InlineFunction.cpp revision 39fa32403e0b5e163f4f05566d6cde65e6c11095
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 begin 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 for (CallGraphNode::iterator I = CalleeNode->begin(), 159 E = CalleeNode->end(); I != E; ++I) { 160 const Instruction *OrigCall = I->first.getInstruction(); 161 162 DenseMap<const Value*, Value*>::iterator VMI = ValueMap.find(OrigCall); 163 // Only copy the edge if the call was inlined! 164 if (VMI != ValueMap.end() && VMI->second) { 165 // If the call was inlined, but then constant folded, there is no edge to 166 // add. Check for this case. 167 if (Instruction *NewCall = dyn_cast<Instruction>(VMI->second)) 168 CallerNode->addCalledFunction(CallSite::get(NewCall), I->second); 169 } 170 } 171 // Update the call graph by deleting the edge from Callee to Caller. We must 172 // do this after the loop above in case Caller and Callee are the same. 173 CallerNode->removeCallEdgeFor(CS); 174} 175 176 177// InlineFunction - This function inlines the called function into the basic 178// block of the caller. This returns false if it is not possible to inline this 179// call. The program is still in a well defined state if this occurs though. 180// 181// Note that this only does one level of inlining. For example, if the 182// instruction 'call B' is inlined, and 'B' calls 'C', then the call to 'C' now 183// exists in the instruction stream. Similiarly this will inline a recursive 184// function by one level. 185// 186bool llvm::InlineFunction(CallSite CS, CallGraph *CG, const TargetData *TD) { 187 Instruction *TheCall = CS.getInstruction(); 188 assert(TheCall->getParent() && TheCall->getParent()->getParent() && 189 "Instruction not in function!"); 190 191 const Function *CalledFunc = CS.getCalledFunction(); 192 if (CalledFunc == 0 || // Can't inline external function or indirect 193 CalledFunc->isDeclaration() || // call, or call to a vararg function! 194 CalledFunc->getFunctionType()->isVarArg()) return false; 195 196 197 // If the call to the callee is a non-tail call, we must clear the 'tail' 198 // flags on any calls that we inline. 199 bool MustClearTailCallFlags = 200 isa<CallInst>(TheCall) && !cast<CallInst>(TheCall)->isTailCall(); 201 202 // If the call to the callee cannot throw, set the 'nounwind' flag on any 203 // calls that we inline. 204 bool MarkNoUnwind = CS.doesNotThrow(); 205 206 BasicBlock *OrigBB = TheCall->getParent(); 207 Function *Caller = OrigBB->getParent(); 208 209 // GC poses two hazards to inlining, which only occur when the callee has GC: 210 // 1. If the caller has no GC, then the callee's GC must be propagated to the 211 // caller. 212 // 2. If the caller has a differing GC, it is invalid to inline. 213 if (CalledFunc->hasGC()) { 214 if (!Caller->hasGC()) 215 Caller->setGC(CalledFunc->getGC()); 216 else if (CalledFunc->getGC() != Caller->getGC()) 217 return false; 218 } 219 220 // Get an iterator to the last basic block in the function, which will have 221 // the new function inlined after it. 222 // 223 Function::iterator LastBlock = &Caller->back(); 224 225 // Make sure to capture all of the return instructions from the cloned 226 // function. 227 std::vector<ReturnInst*> Returns; 228 ClonedCodeInfo InlinedFunctionInfo; 229 Function::iterator FirstNewBlock; 230 231 { // Scope to destroy ValueMap after cloning. 