InlineFunction.cpp revision 0744f09efc53d3352ac1caffc61f6e8239201c3b
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 BasicBlock *InvokeDest = II->getUnwindDest(); 46 std::vector<Value*> InvokeDestPHIValues; 47 48 // If there are PHI nodes in the unwind destination block, we need to 49 // keep track of which values came into them from this invoke, then remove 50 // the entry for this block. 51 BasicBlock *InvokeBlock = II->getParent(); 52 for (BasicBlock::iterator I = InvokeDest->begin(); isa<PHINode>(I); ++I) { 53 PHINode *PN = cast<PHINode>(I); 54 // Save the value to use for this edge. 55 InvokeDestPHIValues.push_back(PN->getIncomingValueForBlock(InvokeBlock)); 56 } 57 58 Function *Caller = FirstNewBlock->getParent(); 59 60 // The inlined code is currently at the end of the function, scan from the 61 // start of the inlined code to its end, checking for stuff we need to 62 // rewrite. 63 if (InlinedCodeInfo.ContainsCalls || InlinedCodeInfo.ContainsUnwinds) { 64 for (Function::iterator BB = FirstNewBlock, E = Caller->end(); 65 BB != E; ++BB) { 66 if (InlinedCodeInfo.ContainsCalls) { 67 for (BasicBlock::iterator BBI = BB->begin(), E = BB->end(); BBI != E; ){ 68 Instruction *I = BBI++; 69 70 // We only need to check for function calls: inlined invoke 71 // instructions require no special handling. 72 if (!isa<CallInst>(I)) continue; 73 CallInst *CI = cast<CallInst>(I); 74 75 // If this call cannot unwind, don't convert it to an invoke. 76 if (CI->doesNotThrow()) 77 continue; 78 79 // Convert this function call into an invoke instruction. 80 // First, split the basic block. 81 BasicBlock *Split = BB->splitBasicBlock(CI, CI->getName()+".noexc"); 82 83 // Next, create the new invoke instruction, inserting it at the end 84 // of the old basic block. 85 SmallVector<Value*, 8> InvokeArgs(CI->op_begin()+1, CI->op_end()); 86 InvokeInst *II = 87 InvokeInst::Create(CI->getCalledValue(), Split, InvokeDest, 88 InvokeArgs.begin(), InvokeArgs.end(), 89 CI->getName(), BB->getTerminator()); 90 II->setCallingConv(CI->getCallingConv()); 91 II->setAttributes(CI->getAttributes()); 92 93 // Make sure that anything using the call now uses the invoke! 94 CI->replaceAllUsesWith(II); 95 96 // Delete the unconditional branch inserted by splitBasicBlock 97 BB->getInstList().pop_back(); 98 Split->getInstList().pop_front(); // Delete the original call 99 100 // Update any PHI nodes in the exceptional block to indicate that 101 // there is now a new entry in them. 102 unsigned i = 0; 103 for (BasicBlock::iterator I = InvokeDest->begin(); 104 isa<PHINode>(I); ++I, ++i) { 105 PHINode *PN = cast<PHINode>(I); 106 PN->addIncoming(InvokeDestPHIValues[i], BB); 107 } 108 109 // This basic block is now complete, start scanning the next one. 110 break; 111 } 112 } 113 114 if (UnwindInst *UI = dyn_cast<UnwindInst>(BB->getTerminator())) { 115 // An UnwindInst requires special handling when it gets inlined into an 116 // invoke site. Once this happens, we know that the unwind would cause 117 // a control transfer to the invoke exception destination, so we can 118 // transform it into a direct branch to the exception destination. 119 BranchInst::Create(InvokeDest, UI); 120 121 // Delete the unwind instruction! 