN = INTMIN 854 HiOverflow = 1; // [INTMIN+1, overflow) 855 HiBound = 0; // e.g. X/INTMIN = 0 --> X > INTMIN 856 } 857 } else if (CmpRHSV.isStrictlyPositive()) { // (X / neg) op pos 858 // e.g. X/-5 op 3 --> [-19, -14) 859 HiBound = AddOne(Prod); 860 HiOverflow = LoOverflow = ProdOV ? -1 : 0; 861 if (!LoOverflow) 862 LoOverflow = AddWithOverflow(LoBound, HiBound, DivRHS, true) ? -1 : 0; 863 } else { // (X / neg) op neg 864 LoBound = Prod; // e.g. X/-5 op -3 --> [15, 20) 865 LoOverflow = HiOverflow = ProdOV; 866 if (!HiOverflow) 867 HiOverflow = SubWithOverflow(HiBound, Prod, DivRHS, true); 868 } 869 870 // Dividing by a negative swaps the condition. LT <-> GT 871 Pred = ICmpInst::getSwappedPredicate(Pred); 872 } 873 874 Value *X = DivI->getOperand(0); 875 switch (Pred) { 876 default: llvm_unreachable("Unhandled icmp opcode!"); 877 case ICmpInst::ICMP_EQ: 878 if (LoOverflow && HiOverflow) 879 return ReplaceInstUsesWith(ICI, ConstantInt::getFalse(ICI.getContext())); 880 if (HiOverflow) 881 return new ICmpInst(DivIsSigned ? ICmpInst::ICMP_SGE : 882 ICmpInst::ICMP_UGE, X, LoBound); 883 if (LoOverflow) 884 return new ICmpInst(DivIsSigned ? ICmpInst::ICMP_SLT : 885 ICmpInst::ICMP_ULT, X, HiBound); 886 return ReplaceInstUsesWith(ICI, 887 InsertRangeTest(X, LoBound, HiBound, DivIsSigned, 888 true)); 889 case ICmpInst::ICMP_NE: 890 if (LoOverflow && HiOverflow) 891 return ReplaceInstUsesWith(ICI, ConstantInt::getTrue(ICI.getContext())); 892 if (HiOverflow) 893 return new ICmpInst(DivIsSigned ? ICmpInst::ICMP_SLT : 894 ICmpInst::ICMP_ULT, X, LoBound); 895 if (LoOverflow) 896 return new ICmpInst(DivIsSigned ? ICmpInst::ICMP_SGE : 897 ICmpInst::ICMP_UGE, X, HiBound); 898 return ReplaceInstUsesWith(ICI, InsertRangeTest(X, LoBound, HiBound, 899 DivIsSigned, false)); 900 case ICmpInst::ICMP_ULT: 901 case ICmpInst::ICMP_SLT: 902 if (LoOverflow == +1) // Low bound is greater than input range. 903 return ReplaceInstUsesWith(ICI, ConstantInt::getTrue(ICI.getContext())); 904 if (LoOverflow == -1) // Low bound is less than input range. 905 return ReplaceInstUsesWith(ICI, ConstantInt::getFalse(ICI.getContext())); 906 return new ICmpInst(Pred, X, LoBound); 907 case ICmpInst::ICMP_UGT: 908 case ICmpInst::ICMP_SGT: 909 if (HiOverflow == +1) // High bound greater than input range. 910 return ReplaceInstUsesWith(ICI, ConstantInt::getFalse(ICI.getContext())); 911 else if (HiOverflow == -1) // High bound less than input range. 912 return ReplaceInstUsesWith(ICI, ConstantInt::getTrue(ICI.getContext())); 913 if (Pred == ICmpInst::ICMP_UGT) 914 return new ICmpInst(ICmpInst::ICMP_UGE, X, HiBound); 915 else 916 return new ICmpInst(ICmpInst::ICMP_SGE, X, HiBound); 917 } 918} 919 920 921/// visitICmpInstWithInstAndIntCst - Handle "icmp (instr, intcst)". 922/// 923Instruction *InstCombiner::visitICmpInstWithInstAndIntCst(ICmpInst &ICI, 924 Instruction *LHSI, 925 ConstantInt *RHS) { 926 const APInt &RHSV = RHS->getValue(); 927 928 switch (LHSI->getOpcode()) { 929 case Instruction::Trunc: 930 if (ICI.isEquality() && LHSI->hasOneUse()) { 931 // Simplify icmp eq (trunc x to i8), 42 -> icmp eq x, 42|highbits if all 932 // of the high bits truncated out of x are known. 933 unsigned DstBits = LHSI->getType()->getPrimitiveSizeInBits(), 934 SrcBits = LHSI->getOperand(0)->getType()->getPrimitiveSizeInBits(); 935 APInt Mask(APInt::getHighBitsSet(SrcBits, SrcBits-DstBits)); 936 APInt KnownZero(SrcBits, 0), KnownOne(SrcBits, 0); 937 ComputeMaskedBits(LHSI->getOperand(0), Mask, KnownZero, KnownOne); 938 939 // If all the high bits are known, we can do this xform. 940 if ((KnownZero|KnownOne).countLeadingOnes() >= SrcBits-DstBits) { 941 // Pull in the high bits from known-ones set. 942 APInt NewRHS(RHS->getValue()); 943 NewRHS.zext(SrcBits); 944 NewRHS |= KnownOne; 945 return new ICmpInst(ICI.getPredicate(), LHSI->getOperand(0), 946 ConstantInt::get(ICI.getContext(), NewRHS)); 947 } 948 } 949 break; 950 951 case Instruction::Xor: // (icmp pred (xor X, XorCST), CI) 952 if (ConstantInt *XorCST = dyn_cast<ConstantInt>(LHSI->getOperand(1))) { 953 // If this is a comparison that tests the signbit (X < 0) or (x > -1), 954 // fold the xor. 955 if ((ICI.getPredicate() == ICmpInst::ICMP_SLT && RHSV == 0) || 956 (ICI.getPredicate() == ICmpInst::ICMP_SGT && RHSV.isAllOnesValue())) { 957 Value *CompareVal = LHSI->getOperand(0); 958 959 // If the sign bit of the XorCST is not set, there is no change to 960 // the operation, just stop using the Xor. 961 if (!XorCST->getValue().isNegative()) { 962 ICI.setOperand(0, CompareVal); 963 Worklist.Add(LHSI); 964 return &ICI; 965 } 966 967 // Was the old condition true if the operand is positive? 968 bool isTrueIfPositive = ICI.getPredicate() == ICmpInst::ICMP_SGT; 969 970 // If so, the new one isn't. 971 isTrueIfPositive ^= true; 972 973 if (isTrueIfPositive) 974 return new ICmpInst(ICmpInst::ICMP_SGT, CompareVal, 975 SubOne(RHS)); 976 else 977 return new ICmpInst(ICmpInst::ICMP_SLT, CompareVal, 978 AddOne(RHS)); 979 } 980 981 if (LHSI->hasOneUse()) { 982 // (icmp u/s (xor A SignBit), C) -> (icmp s/u A, (xor C SignBit)) 983 if (!ICI.isEquality() && XorCST->getValue().isSignBit()) { 984 const APInt &SignBit = XorCST->getValue(); 985 ICmpInst::Predicate Pred = ICI.isSigned() 986 ? ICI.getUnsignedPredicate() 987 : ICI.getSignedPredicate(); 988 return new ICmpInst(Pred, LHSI->getOperand(0), 989 ConstantInt::get(ICI.getContext(), 990 RHSV ^ SignBit)); 991 } 992 993 // (icmp u/s (xor A ~SignBit), C) -> (icmp s/u (xor C ~SignBit), A) 994 if (!ICI.isEquality() && XorCST->getValue().isMaxSignedValue()) { 995 const APInt &NotSignBit = XorCST->getValue(); 996 ICmpInst::Predicate Pred = ICI.isSigned() 997 ? ICI.getUnsignedPredicate() 998 : ICI.getSignedPredicate(); 999 Pred = ICI.getSwappedPredicate(Pred); 1000 return new ICmpInst(Pred, LHSI->getOperand(0), 1001 ConstantInt::get(ICI.getContext(), 1002 RHSV ^ NotSignBit)); 1003 } 1004 } 1005 } 1006 break; 1007 case Instruction::And: // (icmp pred (and X, AndCST), RHS) 1008 if (LHSI->hasOneUse() && isa<ConstantInt>(LHSI->getOperand(1)) && 1009 LHSI->getOperand(0)->hasOneUse()) { 1010 ConstantInt *AndCST = cast<ConstantInt>(LHSI->getOperand(1)); 1011 1012 // If the LHS is an AND of a truncating cast, we can widen the 1013 // and/compare to be the input width without changing the value 1014 // produced, eliminating a cast. 1015 if (TruncInst *Cast = dyn_cast<TruncInst>(LHSI->getOperand(0))) { 1016 // We can do this transformation if either the AND constant does not 1017 // have its sign bit set or if it is an equality comparison. 1018 // Extending a relational comparison when we're checking the sign 1019 // bit would not work. 1020 if (Cast->hasOneUse() && 1021 (ICI.isEquality() || 1022 (AndCST->getValue().isNonNegative() && RHSV.isNonNegative()))) { 1023 uint32_t BitWidth = 1024 cast<IntegerType>(Cast->getOperand(0)->getType())->getBitWidth(); 1025 APInt NewCST = AndCST->getValue(); 1026 NewCST.zext(BitWidth); 1027 APInt NewCI = RHSV; 1028 NewCI.zext(BitWidth); 1029 Value *NewAnd = 1030 Builder->CreateAnd(Cast->getOperand(0), 1031 ConstantInt::get(ICI.getContext(), NewCST), 1032 LHSI->getName()); 1033 return new ICmpInst(ICI.getPredicate(), NewAnd, 1034 ConstantInt::get(ICI.getContext(), NewCI)); 1035 } 1036 } 1037 1038 // If this is: (X >> C1) & C2 != C3 (where any shift and any compare 1039 // could exist), turn it into (X & (C2 << C1)) != (C3 << C1). This 1040 // happens a LOT in code produced by the C front-end, for bitfield 1041 // access. 1042 BinaryOperator *Shift = dyn_cast<BinaryOperator>(LHSI->getOperand(0)); 1043 if (Shift && !Shift->isShift()) 1044 Shift = 0; 1045 1046 ConstantInt *ShAmt; 1047 ShAmt = Shift ? dyn_cast<ConstantInt>(Shift->getOperand(1)) : 0; 1048 const Type *Ty = Shift ? Shift->getType() : 0; // Type of the shift. 1049 const Type *AndTy = AndCST->getType(); // Type of the and. 1050 1051 // We can fold this as long as we can't shift unknown bits 1052 // into the mask. This can only happen with signed shift 1053 // rights, as they sign-extend. 