InlineFunction.cpp revision 28c531cdbb403c59f492d3361ec9e8581f2a7ab2
1//===- InlineFunction.cpp - Code to perform function inlining -------------===// 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 inlining of a function into a call site, resolving 11// parameters and the return value as appropriate. 12// 13//===----------------------------------------------------------------------===// 14 15#include "llvm/Transforms/Utils/Cloning.h" 16#include "llvm/Constants.h" 17#include "llvm/DerivedTypes.h" 18#include "llvm/Module.h" 19#include "llvm/Instructions.h" 20#include "llvm/Intrinsics.h" 21#include "llvm/Attributes.h" 22#include "llvm/Analysis/CallGraph.h" 23#include "llvm/Target/TargetData.h" 24#include "llvm/ADT/SmallVector.h" 25#include "llvm/ADT/StringExtras.h" 26#include "llvm/Support/CallSite.h" 27using namespace llvm; 28 29bool llvm::InlineFunction(CallInst *CI, CallGraph *CG, const TargetData *TD) { 30 return InlineFunction(CallSite(CI), CG, TD); 31} 32bool llvm::InlineFunction(InvokeInst *II, CallGraph *CG, const TargetData *TD) { 33 return InlineFunction(CallSite(II), CG, TD); 34} 35 36/// HandleInlinedInvoke - If we inlined an invoke site, we need to convert calls 37/// in the body of the inlined function into invokes and turn unwind 38/// instructions into branches to the invoke unwind dest. 39/// 40/// II is the invoke instruction being inlined. FirstNewBlock is the first 41/// block of the inlined code (the last block is the end of the function), 42/// and InlineCodeInfo is information about the code that got inlined. 43static void HandleInlinedInvoke(InvokeInst *II, BasicBlock *FirstNewBlock, 44 ClonedCodeInfo &InlinedCodeInfo, 45 CallGraph *CG) { 46 BasicBlock *InvokeDest = II->getUnwindDest(); 47 std::vector<Value*> InvokeDestPHIValues; 48 49 // If there are PHI nodes in the unwind destination block, we need to 50 // keep track of which values came into them from this invoke, then remove 51 // the entry for this block. 52 BasicBlock *InvokeBlock = II->getParent(); 53 for (BasicBlock::iterator I = InvokeDest->begin(); isa<PHINode>(I); ++I) { 54 PHINode *PN = cast<PHINode>(I); 55 // Save the value to use for this edge. 56 InvokeDestPHIValues.push_back(PN->getIncomingValueForBlock(InvokeBlock)); 57 } 58 59 Function *Caller = FirstNewBlock->getParent(); 60 61 // The inlined code is currently at the end of the function, scan from the 62 // start of the inlined code to its end, checking for stuff we need to 63 // rewrite. 64 if (InlinedCodeInfo.ContainsCalls || InlinedCodeInfo.ContainsUnwinds) { 65 for (Function::iterator BB = FirstNewBlock, E = Caller->end(); 66 BB != E; ++BB) { 67 if (InlinedCodeInfo.ContainsCalls) { 68 for (BasicBlock::iterator BBI = BB->begin(), E = BB->end(); BBI != E; ){ 69 Instruction *I = BBI++; 70 71 // We only need to check for function calls: inlined invoke 72 // instructions require no special handling. 73 if (!isa<CallInst>(I)) continue; 74 CallInst *CI = cast<CallInst>(I); 75 76 // If this call cannot unwind, don't convert it to an invoke. 77 if (CI->doesNotThrow()) 78 continue; 79 80 // Convert this function call into an invoke instruction. 81 // First, split the basic block. 82 BasicBlock *Split = BB->splitBasicBlock(CI, CI->getName()+".noexc"); 83 84 // Next, create the new invoke instruction, inserting it at the end 85 // of the old basic block. 