| //===- InlineFunction.cpp - Code to perform function inlining -------------===// |
| // |
| // The LLVM Compiler Infrastructure |
| // |
| // This file was developed by the LLVM research group and 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. |
| // |
| // FIXME: This pass should transform alloca instructions in the called function |
| // into malloc/free pairs! Or perhaps it should refuse to inline them! |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "llvm/Transforms/Utils/Cloning.h" |
| #include "llvm/Constant.h" |
| #include "llvm/DerivedTypes.h" |
| #include "llvm/Module.h" |
| #include "llvm/Instructions.h" |
| #include "llvm/Intrinsics.h" |
| #include "llvm/Support/CallSite.h" |
| #include "llvm/Transforms/Utils/Local.h" |
| |
| bool InlineFunction(CallInst *CI) { return InlineFunction(CallSite(CI)); } |
| bool InlineFunction(InvokeInst *II) { return InlineFunction(CallSite(II)); } |
| |
| // 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 InlineFunction(CallSite CS) { |
| Instruction *TheCall = CS.getInstruction(); |
| assert(TheCall->getParent() && TheCall->getParent()->getParent() && |
| "Instruction not in function!"); |
| |
| const Function *CalledFunc = CS.getCalledFunction(); |
| if (CalledFunc == 0 || // Can't inline external function or indirect |
| CalledFunc->isExternal() || // call, or call to a vararg function! |
| CalledFunc->getFunctionType()->isVarArg()) return false; |
| |
| BasicBlock *OrigBB = TheCall->getParent(); |
| Function *Caller = OrigBB->getParent(); |
| |
| // We want to clone the entire callee function into the whole between the |
| // "starter" and "ender" blocks. How we accomplish this depends on whether |
| // this is an invoke instruction or a call instruction. |
| |
| BasicBlock *InvokeDest = 0; // Exception handling destination |
| std::vector<Value*> InvokeDestPHIValues; // Values for PHI nodes in InvokeDest |
| BasicBlock *AfterCallBB; |
| |
| if (InvokeInst *II = dyn_cast<InvokeInst>(TheCall)) { |
| InvokeDest = II->getExceptionalDest(); |
| |
| // Add an unconditional branch to make this look like the CallInst case... |
| BranchInst *NewBr = new BranchInst(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()+".entry"); |
| |
| // If there are PHI nodes in the exceptional destination block, we need to |
| // keep track of which values came into them from this invoke, then remove |
| // the entry for this block. |
| for (BasicBlock::iterator I = InvokeDest->begin(); |
| PHINode *PN = dyn_cast<PHINode>(I); ++I) { |
| // Save the value to use for this edge... |
| InvokeDestPHIValues.push_back(PN->getIncomingValueForBlock(AfterCallBB)); |
| } |
| |
| // Remove (unlink) the InvokeInst from the function... |
| OrigBB->getInstList().remove(TheCall); |
| |
| } 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()+".entry"); |
| // Remove (unlink) the CallInst from the function... |
| AfterCallBB->getInstList().remove(TheCall); |
| } |
| |
| // If we have a return value generated by this call, convert it into a PHI |
| // node that gets values from each of the old RET instructions in the original |
| // function. |
| // |
| PHINode *PHI = 0; |
| if (!TheCall->use_empty()) { |
| // The PHI node should go at the front of the new basic block to merge all |
| // possible incoming values. |
| // |
| PHI = new PHINode(CalledFunc->getReturnType(), 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); |
| } |
| |
| // 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(); |
| |
| // Calculate the vector of arguments to pass into the function cloner... |
| std::map<const Value*, Value*> ValueMap; |
| assert(std::distance(CalledFunc->abegin(), CalledFunc->aend()) == |
| std::distance(CS.arg_begin(), CS.arg_end()) && |
| "No varargs calls can be inlined!"); |
| |
| CallSite::arg_iterator AI = CS.arg_begin(); |
| for (Function::const_aiterator I = CalledFunc->abegin(), E=CalledFunc->aend(); |
| I != E; ++I, ++AI) |
| ValueMap[I] = *AI; |
| |
| // Since we are now done with the Call/Invoke, we can delete it. |
| delete TheCall; |
| |
| // Make a vector to capture the return instructions in the cloned function... |
