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Diffstat (limited to 'contrib/llvm/lib/Transforms/Utils/InlineFunction.cpp')
| -rw-r--r-- | contrib/llvm/lib/Transforms/Utils/InlineFunction.cpp | 662 |
1 files changed, 662 insertions, 0 deletions
diff --git a/contrib/llvm/lib/Transforms/Utils/InlineFunction.cpp b/contrib/llvm/lib/Transforms/Utils/InlineFunction.cpp new file mode 100644 index 0000000..91390bc --- /dev/null +++ b/contrib/llvm/lib/Transforms/Utils/InlineFunction.cpp @@ -0,0 +1,662 @@ +//===- 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/Target/TargetData.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. + SmallVector<Value*, 8> InvokeArgs(CI->op_begin()+1, CI->op_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, + DenseMap<const Value*, Value*> &ValueMap, + 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; + + DenseMap<const Value*, Value*>::iterator VMI = ValueMap.find(OrigCall); + // Only copy the edge if the call was inlined! + if (VMI == ValueMap.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::get(NewCall), CG[F]); + + continue; + } + + CallerNode->addCalledFunction(CallSite::get(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); +} + +// 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. Similiarly 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 ValueMap after cloning. + DenseMap<const Value*, Value*> ValueMap; + + 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) && + !CalledFunc->onlyReadsMemory()) { + const Type *AggTy = cast<PointerType>(I->getType())->getElementType(); + 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); + Value *NewAlloca = new AllocaInst(AggTy, 0, Align, + I->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(*AI, 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::get(Type::getInt1Ty(Context), 0) + }; + 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. + ActualArg = NewAlloca; + } + + ValueMap[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, ValueMap, 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, ValueMap, 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 if the + // StaticAllocas pointer is non-null. + 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(); + + if (Returns.size() > 1) { + // The PHI node should go at the front of the new basic block to merge all + // possible incoming values. + PHINode *PHI = 0; + if (!TheCall->use_empty()) { + PHI = PHINode::Create(RTy, 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()); + } + + // Now that we inserted the PHI, 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 (Value *V = PHI->hasConstantValue()) { + PHI->replaceAllUsesWith(V); + PHI->eraseFromParent(); + } + } + + + // 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); + + return true; +} |