122 UI->eraseFromParent(); 123 124 // Update any PHI nodes in the exceptional block to indicate that 125 // there is now a new entry in them. 126 unsigned i = 0; 127 for (BasicBlock::iterator I = InvokeDest->begin(); 128 isa<PHINode>(I); ++I, ++i) { 129 PHINode *PN = cast<PHINode>(I); 130 PN->addIncoming(InvokeDestPHIValues[i], BB); 131 } 132 } 133 } 134 } 135 136 // Now that everything is happy, we have one final detail. The PHI nodes in 137 // the exception destination block still have entries due to the original 138 // invoke instruction. Eliminate these entries (which might even delete the 139 // PHI node) now. 140 InvokeDest->removePredecessor(II->getParent()); 141} 142 143/// UpdateCallGraphAfterInlining - Once we have cloned code over from a callee 144/// into the caller, update the specified callgraph to reflect the changes we 145/// made. Note that it's possible that not all code was copied over, so only 146/// some edges of the callgraph may remain. 147static void UpdateCallGraphAfterInlining(CallSite CS, 148 Function::iterator FirstNewBlock, 149 DenseMap<const Value*, Value*> &ValueMap, 150 CallGraph &CG) { 151 const Function *Caller = CS.getInstruction()->getParent()->getParent(); 152 const Function *Callee = CS.getCalledFunction(); 153 CallGraphNode *CalleeNode = CG[Callee]; 154 CallGraphNode *CallerNode = CG[Caller]; 155 156 // Since we inlined some uninlined call sites in the callee into the caller, 157 // add edges from the caller to all of the callees of the callee. 158 CallGraphNode::iterator I = CalleeNode->begin(), E = CalleeNode->end(); 159 160 // Consider the case where CalleeNode == CallerNode. 161 CallGraphNode::CalledFunctionsVector CallCache; 162 if (CalleeNode == CallerNode) { 163 CallCache.assign(I, E); 164 I = CallCache.begin(); 165 E = CallCache.end(); 166 } 167 168 for (; I != E; ++I) { 169 const Instruction *OrigCall = I->first.getInstruction(); 170 171 DenseMap<const Value*, Value*>::iterator VMI = ValueMap.find(OrigCall); 172 // Only copy the edge if the call was inlined! 173 if (VMI != ValueMap.end() && VMI->second) { 174 // If the call was inlined, but then constant folded, there is no edge to 175 // add. Check for this case. 176 if (Instruction *NewCall = dyn_cast<Instruction>(VMI->second)) 177 CallerNode->addCalledFunction(CallSite::get(NewCall), I->second); 178 } 179 } 180 // Update the call graph by deleting the edge from Callee to Caller. We must 181 // do this after the loop above in case Caller and Callee are the same. 182 CallerNode->removeCallEdgeFor(CS); 183} 184 185 186// InlineFunction - This function inlines the called function into the basic 187// block of the caller. This returns false if it is not possible to inline this 188// call. The program is still in a well defined state if this occurs though. 189// 190// Note that this only does one level of inlining. For example, if the 191// instruction 'call B' is inlined, and 'B' calls 'C', then the call to 'C' now 192// exists in the instruction stream. Similiarly this will inline a recursive 193// function by one level. 194// 195bool llvm::InlineFunction(CallSite CS, CallGraph *CG, const TargetData *TD) { 196 Instruction *TheCall = CS.getInstruction(); 197 assert(TheCall->getParent() && TheCall->getParent()->getParent() && 198 "Instruction not in function!"); 199 200 const Function *CalledFunc = CS.getCalledFunction(); 201 if (CalledFunc == 0 || // Can't inline external function or indirect 202 CalledFunc->isDeclaration() || // call, or call to a vararg function! 203 CalledFunc->getFunctionType()->isVarArg()) return false; 204 205 206 // If the call to the callee is not a tail call, we must clear the 'tail' 207 // flags on any calls that we inline. 208 bool MustClearTailCallFlags = 209 !(isa<CallInst>(TheCall) && cast<CallInst>(TheCall)->isTailCall()); 210 211 // If the call to the callee cannot throw, set the 'nounwind' flag on any 212 // calls that we inline. 213 bool MarkNoUnwind = CS.doesNotThrow(); 214 215 BasicBlock *OrigBB = TheCall->getParent(); 216 Function *Caller = OrigBB->getParent(); 217 218 // GC poses two hazards to inlining, which only occur when the callee has GC: 219 // 1. If the caller has no GC, then the callee's GC must be propagated to the 220 // caller. 