InlineFunction.cpp revision de62aeaec49ddcf4a4c61fbbb3a22d3a4dd448f0
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 CallGraphNode::iterator I = CalleeNode->begin(), E = CalleeNode->end(); 159 160 // Consider the case where CalleeNode == CallerNode. 161 typedef std::pair<CallSite, CallGraphNode*> CallRecord; 162 std::vector<CallRecord> CallCache; 163 if (CalleeNode == CallerNode) { 164 CallCache.assign(I, E); 165 I = CallCache.begin(); 166 E = CallCache.end(); 167 } 168 169 for (; I != E; ++I) { 170 const Instruction *OrigCall = I->first.getInstruction(); 171 172 DenseMap<const Value*, Value*>::iterator VMI = ValueMap.find(OrigCall); 173 // Only copy the edge if the call was inlined! 174 if (VMI != ValueMap.end() && VMI->second) { 175 // If the call was inlined, but then constant folded, there is no edge to 176 // add. Check for this case. 177 if (Instruction *NewCall = dyn_cast<Instruction>(VMI->second)) 178 CallerNode->addCalledFunction(CallSite::get(NewCall), I->second); 179 } 180 } 181 // Update the call graph by deleting the edge from Callee to Caller. We must 182 // do this after the loop above in case Caller and Callee are the same. 183 CallerNode->removeCallEdgeFor(CS); 184} 185 186 187// InlineFunction - This function inlines the called function into the basic 188// block of the caller. This returns false if it is not possible to inline this 189// call. The program is still in a well defined state if this occurs though. 190// 191// Note that this only does one level of inlining. For example, if the 192// instruction 'call B' is inlined, and 'B' calls 'C', then the call to 'C' now 193// exists in the instruction stream. Similiarly this will inline a recursive 194// function by one level. 195// 196bool llvm::InlineFunction(CallSite CS, CallGraph *CG, const TargetData *TD) { 197 Instruction *TheCall = CS.getInstruction(); 198 assert(TheCall->getParent() && TheCall->getParent()->getParent() && 199 "Instruction not in function!"); 200 201 const Function *CalledFunc = CS.getCalledFunction(); 202 if (CalledFunc == 0 || // Can't inline external function or indirect 203 CalledFunc->isDeclaration() || // call, or call to a vararg function! 204 CalledFunc->getFunctionType()->isVarArg()) return false; 205 206 207 // If the call to the callee is a non-tail call, we must clear the 'tail' 208 // flags on any calls that we inline. 209 bool MustClearTailCallFlags = 210 isa<CallInst>(TheCall) && !cast<CallInst>(TheCall)->isTailCall(); 211 212 // If the call to the callee cannot throw, set the 'nounwind' flag on any 213 // calls that we inline. 214 bool MarkNoUnwind = CS.doesNotThrow(); 215 216 BasicBlock *OrigBB = TheCall->getParent(); 217 Function *Caller = OrigBB->getParent(); 218 219 // GC poses two hazards to inlining, which only occur when the callee has GC: 220 // 1. If the caller has no GC, then the callee's GC must be propagated to the 221 // caller. 222 // 2. If the caller has a differing GC, it is invalid to inline. 223 if (CalledFunc->hasGC()) { 224 if (!Caller->hasGC()) 225 Caller->setGC(CalledFunc->getGC()); 226 else if (CalledFunc->getGC() != Caller->getGC()) 227 return false; 228 } 229 230 // Get an iterator to the last basic block in the function, which will have 231 // the new function inlined after it. 232 // 233 Function::iterator LastBlock = &Caller->back(); 234 235 // Make sure to capture all of the return instructions from the cloned 236 // function. 237 std::vector<ReturnInst*> Returns; 238 ClonedCodeInfo InlinedFunctionInfo; 239 Function::iterator FirstNewBlock; 240 241 { // Scope to destroy ValueMap after cloning. 