1054 if (ShAmt) { 1055 bool CanFold = Shift->isLogicalShift(); 1056 if (!CanFold) { 1057 // To test for the bad case of the signed shr, see if any 1058 // of the bits shifted in could be tested after the mask. 1059 uint32_t TyBits = Ty->getPrimitiveSizeInBits(); 1060 int ShAmtVal = TyBits - ShAmt->getLimitedValue(TyBits); 1061 1062 uint32_t BitWidth = AndTy->getPrimitiveSizeInBits(); 1063 if ((APInt::getHighBitsSet(BitWidth, BitWidth-ShAmtVal) & 1064 AndCST->getValue()) == 0) 1065 CanFold = true; 1066 } 1067 1068 if (CanFold) { 1069 Constant *NewCst; 1070 if (Shift->getOpcode() == Instruction::Shl) 1071 NewCst = ConstantExpr::getLShr(RHS, ShAmt); 1072 else 1073 NewCst = ConstantExpr::getShl(RHS, ShAmt); 1074 1075 // Check to see if we are shifting out any of the bits being 1076 // compared. 1077 if (ConstantExpr::get(Shift->getOpcode(), 1078 NewCst, ShAmt) != RHS) { 1079 // If we shifted bits out, the fold is not going to work out. 1080 // As a special case, check to see if this means that the 1081 // result is always true or false now. 1082 if (ICI.getPredicate() == ICmpInst::ICMP_EQ) 1083 return ReplaceInstUsesWith(ICI, 1084 ConstantInt::getFalse(ICI.getContext())); 1085 if (ICI.getPredicate() == ICmpInst::ICMP_NE) 1086 return ReplaceInstUsesWith(ICI, 1087 ConstantInt::getTrue(ICI.getContext())); 1088 } else { 1089 ICI.setOperand(1, NewCst); 1090 Constant *NewAndCST; 1091 if (Shift->getOpcode() == Instruction::Shl) 1092 NewAndCST = ConstantExpr::getLShr(AndCST, ShAmt); 1093 else 1094 NewAndCST = ConstantExpr::getShl(AndCST, ShAmt); 1095 LHSI->setOperand(1, NewAndCST); 1096 LHSI->setOperand(0, Shift->getOperand(0)); 1097 Worklist.Add(Shift); // Shift is dead. 1098 return &ICI; 1099 } 1100 } 1101 } 1102 1103 // Turn ((X >> Y) & C) == 0 into (X & (C << Y)) == 0. The later is 1104 // preferable because it allows the C<<Y expression to be hoisted out 1105 // of a loop if Y is invariant and X is not. 1106 if (Shift && Shift->hasOneUse() && RHSV == 0 && 1107 ICI.isEquality() && !Shift->isArithmeticShift() && 1108 !isa<Constant>(Shift->getOperand(0))) { 1109 // Compute C << Y. 1110 Value *NS; 1111 if (Shift->getOpcode() == Instruction::LShr) { 1112 NS = Builder->CreateShl(AndCST, Shift->getOperand(1), "tmp"); 1113 } else { 1114 // Insert a logical shift. 1115 NS = Builder->CreateLShr(AndCST, Shift->getOperand(1), "tmp"); 1116 } 1117 1118 // Compute X & (C << Y). 1119 Value *NewAnd = 1120 Builder->CreateAnd(Shift->getOperand(0), NS, LHSI->getName()); 1121 1122 ICI.setOperand(0, NewAnd); 1123 return &ICI; 1124 } 1125 } 1126 1127 // Try to optimize things like "A[i]&42 == 0" to index computations. 1128 if (LoadInst *LI = dyn_cast<LoadInst>(LHSI->getOperand(0))) { 1129 if (GetElementPtrInst *GEP = 1130 dyn_cast<GetElementPtrInst>(LI->getOperand(0))) 1131 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(GEP->getOperand(0))) 1132 if (GV->isConstant() && GV->hasDefinitiveInitializer() && 1133 !LI->isVolatile() && isa<ConstantInt>(LHSI->getOperand(1))) { 1134 ConstantInt *C = cast<ConstantInt>(LHSI->getOperand(1)); 1135 if (Instruction *Res = FoldCmpLoadFromIndexedGlobal(GEP, GV,ICI, C)) 1136 return Res; 1137 } 1138 } 1139 break; 1140 1141 case Instruction::Or: { 1142 if (!ICI.isEquality() || !RHS->isNullValue() || !LHSI->hasOneUse()) 1143 break; 1144 Value *P, *Q; 1145 if (match(LHSI, m_Or(m_PtrToInt(m_Value(P)), m_PtrToInt(m_Value(Q))))) { 1146 // Simplify icmp eq (or (ptrtoint P), (ptrtoint Q)), 0 1147 // -> and (icmp eq P, null), (icmp eq Q, null). 1148 1149 Value *ICIP = Builder->CreateICmp(ICI.getPredicate(), P, 1150 Constant::getNullValue(P->getType())); 1151 Value *ICIQ = Builder->CreateICmp(ICI.getPredicate(), Q, 1152 Constant::getNullValue(Q->getType())); 1153 Instruction *Op; 1154 if (ICI.getPredicate() == ICmpInst::ICMP_EQ) 1155 Op = BinaryOperator::CreateAnd(ICIP, ICIQ); 1156 else 1157 Op = BinaryOperator::CreateOr(ICIP, ICIQ); 1158 return Op; 1159 } 1160 break; 1161 } 1162 1163 case Instruction::Shl: { // (icmp pred (shl X, ShAmt), CI) 1164 ConstantInt *ShAmt = dyn_cast<ConstantInt>(LHSI->getOperand(1)); 1165 if (!ShAmt) break; 1166 1167 uint32_t TypeBits = RHSV.getBitWidth(); 1168 1169 // Check that the shift amount is in range. If not, don't perform 1170 // undefined shifts. When the shift is visited it will be 1171 // simplified. 1172 if (ShAmt->uge(TypeBits)) 1173 break; 1174 1175 if (ICI.isEquality()) { 1176 // If we are comparing against bits always shifted out, the 1177 // comparison cannot succeed. 1178 Constant *Comp = 1179 ConstantExpr::getShl(ConstantExpr::getLShr(RHS, ShAmt), 1180 ShAmt); 1181 if (Comp != RHS) {// Comparing against a bit that we know is zero. 1182 bool IsICMP_NE = ICI.getPredicate() == ICmpInst::ICMP_NE; 1183 Constant *Cst = 1184 ConstantInt::get(Type::getInt1Ty(ICI.getContext()), IsICMP_NE); 1185 return ReplaceInstUsesWith(ICI, Cst); 1186 } 1187 1188 if (LHSI->hasOneUse()) { 1189 // Otherwise strength reduce the shift into an and. 1190 uint32_t ShAmtVal = (uint32_t)ShAmt->getLimitedValue(TypeBits); 1191 Constant *Mask = 1192 ConstantInt::get(ICI.getContext(), APInt::getLowBitsSet(TypeBits, 1193 TypeBits-ShAmtVal)); 1194 1195 Value *And = 1196 Builder->CreateAnd(LHSI->getOperand(0),Mask, LHSI->getName()+".mask"); 1197 return new ICmpInst(ICI.getPredicate(), And, 1198 ConstantInt::get(ICI.getContext(), 1199 RHSV.lshr(ShAmtVal))); 1200 } 1201 } 1202 1203 // Otherwise, if this is a comparison of the sign bit, simplify to and/test. 1204 bool TrueIfSigned = false; 1205 if (LHSI->hasOneUse() && 1206 isSignBitCheck(ICI.getPredicate(), RHS, TrueIfSigned)) { 1207 // (X << 31) <s 0 --> (X&1) != 0 1208 Constant *Mask = ConstantInt::get(ICI.getContext(), APInt(TypeBits, 1) << 1209 (TypeBits-ShAmt->getZExtValue()-1)); 1210 Value *And = 1211 Builder->CreateAnd(LHSI->getOperand(0), Mask, LHSI->getName()+".mask"); 1212 return new ICmpInst(TrueIfSigned ? ICmpInst::ICMP_NE : ICmpInst::ICMP_EQ, 1213 And, Constant::getNullValue(And->getType())); 1214 } 1215 break; 1216 } 1217 1218 case Instruction::LShr: // (icmp pred (shr X, ShAmt), CI) 1219 case Instruction::AShr: { 1220 // Only handle equality comparisons of shift-by-constant. 1221 ConstantInt *ShAmt = dyn_cast<ConstantInt>(LHSI->getOperand(1)); 1222 if (!ShAmt || !ICI.isEquality()) break; 1223 1224 // Check that the shift amount is in range. If not, don't perform 1225 // undefined shifts. When the shift is visited it will be 1226 // simplified. 1227 uint32_t TypeBits = RHSV.getBitWidth(); 1228 if (ShAmt->uge(TypeBits)) 1229 break; 1230 1231 uint32_t ShAmtVal = (uint32_t)ShAmt->getLimitedValue(TypeBits); 1232 1233 // If we are comparing against bits always shifted out, the 1234 // comparison cannot succeed. 1235 APInt Comp = RHSV << ShAmtVal; 1236 if (LHSI->getOpcode() == Instruction::LShr) 1237 Comp = Comp.lshr(ShAmtVal); 1238 else 1239 Comp = Comp.ashr(ShAmtVal); 1240 1241 if (Comp != RHSV) { // Comparing against a bit that we know is zero. 1242 bool IsICMP_NE = ICI.getPredicate() == ICmpInst::ICMP_NE; 1243 Constant *Cst = ConstantInt::get(Type::getInt1Ty(ICI.getContext()), 1244 IsICMP_NE); 1245 return ReplaceInstUsesWith(ICI, Cst); 1246 } 1247 1248 // Otherwise, check to see if the bits shifted out are known to be zero. 1249 // If so, we can compare against the unshifted value: 1250 // (X & 4) >> 1 == 2 --> (X & 4) == 4. 1251 if (LHSI->hasOneUse() && 1252 MaskedValueIsZero(LHSI->getOperand(0), 1253 APInt::getLowBitsSet(Comp.getBitWidth(), ShAmtVal))) { 1254 return new ICmpInst(ICI.getPredicate(), LHSI->getOperand(0), 1255 ConstantExpr::getShl(RHS, ShAmt)); 1256 } 1257 1258 if (LHSI->hasOneUse()) { 1259 // Otherwise strength reduce the shift into an and. 1260 APInt Val(APInt::getHighBitsSet(TypeBits, TypeBits - ShAmtVal)); 1261 Constant *Mask = ConstantInt::get(ICI.getContext(), Val); 1262 1263 Value *And = Builder->CreateAnd(LHSI->getOperand(0), 1264 Mask, LHSI->getName()+".mask"); 1265 return new ICmpInst(ICI.getPredicate(), And, 1266 ConstantExpr::getShl(RHS, ShAmt)); 1267 } 1268 break; 1269 } 1270 1271 case Instruction::SDiv: 1272 case Instruction::UDiv: 1273 // Fold: icmp pred ([us]div X, C1), C2 -> range test 1274 // Fold this div into the comparison, producing a range check. 