221 // 2. If the caller has a differing GC, it is invalid to inline. 222 if (CalledFunc->hasGC()) { 223 if (!Caller->hasGC()) 224 Caller->setGC(CalledFunc->getGC()); 225 else if (CalledFunc->getGC() != Caller->getGC()) 226 return false; 227 } 228 229 // Get an iterator to the last basic block in the function, which will have 230 // the new function inlined after it. 231 // 232 Function::iterator LastBlock = &Caller->back(); 233 234 // Make sure to capture all of the return instructions from the cloned 235 // function. 236 std::vector<ReturnInst*> Returns; 237 ClonedCodeInfo InlinedFunctionInfo; 238 Function::iterator FirstNewBlock; 239 240 { // Scope to destroy ValueMap after cloning. 241 DenseMap<const Value*, Value*> ValueMap; 242 243 assert(CalledFunc->arg_size() == CS.arg_size() && 244 "No varargs calls can be inlined!"); 245 246 // Calculate the vector of arguments to pass into the function cloner, which 247 // matches up the formal to the actual argument values. 248 CallSite::arg_iterator AI = CS.arg_begin(); 249 unsigned ArgNo = 0; 250 for (Function::const_arg_iterator I = CalledFunc->arg_begin(), 251 E = CalledFunc->arg_end(); I != E; ++I, ++AI, ++ArgNo) { 252 Value *ActualArg = *AI; 253 254 // When byval arguments actually inlined, we need to make the copy implied 255 // by them explicit. However, we don't do this if the callee is readonly 256 // or readnone, because the copy would be unneeded: the callee doesn't 257 // modify the struct. 258 if (CalledFunc->paramHasAttr(ArgNo+1, Attribute::ByVal) && 259 !CalledFunc->onlyReadsMemory()) { 260 const Type *AggTy = cast<PointerType>(I->getType())->getElementType(); 261 const Type *VoidPtrTy = PointerType::getUnqual(Type::Int8Ty); 262 263 // Create the alloca. If we have TargetData, use nice alignment. 264 unsigned Align = 1; 265 if (TD) Align = TD->getPrefTypeAlignment(AggTy); 266 Value *NewAlloca = new AllocaInst(AggTy, 0, Align, I->getName(), 267 Caller->begin()->begin()); 268 // Emit a memcpy. 269 const Type *Tys[] = { Type::Int64Ty }; 270 Function *MemCpyFn = Intrinsic::getDeclaration(Caller->getParent(), 271 Intrinsic::memcpy, 272 Tys, 1); 273 Value *DestCast = new BitCastInst(NewAlloca, VoidPtrTy, "tmp", TheCall); 274 Value *SrcCast = new BitCastInst(*AI, VoidPtrTy, "tmp", TheCall); 275 276 Value *Size; 277 if (TD == 0) 278 Size = ConstantExpr::getSizeOf(AggTy); 279 else 280 Size = ConstantInt::get(Type::Int64Ty, TD->getTypeStoreSize(AggTy)); 281 282 // Always generate a memcpy of alignment 1 here because we don't know 283 // the alignment of the src pointer. Other optimizations can infer 284 // better alignment. 285 Value *CallArgs[] = { 286 DestCast, SrcCast, Size, ConstantInt::get(Type::Int32Ty, 1) 287 }; 288 CallInst *TheMemCpy = 289 CallInst::Create(MemCpyFn, CallArgs, CallArgs+4, "", TheCall); 290 291 // If we have a call graph, update it. 292 if (CG) { 293 CallGraphNode *MemCpyCGN = CG->getOrInsertFunction(MemCpyFn); 294 CallGraphNode *CallerNode = (*CG)[Caller]; 295 CallerNode->addCalledFunction(TheMemCpy, MemCpyCGN); 296 } 297 298 // Uses of the argument in the function should use our new alloca 299 // instead. 300 ActualArg = NewAlloca; 301 } 302 303 ValueMap[I] = ActualArg; 304 } 305 306 // We want the inliner to prune the code as it copies. We would LOVE to 307 // have no dead or constant instructions leftover after inlining occurs 308 // (which can happen, e.g., because an argument was constant), but we'll be 309 // happy with whatever the cloner can do. 310 CloneAndPruneFunctionInto(Caller, CalledFunc, ValueMap, Returns, ".i", 311 &InlinedFunctionInfo, TD); 312 313 // Remember the first block that is newly cloned over. 314 FirstNewBlock = LastBlock; ++FirstNewBlock; 315 316 // Update the callgraph if requested. 