86 SmallVector<Value*, 8> InvokeArgs(CI->op_begin()+1, CI->op_end()); 87 InvokeInst *II = 88 InvokeInst::Create(CI->getCalledValue(), Split, InvokeDest, 89 InvokeArgs.begin(), InvokeArgs.end(), 90 CI->getName(), BB->getTerminator()); 91 II->setCallingConv(CI->getCallingConv()); 92 II->setAttributes(CI->getAttributes()); 93 94 // Make sure that anything using the call now uses the invoke! 95 CI->replaceAllUsesWith(II); 96 97 // Update the callgraph. 98 if (CG) { 99 // We should be able to do this: 100 // (*CG)[Caller]->replaceCallSite(CI, II); 101 // but that fails if the old call site isn't in the call graph, 102 // which, because of LLVM bug 3601, it sometimes isn't. 103 CallGraphNode *CGN = (*CG)[Caller]; 104 for (CallGraphNode::iterator NI = CGN->begin(), NE = CGN->end(); 105 NI != NE; ++NI) { 106 if (NI->first == CI) { 107 NI->first = II; 108 break; 109 } 110 } 111 } 112 113 // Delete the unconditional branch inserted by splitBasicBlock 114 BB->getInstList().pop_back(); 115 Split->getInstList().pop_front(); // Delete the original call 116 117 // Update any PHI nodes in the exceptional block to indicate that 118 // there is now a new entry in them. 119 unsigned i = 0; 120 for (BasicBlock::iterator I = InvokeDest->begin(); 121 isa<PHINode>(I); ++I, ++i) { 122 PHINode *PN = cast<PHINode>(I); 123 PN->addIncoming(InvokeDestPHIValues[i], BB); 124 } 125 126 // This basic block is now complete, start scanning the next one. 127 break; 128 } 129 } 130 131 if (UnwindInst *UI = dyn_cast<UnwindInst>(BB->getTerminator())) { 132 // An UnwindInst requires special handling when it gets inlined into an 133 // invoke site. Once this happens, we know that the unwind would cause 134 // a control transfer to the invoke exception destination, so we can 135 // transform it into a direct branch to the exception destination. 136 BranchInst::Create(InvokeDest, UI); 137 138 // Delete the unwind instruction! 139 UI->eraseFromParent(); 140 141 // Update any PHI nodes in the exceptional block to indicate that 142 // there is now a new entry in them. 143 unsigned i = 0; 144 for (BasicBlock::iterator I = InvokeDest->begin(); 145 isa<PHINode>(I); ++I, ++i) { 146 PHINode *PN = cast<PHINode>(I); 147 PN->addIncoming(InvokeDestPHIValues[i], BB); 148 } 149 } 150 } 151 } 152 153 // Now that everything is happy, we have one final detail. The PHI nodes in 154 // the exception destination block still have entries due to the original 155 // invoke instruction. Eliminate these entries (which might even delete the 156 // PHI node) now. 157 InvokeDest->removePredecessor(II->getParent()); 158} 159 160/// UpdateCallGraphAfterInlining - Once we have cloned code over from a callee 161/// into the caller, update the specified callgraph to reflect the changes we 162/// made. Note that it's possible that not all code was copied over, so only 163/// some edges of the callgraph may remain. 164static void UpdateCallGraphAfterInlining(CallSite CS, 165 Function::iterator FirstNewBlock, 166 DenseMap<const Value*, Value*> &ValueMap, 167 CallGraph &CG) { 168 const Function *Caller = CS.getInstruction()->getParent()->getParent(); 169 const Function *Callee = CS.getCalledFunction(); 170 CallGraphNode *CalleeNode = CG[Callee]; 171 CallGraphNode *CallerNode = CG[Caller]; 172 173 // Since we inlined some uninlined call sites in the callee into the caller, 174 // add edges from the caller to all of the callees of the callee. 175 CallGraphNode::iterator I = CalleeNode->begin(), E = CalleeNode->end(); 176 177 // Consider the case where CalleeNode == CallerNode. 