//===- InlineFunction.cpp - Code to perform function inlining -------------===// // // The LLVM Compiler Infrastructure // // This file is distributed under the University of Illinois Open Source // License. See LICENSE.TXT for details. // //===----------------------------------------------------------------------===// // // This file implements inlining of a function into a call site, resolving // parameters and the return value as appropriate. // //===----------------------------------------------------------------------===// #include "llvm/Transforms/Utils/Cloning.h" #include "llvm/Constants.h" #include "llvm/DerivedTypes.h" #include "llvm/Module.h" #include "llvm/Instructions.h" #include "llvm/IntrinsicInst.h" #include "llvm/Intrinsics.h" #include "llvm/Attributes.h" #include "llvm/Analysis/CallGraph.h" #include "llvm/Analysis/DebugInfo.h" #include "llvm/Analysis/InstructionSimplify.h" #include "llvm/Target/TargetData.h" #include "llvm/Transforms/Utils/Local.h" #include "llvm/ADT/SmallVector.h" #include "llvm/ADT/StringExtras.h" #include "llvm/Support/CallSite.h" using namespace llvm; bool llvm::InlineFunction(CallInst *CI, InlineFunctionInfo &IFI) { return InlineFunction(CallSite(CI), IFI); } bool llvm::InlineFunction(InvokeInst *II, InlineFunctionInfo &IFI) { return InlineFunction(CallSite(II), IFI); } /// HandleCallsInBlockInlinedThroughInvoke - When we inline a basic block into /// an invoke, we have to turn all of the calls that can throw into /// invokes. This function analyze BB to see if there are any calls, and if so, /// it rewrites them to be invokes that jump to InvokeDest and fills in the PHI /// nodes in that block with the values specified in InvokeDestPHIValues. /// static void HandleCallsInBlockInlinedThroughInvoke(BasicBlock *BB, BasicBlock *InvokeDest, const SmallVectorImpl<Value*> &InvokeDestPHIValues) { for (BasicBlock::iterator BBI = BB->begin(), E = BB->end(); BBI != E; ) { Instruction *I = BBI++; // We only need to check for function calls: inlined invoke // instructions require no special handling. CallInst *CI = dyn_cast<CallInst>(I); if (CI == 0) continue; // If this call cannot unwind, don't convert it to an invoke. if (CI->doesNotThrow()) continue; // Convert this function call into an invoke instruction. // First, split the basic block. BasicBlock *Split = BB->splitBasicBlock(CI, CI->getName()+".noexc"); // Next, create the new invoke instruction, inserting it at the end // of the old basic block. ImmutableCallSite CS(CI); SmallVector<Value*, 8> InvokeArgs(CS.arg_begin(), CS.arg_end()); InvokeInst *II = InvokeInst::Create(CI->getCalledValue(), Split, InvokeDest, InvokeArgs.begin(), InvokeArgs.end(), CI->getName(), BB->getTerminator()); II->setCallingConv(CI->getCallingConv()); II->setAttributes(CI->getAttributes()); // Make sure that anything using the call now uses the invoke! This also // updates the CallGraph if present, because it uses a WeakVH. CI->replaceAllUsesWith(II); // Delete the unconditional branch inserted by splitBasicBlock BB->getInstList().pop_back(); Split->getInstList().pop_front(); // Delete the original call // Update any PHI nodes in the exceptional block to indicate that // there is now a new entry in them. unsigned i = 0; for (BasicBlock::iterator I = InvokeDest->begin(); isa<PHINode>(I); ++I, ++i) cast<PHINode>(I)->addIncoming(InvokeDestPHIValues[i], BB); // This basic block is now complete, the caller will continue scanning the // next one. return; } } /// HandleInlinedInvoke - If we inlined an invoke site, we need to convert calls /// in the body of the inlined function into invokes and turn unwind /// instructions into branches to the invoke unwind dest. /// /// II is the invoke instruction being inlined. FirstNewBlock is the first /// block of the inlined code (the last block is the end of the function), /// and InlineCodeInfo is information about the code that got inlined. static void HandleInlinedInvoke(InvokeInst *II, BasicBlock *FirstNewBlock, ClonedCodeInfo &InlinedCodeInfo) { BasicBlock *InvokeDest = II->getUnwindDest(); SmallVector<Value*, 8> InvokeDestPHIValues; // If there are PHI nodes in the unwind destination block, we need to // keep track of which values came into them from this invoke, then remove // the entry for this block. BasicBlock *InvokeBlock = II->getParent(); for (BasicBlock::iterator I = InvokeDest->begin(); isa<PHINode>(I); ++I) { PHINode *PN = cast<PHINode>(I); // Save the value to use for this edge. InvokeDestPHIValues.push_back(PN->getIncomingValueForBlock(InvokeBlock)); } Function *Caller = FirstNewBlock->getParent(); // The inlined code is currently at the end of the function, scan from the // start of the inlined code to its end, checking for stuff we need to // rewrite. If the code doesn't have calls or unwinds, we know there is // nothing to rewrite. if (!InlinedCodeInfo.ContainsCalls && !InlinedCodeInfo.ContainsUnwinds) { // Now that everything is happy, we have one final detail. The PHI nodes in // the exception destination block still have entries due to the original // invoke instruction. Eliminate these entries (which might even delete the // PHI node) now. InvokeDest->removePredecessor(II->getParent()); return; } for (Function::iterator BB = FirstNewBlock, E = Caller->end(); BB != E; ++BB){ if (InlinedCodeInfo.ContainsCalls) HandleCallsInBlockInlinedThroughInvoke(BB, InvokeDest, InvokeDestPHIValues); if (UnwindInst *UI = dyn_cast<UnwindInst>(BB->getTerminator())) { // An UnwindInst requires special handling when it gets inlined into an // invoke site. Once this happens, we know that the unwind would cause // a control transfer to the invoke exception destination, so we can // transform it into a direct branch to the exception destination. BranchInst::Create(InvokeDest, UI); // Delete the unwind instruction! UI->eraseFromParent(); // Update any PHI nodes in the exceptional block to indicate that // there is now a new entry in them. unsigned i = 0; for (BasicBlock::iterator I = InvokeDest->begin(); isa<PHINode>(I); ++I, ++i) { PHINode *PN = cast<PHINode>(I); PN->addIncoming(InvokeDestPHIValues[i], BB); } } } // Now that everything is happy, we have one final detail. The PHI nodes in // the exception destination block still have entries due to the original // invoke instruction. Eliminate these entries (which might even delete the // PHI node) now. InvokeDest->removePredecessor(II->getParent()); } /// UpdateCallGraphAfterInlining - Once we have cloned code over from a callee /// into the caller, update the specified callgraph to reflect the changes we /// made. Note that it's possible that not all code was copied over, so only /// some edges of the callgraph may remain. static void UpdateCallGraphAfterInlining(CallSite CS, Function::iterator FirstNewBlock, ValueToValueMapTy &VMap, InlineFunctionInfo &IFI) { CallGraph &CG = *IFI.CG; const Function *Caller = CS.getInstruction()->getParent()->getParent(); const Function *Callee = CS.getCalledFunction(); CallGraphNode *CalleeNode = CG[Callee]; CallGraphNode *CallerNode = CG[Caller]; // Since we inlined some uninlined call sites in the callee into the caller, // add edges from the caller to all of the callees of the callee. CallGraphNode::iterator I = CalleeNode->begin(), E = CalleeNode->end(); // Consider the case where CalleeNode == CallerNode. CallGraphNode::CalledFunctionsVector CallCache; if (CalleeNode == CallerNode) { CallCache.assign(I, E); I = CallCache.begin(); E = CallCache.end(); } for (; I != E; ++I) { const Value *OrigCall = I->first; ValueToValueMapTy::iterator VMI = VMap.find(OrigCall); // Only copy the edge if the call was inlined! if (VMI == VMap.end() || VMI->second == 0) continue; // If the call was inlined, but then constant folded, there is no edge to // add. Check for this case. Instruction *NewCall = dyn_cast<Instruction>(VMI->second); if (NewCall == 0) continue; // Remember that this call site got inlined for the client of // InlineFunction. IFI.InlinedCalls.push_back(NewCall); // It's possible that inlining the callsite will cause it to go from an // indirect to a direct call by resolving a function pointer. If this // happens, set the callee of the new call site to a more precise // destination. This can also happen if the call graph node of the caller // was just unnecessarily imprecise. if (I->second->getFunction() == 0) if (Function *F = CallSite(NewCall).getCalledFunction()) { // Indirect call site resolved to direct call. CallerNode->addCalledFunction(CallSite(NewCall), CG[F]); continue; } CallerNode->addCalledFunction(CallSite(NewCall), I->second); } // Update the call graph by deleting the edge from Callee to Caller. We must // do this after the loop above in case Caller and Callee are the same. CallerNode->removeCallEdgeFor(CS); } /// HandleByValArgument - When inlining a call site that has a byval argument, /// we have to make the implicit memcpy explicit by adding it. static Value *HandleByValArgument(Value *Arg, Instruction *TheCall, const Function *CalledFunc, InlineFunctionInfo &IFI, unsigned ByValAlignment) { const Type *AggTy = cast<PointerType>(Arg->getType())->getElementType(); // If the called function is readonly, then it could not mutate the caller's // copy of the byval'd memory. In this case, it is safe to elide the copy and // temporary. if (CalledFunc->onlyReadsMemory()) { // If the byval argument has a specified alignment that is greater than the // passed in pointer, then we either have to round up the input pointer or // give up on this transformation. if (ByValAlignment <= 1) // 0 = unspecified, 1 = no particular alignment. return Arg; // If the pointer is already known to be sufficiently aligned, or if we can // round it up to a larger alignment, then we don't need a temporary. if (getOrEnforceKnownAlignment(Arg, ByValAlignment, IFI.TD) >= ByValAlignment) return Arg; // Otherwise, we have to make a memcpy to get a safe alignment. This is bad // for code quality, but rarely happens and is required for correctness. } LLVMContext &Context = Arg->getContext(); const Type *VoidPtrTy = Type::getInt8PtrTy(Context); // Create the alloca. If we have TargetData, use nice alignment. unsigned Align = 1; if (IFI.TD) Align = IFI.TD->getPrefTypeAlignment(AggTy); // If the byval had an alignment specified, we *must* use at least that // alignment, as it is required by the byval argument (and uses of the // pointer inside the callee). Align = std::max(Align, ByValAlignment); Function *Caller = TheCall->getParent()->getParent(); Value *NewAlloca = new AllocaInst(AggTy, 0, Align, Arg->getName(), &*Caller->begin()->begin()); // Emit a memcpy. const Type *Tys[3] = {VoidPtrTy, VoidPtrTy, Type::getInt64Ty(Context)}; Function *MemCpyFn = Intrinsic::getDeclaration(Caller->getParent(), Intrinsic::memcpy, Tys, 3); Value *DestCast = new BitCastInst(NewAlloca, VoidPtrTy, "tmp", TheCall); Value *SrcCast = new BitCastInst(Arg, VoidPtrTy, "tmp", TheCall); Value *Size; if (IFI.TD == 0) Size = ConstantExpr::getSizeOf(AggTy); else Size = ConstantInt::get(Type::getInt64Ty(Context), IFI.TD->getTypeStoreSize(AggTy)); // Always generate a memcpy of alignment 1 here because we don't know // the alignment of the src pointer. Other optimizations can infer // better alignment. Value *CallArgs[] = { DestCast, SrcCast, Size, ConstantInt::get(Type::getInt32Ty(Context), 