1275 // Determine, based on the divide type, what the range is being 1276 // checked. If there is an overflow on the low or high side, remember 1277 // it, otherwise compute the range [low, hi) bounding the new value. 1278 // See: InsertRangeTest above for the kinds of replacements possible. 1279 if (ConstantInt *DivRHS = dyn_cast<ConstantInt>(LHSI->getOperand(1))) 1280 if (Instruction *R = FoldICmpDivCst(ICI, cast<BinaryOperator>(LHSI), 1281 DivRHS)) 1282 return R; 1283 break; 1284 1285 case Instruction::Add: 1286 // Fold: icmp pred (add X, C1), C2 1287 if (!ICI.isEquality()) { 1288 ConstantInt *LHSC = dyn_cast<ConstantInt>(LHSI->getOperand(1)); 1289 if (!LHSC) break; 1290 const APInt &LHSV = LHSC->getValue(); 1291 1292 ConstantRange CR = ICI.makeConstantRange(ICI.getPredicate(), RHSV) 1293 .subtract(LHSV); 1294 1295 if (ICI.isSigned()) { 1296 if (CR.getLower().isSignBit()) { 1297 return new ICmpInst(ICmpInst::ICMP_SLT, LHSI->getOperand(0), 1298 ConstantInt::get(ICI.getContext(),CR.getUpper())); 1299 } else if (CR.getUpper().isSignBit()) { 1300 return new ICmpInst(ICmpInst::ICMP_SGE, LHSI->getOperand(0), 1301 ConstantInt::get(ICI.getContext(),CR.getLower())); 1302 } 1303 } else { 1304 if (CR.getLower().isMinValue()) { 1305 return new ICmpInst(ICmpInst::ICMP_ULT, LHSI->getOperand(0), 1306 ConstantInt::get(ICI.getContext(),CR.getUpper())); 1307 } else if (CR.getUpper().isMinValue()) { 1308 return new ICmpInst(ICmpInst::ICMP_UGE, LHSI->getOperand(0), 1309 ConstantInt::get(ICI.getContext(),CR.getLower())); 1310 } 1311 } 1312 } 1313 break; 1314 } 1315 1316 // Simplify icmp_eq and icmp_ne instructions with integer constant RHS. 1317 if (ICI.isEquality()) { 1318 bool isICMP_NE = ICI.getPredicate() == ICmpInst::ICMP_NE; 1319 1320 // If the first operand is (add|sub|and|or|xor|rem) with a constant, and 1321 // the second operand is a constant, simplify a bit. 1322 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(LHSI)) { 1323 switch (BO->getOpcode()) { 1324 case Instruction::SRem: 1325 // If we have a signed (X % (2^c)) == 0, turn it into an unsigned one. 1326 if (RHSV == 0 && isa<ConstantInt>(BO->getOperand(1)) &&BO->hasOneUse()){ 1327 const APInt &V = cast<ConstantInt>(BO->getOperand(1))->getValue(); 1328 if (V.sgt(1) && V.isPowerOf2()) { 1329 Value *NewRem = 1330 Builder->CreateURem(BO->getOperand(0), BO->getOperand(1), 1331 BO->getName()); 1332 return new ICmpInst(ICI.getPredicate(), NewRem, 1333 Constant::getNullValue(BO->getType())); 1334 } 1335 } 1336 break; 1337 case Instruction::Add: 1338 // Replace ((add A, B) != C) with (A != C-B) if B & C are constants. 1339 if (ConstantInt *BOp1C = dyn_cast<ConstantInt>(BO->getOperand(1))) { 1340 if (BO->hasOneUse()) 1341 return new ICmpInst(ICI.getPredicate(), BO->getOperand(0), 1342 ConstantExpr::getSub(RHS, BOp1C)); 1343 } else if (RHSV == 0) { 1344 // Replace ((add A, B) != 0) with (A != -B) if A or B is 1345 // efficiently invertible, or if the add has just this one use. 1346 Value *BOp0 = BO->getOperand(0), *BOp1 = BO->getOperand(1); 1347 1348 if (Value *NegVal = dyn_castNegVal(BOp1)) 1349 return new ICmpInst(ICI.getPredicate(), BOp0, NegVal); 1350 else if (Value *NegVal = dyn_castNegVal(BOp0)) 1351 return new ICmpInst(ICI.getPredicate(), NegVal, BOp1); 1352 else if (BO->hasOneUse()) { 1353 Value *Neg = Builder->CreateNeg(BOp1); 1354 Neg->takeName(BO); 1355 return new ICmpInst(ICI.getPredicate(), BOp0, Neg); 1356 } 1357 } 1358 break; 1359 case Instruction::Xor: 1360 // For the xor case, we can xor two constants together, eliminating 1361 // the explicit xor. 1362 if (Constant *BOC = dyn_cast<Constant>(BO->getOperand(1))) 1363 return new ICmpInst(ICI.getPredicate(), BO->getOperand(0), 1364 ConstantExpr::getXor(RHS, BOC)); 1365 1366 // FALLTHROUGH 1367 case Instruction::Sub: 1368 // Replace (([sub|xor] A, B) != 0) with (A != B) 1369 if (RHSV == 0) 1370 return new ICmpInst(ICI.getPredicate(), BO->getOperand(0), 1371 BO->getOperand(1)); 1372 break; 1373 1374 case Instruction::Or: 1375 // If bits are being or'd in that are not present in the constant we 1376 // are comparing against, then the comparison could never succeed! 1377 if (Constant *BOC = dyn_cast<Constant>(BO->getOperand(1))) { 1378 Constant *NotCI = ConstantExpr::getNot(RHS); 1379 if (!ConstantExpr::getAnd(BOC, NotCI)->isNullValue()) 1380 return ReplaceInstUsesWith(ICI, 1381 ConstantInt::get(Type::getInt1Ty(ICI.getContext()), 1382 isICMP_NE)); 1383 } 1384 break; 1385 1386 case Instruction::And: 1387 if (ConstantInt *BOC = dyn_cast<ConstantInt>(BO->getOperand(1))) { 1388 // If bits are being compared against that are and'd out, then the 1389 // comparison can never succeed! 1390 if ((RHSV & ~BOC->getValue()) != 0) 1391 return ReplaceInstUsesWith(ICI, 1392 ConstantInt::get(Type::getInt1Ty(ICI.getContext()), 1393 isICMP_NE)); 1394 1395 // If we have ((X & C) == C), turn it into ((X & C) != 0). 1396 if (RHS == BOC && RHSV.isPowerOf2()) 1397 return new ICmpInst(isICMP_NE ? ICmpInst::ICMP_EQ : 1398 ICmpInst::ICMP_NE, LHSI, 1399 Constant::getNullValue(RHS->getType())); 1400 1401 // Replace (and X, (1 << size(X)-1) != 0) with x s< 0 1402 if (BOC->getValue().isSignBit()) { 1403 Value *X = BO->getOperand(0); 1404 Constant *Zero = Constant::getNullValue(X->getType()); 1405 ICmpInst::Predicate pred = isICMP_NE ? 1406 ICmpInst::ICMP_SLT : ICmpInst::ICMP_SGE; 1407 return new ICmpInst(pred, X, Zero); 1408 } 1409 1410 // ((X & ~7) == 0) --> X < 8 1411 if (RHSV == 0 && isHighOnes(BOC)) { 1412 Value *X = BO->getOperand(0); 1413 Constant *NegX = ConstantExpr::getNeg(BOC); 1414 ICmpInst::Predicate pred = isICMP_NE ? 1415 ICmpInst::ICMP_UGE : ICmpInst::ICMP_ULT; 1416 return new ICmpInst(pred, X, NegX); 1417 } 1418 } 1419 default: break; 1420 } 1421 } else if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(LHSI)) { 1422 // Handle icmp {eq|ne} <intrinsic>, intcst. 1423 switch (II->getIntrinsicID()) { 1424 case Intrinsic::bswap: 1425 Worklist.Add(II); 1426 ICI.setOperand(0, II->getArgOperand(0)); 1427 ICI.setOperand(1, ConstantInt::get(II->getContext(), RHSV.byteSwap())); 1428 return &ICI; 1429 case Intrinsic::ctlz: 1430 case Intrinsic::cttz: 1431 // ctz(A) == bitwidth(a) -> A == 0 and likewise for != 1432 if (RHSV == RHS->getType()->getBitWidth()) { 1433 Worklist.Add(II); 1434 ICI.setOperand(0, II->getArgOperand(0)); 1435 ICI.setOperand(1, ConstantInt::get(RHS->getType(), 0)); 1436 return &ICI; 1437 } 1438 break; 1439 case Intrinsic::ctpop: 1440 // popcount(A) == 0 -> A == 0 and likewise for != 1441 if (RHS->isZero()) { 1442 Worklist.Add(II); 1443 ICI.setOperand(0, II->getArgOperand(0)); 1444 ICI.setOperand(1, RHS); 1445 return &ICI; 1446 } 1447 break; 1448 default: 1449 break; 1450 } 1451 } 1452 } 1453 return 0; 1454} 1455 1456/// visitICmpInstWithCastAndCast - Handle icmp (cast x to y), (cast/cst). 1457/// We only handle extending casts so far. 1458/// 1459Instruction *InstCombiner::visitICmpInstWithCastAndCast(ICmpInst &ICI) { 1460 const CastInst *LHSCI = cast<CastInst>(ICI.getOperand(0)); 1461 Value *LHSCIOp = LHSCI->getOperand(0); 1462 const Type *SrcTy = LHSCIOp->getType(); 1463 const Type *DestTy = LHSCI->getType(); 1464 Value *RHSCIOp; 1465 1466 // Turn icmp (ptrtoint x), (ptrtoint/c) into a compare of the input if the 1467 // integer type is the same size as the pointer type. 1468 if (TD && LHSCI->getOpcode() == Instruction::PtrToInt && 1469 TD->getPointerSizeInBits() == 1470 cast<IntegerType>(DestTy)->getBitWidth()) { 1471 Value *RHSOp = 0; 1472 if (Constant *RHSC = dyn_cast<Constant>(ICI.getOperand(1))) { 1473 RHSOp = ConstantExpr::getIntToPtr(RHSC, SrcTy); 1474 } else if (PtrToIntInst *RHSC = dyn_cast<PtrToIntInst>(ICI.getOperand(1))) { 1475 RHSOp = RHSC->getOperand(0); 1476 // If the pointer types don't match, insert a bitcast. 