| std::vector<ReturnInst*> Returns; |
| |
| // Do all of the hard part of cloning the callee into the caller... |
| CloneFunctionInto(Caller, CalledFunc, ValueMap, Returns, ".i"); |
| |
| // Loop over all of the return instructions, turning them into unconditional |
| // branches to the merge point now... |
| for (unsigned i = 0, e = Returns.size(); i != e; ++i) { |
| ReturnInst *RI = Returns[i]; |
| BasicBlock *BB = RI->getParent(); |
| |
| // Add a branch to the merge point where the PHI node lives if it exists. |
| new BranchInst(AfterCallBB, RI); |
| |
| if (PHI) { // The PHI node should include this value! |
| assert(RI->getReturnValue() && "Ret should have value!"); |
| assert(RI->getReturnValue()->getType() == PHI->getType() && |
| "Ret value not consistent in function!"); |
| PHI->addIncoming(RI->getReturnValue(), BB); |
| } |
| |
| // Delete the return instruction now |
| BB->getInstList().erase(RI); |
| } |
| |
| // Check to see if the PHI node only has one argument. This is a common |
| // case resulting from there only being a single return instruction in the |
| // function call. Because this is so common, eliminate the PHI node. |
| // |
| if (PHI && PHI->getNumIncomingValues() == 1) { |
| PHI->replaceAllUsesWith(PHI->getIncomingValue(0)); |
| PHI->getParent()->getInstList().erase(PHI); |
| } |
| |
| // 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, ++LastBlock); |
| |
| // 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. |
| // |
| if (isa<AllocaInst>(LastBlock->begin())) { |
| BasicBlock::iterator InsertPoint = Caller->begin()->begin(); |
| while (isa<AllocaInst>(InsertPoint)) ++InsertPoint; |
| |
| for (BasicBlock::iterator I = LastBlock->begin(), E = LastBlock->end(); |
| I != E; ) |
| if (AllocaInst *AI = dyn_cast<AllocaInst>(I++)) |
| if (isa<Constant>(AI->getArraySize())) { |
| LastBlock->getInstList().remove(AI); |
| Caller->front().getInstList().insert(InsertPoint, AI); |
| } |
| } |
| |
| // If we just inlined a call due to an invoke instruction, scan the inlined |
| // function checking for function calls that should now be made into invoke |
| // instructions, and for unwind's which should be turned into branches. |
| if (InvokeDest) { |
| for (Function::iterator BB = LastBlock, E = Caller->end(); BB != E; ++BB) { |
| for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ) { |
| // We only need to check for function calls: inlined invoke instructions |
| // require no special handling... |
| if (CallInst *CI = dyn_cast<CallInst>(I)) { |
| // 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. |
| InvokeInst *II = |
| new InvokeInst(CI->getCalledValue(), Split, InvokeDest, |
| std::vector<Value*>(CI->op_begin()+1, CI->op_end()), |
| CI->getName(), BB->getTerminator()); |
| |
| // Make sure that anything using the call now uses the invoke! |
| 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(); |
| PHINode *PN = dyn_cast<PHINode>(I); ++I, ++i) |
| PN->addIncoming(InvokeDestPHIValues[i], BB); |
| |
| // This basic block is now complete, start scanning the next one. |
| break; |
| } else { |
| ++I; |
| } |
| } |
| |
| 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 *BI = new BranchInst(InvokeDest, UI); |
| |
| // Delete the unwind instruction! |
| UI->getParent()->getInstList().pop_back(); |
| } |
| } |
| |
| // 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. |
| for (BasicBlock::iterator I = InvokeDest->begin(); |
| PHINode *PN = dyn_cast<PHINode>(I); ++I) |
| PN->removeIncomingValue(AfterCallBB); |
| } |
| // 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(), |
| LastBlock, Caller->end()); |
| |
| // 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); |
| SimplifyCFG(CalleeEntry); |
| |
| // Okay, continue the CFG cleanup. It's often the case that there is only a |
| // single return instruction in the callee function. If this is the case, |
| // then we have an unconditional branch from the return block to the |
| // 'AfterCallBB'. Check for this case, and eliminate the branch is possible. |
| SimplifyCFG(AfterCallBB); |
| return true; |
| } |