232 DenseMap<const Value*, Value*> ValueMap; 233 234 assert(CalledFunc->arg_size() == CS.arg_size() && 235 "No varargs calls can be inlined!"); 236 237 // Calculate the vector of arguments to pass into the function cloner, which 238 // matches up the formal to the actual argument values. 239 CallSite::arg_iterator AI = CS.arg_begin(); 240 unsigned ArgNo = 0; 241 for (Function::const_arg_iterator I = CalledFunc->arg_begin(), 242 E = CalledFunc->arg_end(); I != E; ++I, ++AI, ++ArgNo) { 243 Value *ActualArg = *AI; 244 245 // When byval arguments actually inlined, we need to make the copy implied 246 // by them explicit. However, we don't do this if the callee is readonly 247 // or readnone, because the copy would be unneeded: the callee doesn't 248 // modify the struct. 249 if (CalledFunc->paramHasAttr(ArgNo+1, Attribute::ByVal) && 250 !CalledFunc->onlyReadsMemory()) { 251 const Type *AggTy = cast<PointerType>(I->getType())->getElementType(); 252 const Type *VoidPtrTy = PointerType::getUnqual(Type::Int8Ty); 253 254 // Create the alloca. If we have TargetData, use nice alignment. 255 unsigned Align = 1; 256 if (TD) Align = TD->getPrefTypeAlignment(AggTy); 257 Value *NewAlloca = new AllocaInst(AggTy, 0, Align, I->getName(), 258 Caller->begin()->begin()); 259 // Emit a memcpy. 260 const Type *Tys[] = { Type::Int64Ty }; 261 Function *MemCpyFn = Intrinsic::getDeclaration(Caller->getParent(), 262 Intrinsic::memcpy, 263 Tys, 1); 264 Value *DestCast = new BitCastInst(NewAlloca, VoidPtrTy, "tmp", TheCall); 265 Value *SrcCast = new BitCastInst(*AI, VoidPtrTy, "tmp", TheCall); 266 267 Value *Size; 268 if (TD == 0) 269 Size = ConstantExpr::getSizeOf(AggTy); 270 else 271 Size = ConstantInt::get(Type::Int64Ty, TD->getTypeStoreSize(AggTy)); 272 273 // Always generate a memcpy of alignment 1 here because we don't know 274 // the alignment of the src pointer. Other optimizations can infer 275 // better alignment. 276 Value *CallArgs[] = { 277 DestCast, SrcCast, Size, ConstantInt::get(Type::Int32Ty, 1) 278 }; 279 CallInst *TheMemCpy = 280 CallInst::Create(MemCpyFn, CallArgs, CallArgs+4, "", TheCall); 281 282 // If we have a call graph, update it. 283 if (CG) { 284 CallGraphNode *MemCpyCGN = CG->getOrInsertFunction(MemCpyFn); 285 CallGraphNode *CallerNode = (*CG)[Caller]; 286 CallerNode->addCalledFunction(TheMemCpy, MemCpyCGN); 287 } 288 289 // Uses of the argument in the function should use our new alloca 290 // instead. 291 ActualArg = NewAlloca; 292 } 293 294 ValueMap[I] = ActualArg; 295 } 296 297 // We want the inliner to prune the code as it copies. We would LOVE to 298 // have no dead or constant instructions leftover after inlining occurs 299 // (which can happen, e.g., because an argument was constant), but we'll be 300 // happy with whatever the cloner can do. 301 CloneAndPruneFunctionInto(Caller, CalledFunc, ValueMap, Returns, ".i", 302 &InlinedFunctionInfo, TD); 303 304 // Remember the first block that is newly cloned over. 305 FirstNewBlock = LastBlock; ++FirstNewBlock; 306 307 // Update the callgraph if requested. 308 if (CG) 309 UpdateCallGraphAfterInlining(CS, FirstNewBlock, ValueMap, *CG); 310 } 311 312 // If there are any alloca instructions in the block that used to be the entry 313 // block for the callee, move them to the entry block of the caller. First 314 // calculate which instruction they should be inserted before. We insert the 315 // instructions at the end of the current alloca list. 316 // 317 { 318 BasicBlock::iterator InsertPoint = Caller->begin()->begin(); 319 for (BasicBlock::iterator I = FirstNewBlock->begin(), 320 E = FirstNewBlock->end(); I != E; ) 321 if (AllocaInst *AI = dyn_cast<AllocaInst>(I++)) { 322 // If the alloca is now dead, remove it. This often occurs due to code 323 // specialization. 