1477 if (LHSCIOp->getType() != RHSOp->getType()) 1478 RHSOp = Builder->CreateBitCast(RHSOp, LHSCIOp->getType()); 1479 } 1480 1481 if (RHSOp) 1482 return new ICmpInst(ICI.getPredicate(), LHSCIOp, RHSOp); 1483 } 1484 1485 // The code below only handles extension cast instructions, so far. 1486 // Enforce this. 1487 if (LHSCI->getOpcode() != Instruction::ZExt && 1488 LHSCI->getOpcode() != Instruction::SExt) 1489 return 0; 1490 1491 bool isSignedExt = LHSCI->getOpcode() == Instruction::SExt; 1492 bool isSignedCmp = ICI.isSigned(); 1493 1494 if (CastInst *CI = dyn_cast<CastInst>(ICI.getOperand(1))) { 1495 // Not an extension from the same type? 1496 RHSCIOp = CI->getOperand(0); 1497 if (RHSCIOp->getType() != LHSCIOp->getType()) 1498 return 0; 1499 1500 // If the signedness of the two casts doesn't agree (i.e. one is a sext 1501 // and the other is a zext), then we can't handle this. 1502 if (CI->getOpcode() != LHSCI->getOpcode()) 1503 return 0; 1504 1505 // Deal with equality cases early. 1506 if (ICI.isEquality()) 1507 return new ICmpInst(ICI.getPredicate(), LHSCIOp, RHSCIOp); 1508 1509 // A signed comparison of sign extended values simplifies into a 1510 // signed comparison. 1511 if (isSignedCmp && isSignedExt) 1512 return new ICmpInst(ICI.getPredicate(), LHSCIOp, RHSCIOp); 1513 1514 // The other three cases all fold into an unsigned comparison. 1515 return new ICmpInst(ICI.getUnsignedPredicate(), LHSCIOp, RHSCIOp); 1516 } 1517 1518 // If we aren't dealing with a constant on the RHS, exit early 1519 ConstantInt *CI = dyn_cast<ConstantInt>(ICI.getOperand(1)); 1520 if (!CI) 1521 return 0; 1522 1523 // Compute the constant that would happen if we truncated to SrcTy then 1524 // reextended to DestTy. 1525 Constant *Res1 = ConstantExpr::getTrunc(CI, SrcTy); 1526 Constant *Res2 = ConstantExpr::getCast(LHSCI->getOpcode(), 1527 Res1, DestTy); 1528 1529 // If the re-extended constant didn't change... 1530 if (Res2 == CI) { 1531 // Deal with equality cases early. 1532 if (ICI.isEquality()) 1533 return new ICmpInst(ICI.getPredicate(), LHSCIOp, Res1); 1534 1535 // A signed comparison of sign extended values simplifies into a 1536 // signed comparison. 1537 if (isSignedExt && isSignedCmp) 1538 return new ICmpInst(ICI.getPredicate(), LHSCIOp, Res1); 1539 1540 // The other three cases all fold into an unsigned comparison. 1541 return new ICmpInst(ICI.getUnsignedPredicate(), LHSCIOp, Res1); 1542 } 1543 1544 // The re-extended constant changed so the constant cannot be represented 1545 // in the shorter type. Consequently, we cannot emit a simple comparison. 1546 1547 // First, handle some easy cases. We know the result cannot be equal at this 1548 // point so handle the ICI.isEquality() cases 1549 if (ICI.getPredicate() == ICmpInst::ICMP_EQ) 1550 return ReplaceInstUsesWith(ICI, ConstantInt::getFalse(ICI.getContext())); 1551 if (ICI.getPredicate() == ICmpInst::ICMP_NE) 1552 return ReplaceInstUsesWith(ICI, ConstantInt::getTrue(ICI.getContext())); 1553 1554 // Evaluate the comparison for LT (we invert for GT below). LE and GE cases 1555 // should have been folded away previously and not enter in here. 1556 Value *Result; 1557 if (isSignedCmp) { 1558 // We're performing a signed comparison. 1559 if (cast<ConstantInt>(CI)->getValue().isNegative()) 1560 Result = ConstantInt::getFalse(ICI.getContext()); // X < (small) --> false 1561 else 1562 Result = ConstantInt::getTrue(ICI.getContext()); // X < (large) --> true 1563 } else { 1564 // We're performing an unsigned comparison. 1565 if (isSignedExt) { 1566 // We're performing an unsigned comp with a sign extended value. 1567 // This is true if the input is >= 0. [aka >s -1] 1568 Constant *NegOne = Constant::getAllOnesValue(SrcTy); 1569 Result = Builder->CreateICmpSGT(LHSCIOp, NegOne, ICI.getName()); 1570 } else { 1571 // Unsigned extend & unsigned compare -> always true. 1572 Result = ConstantInt::getTrue(ICI.getContext()); 1573 } 1574 } 1575 1576 // Finally, return the value computed. 1577 if (ICI.getPredicate() == ICmpInst::ICMP_ULT || 1578 ICI.getPredicate() == ICmpInst::ICMP_SLT) 1579 return ReplaceInstUsesWith(ICI, Result); 1580 1581 assert((ICI.getPredicate()==ICmpInst::ICMP_UGT || 1582 ICI.getPredicate()==ICmpInst::ICMP_SGT) && 1583 "ICmp should be folded!"); 1584 if (Constant *CI = dyn_cast<Constant>(Result)) 1585 return ReplaceInstUsesWith(ICI, ConstantExpr::getNot(CI)); 1586 return BinaryOperator::CreateNot(Result); 1587} 1588 1589 1590 1591Instruction *InstCombiner::visitICmpInst(ICmpInst &I) { 1592 bool Changed = false; 1593 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1); 1594 1595 /// Orders the operands of the compare so that they are listed from most 1596 /// complex to least complex. This puts constants before unary operators, 1597 /// before binary operators. 1598 if (getComplexity(Op0) < getComplexity(Op1)) { 1599 I.swapOperands(); 1600 std::swap(Op0, Op1); 1601 Changed = true; 1602 } 1603 1604 if (Value *V = SimplifyICmpInst(I.getPredicate(), Op0, Op1, TD)) 1605 return ReplaceInstUsesWith(I, V); 1606 1607 const Type *Ty = Op0->getType(); 1608 1609 // icmp's with boolean values can always be turned into bitwise operations 1610 if (Ty->isIntegerTy(1)) { 1611 switch (I.getPredicate()) { 1612 default: llvm_unreachable("Invalid icmp instruction!"); 1613 case ICmpInst::ICMP_EQ: { // icmp eq i1 A, B -> ~(A^B) 1614 Value *Xor = Builder->CreateXor(Op0, Op1, I.getName()+"tmp"); 1615 return BinaryOperator::CreateNot(Xor); 1616 } 1617 case ICmpInst::ICMP_NE: // icmp eq i1 A, B -> A^B 1618 return BinaryOperator::CreateXor(Op0, Op1); 1619 1620 case ICmpInst::ICMP_UGT: 1621 std::swap(Op0, Op1); // Change icmp ugt -> icmp ult 1622 // FALL THROUGH 1623 case ICmpInst::ICMP_ULT:{ // icmp ult i1 A, B -> ~A & B 1624 Value *Not = Builder->CreateNot(Op0, I.getName()+"tmp"); 1625 return BinaryOperator::CreateAnd(Not, Op1); 1626 } 1627 case ICmpInst::ICMP_SGT: 1628 std::swap(Op0, Op1); // Change icmp sgt -> icmp slt 1629 // FALL THROUGH 1630 case ICmpInst::ICMP_SLT: { // icmp slt i1 A, B -> A & ~B 1631 Value *Not = Builder->CreateNot(Op1, I.getName()+"tmp"); 1632 return BinaryOperator::CreateAnd(Not, Op0); 1633 } 1634 case ICmpInst::ICMP_UGE: 1635 std::swap(Op0, Op1); // Change icmp uge -> icmp ule 1636 // FALL THROUGH 1637 case ICmpInst::ICMP_ULE: { // icmp ule i1 A, B -> ~A | B 1638 Value *Not = Builder->CreateNot(Op0, I.getName()+"tmp"); 1639 return BinaryOperator::CreateOr(Not, Op1); 1640 } 1641 case ICmpInst::ICMP_SGE: 1642 std::swap(Op0, Op1); // Change icmp sge -> icmp sle 1643 // FALL THROUGH 1644 case ICmpInst::ICMP_SLE: { // icmp sle i1 A, B -> A | ~B 1645 Value *Not = Builder->CreateNot(Op1, I.getName()+"tmp"); 1646 return BinaryOperator::CreateOr(Not, Op0); 1647 } 1648 } 1649 } 1650 1651 unsigned BitWidth = 0; 1652 if (TD) 1653 BitWidth = TD->getTypeSizeInBits(Ty->getScalarType()); 1654 else if (Ty->isIntOrIntVectorTy()) 1655 BitWidth = Ty->getScalarSizeInBits(); 1656 1657 bool isSignBit = false; 1658 1659 // See if we are doing a comparison with a constant. 