1), ConstantInt::getFalse(Context) // isVolatile }; CallInst *TheMemCpy = CallInst::Create(MemCpyFn, CallArgs, CallArgs+5, "", TheCall); // If we have a call graph, update it. if (CallGraph *CG = IFI.CG) { CallGraphNode *MemCpyCGN = CG->getOrInsertFunction(MemCpyFn); CallGraphNode *CallerNode = (*CG)[Caller]; CallerNode->addCalledFunction(TheMemCpy, MemCpyCGN); } // Uses of the argument in the function should use our new alloca // instead. return NewAlloca; } // InlineFunction - This function inlines the called function into the basic // block of the caller. This returns false if it is not possible to inline this // call. The program is still in a well defined state if this occurs though. // // Note that this only does one level of inlining. For example, if the // instruction 'call B' is inlined, and 'B' calls 'C', then the call to 'C' now // exists in the instruction stream. Similarly this will inline a recursive // function by one level. // bool llvm::InlineFunction(CallSite CS, InlineFunctionInfo &IFI) { Instruction *TheCall = CS.getInstruction(); LLVMContext &Context = TheCall->getContext(); assert(TheCall->getParent() && TheCall->getParent()->getParent() && "Instruction not in function!"); // If IFI has any state in it, zap it before we fill it in. IFI.reset(); const Function *CalledFunc = CS.getCalledFunction(); if (CalledFunc == 0 || // Can't inline external function or indirect CalledFunc->isDeclaration() || // call, or call to a vararg function! CalledFunc->getFunctionType()->isVarArg()) return false; // If the call to the callee is not a tail call, we must clear the 'tail' // flags on any calls that we inline. bool MustClearTailCallFlags = !(isa<CallInst>(TheCall) && cast<CallInst>(TheCall)->isTailCall()); // If the call to the callee cannot throw, set the 'nounwind' flag on any // calls that we inline. bool MarkNoUnwind = CS.doesNotThrow(); BasicBlock *OrigBB = TheCall->getParent(); Function *Caller = OrigBB->getParent(); // GC poses two hazards to inlining, which only occur when the callee has GC: // 1. If the caller has no GC, then the callee's GC must be propagated to the // caller. // 2. If the caller has a differing GC, it is invalid to inline. if (CalledFunc->hasGC()) { if (!Caller->hasGC()) Caller->setGC(CalledFunc->getGC()); else if (CalledFunc->getGC() != Caller->getGC()) return false; } // Get an iterator to the last basic block in the function, which will have // the new function inlined after it. // Function::iterator LastBlock = &Caller->back(); // Make sure to capture all of the return instructions from the cloned // function. SmallVector<ReturnInst*, 8> Returns; ClonedCodeInfo InlinedFunctionInfo; Function::iterator FirstNewBlock; { // Scope to destroy VMap after cloning. ValueToValueMapTy VMap; assert(CalledFunc->arg_size() == CS.arg_size() && "No varargs calls can be inlined!"); // Calculate the vector of arguments to pass into the function cloner, which // matches up the formal to the actual argument values. CallSite::arg_iterator AI = CS.arg_begin(); unsigned ArgNo = 0; for (Function::const_arg_iterator I = CalledFunc->arg_begin(), E = CalledFunc->arg_end(); I != E; ++I, ++AI, ++ArgNo) { Value *ActualArg = *AI; // When byval arguments actually inlined, we need to make the copy implied // by them explicit. However, we don't do this if the callee is readonly // or readnone, because the copy would be unneeded: the callee doesn't // modify the struct. if (CalledFunc->paramHasAttr(ArgNo+1, Attribute::ByVal)) { ActualArg = HandleByValArgument(ActualArg, TheCall, CalledFunc, IFI, CalledFunc->getParamAlignment(ArgNo+1)); // Calls that we inline may use the new alloca, so we need to clear // their 'tail' flags if HandleByValArgument