324 if (AI->use_empty()) { 325 AI->eraseFromParent(); 326 continue; 327 } 328 329 if (isa<Constant>(AI->getArraySize())) { 330 // Scan for the block of allocas that we can move over, and move them 331 // all at once. 332 while (isa<AllocaInst>(I) && 333 isa<Constant>(cast<AllocaInst>(I)->getArraySize())) 334 ++I; 335 336 // Transfer all of the allocas over in a block. Using splice means 337 // that the instructions aren't removed from the symbol table, then 338 // reinserted. 339 Caller->getEntryBlock().getInstList().splice( 340 InsertPoint, 341 FirstNewBlock->getInstList(), 342 AI, I); 343 } 344 } 345 } 346 347 // If the inlined code contained dynamic alloca instructions, wrap the inlined 348 // code with llvm.stacksave/llvm.stackrestore intrinsics. 349 if (InlinedFunctionInfo.ContainsDynamicAllocas) { 350 Module *M = Caller->getParent(); 351 // Get the two intrinsics we care about. 352 Constant *StackSave, *StackRestore; 353 StackSave = Intrinsic::getDeclaration(M, Intrinsic::stacksave); 354 StackRestore = Intrinsic::getDeclaration(M, Intrinsic::stackrestore); 355 356 // If we are preserving the callgraph, add edges to the stacksave/restore 357 // functions for the calls we insert. 358 CallGraphNode *StackSaveCGN = 0, *StackRestoreCGN = 0, *CallerNode = 0; 359 if (CG) { 360 // We know that StackSave/StackRestore are Function*'s, because they are 361 // intrinsics which must have the right types. 362 StackSaveCGN = CG->getOrInsertFunction(cast<Function>(StackSave)); 363 StackRestoreCGN = CG->getOrInsertFunction(cast<Function>(StackRestore)); 364 CallerNode = (*CG)[Caller]; 365 } 366 367 // Insert the llvm.stacksave. 368 CallInst *SavedPtr = CallInst::Create(StackSave, "savedstack", 369 FirstNewBlock->begin()); 370 if (CG) CallerNode->addCalledFunction(SavedPtr, StackSaveCGN); 371 372 // Insert a call to llvm.stackrestore before any return instructions in the 373 // inlined function. 374 for (unsigned i = 0, e = Returns.size(); i != e; ++i) { 375 CallInst *CI = CallInst::Create(StackRestore, SavedPtr, "", Returns[i]); 376 if (CG) CallerNode->addCalledFunction(CI, StackRestoreCGN); 377 } 378 379 // Count the number of StackRestore calls we insert. 380 unsigned NumStackRestores = Returns.size(); 381 382 // If we are inlining an invoke instruction, insert restores before each 383 // unwind. These unwinds will be rewritten into branches later. 384 if (InlinedFunctionInfo.ContainsUnwinds && isa<InvokeInst>(TheCall)) { 385 for (Function::iterator BB = FirstNewBlock, E = Caller->end(); 386 BB != E; ++BB) 387 if (UnwindInst *UI = dyn_cast<UnwindInst>(BB->getTerminator())) { 388 CallInst::Create(StackRestore, SavedPtr, "", UI); 389 ++NumStackRestores; 390 } 391 } 392 } 393 394 // If we are inlining tail call instruction through a call site that isn't 395 // marked 'tail', we must remove the tail marker for any calls in the inlined 396 // code. Also, calls inlined through a 'nounwind' call site should be marked 397 // 'nounwind'. 398 if (InlinedFunctionInfo.ContainsCalls && 399 (MustClearTailCallFlags || MarkNoUnwind)) { 400 for (Function::iterator BB = FirstNewBlock, E = Caller->end(); 401 BB != E; ++BB) 402 for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) 403 if (CallInst *CI = dyn_cast<CallInst>(I)) { 404 if (MustClearTailCallFlags) 405 CI->setTailCall(false); 406 if (MarkNoUnwind) 407 CI->setDoesNotThrow(); 408 } 409 } 410 411 // If we are inlining through a 'nounwind' call site then any inlined 'unwind' 412 // instructions are unreachable. 