1660 if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) { 1661 Value *A = 0, *B = 0; 1662 1663 // (icmp ne/eq (sub A B) 0) -> (icmp ne/eq A, B) 1664 if (I.isEquality() && CI->isZero() && 1665 match(Op0, m_Sub(m_Value(A), m_Value(B)))) { 1666 // (icmp cond A B) if cond is equality 1667 return new ICmpInst(I.getPredicate(), A, B); 1668 } 1669 1670 // If we have an icmp le or icmp ge instruction, turn it into the 1671 // appropriate icmp lt or icmp gt instruction. This allows us to rely on 1672 // them being folded in the code below. The SimplifyICmpInst code has 1673 // already handled the edge cases for us, so we just assert on them. 1674 switch (I.getPredicate()) { 1675 default: break; 1676 case ICmpInst::ICMP_ULE: 1677 assert(!CI->isMaxValue(false)); // A <=u MAX -> TRUE 1678 return new ICmpInst(ICmpInst::ICMP_ULT, Op0, 1679 ConstantInt::get(CI->getContext(), CI->getValue()+1)); 1680 case ICmpInst::ICMP_SLE: 1681 assert(!CI->isMaxValue(true)); // A <=s MAX -> TRUE 1682 return new ICmpInst(ICmpInst::ICMP_SLT, Op0, 1683 ConstantInt::get(CI->getContext(), CI->getValue()+1)); 1684 case ICmpInst::ICMP_UGE: 1685 assert(!CI->isMinValue(false)); // A >=u MIN -> TRUE 1686 return new ICmpInst(ICmpInst::ICMP_UGT, Op0, 1687 ConstantInt::get(CI->getContext(), CI->getValue()-1)); 1688 case ICmpInst::ICMP_SGE: 1689 assert(!CI->isMinValue(true)); // A >=s MIN -> TRUE 1690 return new ICmpInst(ICmpInst::ICMP_SGT, Op0, 1691 ConstantInt::get(CI->getContext(), CI->getValue()-1)); 1692 } 1693 1694 // If this comparison is a normal comparison, it demands all 1695 // bits, if it is a sign bit comparison, it only demands the sign bit. 1696 bool UnusedBit; 1697 isSignBit = isSignBitCheck(I.getPredicate(), CI, UnusedBit); 1698 } 1699 1700 // See if we can fold the comparison based on range information we can get 1701 // by checking whether bits are known to be zero or one in the input. 1702 if (BitWidth != 0) { 1703 APInt Op0KnownZero(BitWidth, 0), Op0KnownOne(BitWidth, 0); 1704 APInt Op1KnownZero(BitWidth, 0), Op1KnownOne(BitWidth, 0); 1705 1706 if (SimplifyDemandedBits(I.getOperandUse(0), 1707 isSignBit ? APInt::getSignBit(BitWidth) 1708 : APInt::getAllOnesValue(BitWidth), 1709 Op0KnownZero, Op0KnownOne, 0)) 1710 return &I; 1711 if (SimplifyDemandedBits(I.getOperandUse(1), 1712 APInt::getAllOnesValue(BitWidth), 1713 Op1KnownZero, Op1KnownOne, 0)) 1714 return &I; 1715 1716 // Given the known and unknown bits, compute a range that the LHS could be 1717 // in. Compute the Min, Max and RHS values based on the known bits. For the 1718 // EQ and NE we use unsigned values. 1719 APInt Op0Min(BitWidth, 0), Op0Max(BitWidth, 0); 1720 APInt Op1Min(BitWidth, 0), Op1Max(BitWidth, 0); 1721 if (I.isSigned()) { 1722 ComputeSignedMinMaxValuesFromKnownBits(Op0KnownZero, Op0KnownOne, 1723 Op0Min, Op0Max); 1724 ComputeSignedMinMaxValuesFromKnownBits(Op1KnownZero, Op1KnownOne, 1725 Op1Min, Op1Max); 1726 } else { 1727 ComputeUnsignedMinMaxValuesFromKnownBits(Op0KnownZero, Op0KnownOne, 1728 Op0Min, Op0Max); 1729 ComputeUnsignedMinMaxValuesFromKnownBits(Op1KnownZero, Op1KnownOne, 1730 Op1Min, Op1Max); 1731 } 1732 1733 // If Min and Max are known to be the same, then SimplifyDemandedBits 1734 // figured out that the LHS is a constant. Just constant fold this now so 1735 // that code below can assume that Min != Max. 1736 if (!isa<Constant>(Op0) && Op0Min == Op0Max) 1737 return new ICmpInst(I.getPredicate(), 1738 ConstantInt::get(I.getContext(), Op0Min), Op1); 1739 if (!isa<Constant>(Op1) && Op1Min == Op1Max) 1740 return new ICmpInst(I.getPredicate(), Op0, 1741 ConstantInt::get(I.getContext(), Op1Min)); 1742 1743 // Based on the range information we know about the LHS, see if we can 1744 // simplify this comparison. For example, (x&4) < 8 is always true. 1745 switch (I.getPredicate()) { 1746 default: llvm_unreachable("Unknown icmp opcode!"); 1747 case ICmpInst::ICMP_EQ: 1748 if (Op0Max.ult(Op1Min) || Op0Min.ugt(Op1Max)) 1749 return ReplaceInstUsesWith(I, ConstantInt::getFalse(I.getContext())); 1750 break; 1751 case ICmpInst::ICMP_NE: 1752 if (Op0Max.ult(Op1Min) || Op0Min.ugt(Op1Max)) 1753 return ReplaceInstUsesWith(I, ConstantInt::getTrue(I.getContext())); 1754 break; 1755 case ICmpInst::ICMP_ULT: 1756 if (Op0Max.ult(Op1Min)) // A <u B -> true if max(A) < min(B) 1757 return ReplaceInstUsesWith(I, ConstantInt::getTrue(I.getContext())); 1758 if (Op0Min.uge(Op1Max)) // A <u B -> false if min(A) >= max(B) 1759 return ReplaceInstUsesWith(I, ConstantInt::getFalse(I.getContext())); 1760 if (Op1Min == Op0Max) // A <u B -> A != B if max(A) == min(B) 1761 return new ICmpInst(ICmpInst::ICMP_NE, Op0, Op1); 1762 if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) { 1763 if (Op1Max == Op0Min+1) // A <u C -> A == C-1 if min(A)+1 == C 1764 return new ICmpInst(ICmpInst::ICMP_EQ, Op0, 1765 ConstantInt::get(CI->getContext(), CI->getValue()-1)); 1766 1767 // (x <u 2147483648) -> (x >s -1) -> true if sign bit clear 1768 if (CI->isMinValue(true)) 1769 return new ICmpInst(ICmpInst::ICMP_SGT, Op0, 1770 Constant::getAllOnesValue(Op0->getType())); 1771 } 1772 break; 1773 case ICmpInst::ICMP_UGT: 1774 if (Op0Min.ugt(Op1Max)) // A >u B -> true if min(A) > max(B) 1775 return ReplaceInstUsesWith(I, ConstantInt::getTrue(I.getContext())); 1776 if (Op0Max.ule(Op1Min)) // A >u B -> false if max(A) <= max(B) 1777 return ReplaceInstUsesWith(I, ConstantInt::getFalse(I.getContext())); 1778 1779 if (Op1Max == Op0Min) // A >u B -> A != B if min(A) == max(B) 1780 return new ICmpInst(ICmpInst::ICMP_NE, Op0, Op1); 1781 if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) { 1782 if (Op1Min == Op0Max-1) // A >u C -> A == C+1 if max(a)-1 == C 1783 return new ICmpInst(ICmpInst::ICMP_EQ, Op0, 1784 ConstantInt::get(CI->getContext(), CI->getValue()+1)); 1785 1786 // (x >u 2147483647) -> (x <s 0) -> true if sign bit set 1787 if (CI->isMaxValue(true)) 1788 return new ICmpInst(ICmpInst::ICMP_SLT, Op0, 1789 Constant::getNullValue(Op0->getType())); 1790 } 1791 break; 1792 case ICmpInst::ICMP_SLT: 1793 if (Op0Max.slt(Op1Min)) // A <s B -> true if max(A) < min(C) 1794 return ReplaceInstUsesWith(I, ConstantInt::getTrue(I.getContext())); 1795 if (Op0Min.sge(Op1Max)) // A <s B -> false if min(A) >= max(C) 1796 return ReplaceInstUsesWith(I, ConstantInt::getFalse(I.getContext())); 1797 if (Op1Min == Op0Max) // A <s B -> A != B if max(A) == min(B) 1798 return new ICmpInst(ICmpInst::ICMP_NE, Op0, Op1); 1799 if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) { 1800 if (Op1Max == Op0Min+1) // A <s C -> A == C-1 if min(A)+1 == C 1801 return new ICmpInst(ICmpInst::ICMP_EQ, Op0, 1802 ConstantInt::get(CI->getContext(), CI->getValue()-1)); 1803 } 1804 break; 1805 case ICmpInst::ICMP_SGT: 1806 if (Op0Min.sgt(Op1Max)) // A >s B -> true if min(A) > max(B) 1807 return ReplaceInstUsesWith(I, ConstantInt::getTrue(I.getContext())); 1808 if (Op0Max.sle(Op1Min)) // A >s B -> false if max(A) <= min(B) 1809 return ReplaceInstUsesWith(I, ConstantInt::getFalse(I.getContext())); 1810 1811 if (Op1Max == Op0Min) // A >s B -> A != B if min(A) == max(B) 1812 return new ICmpInst(ICmpInst::ICMP_NE, Op0, Op1); 1813 if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) { 1814 if (Op1Min == Op0Max-1) // A >s C -> A == C+1 if max(A)-1 == C 1815 return new ICmpInst(ICmpInst::ICMP_EQ, Op0, 1816 ConstantInt::get(CI->getContext(), CI->getValue()+1)); 1817 } 1818 break; 1819 case ICmpInst::ICMP_SGE: 1820 assert(!isa<ConstantInt>(Op1) && "ICMP_SGE with ConstantInt not folded!"); 1821 if (Op0Min.sge(Op1Max)) // A >=s B -> true if min(A) >= max(B) 1822 return ReplaceInstUsesWith(I, ConstantInt::getTrue(I.getContext())); 1823 if (Op0Max.slt(Op1Min)) // A >=s B -> false if max(A) < min(B) 1824 return ReplaceInstUsesWith(I, ConstantInt::getFalse(I.getContext())); 1825 break; 1826 case ICmpInst::ICMP_SLE: 1827 assert(!isa<ConstantInt>(Op1) && "ICMP_SLE with ConstantInt not folded!"); 1828 if (Op0Max.sle(Op1Min)) // A <=s B -> true if max(A) <= min(B) 1829 return ReplaceInstUsesWith(I, ConstantInt::getTrue(I.getContext())); 1830 if (Op0Min.sgt(Op1Max)) // A <=s B -> false if min(A) > max(B) 1831 return ReplaceInstUsesWith(I, ConstantInt::getFalse(I.getContext())); 1832 break; 1833 case ICmpInst::ICMP_UGE: 1834 assert(!isa<ConstantInt>(Op1) && "ICMP_UGE with ConstantInt not folded!"); 1835 if (Op0Min.uge(Op1Max)) // A >=u B -> true if min(A) >= max(B) 1836 return ReplaceInstUsesWith(I, ConstantInt::getTrue(I.getContext())); 1837 if (Op0Max.ult(Op1Min)) // A >=u B -> false if max(A) < min(B) 1838 return ReplaceInstUsesWith(I, ConstantInt::getFalse(I.getContext())); 1839 break; 1840 case ICmpInst::ICMP_ULE: 1841 assert(!isa<ConstantInt>(Op1) && "ICMP_ULE with ConstantInt not folded!"); 1842 if (Op0Max.ule(Op1Min)) // A <=u B -> true if max(A) <= min(B) 1843 return ReplaceInstUsesWith(I, ConstantInt::getTrue(I.getContext())); 1844 if (Op0Min.ugt(Op1Max)) // A <=u B -> false if min(A) > max(B) 1845 return ReplaceInstUsesWith(I, ConstantInt::getFalse(I.getContext())); 1846 break; 1847 } 1848 1849 // Turn a signed comparison into an unsigned one if both operands 1850 // are known to have the same sign. 1851 if (I.isSigned() && 1852 ((Op0KnownZero.isNegative() && Op1KnownZero.isNegative()) || 1853 (Op0KnownOne.isNegative() && Op1KnownOne.isNegative()))) 1854 return new ICmpInst(I.getUnsignedPredicate(), Op0, Op1); 1855 } 1856 1857 // Test if the ICmpInst instruction is used exclusively by a select as 1858 // part of a minimum or maximum operation. If so, refrain from doing 1859 // any other folding. This helps out other analyses which understand 1860 // non-obfuscated minimum and maximum idioms, such as ScalarEvolution 1861 // and CodeGen. And in this case, at least one of the comparison 1862 // operands has at least one user besides the compare (the select), 1863 // which would often largely negate the benefit of folding anyway. 