317 if (CG) 318 UpdateCallGraphAfterInlining(CS, FirstNewBlock, ValueMap, *CG); 319 } 320 321 // If there are any alloca instructions in the block that used to be the entry 322 // block for the callee, move them to the entry block of the caller. First 323 // calculate which instruction they should be inserted before. We insert the 324 // instructions at the end of the current alloca list. 325 // 326 { 327 BasicBlock::iterator InsertPoint = Caller->begin()->begin(); 328 for (BasicBlock::iterator I = FirstNewBlock->begin(), 329 E = FirstNewBlock->end(); I != E; ) 330 if (AllocaInst *AI = dyn_cast<AllocaInst>(I++)) { 331 // If the alloca is now dead, remove it. This often occurs due to code 332 // specialization. 333 if (AI->use_empty()) { 334 AI->eraseFromParent(); 335 continue; 336 } 337 338 if (isa<Constant>(AI->getArraySize())) { 339 // Scan for the block of allocas that we can move over, and move them 340 // all at once. 341 while (isa<AllocaInst>(I) && 342 isa<Constant>(cast<AllocaInst>(I)->getArraySize())) 343 ++I; 344 345 // Transfer all of the allocas over in a block. Using splice means 346 // that the instructions aren't removed from the symbol table, then 347 // reinserted. 348 Caller->getEntryBlock().getInstList().splice( 349 InsertPoint, 350 FirstNewBlock->getInstList(), 351 AI, I); 352 } 353 } 354 } 355 356 // If the inlined code contained dynamic alloca instructions, wrap the inlined 357 // code with llvm.stacksave/llvm.stackrestore intrinsics. 358 if (InlinedFunctionInfo.ContainsDynamicAllocas) { 359 Module *M = Caller->getParent(); 360 // Get the two intrinsics we care about. 361 Constant *StackSave, *StackRestore; 362 StackSave = Intrinsic::getDeclaration(M, Intrinsic::stacksave); 363 StackRestore = Intrinsic::getDeclaration(M, Intrinsic::stackrestore); 364 365 // If we are preserving the callgraph, add edges to the stacksave/restore 366 // functions for the calls we insert. 367 CallGraphNode *StackSaveCGN = 0, *StackRestoreCGN = 0, *CallerNode = 0; 368 if (CG) { 369 // We know that StackSave/StackRestore are Function*'s, because they are 370 // intrinsics which must have the right types. 371 StackSaveCGN = CG->getOrInsertFunction(cast<Function>(StackSave)); 372 StackRestoreCGN = CG->getOrInsertFunction(cast<Function>(StackRestore)); 373 CallerNode = (*CG)[Caller]; 374 } 375 376 // Insert the llvm.stacksave. 377 CallInst *SavedPtr = CallInst::Create(StackSave, "savedstack", 378 FirstNewBlock->begin()); 379 if (CG) CallerNode->addCalledFunction(SavedPtr, StackSaveCGN); 380 381 // Insert a call to llvm.stackrestore before any return instructions in the 382 // inlined function. 383 for (unsigned i = 0, e = Returns.size(); i != e; ++i) { 384 CallInst *CI = CallInst::Create(StackRestore, SavedPtr, "", Returns[i]); 385 if (CG) CallerNode->addCalledFunction(CI, StackRestoreCGN); 386 } 387 388 // Count the number of StackRestore calls we insert. 389 unsigned NumStackRestores = Returns.size(); 390 391 // If we are inlining an invoke instruction, insert restores before each 392 // unwind. These unwinds will be rewritten into branches later. 393 if (InlinedFunctionInfo.ContainsUnwinds && isa<InvokeInst>(TheCall)) { 394 for (Function::iterator BB = FirstNewBlock, E = Caller->end(); 395 BB != E; ++BB) 396 if (UnwindInst *UI = dyn_cast<UnwindInst>(BB->getTerminator())) { 397 CallInst::Create(StackRestore, SavedPtr, "", UI); 398 ++NumStackRestores; 399 } 400 } 401 } 402 403 // If we are inlining tail call instruction through a call site that isn't 404 // marked 'tail', we must remove the tail marker for any calls in the inlined 405 // code. Also, calls inlined through a 'nounwind' call site should be marked 406 // 'nounwind'. 