413 if (InlinedFunctionInfo.ContainsUnwinds && MarkNoUnwind) 414 for (Function::iterator BB = FirstNewBlock, E = Caller->end(); 415 BB != E; ++BB) { 416 TerminatorInst *Term = BB->getTerminator(); 417 if (isa<UnwindInst>(Term)) { 418 new UnreachableInst(Term); 419 BB->getInstList().erase(Term); 420 } 421 } 422 423 // If we are inlining for an invoke instruction, we must make sure to rewrite 424 // any inlined 'unwind' instructions into branches to the invoke exception 425 // destination, and call instructions into invoke instructions. 426 if (InvokeInst *II = dyn_cast<InvokeInst>(TheCall)) 427 HandleInlinedInvoke(II, FirstNewBlock, InlinedFunctionInfo); 428 429 // If we cloned in _exactly one_ basic block, and if that block ends in a 430 // return instruction, we splice the body of the inlined callee directly into 431 // the calling basic block. 432 if (Returns.size() == 1 && std::distance(FirstNewBlock, Caller->end()) == 1) { 433 // Move all of the instructions right before the call. 434 OrigBB->getInstList().splice(TheCall, FirstNewBlock->getInstList(), 435 FirstNewBlock->begin(), FirstNewBlock->end()); 436 // Remove the cloned basic block. 437 Caller->getBasicBlockList().pop_back(); 438 439 // If the call site was an invoke instruction, add a branch to the normal 440 // destination. 441 if (InvokeInst *II = dyn_cast<InvokeInst>(TheCall)) 442 BranchInst::Create(II->getNormalDest(), TheCall); 443 444 // If the return instruction returned a value, replace uses of the call with 445 // uses of the returned value. 446 if (!TheCall->use_empty()) { 447 ReturnInst *R = Returns[0]; 448 TheCall->replaceAllUsesWith(R->getReturnValue()); 449 } 450 // Since we are now done with the Call/Invoke, we can delete it. 451 TheCall->eraseFromParent(); 452 453 // Since we are now done with the return instruction, delete it also. 454 Returns[0]->eraseFromParent(); 455 456 // We are now done with the inlining. 457 return true; 458 } 459 460 // Otherwise, we have the normal case, of more than one block to inline or 461 // multiple return sites. 462 463 // We want to clone the entire callee function into the hole between the 464 // "starter" and "ender" blocks. How we accomplish this depends on whether 465 // this is an invoke instruction or a call instruction. 466 BasicBlock *AfterCallBB; 467 if (InvokeInst *II = dyn_cast<InvokeInst>(TheCall)) { 468 469 // Add an unconditional branch to make this look like the CallInst case... 470 BranchInst *NewBr = BranchInst::Create(II->getNormalDest(), TheCall); 471 472 // Split the basic block. This guarantees that no PHI nodes will have to be 473 // updated due to new incoming edges, and make the invoke case more 474 // symmetric to the call case. 475 AfterCallBB = OrigBB->splitBasicBlock(NewBr, 476 CalledFunc->getName()+".exit"); 477 478 } else { // It's a call 479 // If this is a call instruction, we need to split the basic block that 480 // the call lives in. 481 // 482 AfterCallBB = OrigBB->splitBasicBlock(TheCall, 483 CalledFunc->getName()+".exit"); 484 } 485 486 // Change the branch that used to go to AfterCallBB to branch to the first 487 // basic block of the inlined function. 