178 CallGraphNode::CalledFunctionsVector CallCache; 179 if (CalleeNode == CallerNode) { 180 CallCache.assign(I, E); 181 I = CallCache.begin(); 182 E = CallCache.end(); 183 } 184 185 for (; I != E; ++I) { 186 const Instruction *OrigCall = I->first.getInstruction(); 187 188 DenseMap<const Value*, Value*>::iterator VMI = ValueMap.find(OrigCall); 189 // Only copy the edge if the call was inlined! 190 if (VMI != ValueMap.end() && VMI->second) { 191 // If the call was inlined, but then constant folded, there is no edge to 192 // add. Check for this case. 193 if (Instruction *NewCall = dyn_cast<Instruction>(VMI->second)) 194 CallerNode->addCalledFunction(CallSite::get(NewCall), I->second); 195 } 196 } 197 // Update the call graph by deleting the edge from Callee to Caller. We must 198 // do this after the loop above in case Caller and Callee are the same. 199 CallerNode->removeCallEdgeFor(CS); 200} 201 202 203// InlineFunction - This function inlines the called function into the basic 204// block of the caller. This returns false if it is not possible to inline this 205// call. The program is still in a well defined state if this occurs though. 206// 207// Note that this only does one level of inlining. For example, if the 208// instruction 'call B' is inlined, and 'B' calls 'C', then the call to 'C' now 209// exists in the instruction stream. Similiarly this will inline a recursive 210// function by one level. 211// 212bool llvm::InlineFunction(CallSite CS, CallGraph *CG, const TargetData *TD) { 213 Instruction *TheCall = CS.getInstruction(); 214 assert(TheCall->getParent() && TheCall->getParent()->getParent() && 215 "Instruction not in function!"); 216 217 const Function *CalledFunc = CS.getCalledFunction(); 218 if (CalledFunc == 0 || // Can't inline external function or indirect 219 CalledFunc->isDeclaration() || // call, or call to a vararg function! 220 CalledFunc->getFunctionType()->isVarArg()) return false; 221 222 223 // If the call to the callee is not a tail call, we must clear the 'tail' 224 // flags on any calls that we inline. 225 bool MustClearTailCallFlags = 226 !(isa<CallInst>(TheCall) && cast<CallInst>(TheCall)->isTailCall()); 227 228 // If the call to the callee cannot throw, set the 'nounwind' flag on any 229 // calls that we inline. 230 bool MarkNoUnwind = CS.doesNotThrow(); 231 232 BasicBlock *OrigBB = TheCall->getParent(); 233 Function *Caller = OrigBB->getParent(); 234 235 // GC poses two hazards to inlining, which only occur when the callee has GC: 236 // 1. If the caller has no GC, then the callee's GC must be propagated to the 237 // caller. 238 // 2. If the caller has a differing GC, it is invalid to inline. 239 if (CalledFunc->hasGC()) { 240 if (!Caller->hasGC()) 241 Caller->setGC(CalledFunc->getGC()); 242 else if (CalledFunc->getGC() != Caller->getGC()) 243 return false; 244 } 245 246 // Get an iterator to the last basic block in the function, which will have 247 // the new function inlined after it. 248 // 249 Function::iterator LastBlock = &Caller->back(); 250 251 // Make sure to capture all of the return instructions from the cloned 252 // function. 253 std::vector<ReturnInst*> Returns; 254 ClonedCodeInfo InlinedFunctionInfo; 255 Function::iterator FirstNewBlock; 256 257 { // Scope to destroy ValueMap after cloning. 258 DenseMap<const Value*, Value*> ValueMap; 259 260 assert(CalledFunc->arg_size() == CS.arg_size() && 261 "No varargs calls can be inlined!"); 262 263 // Calculate the vector of arguments to pass into the function cloner, which 264 // matches up the formal to the actual argument values. 