void PromoteMem2Reg::run() { Function &F = *DF.getRoot()->getParent(); if (AST) PointerAllocaValues.resize(Allocas.size()); AllocaDbgDeclares.resize(Allocas.size()); AllocaInfo Info; LargeBlockInfo LBI; for (unsigned AllocaNum = 0; AllocaNum != Allocas.size(); ++AllocaNum) { AllocaInst *AI = Allocas[AllocaNum]; assert(isAllocaPromotable(AI) && "Cannot promote non-promotable alloca!"); assert(AI->getParent()->getParent() == &F && "All allocas should be in the same function, which is same as DF!"); if (AI->use_empty()) { // If there are no uses of the alloca, just delete it now. if (AST) AST->deleteValue(AI); AI->eraseFromParent(); // Remove the alloca from the Allocas list, since it has been processed RemoveFromAllocasList(AllocaNum); ++NumDeadAlloca; continue; } // Calculate the set of read and write-locations for each alloca. This is // analogous to finding the 'uses' and 'definitions' of each variable. Info.AnalyzeAlloca(AI); // If there is only a single store to this value, replace any loads of // it that are directly dominated by the definition with the value stored. if (Info.DefiningBlocks.size() == 1) { RewriteSingleStoreAlloca(AI, Info, LBI); // Finally, after the scan, check to see if the store is all that is left. if (Info.UsingBlocks.empty()) { // Record debuginfo for the store and remove the declaration's debuginfo. if (DbgDeclareInst *DDI = Info.DbgDeclare) { ConvertDebugDeclareToDebugValue(DDI, Info.OnlyStore); DDI->eraseFromParent(); } // Remove the (now dead) store and alloca. Info.OnlyStore->eraseFromParent(); LBI.deleteValue(Info.OnlyStore); if (AST) AST->deleteValue(AI); AI->eraseFromParent(); LBI.deleteValue(AI); // The alloca has been processed, move on. RemoveFromAllocasList(AllocaNum); ++NumSingleStore; continue; } } // If the alloca is only read and written in one basic block, just perform a // linear sweep over the block to eliminate it. if (Info.OnlyUsedInOneBlock) { PromoteSingleBlockAlloca(AI, Info, LBI); // Finally, after the scan, check to see if the stores are all that is // left. if (Info.UsingBlocks.empty()) { // Remove the (now dead) stores and alloca. while (!AI->use_empty()) { StoreInst *SI = cast<StoreInst>(AI->use_back()); // Record debuginfo for the store before removing it. if (DbgDeclareInst *DDI = Info.DbgDeclare) ConvertDebugDeclareToDebugValue(DDI, SI); SI->eraseFromParent(); LBI.deleteValue(SI); } if (AST) AST->deleteValue(AI); AI->eraseFromParent(); LBI.deleteValue(AI); // The alloca has been processed, move on. RemoveFromAllocasList(AllocaNum); // The alloca's debuginfo can be removed as well. if (DbgDeclareInst *DDI = Info.DbgDeclare) DDI->eraseFromParent(); ++NumLocalPromoted; continue; } } // If we haven't computed a numbering for the BB's in the function, do so // now. if (BBNumbers.empty()) { unsigned ID = 0; for (Function::iterator I = F.begin(), E = F.end(); I != E; ++I) BBNumbers[I] = ID++; } // If we have an AST to keep updated, remember some pointer value that is // stored into the alloca. if (AST) PointerAllocaValues[AllocaNum] = Info.AllocaPointerVal; // Remember the dbg.declare intrinsic describing this alloca, if any. if (Info.DbgDeclare) AllocaDbgDeclares[AllocaNum] = Info.DbgDeclare; // Keep the reverse mapping of the 'Allocas' array for the rename pass. AllocaLookup[Allocas[AllocaNum]] = AllocaNum; // At this point, we're committed to promoting the alloca using IDF's, and // the standard SSA construction algorithm. Determine which blocks need PHI // nodes and see if we can optimize out some work by avoiding insertion of // dead phi nodes. DetermineInsertionPoint(AI, AllocaNum, Info); } if (Allocas.empty()) return; // All of the allocas must have been trivial! LBI.clear(); // Set the incoming values for the basic block to be null values for all of // the alloca's. We do this in case there is a load of a value that has not // been stored yet. In this case, it