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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@18799 91177308-0d34-0410-b5e6-96231b3b80d8
347 lines
15 KiB
C++
347 lines
15 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 alloca/dealloca 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/Constants.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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using namespace llvm;
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bool llvm::InlineFunction(CallInst *CI) { return InlineFunction(CallSite(CI)); }
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bool llvm::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 llvm::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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// 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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// Make sure to capture all of the return instructions from the cloned
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// function.
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std::vector<ReturnInst*> Returns;
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{ // Scope to destroy ValueMap after cloning.
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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(),
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E = CalledFunc->aend(); I != E; ++I, ++AI)
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ValueMap[I] = *AI;
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// Clone the entire body of the callee into the caller.
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CloneFunctionInto(Caller, CalledFunc, ValueMap, Returns, ".i");
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}
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// Remember the first block that is newly cloned over.
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Function::iterator FirstNewBlock = LastBlock; ++FirstNewBlock;
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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>(FirstNewBlock->begin())) {
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BasicBlock::iterator InsertPoint = Caller->begin()->begin();
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for (BasicBlock::iterator I = FirstNewBlock->begin(),
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E = FirstNewBlock->end(); 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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// Scan for the block of allocas that we can move over.
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while (isa<AllocaInst>(I) &&
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isa<Constant>(cast<AllocaInst>(I)->getArraySize()))
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++I;
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// Transfer all of the allocas over in a block. Using splice means
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// that they instructions aren't removed from the symbol table, then
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// reinserted.
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Caller->front().getInstList().splice(InsertPoint,
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FirstNewBlock->getInstList(),
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AI, I);
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}
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}
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// If we are inlining for an invoke instruction, we must make sure to rewrite
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// any inlined 'unwind' instructions into branches to the invoke exception
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// destination, and call instructions into invoke instructions.
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if (InvokeInst *II = dyn_cast<InvokeInst>(TheCall)) {
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BasicBlock *InvokeDest = II->getUnwindDest();
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std::vector<Value*> InvokeDestPHIValues;
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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(); isa<PHINode>(I); ++I) {
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PHINode *PN = cast<PHINode>(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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for (Function::iterator BB = FirstNewBlock, E = Caller->end();
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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... if it's
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// not an intrinsic function call (which are known to not throw).
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if (CI->getCalledFunction() &&
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CI->getCalledFunction()->getIntrinsicID()) {
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++I;
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} else {
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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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isa<PHINode>(I); ++I, ++i) {
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PHINode *PN = cast<PHINode>(I);
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PN->addIncoming(InvokeDestPHIValues[i], BB);
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}
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// This basic block is now complete, start scanning the next one.
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break;
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}
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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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isa<PHINode>(I); ++I, ++i) {
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PHINode *PN = cast<PHINode>(I);
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PN->addIncoming(InvokeDestPHIValues[i], BB);
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}
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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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InvokeDest->removePredecessor(II->getParent());
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}
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// If we cloned in _exactly one_ basic block, and if that block ends in a
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// return instruction, we splice the body of the inlined callee directly into
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// the calling basic block.
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if (Returns.size() == 1 && std::distance(FirstNewBlock, Caller->end()) == 1) {
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// Move all of the instructions right before the call.
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OrigBB->getInstList().splice(TheCall, FirstNewBlock->getInstList(),
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FirstNewBlock->begin(), FirstNewBlock->end());
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// Remove the cloned basic block.
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Caller->getBasicBlockList().pop_back();
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// If the call site was an invoke instruction, add a branch to the normal
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// destination.
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if (InvokeInst *II = dyn_cast<InvokeInst>(TheCall))
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new BranchInst(II->getNormalDest(), TheCall);
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// If the return instruction returned a value, replace uses of the call with
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// uses of the returned value.
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if (!TheCall->use_empty())
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TheCall->replaceAllUsesWith(Returns[0]->getReturnValue());
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// Since we are now done with the Call/Invoke, we can delete it.
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TheCall->getParent()->getInstList().erase(TheCall);
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// Since we are now done with the return instruction, delete it also.
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Returns[0]->getParent()->getInstList().erase(Returns[0]);
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// We are now done with the inlining.
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return true;
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}
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// Otherwise, we have the normal case, of more than one block to inline or
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// multiple return sites.
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// We want to clone the entire callee function into the hole 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 *AfterCallBB;
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if (InvokeInst *II = dyn_cast<InvokeInst>(TheCall)) {
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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()+".exit");
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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
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// the call lives in.
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//
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AfterCallBB = OrigBB->splitBasicBlock(TheCall,
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CalledFunc->getName()+".exit");
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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, FirstNewBlock);
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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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FirstNewBlock, Caller->end());
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// Handle all of the return instructions that we just cloned in, and eliminate
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// any users of the original call/invoke instruction.
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if (Returns.size() > 1) {
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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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PHINode *PHI = 0;
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if (!TheCall->use_empty()) {
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PHI = new PHINode(CalledFunc->getReturnType(),
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TheCall->getName(), AfterCallBB->begin());
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// Anything that used the result of the function call should now use the
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// PHI node as their operand.
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//
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TheCall->replaceAllUsesWith(PHI);
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}
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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, and adding entries to the PHI node as
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// appropriate.
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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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if (PHI) {
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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(), RI->getParent());
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}
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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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// Delete the return instruction now
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RI->getParent()->getInstList().erase(RI);
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}
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} else if (!Returns.empty()) {
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// Otherwise, if there is exactly one return value, just replace anything
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// using the return value of the call with the computed value.
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if (!TheCall->use_empty())
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TheCall->replaceAllUsesWith(Returns[0]->getReturnValue());
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// Splice the code from the return block into the block that it will return
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// to, which contains the code that was after the call.
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BasicBlock *ReturnBB = Returns[0]->getParent();
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AfterCallBB->getInstList().splice(AfterCallBB->begin(),
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ReturnBB->getInstList());
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// Update PHI nodes that use the ReturnBB to use the AfterCallBB.
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ReturnBB->replaceAllUsesWith(AfterCallBB);
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// Delete the return instruction now and empty ReturnBB now.
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Returns[0]->eraseFromParent();
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ReturnBB->eraseFromParent();
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} else if (!TheCall->use_empty()) {
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// No returns, but something is using the return value of the call. Just
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// nuke the result.
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TheCall->replaceAllUsesWith(UndefValue::get(TheCall->getType()));
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}
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// Since we are now done with the Call/Invoke, we can delete it.
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TheCall->eraseFromParent();
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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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// Splice the code entry block into calling block, right before the
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// unconditional branch.
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OrigBB->getInstList().splice(Br, CalleeEntry->getInstList());
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CalleeEntry->replaceAllUsesWith(OrigBB); // Update PHI nodes
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// Remove the unconditional branch.
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OrigBB->getInstList().erase(Br);
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// Now we can remove the CalleeEntry block, which is now empty.
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Caller->getBasicBlockList().erase(CalleeEntry);
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return true;
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}
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