265 CallSite::arg_iterator AI = CS.arg_begin(); 266 unsigned ArgNo = 0; 267 for (Function::const_arg_iterator I = CalledFunc->arg_begin(), 268 E = CalledFunc->arg_end(); I != E; ++I, ++AI, ++ArgNo) { 269 Value *ActualArg = *AI; 270 271 // When byval arguments actually inlined, we need to make the copy implied 272 // by them explicit. However, we don't do this if the callee is readonly 273 // or readnone, because the copy would be unneeded: the callee doesn't 274 // modify the struct. 275 if (CalledFunc->paramHasAttr(ArgNo+1, Attribute::ByVal) && 276 !CalledFunc->onlyReadsMemory()) { 277 const Type *AggTy = cast<PointerType>(I->getType())->getElementType(); 278 const Type *VoidPtrTy = PointerType::getUnqual(Type::Int8Ty); 279 280 // Create the alloca. If we have TargetData, use nice alignment. 281 unsigned Align = 1; 282 if (TD) Align = TD->getPrefTypeAlignment(AggTy); 283 Value *NewAlloca = new AllocaInst(AggTy, 0, Align, I->getName(), 284 Caller->begin()->begin()); 285 // Emit a memcpy. 286 const Type *Tys[] = { Type::Int64Ty }; 287 Function *MemCpyFn = Intrinsic::getDeclaration(Caller->getParent(), 288 Intrinsic::memcpy, 289 Tys, 1); 290 Value *DestCast = new BitCastInst(NewAlloca, VoidPtrTy, "tmp", TheCall); 291 Value *SrcCast = new BitCastInst(*AI, VoidPtrTy, "tmp", TheCall); 292 293 Value *Size; 294 if (TD == 0) 295 Size = ConstantExpr::getSizeOf(AggTy); 296 else 297 Size = ConstantInt::get(Type::Int64Ty, TD->getTypeStoreSize(AggTy)); 298 299 // Always generate a memcpy of alignment 1 here because we don't know 300 // the alignment of the src pointer. Other optimizations can infer 301 // better alignment. 302 Value *CallArgs[] = { 303 DestCast, SrcCast, Size, ConstantInt::get(Type::Int32Ty, 1) 304 }; 305 CallInst *TheMemCpy = 306 CallInst::Create(MemCpyFn, CallArgs, CallArgs+4, "", TheCall); 307 308 // If we have a call graph, update it. 309 if (CG) { 310 CallGraphNode *MemCpyCGN = CG->getOrInsertFunction(MemCpyFn); 311 CallGraphNode *CallerNode = (*CG)[Caller]; 312 CallerNode->addCalledFunction(TheMemCpy, MemCpyCGN); 313 } 314 315 // Uses of the argument in the function should use our new alloca 316 // instead. 317 ActualArg = NewAlloca; 318 } 319 320 ValueMap[I] = ActualArg; 321 } 322 323 // We want the inliner to prune the code as it copies. We would LOVE to 324 // have no dead or constant instructions leftover after inlining occurs 325 // (which can happen, e.g., because an argument was constant), but we'll be 326 // happy with whatever the cloner can do. 327 CloneAndPruneFunctionInto(Caller, CalledFunc, ValueMap, Returns, ".i", 328 &InlinedFunctionInfo, TD); 329 330 // Remember the first block that is newly cloned over. 331 FirstNewBlock = LastBlock; ++FirstNewBlock; 332 333 // Update the callgraph if requested. 334 if (CG) 335 UpdateCallGraphAfterInlining(CS, FirstNewBlock, ValueMap, *CG); 336 } 337 338 // If there are any alloca instructions in the block that used to be the entry 339 // block for the callee, move them to the entry block of the caller. First 340 // calculate which instruction they should be inserted before. We insert the 341 // instructions at the end of the current alloca list. 342 // 343 { 344 BasicBlock::iterator InsertPoint = Caller->begin()->begin(); 345 for (BasicBlock::iterator I = FirstNewBlock->begin(), 346 E = FirstNewBlock->end(); I != E; ) 347 if (AllocaInst *AI = dyn_cast<AllocaInst>(I++)) { 348 // If the alloca is now dead, remove it. This often occurs due to code 349 // specialization. 