will get this null value. // RenamePassData::ValVector Values(Allocas.size()); for (unsigned i = 0, e = Allocas.size(); i != e; ++i) Values[i] = UndefValue::get(Allocas[i]->getAllocatedType()); // Walks all basic blocks in the function performing the SSA rename algorithm // and inserting the phi nodes we marked as necessary // std::vector<RenamePassData> RenamePassWorkList; RenamePassWorkList.push_back(RenamePassData(F.begin(), 0, Values)); do { RenamePassData RPD; RPD.swap(RenamePassWorkList.back()); RenamePassWorkList.pop_back(); // RenamePass may add new worklist entries. RenamePass(RPD.BB, RPD.Pred, RPD.Values, RenamePassWorkList); } while (!RenamePassWorkList.empty()); // The renamer uses the Visited set to avoid infinite loops. Clear it now. Visited.clear(); // Remove the allocas themselves from the function. for (unsigned i = 0, e = Allocas.size(); i != e; ++i) { Instruction *A = Allocas[i]; // If there are any uses of the alloca instructions left, they must be in // sections of dead code that were not processed on the dominance frontier. // Just delete the users now. // if (!A->use_empty()) A->replaceAllUsesWith(UndefValue::get(A->getType())); if (AST) AST->deleteValue(A); A->eraseFromParent(); } // Remove alloca's dbg.declare instrinsics from the function. for (unsigned i = 0, e = AllocaDbgDeclares.size(); i != e; ++i) if (DbgDeclareInst *DDI = AllocaDbgDeclares[i]) DDI->eraseFromParent(); // Loop over all of the PHI nodes and see if there are any that we can get // rid of because they merge all of the same incoming values. This can // happen due to undef values coming into the PHI nodes. This process is // iterative, because eliminating one PHI node can cause others to be removed. bool EliminatedAPHI = true; while (EliminatedAPHI) { EliminatedAPHI = false; for (DenseMap<std::pair<BasicBlock*, unsigned>, PHINode*>::iterator I = NewPhiNodes.begin(), E = NewPhiNodes.end(); I != E;) { PHINode *PN = I->second; // If this PHI node merges one value and/or undefs, get the value. if (Value *V = PN->hasConstantValue(&DT)) { if (AST && PN->getType()->isPointerTy()) AST->deleteValue(PN); PN->replaceAllUsesWith(V); PN->eraseFromParent(); NewPhiNodes.erase(I++); EliminatedAPHI = true; continue; } ++I; } } // At this point, the renamer has added entries to PHI nodes for all reachable // code. Unfortunately, there may be unreachable blocks which the renamer // hasn't traversed. If this is the case, the PHI nodes may not // have incoming values for all predecessors. Loop over all PHI nodes we have // created, inserting undef values if they are missing any incoming values. // for (DenseMap<std::pair<BasicBlock*, unsigned>, PHINode*>::iterator I = NewPhiNodes.begin(), E = NewPhiNodes.end(); I != E; ++I) { // We want to do this once per basic block. As such, only process a block // when we find the PHI that is the first entry in the block. PHINode *SomePHI = I->second; BasicBlock *BB = SomePHI->getParent(); if (&BB->front() != SomePHI) continue; // Only do work here if there the PHI nodes are missing incoming values. We // know that all PHI nodes that were inserted in a block will have the same // number of incoming values, so we can just check any of them. if (SomePHI->getNumIncomingValues() == getNumPreds(BB)) continue; // Get the preds for BB. SmallVector<BasicBlock*, 16> Preds(pred_begin(BB), pred_end(BB)); // Ok, now we know that all of the PHI nodes are missing entries for some // basic blocks. Start by sorting the incoming predecessors for efficient // access. std::sort(Preds.begin(), Preds.end()); // Now we loop through all BB's which have entries in SomePHI and remove // them from the Preds list. for (unsigned i = 0, e = SomePHI->getNumIncomingValues(); i != e; ++i) { // Do a log(n) search of the Preds list for the entry we want. SmallVector<BasicBlock*, 16>::iterator EntIt = std::lower_bound(Preds.begin(), Preds.end(), SomePHI->getIncomingBlock(i)); assert(EntIt != Preds.end() && *EntIt == SomePHI->getIncomingBlock(i)&& "PHI node has entry for a block which is not a predecessor!"); // Remove the entry Preds.erase(EntIt); } // At this point, the blocks left in the preds list must have dummy // entries inserted into every PHI nodes for the block. Update all the phi // nodes in this block that we are inserting (there could be phis before // mem2reg runs). unsigned NumBadPreds = SomePHI->getNumIncomingValues(); BasicBlock::iterator BBI = BB->begin(); while ((SomePHI = dyn_cast<PHINode>(BBI++)) && SomePHI->getNumIncomingValues() == NumBadPreds) { Value *UndefVal = UndefValue::get(SomePHI->getType()); for (unsigned pred = 0, e = Preds.size(); pred != e; ++pred) SomePHI->addIncoming(UndefVal, Preds[pred]); } } NewPhiNodes.clear(); }
/// 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, bool InsertLifetime) { Instruction *TheCall = CS.getInstruction(); 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 the personality function from the callee if it contains a landing pad. Value *CalleePersonality = 0; for (Function::const_iterator I = CalledFunc->begin(), E = CalledFunc->end(); I != E; ++I) if (const InvokeInst *II = dyn_cast<InvokeInst>(I->getTerminator())) { const BasicBlock *BB = II->getUnwindDest(); const LandingPadInst *LP = BB->getLandingPadInst(); CalleePersonality = LP->getPersonalityFn(); break; } // Find the personality function used by the landing pads of the caller. If it // exists, then check to see that it matches the personality function used in // the callee. if (CalleePersonality) { for (Function::const_iterator I = Caller->begin(), E = Caller->end(); I != E; ++I) if (const InvokeInst *II = dyn_cast<InvokeInst>(I->getTerminator())) { const BasicBlock *BB = II->getUnwindDest(); const LandingPadInst *LP = BB->getLandingPadInst(); // If the personality functions match, then we can perform the // inlining. Otherwise, we can't inline. // TODO: This isn't 100% true. Some personality functions are proper // supersets of others and can be used in place of the other. if (LP->getPersonalityFn() != CalleePersonality) return false; break; } } // 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; const Argument *Arg = I; // 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 (CS.isByValArgument(ArgNo)) { ActualArg = HandleByValArgument(ActualArg, Arg, 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); // Update inlined instructions' line number information. fixupLineNumbers(Caller, FirstNewBlock, TheCall); } // 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); } } // Leave lifetime markers for the static alloca's, scoping them to the // function we just inlined. if (InsertLifetime && !IFI.StaticAllocas.empty()) { IRBuilder<> builder(FirstNewBlock->begin()); for (unsigned ai = 0, ae = IFI.StaticAllocas.size(); ai != ae; ++ai) { AllocaInst *AI = IFI.StaticAllocas[ai]; // If the alloca is already scoped to something smaller than the whole // function then there's no need to add redundant, less accurate markers. if (hasLifetimeMarkers(AI)) continue; // Try to determine the size of the allocation. ConstantInt *AllocaSize = 0; if (ConstantInt *AIArraySize = dyn_cast<ConstantInt>(AI->getArraySize())) { if (IFI.TD) { Type *AllocaType = AI->getAllocatedType(); uint64_t AllocaTypeSize = IFI.TD->getTypeAllocSize(AllocaType); uint64_t AllocaArraySize = AIArraySize->getLimitedValue(); assert(AllocaArraySize > 0 && "array size of AllocaInst is zero"); // Check that array size doesn't saturate uint64_t and doesn't // overflow when it's multiplied by type size. if (AllocaArraySize != ~0ULL && UINT64_MAX / AllocaArraySize >= AllocaTypeSize) { AllocaSize = ConstantInt::get(Type::getInt64Ty(AI->getContext()), AllocaArraySize * AllocaTypeSize); } } } builder.CreateLifetimeStart(AI, AllocaSize); for (unsigned ri = 0, re = Returns.size(); ri != re; ++ri) { IRBuilder<> builder(Returns[ri]); builder.CreateLifetimeEnd(AI, AllocaSize); } } } // 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); // Insert the llvm.stacksave. CallInst *SavedPtr = IRBuilder<>(FirstNewBlock, FirstNewBlock->begin()) .CreateCall(StackSave, "savedstack"); // Insert a call to llvm.stackrestore before any return instructions in the // inlined function. for (unsigned i = 0, e = Returns.size(); i != e; ++i) { IRBuilder<>(Returns[i]).CreateCall(StackRestore, SavedPtr); } } // 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 for an invoke instruction, we must make sure to rewrite // any 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 *NewBr = BranchInst::Create(II->getNormalDest(), TheCall); NewBr->setDebugLoc(Returns[0]->getDebugLoc()); } // 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; BranchInst *CreatedBranchToNormalDest = NULL; if (InvokeInst *II = dyn_cast<InvokeInst>(TheCall)) { // Add an unconditional branch to make this look like the CallInst case... CreatedBranchToNormalDest = 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(CreatedBranchToNormalDest, 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. 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. DebugLoc Loc; for (unsigned i = 0, e = Returns.size(); i != e; ++i) { ReturnInst *RI = Returns[i]; BranchInst* BI = BranchInst::Create(AfterCallBB, RI); Loc = RI->getDebugLoc(); BI->setDebugLoc(Loc); RI->eraseFromParent(); } // We need to set the debug location to *somewhere* inside the // inlined function. The line number may be nonsensical, but the // instruction will at least be associated with the right // function. if (CreatedBranchToNormalDest) CreatedBranchToNormalDest->setDebugLoc(Loc); } 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()); } // Update PHI nodes that use the ReturnBB to use the AfterCallBB. BasicBlock *ReturnBB = Returns[0]->getParent(); ReturnBB->replaceAllUsesWith(AfterCallBB); // Splice the code from the return block into the block that it will return // to, which contains the code that was after the call. AfterCallBB->getInstList().splice(AfterCallBB->begin(), ReturnBB->getInstList()); if (CreatedBranchToNormalDest) CreatedBranchToNormalDest->setDebugLoc(Returns[0]->getDebugLoc()); // 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. CalleeEntry->replaceAllUsesWith(OrigBB); // Update PHI nodes OrigBB->getInstList().splice(Br, CalleeEntry->getInstList()); // 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; }
void PromoteMem2Reg::run() { Function &F = *DT.getRoot()->getParent(); AllocaDbgDeclares.resize(Allocas.size()); AllocaInfo Info; LargeBlockInfo LBI; ForwardIDFCalculator IDF(DT); for (unsigned AllocaNum = 0; AllocaNum != Allocas.size(); ++AllocaNum) { AllocaInst *AI = Allocas[AllocaNum]; assert(isAllocaPromotable(AI) && "Cannot promote non-promotable alloca!"); assert(AI->getParent()->getParent() == &F && "All allocas should be in the same function, which is same as DF!"); removeLifetimeIntrinsicUsers(AI); if (AI->use_empty()) { // If there are no uses of the alloca, just delete it now. AI->eraseFromParent(); // Remove the alloca from the Allocas list, since it has been processed RemoveFromAllocasList(AllocaNum); ++NumDeadAlloca; continue; } // Calculate the set of read and write-locations for each alloca. This is // analogous to finding the 'uses' and 'definitions' of each variable. Info.AnalyzeAlloca(AI); // If there is only a single store to this value, replace any loads of // it that are directly dominated by the definition with the value stored. if (Info.DefiningBlocks.size() == 1) { if (rewriteSingleStoreAlloca(AI, Info, LBI, SQ.DL, DT, AC)) { // The alloca has been processed, move on. RemoveFromAllocasList(AllocaNum); ++NumSingleStore; continue; } } // If the alloca is only read and written in one basic block, just perform a // linear sweep over the block to eliminate it. if (Info.OnlyUsedInOneBlock && promoteSingleBlockAlloca(AI, Info, LBI, SQ.DL, DT, AC)) { // The alloca has been processed, move on. RemoveFromAllocasList(AllocaNum); continue; } // If we haven't computed a numbering for the BB's in the function, do so // now. if (BBNumbers.empty()) { unsigned ID = 0; for (auto &BB : F) BBNumbers[&BB] = ID++; } // Remember the dbg.declare intrinsic describing this alloca, if any. if (!Info.DbgDeclares.empty()) AllocaDbgDeclares[AllocaNum] = Info.DbgDeclares; // Keep the reverse mapping of the 'Allocas' array for the rename pass. AllocaLookup[Allocas[AllocaNum]] = AllocaNum; // At this point, we're committed to promoting the alloca using IDF's, and // the standard SSA construction algorithm. Determine which blocks need PHI // nodes and see if we can optimize out some work by avoiding insertion of // dead phi nodes. // Unique the set of defining blocks for efficient lookup. SmallPtrSet<BasicBlock *, 32> DefBlocks; DefBlocks.insert(Info.DefiningBlocks.begin(), Info.DefiningBlocks.end()); // Determine which blocks the value is live in. These are blocks which lead // to uses. SmallPtrSet<BasicBlock *, 32> LiveInBlocks; ComputeLiveInBlocks(AI, Info, DefBlocks, LiveInBlocks); // At this point, we're committed to promoting the alloca using IDF's, and // the standard SSA construction algorithm. Determine which blocks need phi // nodes and see if we can optimize out some work by avoiding insertion of // dead phi nodes. IDF.setLiveInBlocks(LiveInBlocks); IDF.setDefiningBlocks(DefBlocks); SmallVector<BasicBlock *, 32> PHIBlocks; IDF.calculate(PHIBlocks); if (PHIBlocks.size() > 1) llvm::sort(PHIBlocks, [this](BasicBlock *A, BasicBlock *B) { return BBNumbers.lookup(A) < BBNumbers.lookup(B); }); unsigned CurrentVersion = 0; for (BasicBlock *BB : PHIBlocks) QueuePhiNode(BB, AllocaNum, CurrentVersion); } if (Allocas.empty()) return; // All of the allocas must have been trivial! LBI.clear(); // Set the incoming values for the basic block to be null values for all of // the alloca's. We do this in case there is a load of a value that has not // been stored yet. In this case, it will get this null value. RenamePassData::ValVector Values(Allocas.size()); for (unsigned i = 0, e = Allocas.size(); i != e; ++i) Values[i] = UndefValue::get(Allocas[i]->getAllocatedType()); // When handling debug info, treat all incoming values as if they have unknown // locations until proven otherwise. RenamePassData::LocationVector Locations(Allocas.size()); // Walks all basic blocks in the function performing the SSA rename algorithm // and inserting the phi nodes we marked as necessary std::vector<RenamePassData> RenamePassWorkList; RenamePassWorkList.emplace_back(&F.front(), nullptr, std::move(Values), std::move(Locations)); do { RenamePassData RPD = std::move(RenamePassWorkList.back()); RenamePassWorkList.pop_back(); // RenamePass may add new worklist entries. RenamePass(RPD.BB, RPD.Pred, RPD.Values, RPD.Locations, RenamePassWorkList); } while (!RenamePassWorkList.empty()); // The renamer uses the Visited set to avoid infinite loops. Clear it now. Visited.clear(); // Remove the allocas themselves from the function. for (Instruction *A : Allocas) { // If there are any uses of the alloca instructions left, they must be in // unreachable basic blocks that were not processed by walking the dominator // tree. Just delete the users now. if (!A->use_empty()) A->replaceAllUsesWith(UndefValue::get(A->getType())); A->eraseFromParent(); } // Remove alloca's dbg.declare instrinsics from the function. for (auto &Declares : AllocaDbgDeclares) for (auto *DII : Declares) DII->eraseFromParent(); // Loop over all of the PHI nodes and see if there are any that we can get // rid of because they merge all of the same incoming values. This can // happen due to undef values coming into the PHI