242 DenseMap<const Value*, Value*> ValueMap; 243 244 assert(CalledFunc->arg_size() == CS.arg_size() && 245 "No varargs calls can be inlined!"); 246 247 // Calculate the vector of arguments to pass into the function cloner, which 248 // matches up the formal to the actual argument values. 249 CallSite::arg_iterator AI = CS.arg_begin(); 250 unsigned ArgNo = 0; 251 for (Function::const_arg_iterator I = CalledFunc->arg_begin(), 252 E = CalledFunc->arg_end(); I != E; ++I, ++AI, ++ArgNo) { 253 Value *ActualArg = *AI; 254 255 // When byval arguments actually inlined, we need to make the copy implied 256 // by them explicit. However, we don't do this if the callee is readonly 257 // or readnone, because the copy would be unneeded: the callee doesn't 258 // modify the struct. 259 if (CalledFunc->paramHasAttr(ArgNo+1, Attribute::ByVal) && 260 !CalledFunc->onlyReadsMemory()) { 261 const Type *AggTy = cast<PointerType>(I->getType())->getElementType(); 262 const Type *VoidPtrTy = PointerType::getUnqual(Type::Int8Ty); 263 264 // Create the alloca. If we have TargetData, use nice alignment. 265 unsigned Align = 1; 266 if (TD) Align = TD->getPrefTypeAlignment(AggTy); 267 Value *NewAlloca = new AllocaInst(AggTy, 0, Align, I->getName(), 268 Caller->begin()->begin()); 269 // Emit a memcpy. 270 const Type *Tys[] = { Type::Int64Ty }; 271 Function *MemCpyFn = Intrinsic::getDeclaration(Caller->getParent(), 272 Intrinsic::memcpy, 273 Tys, 1); 274 Value *DestCast = new BitCastInst(NewAlloca, VoidPtrTy, "tmp", TheCall); 275 Value *SrcCast = new BitCastInst(*AI, VoidPtrTy, "tmp", TheCall); 276 277 Value *Size; 278 if (TD == 0) 279 Size = ConstantExpr::getSizeOf(AggTy); 280 else 281 Size = ConstantInt::get(Type::Int64Ty, TD->getTypeStoreSize(AggTy)); 282 283 // Always generate a memcpy of alignment 1 here because we don't know 284 // the alignment of the src pointer. Other optimizations can infer 285 // better alignment. 286 Value *CallArgs[] = { 287 DestCast, SrcCast, Size, ConstantInt::get(Type::Int32Ty, 1) 288 }; 289 CallInst *TheMemCpy = 290 CallInst::Create(MemCpyFn, CallArgs, CallArgs+4, "", TheCall); 291 292 // If we have a call graph, update it. 293 if (CG) { 294 CallGraphNode *MemCpyCGN = CG->getOrInsertFunction(MemCpyFn); 295 CallGraphNode *CallerNode = (*CG)[Caller]; 296 CallerNode->addCalledFunction(TheMemCpy, MemCpyCGN); 297 } 298 299 // Uses of the argument in the function should use our new alloca 300 // instead. 301 ActualArg = NewAlloca; 302 } 303 304 ValueMap[I] = ActualArg; 305 } 306 307 // We want the inliner to prune the code as it copies. We would LOVE to 308 // have no dead or constant instructions leftover after inlining occurs 309 // (which can happen, e.g., because an argument was constant), but we'll be 310 // happy with whatever the cloner can do. 311 CloneAndPruneFunctionInto(Caller, CalledFunc, ValueMap, Returns, ".i", 312 &InlinedFunctionInfo, TD); 313 314 // Remember the first block that is newly cloned over. 315 FirstNewBlock = LastBlock; ++FirstNewBlock; 316 317 // Update the callgraph if requested. 318 if (CG) 319 UpdateCallGraphAfterInlining(CS, FirstNewBlock, ValueMap, *CG); 320 } 321 322 // If there are any alloca instructions in the block that used to be the entry 323 // block for the callee, move them to the entry block of the caller. First 324 // calculate which instruction they should be inserted before. We insert the 325 // instructions at the end of the current alloca list. 326 // 327 { 328 BasicBlock::iterator InsertPoint = Caller->begin()->begin(); 329 for (BasicBlock::iterator I = FirstNewBlock->begin(), 330 E = FirstNewBlock->end(); I != E; ) 331 if (AllocaInst *AI = dyn_cast<AllocaInst>(I++)) { 332 // If the alloca is now dead, remove it. This often occurs due to code 333 // specialization. 