350 if (AI->use_empty()) { 351 AI->eraseFromParent(); 352 continue; 353 } 354 355 if (isa<Constant>(AI->getArraySize())) { 356 // Scan for the block of allocas that we can move over, and move them 357 // all at once. 358 while (isa<AllocaInst>(I) && 359 isa<Constant>(cast<AllocaInst>(I)->getArraySize())) 360 ++I; 361 362 // Transfer all of the allocas over in a block. Using splice means 363 // that the instructions aren't removed from the symbol table, then 364 // reinserted. 365 Caller->getEntryBlock().getInstList().splice( 366 InsertPoint, 367 FirstNewBlock->getInstList(), 368 AI, I); 369 } 370 } 371 } 372 373 // If the inlined code contained dynamic alloca instructions, wrap the inlined 374 // code with llvm.stacksave/llvm.stackrestore intrinsics. 375 if (InlinedFunctionInfo.ContainsDynamicAllocas) { 376 Module *M = Caller->getParent(); 377 // Get the two intrinsics we care about. 378 Constant *StackSave, *StackRestore; 379 StackSave = Intrinsic::getDeclaration(M, Intrinsic::stacksave); 380 StackRestore = Intrinsic::getDeclaration(M, Intrinsic::stackrestore); 381 382 // If we are preserving the callgraph, add edges to the stacksave/restore 383 // functions for the calls we insert. 384 CallGraphNode *StackSaveCGN = 0, *StackRestoreCGN = 0, *CallerNode = 0; 385 if (CG) { 386 // We know that StackSave/StackRestore are Function*'s, because they are 387 // intrinsics which must have the right types. 388 StackSaveCGN = CG->getOrInsertFunction(cast<Function>(StackSave)); 389 StackRestoreCGN = CG->getOrInsertFunction(cast<Function>(StackRestore)); 390 CallerNode = (*CG)[Caller]; 391 } 392 393 // Insert the llvm.stacksave. 394 CallInst *SavedPtr = CallInst::Create(StackSave, "savedstack", 395 FirstNewBlock->begin()); 396 if (CG) CallerNode->addCalledFunction(SavedPtr, StackSaveCGN); 397 398 // Insert a call to llvm.stackrestore before any return instructions in the 399 // inlined function. 400 for (unsigned i = 0, e = Returns.size(); i != e; ++i) { 401 CallInst *CI = CallInst::Create(StackRestore, SavedPtr, "", Returns[i]); 402 if (CG) CallerNode->addCalledFunction(CI, StackRestoreCGN); 403 } 404 405 // Count the number of StackRestore calls we insert. 406 unsigned NumStackRestores = Returns.size(); 407 408 // If we are inlining an invoke instruction, insert restores before each 409 // unwind. These unwinds will be rewritten into branches later. 410 if (InlinedFunctionInfo.ContainsUnwinds && isa<InvokeInst>(TheCall)) { 411 for (Function::iterator BB = FirstNewBlock, E = Caller->end(); 412 BB != E; ++BB) 413 if (UnwindInst *UI = dyn_cast<UnwindInst>(BB->getTerminator())) { 414 CallInst::Create(StackRestore, SavedPtr, "", UI); 415 ++NumStackRestores; 416 } 417 } 418 } 419 420 // If we are inlining tail call instruction through a call site that isn't 421 // marked 'tail', we must remove the tail marker for any calls in the inlined 422 // code. Also, calls inlined through a 'nounwind' call site should be marked 423 // 'nounwind'. 424 if (InlinedFunctionInfo.ContainsCalls && 425 (MustClearTailCallFlags || MarkNoUnwind)) { 426 for (Function::iterator BB = FirstNewBlock, E = Caller->end(); 427 BB != E; ++BB) 428 for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) 429 if (CallInst *CI = dyn_cast<CallInst>(I)) { 430 if (MustClearTailCallFlags) 431 CI->setTailCall(false); 432 if (MarkNoUnwind) 433 CI->setDoesNotThrow(); 434 } 435 } 436 437 // If we are inlining through a 'nounwind' call site then any inlined 'unwind' 438 // instructions are unreachable. 