nodes. This process is // iterative, because eliminating one PHI node can cause others to be removed. bool EliminatedAPHI = true; while (EliminatedAPHI) { EliminatedAPHI = false; // Iterating over NewPhiNodes is deterministic, so it is safe to try to // simplify and RAUW them as we go. If it was not, we could add uses to // the values we replace with in a non-deterministic order, thus creating // non-deterministic def->use chains. for (DenseMap<std::pair<unsigned, unsigned>, PHINode *>::iterator I = NewPhiNodes.begin(), E = NewPhiNodes.end(); I != E;) { PHINode *PN = I->second; // If this PHI node merges one value and/or undefs, get the value. if (Value *V = SimplifyInstruction(PN, SQ)) { PN->replaceAllUsesWith(V); PN->eraseFromParent(); NewPhiNodes.erase(I++); EliminatedAPHI = true; continue; } ++I; } } // At this point, the renamer has added entries to PHI nodes for all reachable // code. Unfortunately, there may be unreachable blocks which the renamer // hasn't traversed. If this is the case, the PHI nodes may not // have incoming values for all predecessors. Loop over all PHI nodes we have // created, inserting undef values if they are missing any incoming values. for (DenseMap<std::pair<unsigned, unsigned>, PHINode *>::iterator I = NewPhiNodes.begin(), E = NewPhiNodes.end(); I != E; ++I) { // We want to do this once per basic block. As such, only process a block // when we find the PHI that is the first entry in the block. PHINode *SomePHI = I->second; BasicBlock *BB = SomePHI->getParent(); if (&BB->front() != SomePHI) continue; // Only do work here if there the PHI nodes are missing incoming values. We // know that all PHI nodes that were inserted in a block will have the same // number of incoming values, so we can just check any of them. if (SomePHI->getNumIncomingValues() == getNumPreds(BB)) continue; // Get the preds for BB. SmallVector<BasicBlock *, 16> Preds(pred_begin(BB), pred_end(BB)); // Ok, now we know that all of the PHI nodes are missing entries for some // basic blocks. Start by sorting the incoming predecessors for efficient // access. auto CompareBBNumbers = [this](BasicBlock *A, BasicBlock *B) { return BBNumbers.lookup(A) < BBNumbers.lookup(B); }; llvm::sort(Preds, CompareBBNumbers); // Now we loop through all BB's which have entries in SomePHI and remove // them from the Preds list. for (unsigned i = 0, e = SomePHI->getNumIncomingValues(); i != e; ++i) { // Do a log(n) search of the Preds list for the entry we want. SmallVectorImpl<BasicBlock *>::iterator EntIt = std::lower_bound( Preds.begin(), Preds.end(), SomePHI->getIncomingBlock(i), CompareBBNumbers); assert(EntIt != Preds.end() && *EntIt == SomePHI->getIncomingBlock(i) && "PHI node has entry for a block which is not a predecessor!"); // Remove the entry Preds.erase(EntIt); } // At this point, the blocks left in the preds list must have dummy // entries inserted into every PHI nodes for the block. Update all the phi // nodes in this block that we are inserting (there could be phis before // mem2reg runs). unsigned NumBadPreds = SomePHI->getNumIncomingValues(); BasicBlock::iterator BBI = BB->begin(); while ((SomePHI = dyn_cast<PHINode>(BBI++)) && SomePHI->getNumIncomingValues() == NumBadPreds) { Value *UndefVal = UndefValue::get(SomePHI->getType()); for (BasicBlock *Pred : Preds) SomePHI->addIncoming(UndefVal, Pred); } } NewPhiNodes.clear(); }
// 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 VMap after cloning. ValueMap<const Value*, Value*> 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) && !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; // Calls that we inline may use the new alloca, so we need to clear // their 'tail' flags. MustClearTailCallFlags = true; } 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, 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 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; }