334 if (AI->use_empty()) { 335 AI->eraseFromParent(); 336 continue; 337 } 338 339 if (isa<Constant>(AI->getArraySize())) { 340 // Scan for the block of allocas that we can move over, and move them 341 // all at once. 342 while (isa<AllocaInst>(I) && 343 isa<Constant>(cast<AllocaInst>(I)->getArraySize())) 344 ++I; 345 346 // Transfer all of the allocas over in a block. Using splice means 347 // that the instructions aren't removed from the symbol table, then 348 // reinserted. 349 Caller->getEntryBlock().getInstList().splice( 350 InsertPoint, 351 FirstNewBlock->getInstList(), 352 AI, I); 353 } 354 } 355 } 356 357 // If the inlined code contained dynamic alloca instructions, wrap the inlined 358 // code with llvm.stacksave/llvm.stackrestore intrinsics. 359 if (InlinedFunctionInfo.ContainsDynamicAllocas) { 360 Module *M = Caller->getParent(); 361 // Get the two intrinsics we care about. 362 Constant *StackSave, *StackRestore; 363 StackSave = Intrinsic::getDeclaration(M, Intrinsic::stacksave); 364 StackRestore = Intrinsic::getDeclaration(M, Intrinsic::stackrestore); 365 366 // If we are preserving the callgraph, add edges to the stacksave/restore 367 // functions for the calls we insert. 368 CallGraphNode *StackSaveCGN = 0, *StackRestoreCGN = 0, *CallerNode = 0; 369 if (CG) { 370 // We know that StackSave/StackRestore are Function*'s, because they are 371 // intrinsics which must have the right types. 372 StackSaveCGN = CG->getOrInsertFunction(cast<Function>(StackSave)); 373 StackRestoreCGN = CG->getOrInsertFunction(cast<Function>(StackRestore)); 374 CallerNode = (*CG)[Caller]; 375 } 376 377 // Insert the llvm.stacksave. 378 CallInst *SavedPtr = CallInst::Create(StackSave, "savedstack", 379 FirstNewBlock->begin()); 380 if (CG) CallerNode->addCalledFunction(SavedPtr, StackSaveCGN); 381 382 // Insert a call to llvm.stackrestore before any return instructions in the 383 // inlined function. 384 for (unsigned i = 0, e = Returns.size(); i != e; ++i) { 385 CallInst *CI = CallInst::Create(StackRestore, SavedPtr, "", Returns[i]); 386 if (CG) CallerNode->addCalledFunction(CI, StackRestoreCGN); 387 } 388 389 // Count the number of StackRestore calls we insert. 390 unsigned NumStackRestores = Returns.size(); 391 392 // If we are inlining an invoke instruction, insert restores before each 393 // unwind. These unwinds will be rewritten into branches later. 394 if (InlinedFunctionInfo.ContainsUnwinds && isa<InvokeInst>(TheCall)) { 395 for (Function::iterator BB = FirstNewBlock, E = Caller->end(); 396 BB != E; ++BB) 397 if (UnwindInst *UI = dyn_cast<UnwindInst>(BB->getTerminator())) { 398 CallInst::Create(StackRestore, SavedPtr, "", UI); 399 ++NumStackRestores; 400 } 401 } 402 } 403 404 // If we are inlining tail call instruction through a call site that isn't 405 // marked 'tail', we must remove the tail marker for any calls in the inlined 406 // code. Also, calls inlined through a 'nounwind' call site should be marked 407 // 'nounwind'. 408 if (InlinedFunctionInfo.ContainsCalls && 409 (MustClearTailCallFlags || MarkNoUnwind)) { 410 for (Function::iterator BB = FirstNewBlock, E = Caller->end(); 411 BB != E; ++BB) 412 for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) 413 if (CallInst *CI = dyn_cast<CallInst>(I)) { 414 if (MustClearTailCallFlags) 415 CI->setTailCall(false); 416 if (MarkNoUnwind) 417 CI->setDoesNotThrow(); 418 } 419 } 420 421 // If we are inlining through a 'nounwind' call site then any inlined 'unwind' 422 // instructions are unreachable. 