439 if (InlinedFunctionInfo.ContainsUnwinds && MarkNoUnwind) 440 for (Function::iterator BB = FirstNewBlock, E = Caller->end(); 441 BB != E; ++BB) { 442 TerminatorInst *Term = BB->getTerminator(); 443 if (isa<UnwindInst>(Term)) { 444 new UnreachableInst(Term); 445 BB->getInstList().erase(Term); 446 } 447 } 448 449 // If we are inlining for an invoke instruction, we must make sure to rewrite 450 // any inlined 'unwind' instructions into branches to the invoke exception 451 // destination, and call instructions into invoke instructions. 452 if (InvokeInst *II = dyn_cast<InvokeInst>(TheCall)) 453 HandleInlinedInvoke(II, FirstNewBlock, InlinedFunctionInfo, CG); 454 455 // If we cloned in _exactly one_ basic block, and if that block ends in a 456 // return instruction, we splice the body of the inlined callee directly into 457 // the calling basic block. 458 if (Returns.size() == 1 && std::distance(FirstNewBlock, Caller->end()) == 1) { 459 // Move all of the instructions right before the call. 460 OrigBB->getInstList().splice(TheCall, FirstNewBlock->getInstList(), 461 FirstNewBlock->begin(), FirstNewBlock->end()); 462 // Remove the cloned basic block. 463 Caller->getBasicBlockList().pop_back(); 464 465 // If the call site was an invoke instruction, add a branch to the normal 466 // destination. 467 if (InvokeInst *II = dyn_cast<InvokeInst>(TheCall)) 468 BranchInst::Create(II->getNormalDest(), TheCall); 469 470 // If the return instruction returned a value, replace uses of the call with 471 // uses of the returned value. 472 if (!TheCall->use_empty()) { 473 ReturnInst *R = Returns[0]; 474 TheCall->replaceAllUsesWith(R->getReturnValue()); 475 } 476 // Since we are now done with the Call/Invoke, we can delete it. 477 TheCall->eraseFromParent(); 478 479 // Since we are now done with the return instruction, delete it also. 480 Returns[0]->eraseFromParent(); 481 482 // We are now done with the inlining. 483 return true; 484 } 485 486 // Otherwise, we have the normal case, of more than one block to inline or 487 // multiple return sites. 488 489 // We want to clone the entire callee function into the hole between the 490 // "starter" and "ender" blocks. How we accomplish this depends on whether 491 // this is an invoke instruction or a call instruction. 492 BasicBlock *AfterCallBB; 493 if (InvokeInst *II = dyn_cast<InvokeInst>(TheCall)) { 494 495 // Add an unconditional branch to make this look like the CallInst case... 496 BranchInst *NewBr = BranchInst::Create(II->getNormalDest(), TheCall); 497 498 // Split the basic block. This guarantees that no PHI nodes will have to be 499 // updated due to new incoming edges, and make the invoke case more 500 // symmetric to the call case. 501 AfterCallBB = OrigBB->splitBasicBlock(NewBr, 502 CalledFunc->getName()+".exit"); 503 504 } else { // It's a call 505 // If this is a call instruction, we need to split the basic block that 506 // the call lives in. 507 // 508 AfterCallBB = OrigBB->splitBasicBlock(TheCall, 509 CalledFunc->getName()+".exit"); 510 } 511 512 // Change the branch that used to go to AfterCallBB to branch to the first 513 // basic block of the inlined function. 