introduced a new alloca and // the callee has calls. MustClearTailCallFlags |= ActualArg != *AI; } VMap[I] = ActualArg; } // We want the inliner to prune the code as it copies. We would LOVE to // have no dead or constant instructions leftover after inlining occurs // (which can happen, e.g., because an argument was constant), but we'll be // happy with whatever the cloner can do. CloneAndPruneFunctionInto(Caller, CalledFunc, VMap, /*ModuleLevelChanges=*/false, Returns, ".i", &InlinedFunctionInfo, IFI.TD, TheCall); // Remember the first block that is newly cloned over. FirstNewBlock = LastBlock; ++FirstNewBlock; // Update the callgraph if requested. if (IFI.CG) UpdateCallGraphAfterInlining(CS, FirstNewBlock, VMap, IFI); } // If there are any alloca instructions in the block that used to be the entry // block for the callee, move them to the entry block of the caller. First // calculate which instruction they should be inserted before. We insert the // instructions at the end of the current alloca list. // { BasicBlock::iterator InsertPoint = Caller->begin()->begin(); for (BasicBlock::iterator I = FirstNewBlock->begin(), E = FirstNewBlock->end(); I != E; ) { AllocaInst *AI = dyn_cast<AllocaInst>(I++); if (AI == 0) continue; // If the alloca is now dead, remove it. This often occurs due to code // specialization. if (AI->use_empty()) { AI->eraseFromParent(); continue; } if (!isa<Constant>(AI->getArraySize())) continue; // Keep track of the static allocas that we inline into the caller. IFI.StaticAllocas.push_back(AI); // Scan for the block of allocas that we can move over, and move them // all at once. while (isa<AllocaInst>(I) && isa<Constant>(cast<AllocaInst>(I)->getArraySize())) { IFI.StaticAllocas.push_back(cast<AllocaInst>(I)); ++I; } // Transfer all of the allocas over in a block. Using splice means // that the instructions aren't removed from the symbol table, then // reinserted. Caller->getEntryBlock().getInstList().splice(InsertPoint, FirstNewBlock->getInstList(), AI, I); } } // If the inlined code contained dynamic alloca instructions, wrap the inlined // code with llvm.stacksave/llvm.stackrestore intrinsics. if (InlinedFunctionInfo.ContainsDynamicAllocas) { Module *M = Caller->getParent(); // Get the two intrinsics we care about. Function *StackSave = Intrinsic::getDeclaration(M, Intrinsic::stacksave); Function *StackRestore=Intrinsic::getDeclaration(M,Intrinsic::stackrestore); // If we are preserving the callgraph, add edges to the stacksave/restore // functions for the calls we insert. CallGraphNode *StackSaveCGN = 0, *StackRestoreCGN = 0, *CallerNode = 0; if (CallGraph *CG = IFI.CG) { StackSaveCGN = CG->getOrInsertFunction(StackSave); StackRestoreCGN = CG->getOrInsertFunction(StackRestore); CallerNode = (*CG)[Caller]; } // Insert the llvm.stacksave. CallInst *SavedPtr = CallInst::Create(StackSave, "savedstack", FirstNewBlock->begin()); if (IFI.CG) CallerNode->addCalledFunction(SavedPtr, StackSaveCGN); // Insert a call to llvm.stackrestore before any return instructions in the // inlined function. for (unsigned i = 0, e = Returns.size(); i != e; ++i) { CallInst *CI = CallInst::Create(StackRestore, SavedPtr, "", Returns[i]); if (IFI.CG) CallerNode->addCalledFunction(CI, StackRestoreCGN); } // Count the number of StackRestore calls we insert. unsigned NumStackRestores = Returns.size(); // If we are inlining an invoke instruction, insert restores before each // unwind. These unwinds will be rewritten into branches later. if (InlinedFunctionInfo.ContainsUnwinds && isa<InvokeInst>(TheCall)) { for (Function::iterator BB = FirstNewBlock, E = Caller->end(); BB != E; ++BB) if (UnwindInst *UI = dyn_cast<UnwindInst>(BB->getTerminator())) { CallInst *CI = CallInst::Create(StackRestore, SavedPtr, "", UI); if (IFI.CG) CallerNode->addCalledFunction(CI, StackRestoreCGN); ++NumStackRestores; } } } // If we are inlining tail call instruction through a call site that isn't // marked 'tail', we must remove the tail marker for any calls in the inlined // code. Also, calls inlined through a 'nounwind' call site should be marked // 'nounwind'. if (InlinedFunctionInfo.ContainsCalls && (MustClearTailCallFlags || MarkNoUnwind)) { for (Function::iterator BB = FirstNewBlock, E = Caller->end(); BB != E; ++BB) for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) if (CallInst *CI = dyn_cast<CallInst>(I)) { if (MustClearTailCallFlags) CI->setTailCall(false); if (MarkNoUnwind) CI->setDoesNotThrow(); } } // If we are inlining through a 'nounwind' call site then any inlined 'unwind' // instructions are unreachable. if (InlinedFunctionInfo.ContainsUnwinds && MarkNoUnwind) for (Function::iterator BB = FirstNewBlock, E = Caller->end(); BB != E; ++BB) { TerminatorInst *Term = BB->getTerminator(); if (isa<UnwindInst>(Term)) { new UnreachableInst(Context, Term); BB->getInstList().erase(Term); } } // If we are inlining for an invoke instruction, we must make sure to rewrite // any inlined 'unwind' instructions into branches to the invoke exception // destination, and call instructions into invoke instructions. if (InvokeInst *II = dyn_cast<InvokeInst>(TheCall)) HandleInlinedInvoke(II, FirstNewBlock, InlinedFunctionInfo); // If we cloned in _exactly one_ basic block, and if that block ends in a // return instruction, we splice the body of the inlined callee directly into // the calling basic block. if (Returns.size() == 1 && std::distance(FirstNewBlock, Caller->end()) == 1) { // Move all of the instructions right before the call. OrigBB->getInstList().splice(TheCall, FirstNewBlock->getInstList(), FirstNewBlock->begin(), FirstNewBlock->end()); // Remove the cloned basic block. Caller->getBasicBlockList().pop_back(); // If the call site was an invoke instruction, add a branch to the normal // destination. if (InvokeInst *II = dyn_cast<InvokeInst>(TheCall)) BranchInst::Create(II->getNormalDest(), TheCall); // If the return instruction returned a value, replace uses of the call with // uses of the returned value. if (!TheCall->use_empty()) { ReturnInst *R = Returns[0]; if (TheCall == R->getReturnValue()) TheCall->replaceAllUsesWith(UndefValue::get(TheCall->getType())); else TheCall->replaceAllUsesWith(R->getReturnValue()); } // Since we are now done with the Call/Invoke, we can delete it. TheCall->eraseFromParent(); // Since we are now done with the return instruction, delete it also. Returns[0]->eraseFromParent(); // We are now done with the inlining. return true; } // Otherwise, we have the normal case, of more than one block to inline or // multiple return sites. // We want to clone the entire callee function into the hole between the // "starter" and "ender" blocks. How we accomplish this depends on whether // this is an invoke instruction or a call instruction. BasicBlock *AfterCallBB; if (InvokeInst *II = dyn_cast<InvokeInst>(TheCall)) { // Add an unconditional branch to make this look like the CallInst case... BranchInst *NewBr = BranchInst::Create(II->getNormalDest(), TheCall); // Split the basic block. This guarantees that no PHI nodes will have to be // updated due to new incoming edges, and make the invoke case more // symmetric to the call case. AfterCallBB = OrigBB->splitBasicBlock(NewBr, CalledFunc->getName()+".exit"); } else { // It's a call // If this is a call instruction, we need to split the basic block that // the call lives in. // AfterCallBB = OrigBB->splitBasicBlock(TheCall, CalledFunc->getName()+".exit"); } // Change the branch that used to go to AfterCallBB to branch to the first // basic block of