423 if (InlinedFunctionInfo.ContainsUnwinds && MarkNoUnwind) 424 for (Function::iterator BB = FirstNewBlock, E = Caller->end(); 425 BB != E; ++BB) { 426 TerminatorInst *Term = BB->getTerminator(); 427 if (isa<UnwindInst>(Term)) { 428 new UnreachableInst(Term); 429 BB->getInstList().erase(Term); 430 } 431 } 432 433 // If we are inlining for an invoke instruction, we must make sure to rewrite 434 // any inlined 'unwind' instructions into branches to the invoke exception 435 // destination, and call instructions into invoke instructions. 436 if (InvokeInst *II = dyn_cast<InvokeInst>(TheCall)) 437 HandleInlinedInvoke(II, FirstNewBlock, InlinedFunctionInfo); 438 439 // If we cloned in _exactly one_ basic block, and if that block ends in a 440 // return instruction, we splice the body of the inlined callee directly into 441 // the calling basic block. 442 if (Returns.size() == 1 && std::distance(FirstNewBlock, Caller->end()) == 1) { 443 // Move all of the instructions right before the call. 444 OrigBB->getInstList().splice(TheCall, FirstNewBlock->getInstList(), 445 FirstNewBlock->begin(), FirstNewBlock->end()); 446 // Remove the cloned basic block. 447 Caller->getBasicBlockList().pop_back(); 448 449 // If the call site was an invoke instruction, add a branch to the normal 450 // destination. 451 if (InvokeInst *II = dyn_cast<InvokeInst>(TheCall)) 452 BranchInst::Create(II->getNormalDest(), TheCall); 453 454 // If the return instruction returned a value, replace uses of the call with 455 // uses of the returned value. 456 if (!TheCall->use_empty()) { 457 ReturnInst *R = Returns[0]; 458 TheCall->replaceAllUsesWith(R->getReturnValue()); 459 } 460 // Since we are now done with the Call/Invoke, we can delete it. 461 TheCall->eraseFromParent(); 462 463 // Since we are now done with the return instruction, delete it also. 464 Returns[0]->eraseFromParent(); 465 466 // We are now done with the inlining. 467 return true; 468 } 469 470 // Otherwise, we have the normal case, of more than one block to inline or 471 // multiple return sites. 472 473 // We want to clone the entire callee function into the hole between the 474 // "starter" and "ender" blocks. How we accomplish this depends on whether 475 // this is an invoke instruction or a call instruction. 476 BasicBlock *AfterCallBB; 477 if (InvokeInst *II = dyn_cast<InvokeInst>(TheCall)) { 478 479 // Add an unconditional branch to make this look like the CallInst case... 480 BranchInst *NewBr = BranchInst::Create(II->getNormalDest(), TheCall); 481 482 // Split the basic block. This guarantees that no PHI nodes will have to be 483 // updated due to new incoming edges, and make the invoke case more 484 // symmetric to the call case. 485 AfterCallBB = OrigBB->splitBasicBlock(NewBr, 486 CalledFunc->getName()+".exit"); 487 488 } else { // It's a call 489 // If this is a call instruction, we need to split the basic block that 490 // the call lives in. 491 // 492 AfterCallBB = OrigBB->splitBasicBlock(TheCall, 493 CalledFunc->getName()+".exit"); 494 } 495 496 // Change the branch that used to go to AfterCallBB to branch to the first 497 // basic block of the inlined function. 