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feeb3261f2
llvm-svn: 10111
285 lines
12 KiB
C++
285 lines
12 KiB
C++
//===- InlineFunction.cpp - Code to perform function inlining -------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file was developed by the LLVM research group and is distributed under
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// the University of Illinois Open Source License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file implements inlining of a function into a call site, resolving
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// parameters and the return value as appropriate.
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//
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// FIXME: This pass should transform alloca instructions in the called function
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// into malloc/free pairs! Or perhaps it should refuse to inline them!
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Transforms/Utils/Cloning.h"
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#include "llvm/Constant.h"
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#include "llvm/DerivedTypes.h"
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#include "llvm/Module.h"
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#include "llvm/Instructions.h"
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#include "llvm/Intrinsics.h"
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#include "llvm/Support/CallSite.h"
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#include "llvm/Transforms/Utils/Local.h"
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namespace llvm {
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bool InlineFunction(CallInst *CI) { return InlineFunction(CallSite(CI)); }
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bool InlineFunction(InvokeInst *II) { return InlineFunction(CallSite(II)); }
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// InlineFunction - This function inlines the called function into the basic
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// block of the caller. This returns false if it is not possible to inline this
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// call. The program is still in a well defined state if this occurs though.
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//
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// Note that this only does one level of inlining. For example, if the
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// instruction 'call B' is inlined, and 'B' calls 'C', then the call to 'C' now
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// exists in the instruction stream. Similiarly this will inline a recursive
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// function by one level.
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//
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bool InlineFunction(CallSite CS) {
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Instruction *TheCall = CS.getInstruction();
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assert(TheCall->getParent() && TheCall->getParent()->getParent() &&
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"Instruction not in function!");
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const Function *CalledFunc = CS.getCalledFunction();
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if (CalledFunc == 0 || // Can't inline external function or indirect
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CalledFunc->isExternal() || // call, or call to a vararg function!
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CalledFunc->getFunctionType()->isVarArg()) return false;
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BasicBlock *OrigBB = TheCall->getParent();
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Function *Caller = OrigBB->getParent();
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// We want to clone the entire callee function into the whole between the
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// "starter" and "ender" blocks. How we accomplish this depends on whether
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// this is an invoke instruction or a call instruction.
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BasicBlock *InvokeDest = 0; // Exception handling destination
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std::vector<Value*> InvokeDestPHIValues; // Values for PHI nodes in InvokeDest
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BasicBlock *AfterCallBB;
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if (InvokeInst *II = dyn_cast<InvokeInst>(TheCall)) {
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InvokeDest = II->getExceptionalDest();
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// If there are PHI nodes in the exceptional destination block, we need to
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// keep track of which values came into them from this invoke, then remove
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// the entry for this block.
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for (BasicBlock::iterator I = InvokeDest->begin();
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PHINode *PN = dyn_cast<PHINode>(I); ++I) {
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// Save the value to use for this edge...
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InvokeDestPHIValues.push_back(PN->getIncomingValueForBlock(OrigBB));
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}
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// Add an unconditional branch to make this look like the CallInst case...
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BranchInst *NewBr = new BranchInst(II->getNormalDest(), TheCall);
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// Split the basic block. This guarantees that no PHI nodes will have to be
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// updated due to new incoming edges, and make the invoke case more
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// symmetric to the call case.
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AfterCallBB = OrigBB->splitBasicBlock(NewBr,
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CalledFunc->getName()+".entry");
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// Remove (unlink) the InvokeInst from the function...
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OrigBB->getInstList().remove(TheCall);
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} else { // It's a call
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// If this is a call instruction, we need to split the basic block that the
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// call lives in.
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//
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AfterCallBB = OrigBB->splitBasicBlock(TheCall,
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CalledFunc->getName()+".entry");
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// Remove (unlink) the CallInst from the function...
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AfterCallBB->getInstList().remove(TheCall);
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}
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// If we have a return value generated by this call, convert it into a PHI
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// node that gets values from each of the old RET instructions in the original
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// function.
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//
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PHINode *PHI = 0;
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if (!TheCall->use_empty()) {
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// The PHI node should go at the front of the new basic block to merge all
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// possible incoming values.
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//
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PHI = new PHINode(CalledFunc->getReturnType(), TheCall->getName(),
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AfterCallBB->begin());
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// Anything that used the result of the function call should now use the PHI
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// node as their operand.
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//
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TheCall->replaceAllUsesWith(PHI);
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}
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// Get an iterator to the last basic block in the function, which will have
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// the new function inlined after it.
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//
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Function::iterator LastBlock = &Caller->back();
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// Calculate the vector of arguments to pass into the function cloner...
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std::map<const Value*, Value*> ValueMap;
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assert(std::distance(CalledFunc->abegin(), CalledFunc->aend()) ==
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std::distance(CS.arg_begin(), CS.arg_end()) &&
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"No varargs calls can be inlined!");
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CallSite::arg_iterator AI = CS.arg_begin();
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for (Function::const_aiterator I = CalledFunc->abegin(), E=CalledFunc->aend();
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I != E; ++I, ++AI)
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ValueMap[I] = *AI;
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// Since we are now done with the Call/Invoke, we can delete it.
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delete TheCall;
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// Make a vector to capture the return instructions in the cloned function...
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std::vector<ReturnInst*> Returns;
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// Do all of the hard part of cloning the callee into the caller...
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CloneFunctionInto(Caller, CalledFunc, ValueMap, Returns, ".i");
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// Loop over all of the return instructions, turning them into unconditional
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// branches to the merge point now...
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for (unsigned i = 0, e = Returns.size(); i != e; ++i) {
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ReturnInst *RI = Returns[i];
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BasicBlock *BB = RI->getParent();
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// Add a branch to the merge point where the PHI node lives if it exists.