514 // 515 TerminatorInst *Br = OrigBB->getTerminator(); 516 assert(Br && Br->getOpcode() == Instruction::Br && 517 "splitBasicBlock broken!"); 518 Br->setOperand(0, FirstNewBlock); 519 520 521 // Now that the function is correct, make it a little bit nicer. In 522 // particular, move the basic blocks inserted from the end of the function 523 // into the space made by splitting the source basic block. 524 Caller->getBasicBlockList().splice(AfterCallBB, Caller->getBasicBlockList(), 525 FirstNewBlock, Caller->end()); 526 527 // Handle all of the return instructions that we just cloned in, and eliminate 528 // any users of the original call/invoke instruction. 529 const Type *RTy = CalledFunc->getReturnType(); 530 531 if (Returns.size() > 1) { 532 // The PHI node should go at the front of the new basic block to merge all 533 // possible incoming values. 534 PHINode *PHI = 0; 535 if (!TheCall->use_empty()) { 536 PHI = PHINode::Create(RTy, TheCall->getName(), 537 AfterCallBB->begin()); 538 // Anything that used the result of the function call should now use the 539 // PHI node as their operand. 540 TheCall->replaceAllUsesWith(PHI); 541 } 542 543 // Loop over all of the return instructions adding entries to the PHI node 544 // as appropriate. 545 if (PHI) { 546 for (unsigned i = 0, e = Returns.size(); i != e; ++i) { 547 ReturnInst *RI = Returns[i]; 548 assert(RI->getReturnValue()->getType() == PHI->getType() && 549 "Ret value not consistent in function!"); 550 PHI->addIncoming(RI->getReturnValue(), RI->getParent()); 551 } 552 } 553 554 // Add a branch to the merge points and remove return instructions. 555 for (unsigned i = 0, e = Returns.size(); i != e; ++i) { 556 ReturnInst *RI = Returns[i]; 557 BranchInst::Create(AfterCallBB, RI); 558 RI->eraseFromParent(); 559 } 560 } else if (!Returns.empty()) { 561 // Otherwise, if there is exactly one return value, just replace anything 562 // using the return value of the call with the computed value. 563 if (!TheCall->use_empty()) 564 TheCall->replaceAllUsesWith(Returns[0]->getReturnValue()); 565 566 // Splice the code from the return block into the block that it will return 567 // to, which contains the code that was after the call. 568 BasicBlock *ReturnBB = Returns[0]->getParent(); 569 AfterCallBB->getInstList().splice(AfterCallBB->begin(), 570 ReturnBB->getInstList()); 571 572 // Update PHI nodes that use the ReturnBB to use the AfterCallBB. 573 ReturnBB->replaceAllUsesWith(AfterCallBB); 574 575 // Delete the return instruction now and empty ReturnBB now. 576 Returns[0]->eraseFromParent(); 577 ReturnBB->eraseFromParent(); 578 } else if (!TheCall->use_empty()) { 579 // No returns, but something is using the return value of the call. Just 580 // nuke the result. 581 TheCall->replaceAllUsesWith(UndefValue::get(TheCall->getType())); 582 } 583 584 // Since we are now done with the Call/Invoke, we can delete it. 585 TheCall->eraseFromParent(); 586 587 // We should always be able to fold the entry block of the function into the 588 // single predecessor of the block... 589 assert(cast<BranchInst>(Br)->isUnconditional() && "splitBasicBlock broken!"); 590 BasicBlock *CalleeEntry = cast<BranchInst>(Br)->getSuccessor(0); 591 592 // Splice the code entry block into calling block, right before the 593 // unconditional branch. 594 OrigBB->getInstList().splice(Br, CalleeEntry->getInstList()); 595 CalleeEntry->replaceAllUsesWith(OrigBB); // Update PHI nodes 596 597 // Remove the unconditional branch. 598 OrigBB->getInstList().erase(Br); 599 600 // Now we can remove the CalleeEntry block, which is now empty. 601 Caller->getBasicBlockList().erase(CalleeEntry); 602 603 return true; 604} 605