498 // 499 TerminatorInst *Br = OrigBB->getTerminator(); 500 assert(Br && Br->getOpcode() == Instruction::Br && 501 "splitBasicBlock broken!"); 502 Br->setOperand(0, FirstNewBlock); 503 504 505 // Now that the function is correct, make it a little bit nicer. In 506 // particular, move the basic blocks inserted from the end of the function 507 // into the space made by splitting the source basic block. 508 Caller->getBasicBlockList().splice(AfterCallBB, Caller->getBasicBlockList(), 509 FirstNewBlock, Caller->end()); 510 511 // Handle all of the return instructions that we just cloned in, and eliminate 512 // any users of the original call/invoke instruction. 513 const Type *RTy = CalledFunc->getReturnType(); 514 515 if (Returns.size() > 1) { 516 // The PHI node should go at the front of the new basic block to merge all 517 // possible incoming values. 518 PHINode *PHI = 0; 519 if (!TheCall->use_empty()) { 520 PHI = PHINode::Create(RTy, TheCall->getName(), 521 AfterCallBB->begin()); 522 // Anything that used the result of the function call should now use the 523 // PHI node as their operand. 524 TheCall->replaceAllUsesWith(PHI); 525 } 526 527 // Loop over all of the return instructions adding entries to the PHI node 528 // as appropriate. 529 if (PHI) { 530 for (unsigned i = 0, e = Returns.size(); i != e; ++i) { 531 ReturnInst *RI = Returns[i]; 532 assert(RI->getReturnValue()->getType() == PHI->getType() && 533 "Ret value not consistent in function!"); 534 PHI->addIncoming(RI->getReturnValue(), RI->getParent()); 535 } 536 } 537 538 // Add a branch to the merge points and remove return instructions. 539 for (unsigned i = 0, e = Returns.size(); i != e; ++i) { 540 ReturnInst *RI = Returns[i]; 541 BranchInst::Create(AfterCallBB, RI); 542 RI->eraseFromParent(); 543 } 544 } else if (!Returns.empty()) { 545 // Otherwise, if there is exactly one return value, just replace anything 546 // using the return value of the call with the computed value. 547 if (!TheCall->use_empty()) 548 TheCall->replaceAllUsesWith(Returns[0]->getReturnValue()); 549 550 // Splice the code from the return block into the block that it will return 551 // to, which contains the code that was after the call. 552 BasicBlock *ReturnBB = Returns[0]->getParent(); 553 AfterCallBB->getInstList().splice(AfterCallBB->begin(), 554 ReturnBB->getInstList()); 555 556 // Update PHI nodes that use the ReturnBB to use the AfterCallBB. 557 ReturnBB->replaceAllUsesWith(AfterCallBB); 558 559 // Delete the return instruction now and empty ReturnBB now. 560 Returns[0]->eraseFromParent(); 561 ReturnBB->eraseFromParent(); 562 } else if (!TheCall->use_empty()) { 563 // No returns, but something is using the return value of the call. Just 564 // nuke the result. 565 TheCall->replaceAllUsesWith(UndefValue::get(TheCall->getType())); 566 } 567 568 // Since we are now done with the Call/Invoke, we can delete it. 569 TheCall->eraseFromParent(); 570 571 // We should always be able to fold the entry block of the function into the 572 // single predecessor of the block... 573 assert(cast<BranchInst>(Br)->isUnconditional() && "splitBasicBlock broken!"); 574 BasicBlock *CalleeEntry = cast<BranchInst>(Br)->getSuccessor(0); 575 576 // Splice the code entry block into calling block, right before the 577 // unconditional branch. 578 OrigBB->getInstList().splice(Br, CalleeEntry->getInstList()); 579 CalleeEntry->replaceAllUsesWith(OrigBB); // Update PHI nodes 580 581 // Remove the unconditional branch. 582 OrigBB->getInstList().erase(Br); 583 584 // Now we can remove the CalleeEntry block, which is now empty. 585 Caller->getBasicBlockList().erase(CalleeEntry); 586 587 return true; 588} 589