1864 if (I.hasOneUse()) 1865 if (SelectInst *SI = dyn_cast<SelectInst>(*I.use_begin())) 1866 if ((SI->getOperand(1) == Op0 && SI->getOperand(2) == Op1) || 1867 (SI->getOperand(2) == Op0 && SI->getOperand(1) == Op1)) 1868 return 0; 1869 1870 // See if we are doing a comparison between a constant and an instruction that 1871 // can be folded into the comparison. 1872 if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) { 1873 // Since the RHS is a ConstantInt (CI), if the left hand side is an 1874 // instruction, see if that instruction also has constants so that the 1875 // instruction can be folded into the icmp 1876 if (Instruction *LHSI = dyn_cast<Instruction>(Op0)) 1877 if (Instruction *Res = visitICmpInstWithInstAndIntCst(I, LHSI, CI)) 1878 return Res; 1879 } 1880 1881 // Handle icmp with constant (but not simple integer constant) RHS 1882 if (Constant *RHSC = dyn_cast<Constant>(Op1)) { 1883 if (Instruction *LHSI = dyn_cast<Instruction>(Op0)) 1884 switch (LHSI->getOpcode()) { 1885 case Instruction::GetElementPtr: 1886 // icmp pred GEP (P, int 0, int 0, int 0), null -> icmp pred P, null 1887 if (RHSC->isNullValue() && 1888 cast<GetElementPtrInst>(LHSI)->hasAllZeroIndices()) 1889 return new ICmpInst(I.getPredicate(), LHSI->getOperand(0), 1890 Constant::getNullValue(LHSI->getOperand(0)->getType())); 1891 break; 1892 case Instruction::PHI: 1893 // Only fold icmp into the PHI if the phi and icmp are in the same 1894 // block. If in the same block, we're encouraging jump threading. If 1895 // not, we are just pessimizing the code by making an i1 phi. 1896 if (LHSI->getParent() == I.getParent()) 1897 if (Instruction *NV = FoldOpIntoPhi(I, true)) 1898 return NV; 1899 break; 1900 case Instruction::Select: { 1901 // If either operand of the select is a constant, we can fold the 1902 // comparison into the select arms, which will cause one to be 1903 // constant folded and the select turned into a bitwise or. 1904 Value *Op1 = 0, *Op2 = 0; 1905 if (Constant *C = dyn_cast<Constant>(LHSI->getOperand(1))) 1906 Op1 = ConstantExpr::getICmp(I.getPredicate(), C, RHSC); 1907 if (Constant *C = dyn_cast<Constant>(LHSI->getOperand(2))) 1908 Op2 = ConstantExpr::getICmp(I.getPredicate(), C, RHSC); 1909 1910 // We only want to perform this transformation if it will not lead to 1911 // additional code. This is true if either both sides of the select 1912 // fold to a constant (in which case the icmp is replaced with a select 1913 // which will usually simplify) or this is the only user of the 1914 // select (in which case we are trading a select+icmp for a simpler 1915 // select+icmp). 1916 if ((Op1 && Op2) || (LHSI->hasOneUse() && (Op1 || Op2))) { 1917 if (!Op1) 1918 Op1 = Builder->CreateICmp(I.getPredicate(), LHSI->getOperand(1), 1919 RHSC, I.getName()); 1920 if (!Op2) 1921 Op2 = Builder->CreateICmp(I.getPredicate(), LHSI->getOperand(2), 1922 RHSC, I.getName()); 1923 return SelectInst::Create(LHSI->getOperand(0), Op1, Op2); 1924 } 1925 break; 1926 } 1927 case Instruction::IntToPtr: 1928 // icmp pred inttoptr(X), null -> icmp pred X, 0 1929 if (RHSC->isNullValue() && TD && 1930 TD->getIntPtrType(RHSC->getContext()) == 1931 LHSI->getOperand(0)->getType()) 1932 return new ICmpInst(I.getPredicate(), LHSI->getOperand(0), 1933 Constant::getNullValue(LHSI->getOperand(0)->getType())); 1934 break; 1935 1936 case Instruction::Load: 1937 // Try to optimize things like "A[i] > 4" to index computations. 1938 if (GetElementPtrInst *GEP = 1939 dyn_cast<GetElementPtrInst>(LHSI->getOperand(0))) { 1940 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(GEP->getOperand(0))) 1941 if (GV->isConstant() && GV->hasDefinitiveInitializer() && 1942 !cast<LoadInst>(LHSI)->isVolatile()) 1943 if (Instruction *Res = FoldCmpLoadFromIndexedGlobal(GEP, GV, I)) 1944 return Res; 1945 } 1946 break; 1947 } 1948 } 1949 1950 // If we can optimize a 'icmp GEP, P' or 'icmp P, GEP', do so now. 1951 if (GEPOperator *GEP = dyn_cast<GEPOperator>(Op0)) 1952 if (Instruction *NI = FoldGEPICmp(GEP, Op1, I.getPredicate(), I)) 1953 return NI; 1954 if (GEPOperator *GEP = dyn_cast<GEPOperator>(Op1)) 1955 if (Instruction *NI = FoldGEPICmp(GEP, Op0, 1956 ICmpInst::getSwappedPredicate(I.getPredicate()), I)) 1957 return NI; 1958 1959 // Test to see if the operands of the icmp are casted versions of other 1960 // values. If the ptr->ptr cast can be stripped off both arguments, we do so 1961 // now. 1962 if (BitCastInst *CI = dyn_cast<BitCastInst>(Op0)) { 1963 if (Op0->getType()->isPointerTy() && 1964 (isa<Constant>(Op1) || isa<BitCastInst>(Op1))) { 1965 // We keep moving the cast from the left operand over to the right 1966 // operand, where it can often be eliminated completely. 1967 Op0 = CI->getOperand(0); 1968 1969 // If operand #1 is a bitcast instruction, it must also be a ptr->ptr cast 1970 // so eliminate it as well. 1971 if (BitCastInst *CI2 = dyn_cast<BitCastInst>(Op1)) 1972 Op1 = CI2->getOperand(0); 1973 1974 // If Op1 is a constant, we can fold the cast into the constant. 1975 if (Op0->getType() != Op1->getType()) { 1976 if (Constant *Op1C = dyn_cast<Constant>(Op1)) { 1977 Op1 = ConstantExpr::getBitCast(Op1C, Op0->getType()); 1978 } else { 1979 // Otherwise, cast the RHS right before the icmp 1980 Op1 = Builder->CreateBitCast(Op1, Op0->getType()); 1981 } 1982 } 1983 return new ICmpInst(I.getPredicate(), Op0, Op1); 1984 } 1985 } 1986 1987 if (isa<CastInst>(Op0)) { 1988 // Handle the special case of: icmp (cast bool to X), <cst> 1989 // This comes up when you have code like 1990 // int X = A < B; 1991 // if (X) ... 1992 // For generality, we handle any zero-extension of any operand comparison 1993 // with a constant or another cast from the same type. 1994 if (isa<Constant>(Op1) || isa<CastInst>(Op1)) 1995 if (Instruction *R = visitICmpInstWithCastAndCast(I)) 1996 return R; 1997 } 1998 1999 // See if it's the same type of instruction on the left and right. 2000 if (BinaryOperator *Op0I = dyn_cast<BinaryOperator>(Op0)) { 2001 if (BinaryOperator *Op1I = dyn_cast<BinaryOperator>(Op1)) { 2002 if (Op0I->getOpcode() == Op1I->getOpcode() && Op0I->hasOneUse() && 2003 Op1I->hasOneUse() && Op0I->getOperand(1) == Op1I->getOperand(1)) { 2004 switch (Op0I->getOpcode()) { 2005 default: break; 2006 case Instruction::Add: 2007 case Instruction::Sub: 2008 case Instruction::Xor: 2009 if (I.isEquality()) // a+x icmp eq/ne b+x --> a icmp b 2010 return new ICmpInst(I.getPredicate(), Op0I->getOperand(0), 2011 Op1I->getOperand(0)); 2012 // icmp u/s (a ^ signbit), (b ^ signbit) --> icmp s/u a, b 2013 if (ConstantInt *CI = dyn_cast<ConstantInt>(Op0I->getOperand(1))) { 2014 if (CI->getValue().isSignBit()) { 2015 ICmpInst::Predicate Pred = I.isSigned() 2016 ? I.getUnsignedPredicate() 2017 : I.getSignedPredicate(); 2018 return new ICmpInst(Pred, Op0I->getOperand(0), 2019 Op1I->getOperand(0)); 2020 } 2021 2022 if (CI->getValue().isMaxSignedValue()) { 2023 ICmpInst::Predicate Pred = I.isSigned() 2024 ? I.getUnsignedPredicate() 2025 : I.getSignedPredicate(); 2026 Pred = I.getSwappedPredicate(Pred); 2027 return new ICmpInst(Pred, Op0I->getOperand(0), 2028 Op1I->getOperand(0)); 2029 } 2030 } 2031 break; 2032 case Instruction::Mul: 2033 if (!I.isEquality()) 2034 break; 2035 2036 if (ConstantInt *CI = dyn_cast<ConstantInt>(Op0I->getOperand(1))) { 2037 // a * Cst icmp eq/ne b * Cst --> a & Mask icmp b & Mask 2038 // Mask = -1 >> count-trailing-zeros(Cst). 