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new BranchInst(AfterCallBB, RI);
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if (PHI) { // The PHI node should include this value!
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assert(RI->getReturnValue() && "Ret should have value!");
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assert(RI->getReturnValue()->getType() == PHI->getType() &&
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"Ret value not consistent in function!");
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PHI->addIncoming(RI->getReturnValue(), BB);
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}
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// Delete the return instruction now
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BB->getInstList().erase(RI);
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}
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// Check to see if the PHI node only has one argument. This is a common
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// case resulting from there only being a single return instruction in the
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// function call. Because this is so common, eliminate the PHI node.
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//
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if (PHI && PHI->getNumIncomingValues() == 1) {
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PHI->replaceAllUsesWith(PHI->getIncomingValue(0));
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PHI->getParent()->getInstList().erase(PHI);
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}
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// Change the branch that used to go to AfterCallBB to branch to the first
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// basic block of the inlined function.
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//
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TerminatorInst *Br = OrigBB->getTerminator();
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assert(Br && Br->getOpcode() == Instruction::Br &&
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"splitBasicBlock broken!");
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Br->setOperand(0, ++LastBlock);
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// If there are any alloca instructions in the block that used to be the entry
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// block for the callee, move them to the entry block of the caller. First
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// calculate which instruction they should be inserted before. We insert the
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// instructions at the end of the current alloca list.
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//
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if (isa<AllocaInst>(LastBlock->begin())) {
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BasicBlock::iterator InsertPoint = Caller->begin()->begin();
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while (isa<AllocaInst>(InsertPoint)) ++InsertPoint;
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for (BasicBlock::iterator I = LastBlock->begin(), E = LastBlock->end();
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I != E; )
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if (AllocaInst *AI = dyn_cast<AllocaInst>(I++))
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if (isa<Constant>(AI->getArraySize())) {
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LastBlock->getInstList().remove(AI);
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Caller->front().getInstList().insert(InsertPoint, AI);
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}
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}
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// If we just inlined a call due to an invoke instruction, scan the inlined
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// function checking for function calls that should now be made into invoke
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// instructions, and for unwind's which should be turned into branches.
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if (InvokeDest) {
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for (Function::iterator BB = LastBlock, E = Caller->end(); BB != E; ++BB) {
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for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ) {
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// We only need to check for function calls: inlined invoke instructions
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// require no special handling...
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if (CallInst *CI = dyn_cast<CallInst>(I)) {
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// Convert this function call into an invoke instruction...
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// First, split the basic block...
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BasicBlock *Split = BB->splitBasicBlock(CI, CI->getName()+".noexc");
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// Next, create the new invoke instruction, inserting it at the end
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// of the old basic block.
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InvokeInst *II =
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new InvokeInst(CI->getCalledValue(), Split, InvokeDest,
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std::vector<Value*>(CI->op_begin()+1, CI->op_end()),
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CI->getName(), BB->getTerminator());
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// Make sure that anything using the call now uses the invoke!
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CI->replaceAllUsesWith(II);
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// Delete the unconditional branch inserted by splitBasicBlock
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BB->getInstList().pop_back();
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Split->getInstList().pop_front(); // Delete the original call
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// Update any PHI nodes in the exceptional block to indicate that
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// there is now a new entry in them.
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unsigned i = 0;
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for (BasicBlock::iterator I = InvokeDest->begin();
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PHINode *PN = dyn_cast<PHINode>(I); ++I, ++i)
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PN->addIncoming(InvokeDestPHIValues[i], BB);
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// This basic block is now complete, start scanning the next one.
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break;
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} else {
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++I;
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}
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}
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if (UnwindInst *UI = dyn_cast<UnwindInst>(BB->getTerminator())) {
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// An UnwindInst requires special handling when it gets inlined into an
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// invoke site. Once this happens, we know that the unwind would cause
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// a control transfer to the invoke exception destination, so we can
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// transform it into a direct branch to the exception destination.
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new BranchInst(InvokeDest, UI);
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// Delete the unwind instruction!
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UI->getParent()->getInstList().pop_back();
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// Update any PHI nodes in the exceptional block to indicate that
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// there is now a new entry in them.
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unsigned i = 0;
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for (BasicBlock::iterator I = InvokeDest->begin();
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PHINode *PN = dyn_cast<PHINode>(I); ++I, ++i)
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PN->addIncoming(InvokeDestPHIValues[i], BB);
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}
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}
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// Now that everything is happy, we have one final detail. The PHI nodes in
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// the exception destination block still have entries due to the original
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// invoke instruction. Eliminate these entries (which might even delete the
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// PHI node) now.
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for (BasicBlock::iterator I = InvokeDest->begin();
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PHINode *PN = dyn_cast<PHINode>(I); ++I)
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PN->removeIncomingValue(AfterCallBB);
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}
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// Now that the function is correct, make it a little bit nicer. In
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// particular, move the basic blocks inserted from the end of the function
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// into the space made by splitting the source basic block.
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//
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Caller->getBasicBlockList().splice(AfterCallBB, Caller->getBasicBlockList(),
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LastBlock, Caller->end());
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// We should always be able to fold the entry block of the function into the
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// single predecessor of the block...
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assert(cast<BranchInst>(Br)->isUnconditional() && "splitBasicBlock broken!");
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BasicBlock *CalleeEntry = cast<BranchInst>(Br)->getSuccessor(0);
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SimplifyCFG(CalleeEntry);
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// Okay, continue the CFG cleanup. It's often the case that there is only a
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// single return instruction in the callee function. If this is the case,
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// then we have an unconditional branch from the return block to the
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// 'AfterCallBB'. Check for this case, and eliminate the branch is possible.
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SimplifyCFG(AfterCallBB);
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return true;
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}
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} // End llvm namespace
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