407 if (InlinedFunctionInfo.ContainsCalls && 408 (MustClearTailCallFlags || MarkNoUnwind)) { 409 for (Function::iterator BB = FirstNewBlock, E = Caller->end(); 410 BB != E; ++BB) 411 for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) 412 if (CallInst *CI = dyn_cast<CallInst>(I)) { 413 if (MustClearTailCallFlags) 414 CI->setTailCall(false); 415 if (MarkNoUnwind) 416 CI->setDoesNotThrow(); 417 } 418 } 419 420 // If we are inlining through a 'nounwind' call site then any inlined 'unwind' 421 // instructions are unreachable. 422 if (InlinedFunctionInfo.ContainsUnwinds && MarkNoUnwind) 423 for (Function::iterator BB = FirstNewBlock, E = Caller->end(); 424 BB != E; ++BB) { 425 TerminatorInst *Term = BB->getTerminator(); 426 if (isa<UnwindInst>(Term)) { 427 new UnreachableInst(Term); 428 BB->getInstList().erase(Term); 429 } 430 } 431 432 // If we are inlining for an invoke instruction, we must make sure to rewrite 433 // any inlined 'unwind' instructions into branches to the invoke exception 434 // destination, and call instructions into invoke instructions. 435 if (InvokeInst *II = dyn_cast<InvokeInst>(TheCall)) 436 HandleInlinedInvoke(II, FirstNewBlock, InlinedFunctionInfo); 437 438 // If we cloned in _exactly one_ basic block, and if that block ends in a 439 // return instruction, we splice the body of the inlined callee directly into 440 // the calling basic block. 441 if (Returns.size() == 1 && std::distance(FirstNewBlock, Caller->end()) == 1) { 442 // Move all of the instructions right before the call. 443 OrigBB->getInstList().splice(TheCall, FirstNewBlock->getInstList(), 444 FirstNewBlock->begin(), FirstNewBlock->end()); 445 // Remove the cloned basic block. 446 Caller->getBasicBlockList().pop_back(); 447 448 // If the call site was an invoke instruction, add a branch to the normal 449 // destination. 450 if (InvokeInst *II = dyn_cast<InvokeInst>(TheCall)) 451 BranchInst::Create(II->getNormalDest(), TheCall); 452 453 // If the return instruction returned a value, replace uses of the call with 454 // uses of the returned value. 455 if (!TheCall->use_empty()) { 456 ReturnInst *R = Returns[0]; 457 TheCall->replaceAllUsesWith(R->getReturnValue()); 458 } 459 // Since we are now done with the Call/Invoke, we can delete it. 460 TheCall->eraseFromParent(); 461 462 // Since we are now done with the return instruction, delete it also. 463 Returns[0]->eraseFromParent(); 464 465 // We are now done with the inlining. 466 return true; 467 } 468 469 // Otherwise, we have the normal case, of more than one block to inline or 470 // multiple return sites. 471 472 // We want to clone the entire callee function into the hole between the 473 // "starter" and "ender" blocks. How we accomplish this depends on whether 474 // this is an invoke instruction or a call instruction. 475 BasicBlock *AfterCallBB; 476 if (InvokeInst *II = dyn_cast<InvokeInst>(TheCall)) { 477 478 // Add an unconditional branch to make this look like the CallInst case... 479 BranchInst *NewBr = BranchInst::Create(II->getNormalDest(), TheCall); 480 481 // Split the basic block. This guarantees that no PHI nodes will have to be 482 // updated due to new incoming edges, and make the invoke case more 483 // symmetric to the call case. 484 AfterCallBB = OrigBB->splitBasicBlock(NewBr, 485 CalledFunc->getName()+".exit"); 486 487 } else { // It's a call 488 // If this is a call instruction, we need to split the basic block that 489 // the call lives in. 490 // 491 AfterCallBB = OrigBB->splitBasicBlock(TheCall, 492 CalledFunc->getName()+".exit"); 493 } 494 495 // Change the branch that used to go to AfterCallBB to branch to the first 496 // basic block of the inlined function. 