2039 if (!CI->isZero() && !CI->isOne()) { 2040 const APInt &AP = CI->getValue(); 2041 ConstantInt *Mask = ConstantInt::get(I.getContext(), 2042 APInt::getLowBitsSet(AP.getBitWidth(), 2043 AP.getBitWidth() - 2044 AP.countTrailingZeros())); 2045 Value *And1 = Builder->CreateAnd(Op0I->getOperand(0), Mask); 2046 Value *And2 = Builder->CreateAnd(Op1I->getOperand(0), Mask); 2047 return new ICmpInst(I.getPredicate(), And1, And2); 2048 } 2049 } 2050 break; 2051 } 2052 } 2053 } 2054 } 2055 2056 // ~x < ~y --> y < x 2057 { Value *A, *B; 2058 if (match(Op0, m_Not(m_Value(A))) && 2059 match(Op1, m_Not(m_Value(B)))) 2060 return new ICmpInst(I.getPredicate(), B, A); 2061 } 2062 2063 if (I.isEquality()) { 2064 Value *A, *B, *C, *D; 2065 2066 // -x == -y --> x == y 2067 if (match(Op0, m_Neg(m_Value(A))) && 2068 match(Op1, m_Neg(m_Value(B)))) 2069 return new ICmpInst(I.getPredicate(), A, B); 2070 2071 if (match(Op0, m_Xor(m_Value(A), m_Value(B)))) { 2072 if (A == Op1 || B == Op1) { // (A^B) == A -> B == 0 2073 Value *OtherVal = A == Op1 ? B : A; 2074 return new ICmpInst(I.getPredicate(), OtherVal, 2075 Constant::getNullValue(A->getType())); 2076 } 2077 2078 if (match(Op1, m_Xor(m_Value(C), m_Value(D)))) { 2079 // A^c1 == C^c2 --> A == C^(c1^c2) 2080 ConstantInt *C1, *C2; 2081 if (match(B, m_ConstantInt(C1)) && 2082 match(D, m_ConstantInt(C2)) && Op1->hasOneUse()) { 2083 Constant *NC = ConstantInt::get(I.getContext(), 2084 C1->getValue() ^ C2->getValue()); 2085 Value *Xor = Builder->CreateXor(C, NC, "tmp"); 2086 return new ICmpInst(I.getPredicate(), A, Xor); 2087 } 2088 2089 // A^B == A^D -> B == D 2090 if (A == C) return new ICmpInst(I.getPredicate(), B, D); 2091 if (A == D) return new ICmpInst(I.getPredicate(), B, C); 2092 if (B == C) return new ICmpInst(I.getPredicate(), A, D); 2093 if (B == D) return new ICmpInst(I.getPredicate(), A, C); 2094 } 2095 } 2096 2097 if (match(Op1, m_Xor(m_Value(A), m_Value(B))) && 2098 (A == Op0 || B == Op0)) { 2099 // A == (A^B) -> B == 0 2100 Value *OtherVal = A == Op0 ? B : A; 2101 return new ICmpInst(I.getPredicate(), OtherVal, 2102 Constant::getNullValue(A->getType())); 2103 } 2104 2105 // (A-B) == A -> B == 0 2106 if (match(Op0, m_Sub(m_Specific(Op1), m_Value(B)))) 2107 return new ICmpInst(I.getPredicate(), B, 2108 Constant::getNullValue(B->getType())); 2109 2110 // A == (A-B) -> B == 0 2111 if (match(Op1, m_Sub(m_Specific(Op0), m_Value(B)))) 2112 return new ICmpInst(I.getPredicate(), B, 2113 Constant::getNullValue(B->getType())); 2114 2115 // (X&Z) == (Y&Z) -> (X^Y) & Z == 0 2116 if (Op0->hasOneUse() && Op1->hasOneUse() && 2117 match(Op0, m_And(m_Value(A), m_Value(B))) && 2118 match(Op1, m_And(m_Value(C), m_Value(D)))) { 2119 Value *X = 0, *Y = 0, *Z = 0; 2120 2121 if (A == C) { 2122 X = B; Y = D; Z = A; 2123 } else if (A == D) { 2124 X = B; Y = C; Z = A; 2125 } else if (B == C) { 2126 X = A; Y = D; Z = B; 2127 } else if (B == D) { 2128 X = A; Y = C; Z = B; 2129 } 2130 2131 if (X) { // Build (X^Y) & Z 2132 Op1 = Builder->CreateXor(X, Y, "tmp"); 2133 Op1 = Builder->CreateAnd(Op1, Z, "tmp"); 2134 I.setOperand(0, Op1); 2135 I.setOperand(1, Constant::getNullValue(Op1->getType())); 2136 return &I; 2137 } 2138 } 2139 } 2140 2141 { 2142 Value *X; ConstantInt *Cst; 2143 // icmp X+Cst, X 2144 if (match(Op0, m_Add(m_Value(X), m_ConstantInt(Cst))) && Op1 == X) 2145 return FoldICmpAddOpCst(I, X, Cst, I.getPredicate(), Op0); 2146 2147 // icmp X, X+Cst 2148 if (match(Op1, m_Add(m_Value(X), m_ConstantInt(Cst))) && Op0 == X) 2149 return FoldICmpAddOpCst(I, X, Cst, I.getSwappedPredicate(), Op1); 2150 } 2151 return Changed ? &I : 0; 2152} 2153 2154 2155 2156 2157 2158 2159/// FoldFCmp_IntToFP_Cst - Fold fcmp ([us]itofp x, cst) if possible. 2160/// 2161Instruction *InstCombiner::FoldFCmp_IntToFP_Cst(FCmpInst &I, 2162 Instruction *LHSI, 2163 Constant *RHSC) { 2164 if (!isa<ConstantFP>(RHSC)) return 0; 2165 const APFloat &RHS = cast<ConstantFP>(RHSC)->getValueAPF(); 2166 2167 // Get the width of the mantissa. We don't want to hack on conversions that 2168 // might lose information from the integer, e.g. "i64 -> float" 2169 int MantissaWidth = LHSI->getType()->getFPMantissaWidth(); 2170 if (MantissaWidth == -1) return 0; // Unknown. 2171 2172 // Check to see that the input is converted from an integer type that is small 2173 // enough that preserves all bits. TODO: check here for "known" sign bits. 2174 // This would allow us to handle (fptosi (x >>s 62) to float) if x is i64 f.e. 2175 unsigned InputSize = LHSI->getOperand(0)->getType()->getScalarSizeInBits(); 2176 2177 // If this is a uitofp instruction, we need an extra bit to hold the sign. 2178 bool LHSUnsigned = isa<UIToFPInst>(LHSI); 2179 if (LHSUnsigned) 2180 ++InputSize; 2181 2182 // If the conversion would lose info, don't hack on this. 2183 if ((int)InputSize > MantissaWidth) 2184 return 0; 2185 2186 // Otherwise, we can potentially simplify the comparison. We know that it 2187 // will always come through as an integer value and we know the constant is 2188 // not a NAN (it would have been previously simplified). 2189 assert(!RHS.isNaN() && "NaN comparison not already folded!"); 2190 2191 ICmpInst::Predicate Pred; 2192 switch (I.getPredicate()) { 2193 default: llvm_unreachable("Unexpected predicate!"); 2194 case FCmpInst::FCMP_UEQ: 2195 case FCmpInst::FCMP_OEQ: 2196 Pred = ICmpInst::ICMP_EQ; 2197 break; 2198 case FCmpInst::FCMP_UGT: 2199 case FCmpInst::FCMP_OGT: 2200 Pred = LHSUnsigned ? ICmpInst::ICMP_UGT : ICmpInst::ICMP_SGT; 2201 break; 2202 case FCmpInst::FCMP_UGE: 2203 case FCmpInst::FCMP_OGE: 2204 Pred = LHSUnsigned ? ICmpInst::ICMP_UGE : ICmpInst::ICMP_SGE; 2205 break; 2206 case FCmpInst::FCMP_ULT: 2207 case FCmpInst::FCMP_OLT: 2208 Pred = LHSUnsigned ? ICmpInst::ICMP_ULT : ICmpInst::ICMP_SLT; 2209 break; 2210 case FCmpInst::FCMP_ULE: 2211 case FCmpInst::FCMP_OLE: 2212 Pred = LHSUnsigned ? ICmpInst::ICMP_ULE : ICmpInst::ICMP_SLE; 2213 break; 2214 case FCmpInst::FCMP_UNE: 2215 case FCmpInst::FCMP_ONE: 2216 Pred = ICmpInst::ICMP_NE; 2217 break; 2218 case FCmpInst::FCMP_ORD: 2219 return ReplaceInstUsesWith(I, ConstantInt::getTrue(I.getContext())); 2220 case FCmpInst::FCMP_UNO: 2221 return ReplaceInstUsesWith(I, ConstantInt::getFalse(I.getContext())); 2222 } 2223 2224 const IntegerType *IntTy = cast<IntegerType>(LHSI->getOperand(0)->getType()); 2225 2226 // Now we know that the APFloat is a normal number, zero or inf. 2227 2228 // See if the FP constant is too large for the integer. For example, 2229 // comparing an i8 to 300.0. 2230 unsigned IntWidth = IntTy->getScalarSizeInBits(); 2231 2232 if (!LHSUnsigned) { 2233 // If the RHS value is > SignedMax, fold the comparison. This handles +INF 2234 // and large values. 2235 APFloat SMax(RHS.getSemantics(), APFloat::fcZero, false); 2236 SMax.convertFromAPInt(APInt::getSignedMaxValue(IntWidth), true, 2237 APFloat::rmNearestTiesToEven); 2238 if (SMax.compare(RHS) == APFloat::cmpLessThan) { // smax < 13123.0 2239 if (Pred == ICmpInst::ICMP_NE || Pred == ICmpInst::ICMP_SLT || 2240 Pred == ICmpInst::ICMP_SLE) 2241 return ReplaceInstUsesWith(I, ConstantInt::getTrue(I.getContext())); 2242 return ReplaceInstUsesWith(I, ConstantInt::getFalse(I.getContext())); 2243 } 2244 } else { 2245 // If the RHS value is > UnsignedMax, fold the comparison. This handles 2246 // +INF and large values. 