488 // 489 TerminatorInst *Br = OrigBB->getTerminator(); 490 assert(Br && Br->getOpcode() == Instruction::Br && 491 "splitBasicBlock broken!"); 492 Br->setOperand(0, FirstNewBlock); 493 494 495 // Now that the function is correct, make it a little bit nicer. In 496 // particular, move the basic blocks inserted from the end of the function 497 // into the space made by splitting the source basic block. 498 Caller->getBasicBlockList().splice(AfterCallBB, Caller->getBasicBlockList(), 499 FirstNewBlock, Caller->end()); 500 501 // Handle all of the return instructions that we just cloned in, and eliminate 502 // any users of the original call/invoke instruction. 503 const Type *RTy = CalledFunc->getReturnType(); 504 505 if (Returns.size() > 1) { 506 // The PHI node should go at the front of the new basic block to merge all 507 // possible incoming values. 508 PHINode *PHI = 0; 509 if (!TheCall->use_empty()) { 510 PHI = PHINode::Create(RTy, TheCall->getName(), 511 AfterCallBB->begin()); 512 // Anything that used the result of the function call should now use the 513 // PHI node as their operand. 514 TheCall->replaceAllUsesWith(PHI); 515 } 516 517 // Loop over all of the return instructions adding entries to the PHI node as 518 // appropriate. 519 if (PHI) { 520 for (unsigned i = 0, e = Returns.size(); i != e; ++i) { 521 ReturnInst *RI = Returns[i]; 522 assert(RI->getReturnValue()->getType() == PHI->getType() && 523 "Ret value not consistent in function!"); 524 PHI->addIncoming(RI->getReturnValue(), RI->getParent()); 525 } 526 } 527 528 // Add a branch to the merge points and remove retrun instructions. 529 for (unsigned i = 0, e = Returns.size(); i != e; ++i) { 530 ReturnInst *RI = Returns[i]; 531 BranchInst::Create(AfterCallBB, RI); 532 RI->eraseFromParent(); 533 } 534 } else if (!Returns.empty()) { 535 // Otherwise, if there is exactly one return value, just replace anything 536 // using the return value of the call with the computed value. 537 if (!TheCall->use_empty()) 538 TheCall->replaceAllUsesWith(Returns[0]->getReturnValue()); 539 540 // Splice the code from the return block into the block that it will return 541 // to, which contains the code that was after the call. 542 BasicBlock *ReturnBB = Returns[0]->getParent(); 543 AfterCallBB->getInstList().splice(AfterCallBB->begin(), 544 ReturnBB->getInstList()); 545 546 // Update PHI nodes that use the ReturnBB to use the AfterCallBB. 547 ReturnBB->replaceAllUsesWith(AfterCallBB); 548 549 // Delete the return instruction now and empty ReturnBB now. 550 Returns[0]->eraseFromParent(); 551 ReturnBB->eraseFromParent(); 552 } else if (!TheCall->use_empty()) { 553 // No returns, but something is using the return value of the call. Just 554 // nuke the result. 555 TheCall->replaceAllUsesWith(UndefValue::get(TheCall->getType())); 556 } 557 558 // Since we are now done with the Call/Invoke, we can delete it. 559 TheCall->eraseFromParent(); 560 561 // We should always be able to fold the entry block of the function into the 562 // single predecessor of the block... 563 assert(cast<BranchInst>(Br)->isUnconditional() && "splitBasicBlock broken!"); 564 BasicBlock *CalleeEntry = cast<BranchInst>(Br)->getSuccessor(0); 565 566 // Splice the code entry block into calling block, right before the 567 // unconditional branch. 568 OrigBB->getInstList().splice(Br, CalleeEntry->getInstList()); 569 CalleeEntry->replaceAllUsesWith(OrigBB); // Update PHI nodes 570 571 // Remove the unconditional branch. 572 OrigBB->getInstList().erase(Br); 573 574 // Now we can remove the CalleeEntry block, which is now empty. 575 Caller->getBasicBlockList().erase(CalleeEntry); 576 577 return true; 578} 579