497 // 498 TerminatorInst *Br = OrigBB->getTerminator(); 499 assert(Br && Br->getOpcode() == Instruction::Br && 500 "splitBasicBlock broken!"); 501 Br->setOperand(0, FirstNewBlock); 502 503 504 // Now that the function is correct, make it a little bit nicer. In 505 // particular, move the basic blocks inserted from the end of the function 506 // into the space made by splitting the source basic block. 507 Caller->getBasicBlockList().splice(AfterCallBB, Caller->getBasicBlockList(), 508 FirstNewBlock, Caller->end()); 509 510 // Handle all of the return instructions that we just cloned in, and eliminate 511 // any users of the original call/invoke instruction. 512 const Type *RTy = CalledFunc->getReturnType(); 513 514 if (Returns.size() > 1) { 515 // The PHI node should go at the front of the new basic block to merge all 516 // possible incoming values. 517 PHINode *PHI = 0; 518 if (!TheCall->use_empty()) { 519 PHI = PHINode::Create(RTy, TheCall->getName(), 520 AfterCallBB->begin()); 521 // Anything that used the result of the function call should now use the 522 // PHI node as their operand. 523 TheCall->replaceAllUsesWith(PHI); 524 } 525 526 // Loop over all of the return instructions adding entries to the PHI node 527 // as appropriate. 528 if (PHI) { 529 for (unsigned i = 0, e = Returns.size(); i != e; ++i) { 530 ReturnInst *RI = Returns[i]; 531 assert(RI->getReturnValue()->getType() == PHI->getType() && 532 "Ret value not consistent in function!"); 533 PHI->addIncoming(RI->getReturnValue(), RI->getParent()); 534 } 535 } 536 537 // Add a branch to the merge points and remove return instructions. 538 for (unsigned i = 0, e = Returns.size(); i != e; ++i) { 539 ReturnInst *RI = Returns[i]; 540 BranchInst::Create(AfterCallBB, RI); 541 RI->eraseFromParent(); 542 } 543 } else if (!Returns.empty()) { 544 // Otherwise, if there is exactly one return value, just replace anything 545 // using the return value of the call with the computed value. 546 if (!TheCall->use_empty()) 547 TheCall->replaceAllUsesWith(Returns[0]->getReturnValue()); 548 549 // Splice the code from the return block into the block that it will return 550 // to, which contains the code that was after the call. 551 BasicBlock *ReturnBB = Returns[0]->getParent(); 552 AfterCallBB->getInstList().splice(AfterCallBB->begin(), 553 ReturnBB->getInstList()); 554 555 // Update PHI nodes that use the ReturnBB to use the AfterCallBB. 556 ReturnBB->replaceAllUsesWith(AfterCallBB); 557 558 // Delete the return instruction now and empty ReturnBB now. 559 Returns[0]->eraseFromParent(); 560 ReturnBB->eraseFromParent(); 561 } else if (!TheCall->use_empty()) { 562 // No returns, but something is using the return value of the call. Just 563 // nuke the result. 564 TheCall->replaceAllUsesWith(UndefValue::get(TheCall->getType())); 565 } 566 567 // Since we are now done with the Call/Invoke, we can delete it. 568 TheCall->eraseFromParent(); 569 570 // We should always be able to fold the entry block of the function into the 571 // single predecessor of the block... 572 assert(cast<BranchInst>(Br)->isUnconditional() && "splitBasicBlock broken!"); 573 BasicBlock *CalleeEntry = cast<BranchInst>(Br)->getSuccessor(0); 574 575 // Splice the code entry block into calling block, right before the 576 // unconditional branch. 577 OrigBB->getInstList().splice(Br, CalleeEntry->getInstList()); 578 CalleeEntry->replaceAllUsesWith(OrigBB); // Update PHI nodes 579 580 // Remove the unconditional branch. 581 OrigBB->getInstList().erase(Br); 582 583 // Now we can remove the CalleeEntry block, which is now empty. 584 Caller->getBasicBlockList().erase(CalleeEntry); 585 586 return true; 587} 588