2247 APFloat UMax(RHS.getSemantics(), APFloat::fcZero, false); 2248 UMax.convertFromAPInt(APInt::getMaxValue(IntWidth), false, 2249 APFloat::rmNearestTiesToEven); 2250 if (UMax.compare(RHS) == APFloat::cmpLessThan) { // umax < 13123.0 2251 if (Pred == ICmpInst::ICMP_NE || Pred == ICmpInst::ICMP_ULT || 2252 Pred == ICmpInst::ICMP_ULE) 2253 return ReplaceInstUsesWith(I, ConstantInt::getTrue(I.getContext())); 2254 return ReplaceInstUsesWith(I, ConstantInt::getFalse(I.getContext())); 2255 } 2256 } 2257 2258 if (!LHSUnsigned) { 2259 // See if the RHS value is < SignedMin. 2260 APFloat SMin(RHS.getSemantics(), APFloat::fcZero, false); 2261 SMin.convertFromAPInt(APInt::getSignedMinValue(IntWidth), true, 2262 APFloat::rmNearestTiesToEven); 2263 if (SMin.compare(RHS) == APFloat::cmpGreaterThan) { // smin > 12312.0 2264 if (Pred == ICmpInst::ICMP_NE || Pred == ICmpInst::ICMP_SGT || 2265 Pred == ICmpInst::ICMP_SGE) 2266 return ReplaceInstUsesWith(I, ConstantInt::getTrue(I.getContext())); 2267 return ReplaceInstUsesWith(I, ConstantInt::getFalse(I.getContext())); 2268 } 2269 } 2270 2271 // Okay, now we know that the FP constant fits in the range [SMIN, SMAX] or 2272 // [0, UMAX], but it may still be fractional. See if it is fractional by 2273 // casting the FP value to the integer value and back, checking for equality. 2274 // Don't do this for zero, because -0.0 is not fractional. 2275 Constant *RHSInt = LHSUnsigned 2276 ? ConstantExpr::getFPToUI(RHSC, IntTy) 2277 : ConstantExpr::getFPToSI(RHSC, IntTy); 2278 if (!RHS.isZero()) { 2279 bool Equal = LHSUnsigned 2280 ? ConstantExpr::getUIToFP(RHSInt, RHSC->getType()) == RHSC 2281 : ConstantExpr::getSIToFP(RHSInt, RHSC->getType()) == RHSC; 2282 if (!Equal) { 2283 // If we had a comparison against a fractional value, we have to adjust 2284 // the compare predicate and sometimes the value. RHSC is rounded towards 2285 // zero at this point. 2286 switch (Pred) { 2287 default: llvm_unreachable("Unexpected integer comparison!"); 2288 case ICmpInst::ICMP_NE: // (float)int != 4.4 --> true 2289 return ReplaceInstUsesWith(I, ConstantInt::getTrue(I.getContext())); 2290 case ICmpInst::ICMP_EQ: // (float)int == 4.4 --> false 2291 return ReplaceInstUsesWith(I, ConstantInt::getFalse(I.getContext())); 2292 case ICmpInst::ICMP_ULE: 2293 // (float)int <= 4.4 --> int <= 4 2294 // (float)int <= -4.4 --> false 2295 if (RHS.isNegative()) 2296 return ReplaceInstUsesWith(I, ConstantInt::getFalse(I.getContext())); 2297 break; 2298 case ICmpInst::ICMP_SLE: 2299 // (float)int <= 4.4 --> int <= 4 2300 // (float)int <= -4.4 --> int < -4 2301 if (RHS.isNegative()) 2302 Pred = ICmpInst::ICMP_SLT; 2303 break; 2304 case ICmpInst::ICMP_ULT: 2305 // (float)int < -4.4 --> false 2306 // (float)int < 4.4 --> int <= 4 2307 if (RHS.isNegative()) 2308 return ReplaceInstUsesWith(I, ConstantInt::getFalse(I.getContext())); 2309 Pred = ICmpInst::ICMP_ULE; 2310 break; 2311 case ICmpInst::ICMP_SLT: 2312 // (float)int < -4.4 --> int < -4 2313 // (float)int < 4.4 --> int <= 4 2314 if (!RHS.isNegative()) 2315 Pred = ICmpInst::ICMP_SLE; 2316 break; 2317 case ICmpInst::ICMP_UGT: 2318 // (float)int > 4.4 --> int > 4 2319 // (float)int > -4.4 --> true 2320 if (RHS.isNegative()) 2321 return ReplaceInstUsesWith(I, ConstantInt::getTrue(I.getContext())); 2322 break; 2323 case ICmpInst::ICMP_SGT: 2324 // (float)int > 4.4 --> int > 4 2325 // (float)int > -4.4 --> int >= -4 2326 if (RHS.isNegative()) 2327 Pred = ICmpInst::ICMP_SGE; 2328 break; 2329 case ICmpInst::ICMP_UGE: 2330 // (float)int >= -4.4 --> true 2331 // (float)int >= 4.4 --> int > 4 2332 if (!RHS.isNegative()) 2333 return ReplaceInstUsesWith(I, ConstantInt::getTrue(I.getContext())); 2334 Pred = ICmpInst::ICMP_UGT; 2335 break; 2336 case ICmpInst::ICMP_SGE: 2337 // (float)int >= -4.4 --> int >= -4 2338 // (float)int >= 4.4 --> int > 4 2339 if (!RHS.isNegative()) 2340 Pred = ICmpInst::ICMP_SGT; 2341 break; 2342 } 2343 } 2344 } 2345 2346 // Lower this FP comparison into an appropriate integer version of the 2347 // comparison. 2348 return new ICmpInst(Pred, LHSI->getOperand(0), RHSInt); 2349} 2350 2351Instruction *InstCombiner::visitFCmpInst(FCmpInst &I) { 2352 bool Changed = false; 2353 2354 /// Orders the operands of the compare so that they are listed from most 2355 /// complex to least complex. This puts constants before unary operators, 2356 /// before binary operators. 2357 if (getComplexity(I.getOperand(0)) < getComplexity(I.getOperand(1))) { 2358 I.swapOperands(); 2359 Changed = true; 2360 } 2361 2362 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1); 2363 2364 if (Value *V = SimplifyFCmpInst(I.getPredicate(), Op0, Op1, TD)) 2365 return ReplaceInstUsesWith(I, V); 2366 2367 // Simplify 'fcmp pred X, X' 2368 if (Op0 == Op1) { 2369 switch (I.getPredicate()) { 2370 default: llvm_unreachable("Unknown predicate!"); 2371 case FCmpInst::FCMP_UNO: // True if unordered: isnan(X) | isnan(Y) 2372 case FCmpInst::FCMP_ULT: // True if unordered or less than 2373 case FCmpInst::FCMP_UGT: // True if unordered or greater than 2374 case FCmpInst::FCMP_UNE: // True if unordered or not equal 2375 // Canonicalize these to be 'fcmp uno %X, 0.0'. 2376 I.setPredicate(FCmpInst::FCMP_UNO); 2377 I.setOperand(1, Constant::getNullValue(Op0->getType())); 2378 return &I; 2379 2380 case FCmpInst::FCMP_ORD: // True if ordered (no nans) 2381 case FCmpInst::FCMP_OEQ: // True if ordered and equal 2382 case FCmpInst::FCMP_OGE: // True if ordered and greater than or equal 2383 case FCmpInst::FCMP_OLE: // True if ordered and less than or equal 2384 // Canonicalize these to be 'fcmp ord %X, 0.0'. 2385 I.setPredicate(FCmpInst::FCMP_ORD); 2386 I.setOperand(1, Constant::getNullValue(Op0->getType())); 2387 return &I; 2388 } 2389 } 2390 2391 // Handle fcmp with constant RHS 2392 if (Constant *RHSC = dyn_cast<Constant>(Op1)) { 2393 if (Instruction *LHSI = dyn_cast<Instruction>(Op0)) 2394 switch (LHSI->getOpcode()) { 2395 case Instruction::PHI: 2396 // Only fold fcmp into the PHI if the phi and fcmp are in the same 2397 // block. If in the same block, we're encouraging jump threading. If 2398 // not, we are just pessimizing the code by making an i1 phi. 2399 if (LHSI->getParent() == I.getParent()) 2400 if (Instruction *NV = FoldOpIntoPhi(I, true)) 2401 return NV; 2402 break; 2403 case Instruction::SIToFP: 2404 case Instruction::UIToFP: 2405 if (Instruction *NV = FoldFCmp_IntToFP_Cst(I, LHSI, RHSC)) 2406 return NV; 2407 break; 2408 case Instruction::Select: { 2409 // If either operand of the select is a constant, we can fold the 2410 // comparison into the select arms, which will cause one to be 2411 // constant folded and the select turned into a bitwise or. 2412 Value *Op1 = 0, *Op2 = 0; 2413 if (LHSI->hasOneUse()) { 2414 if (Constant *C = dyn_cast<Constant>(LHSI->getOperand(1))) { 2415 // Fold the known value into the constant operand. 2416 Op1 = ConstantExpr::getCompare(I.getPredicate(), C, RHSC); 2417 // Insert a new FCmp of the other select operand. 2418 Op2 = Builder->CreateFCmp(I.getPredicate(), 2419 LHSI->getOperand(2), RHSC, I.getName()); 2420 } else if (Constant *C = dyn_cast<Constant>(LHSI->getOperand(2))) { 2421 // Fold the known value into the constant operand. 2422 Op2 = ConstantExpr::getCompare(I.getPredicate(), C, RHSC); 2423 // Insert a new FCmp of the other select operand. 2424 Op1 = Builder->CreateFCmp(I.getPredicate(), LHSI->getOperand(1), 2425 RHSC, I.getName()); 2426 } 2427 } 2428 2429 if (Op1) 2430 return SelectInst::Create(LHSI->getOperand(0), Op1, Op2); 2431 break; 2432 } 2433 case Instruction::Load: 2434 if (GetElementPtrInst *GEP = 2435 dyn_cast<GetElementPtrInst>(LHSI->getOperand(0))) { 2436 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(GEP->getOperand(0))) 2437 if (GV->isConstant() && GV->hasDefinitiveInitializer() && 2438 !cast<LoadInst>(LHSI)->isVolatile()) 2439 if (Instruction *Res = FoldCmpLoadFromIndexedGlobal(GEP, GV, I)) 2440 return Res; 2441 } 2442 break; 2443 } 2444 } 2445 2446 return Changed ? &I : 0; 2447} 2448