the inlined function. // TerminatorInst *Br = OrigBB->getTerminator(); assert(Br && Br->getOpcode() == Instruction::Br && "splitBasicBlock broken!"); Br->setOperand(0, FirstNewBlock); // Now that the function is correct, make it a little bit nicer. In // particular, move the basic blocks inserted from the end of the function // into the space made by splitting the source basic block. Caller->getBasicBlockList().splice(AfterCallBB, Caller->getBasicBlockList(), FirstNewBlock, Caller->end()); // Handle all of the return instructions that we just cloned in, and eliminate // any users of the original call/invoke instruction. const Type *RTy = CalledFunc->getReturnType(); PHINode *PHI = 0; if (Returns.size() > 1) { // The PHI node should go at the front of the new basic block to merge all // possible incoming values. if (!TheCall->use_empty()) { PHI = PHINode::Create(RTy, Returns.size(), TheCall->getName(), AfterCallBB->begin()); // Anything that used the result of the function call should now use the // PHI node as their operand. TheCall->replaceAllUsesWith(PHI); } // Loop over all of the return instructions adding entries to the PHI node // as appropriate. if (PHI) { for (unsigned i = 0, e = Returns.size(); i != e; ++i) { ReturnInst *RI = Returns[i]; assert(RI->getReturnValue()->getType() == PHI->getType() && "Ret value not consistent in function!"); PHI->addIncoming(RI->getReturnValue(), RI->getParent()); } } // Add a branch to the merge points and remove return instructions. for (unsigned i = 0, e = Returns.size(); i != e; ++i) { ReturnInst *RI = Returns[i]; BranchInst::Create(AfterCallBB, RI); RI->eraseFromParent(); } } else if (!Returns.empty()) { // Otherwise, if there is exactly one return value, just replace anything // using the return value of the call with the computed value. if (!TheCall->use_empty()) { if (TheCall == Returns[0]->getReturnValue()) TheCall->replaceAllUsesWith(UndefValue::get(TheCall->getType())); else TheCall->replaceAllUsesWith(Returns[0]->getReturnValue()); } // Splice the code from the return block into the block that it will return // to, which contains the code that was after the call. BasicBlock *ReturnBB = Returns[0]->getParent(); AfterCallBB->getInstList().splice(AfterCallBB->begin(), ReturnBB->getInstList()); // Update PHI nodes that use the ReturnBB to use the AfterCallBB. ReturnBB->replaceAllUsesWith(AfterCallBB); // Delete the return instruction now and empty ReturnBB now. Returns[0]->eraseFromParent(); ReturnBB->eraseFromParent(); } else if (!TheCall->use_empty()) { // No returns, but something is using the return value of the call. Just // nuke the result. TheCall->replaceAllUsesWith(UndefValue::get(TheCall->getType())); } // Since we are now done with the Call/Invoke, we can delete it. TheCall->eraseFromParent(); // We should always be able to fold the entry block of the function into the // single predecessor of the block... assert(cast<BranchInst>(Br)->isUnconditional() && "splitBasicBlock broken!"); BasicBlock *CalleeEntry = cast<BranchInst>(Br)->getSuccessor(0); // Splice the code entry block into calling block, right before the // unconditional branch. OrigBB->getInstList().splice(Br, CalleeEntry->getInstList()); CalleeEntry->replaceAllUsesWith(OrigBB); // Update PHI nodes // Remove the unconditional branch. OrigBB->getInstList().erase(Br); // Now we can remove the CalleeEntry block, which is now empty. Caller->getBasicBlockList().erase(CalleeEntry); // If we inserted a phi node, check to see if it has a single value (e.g. all // the entries are the same or undef). If so, remove the PHI so it doesn't // block other optimizations. if (PHI) if (Value *V = SimplifyInstruction(PHI, IFI.TD)) { PHI->replaceAllUsesWith(V); PHI->eraseFromParent(); } return true; }