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a4646b61e4
This folds unconditional branches that are often produced by code specialization. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@30307 91177308-0d34-0410-b5e6-96231b3b80d8
481 lines
20 KiB
C++
481 lines
20 KiB
C++
//===- CloneFunction.cpp - Clone a function into another function ---------===//
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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 the CloneFunctionInto interface, which is used as the
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// low-level function cloner. This is used by the CloneFunction and function
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// inliner to do the dirty work of copying the body of a function around.
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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/Instructions.h"
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#include "llvm/Function.h"
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#include "llvm/Support/CFG.h"
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#include "ValueMapper.h"
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#include "llvm/Transforms/Utils/Local.h"
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using namespace llvm;
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// CloneBasicBlock - See comments in Cloning.h
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BasicBlock *llvm::CloneBasicBlock(const BasicBlock *BB,
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std::map<const Value*, Value*> &ValueMap,
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const char *NameSuffix, Function *F,
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ClonedCodeInfo *CodeInfo) {
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BasicBlock *NewBB = new BasicBlock("", F);
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if (BB->hasName()) NewBB->setName(BB->getName()+NameSuffix);
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bool hasCalls = false, hasDynamicAllocas = false, hasStaticAllocas = false;
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// Loop over all instructions, and copy them over.
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for (BasicBlock::const_iterator II = BB->begin(), IE = BB->end();
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II != IE; ++II) {
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Instruction *NewInst = II->clone();
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if (II->hasName())
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NewInst->setName(II->getName()+NameSuffix);
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NewBB->getInstList().push_back(NewInst);
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ValueMap[II] = NewInst; // Add instruction map to value.
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hasCalls |= isa<CallInst>(II);
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if (const AllocaInst *AI = dyn_cast<AllocaInst>(II)) {
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if (isa<ConstantInt>(AI->getArraySize()))
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hasStaticAllocas = true;
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else
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hasDynamicAllocas = true;
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}
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}
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if (CodeInfo) {
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CodeInfo->ContainsCalls |= hasCalls;
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CodeInfo->ContainsUnwinds |= isa<UnwindInst>(BB->getTerminator());
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CodeInfo->ContainsDynamicAllocas |= hasDynamicAllocas;
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CodeInfo->ContainsDynamicAllocas |= hasStaticAllocas &&
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BB != &BB->getParent()->front();
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}
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return NewBB;
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}
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// Clone OldFunc into NewFunc, transforming the old arguments into references to
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// ArgMap values.
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//
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void llvm::CloneFunctionInto(Function *NewFunc, const Function *OldFunc,
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std::map<const Value*, Value*> &ValueMap,
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std::vector<ReturnInst*> &Returns,
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const char *NameSuffix, ClonedCodeInfo *CodeInfo) {
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assert(NameSuffix && "NameSuffix cannot be null!");
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#ifndef NDEBUG
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for (Function::const_arg_iterator I = OldFunc->arg_begin(),
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E = OldFunc->arg_end(); I != E; ++I)
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assert(ValueMap.count(I) && "No mapping from source argument specified!");
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#endif
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// Loop over all of the basic blocks in the function, cloning them as
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// appropriate. Note that we save BE this way in order to handle cloning of
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// recursive functions into themselves.
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//
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for (Function::const_iterator BI = OldFunc->begin(), BE = OldFunc->end();
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BI != BE; ++BI) {
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const BasicBlock &BB = *BI;
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// Create a new basic block and copy instructions into it!
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BasicBlock *CBB = CloneBasicBlock(&BB, ValueMap, NameSuffix, NewFunc,
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CodeInfo);
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ValueMap[&BB] = CBB; // Add basic block mapping.
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if (ReturnInst *RI = dyn_cast<ReturnInst>(CBB->getTerminator()))
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Returns.push_back(RI);
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}
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// Loop over all of the instructions in the function, fixing up operand
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// references as we go. This uses ValueMap to do all the hard work.
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//
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for (Function::iterator BB = cast<BasicBlock>(ValueMap[OldFunc->begin()]),
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BE = NewFunc->end(); BB != BE; ++BB)
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// Loop over all instructions, fixing each one as we find it...
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for (BasicBlock::iterator II = BB->begin(); II != BB->end(); ++II)
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RemapInstruction(II, ValueMap);
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}
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/// CloneFunction - Return a copy of the specified function, but without
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/// embedding the function into another module. Also, any references specified
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/// in the ValueMap are changed to refer to their mapped value instead of the
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/// original one. If any of the arguments to the function are in the ValueMap,
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/// the arguments are deleted from the resultant function. The ValueMap is
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/// updated to include mappings from all of the instructions and basicblocks in
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/// the function from their old to new values.
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///
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Function *llvm::CloneFunction(const Function *F,
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std::map<const Value*, Value*> &ValueMap,
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ClonedCodeInfo *CodeInfo) {
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std::vector<const Type*> ArgTypes;
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// The user might be deleting arguments to the function by specifying them in
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// the ValueMap. If so, we need to not add the arguments to the arg ty vector
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//
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for (Function::const_arg_iterator I = F->arg_begin(), E = F->arg_end();
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I != E; ++I)
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if (ValueMap.count(I) == 0) // Haven't mapped the argument to anything yet?
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ArgTypes.push_back(I->getType());
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// Create a new function type...
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FunctionType *FTy = FunctionType::get(F->getFunctionType()->getReturnType(),
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ArgTypes, F->getFunctionType()->isVarArg());
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// Create the new function...
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Function *NewF = new Function(FTy, F->getLinkage(), F->getName());
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// Loop over the arguments, copying the names of the mapped arguments over...
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Function::arg_iterator DestI = NewF->arg_begin();
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for (Function::const_arg_iterator I = F->arg_begin(), E = F->arg_end();
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I != E; ++I)
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if (ValueMap.count(I) == 0) { // Is this argument preserved?
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DestI->setName(I->getName()); // Copy the name over...
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ValueMap[I] = DestI++; // Add mapping to ValueMap
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}
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std::vector<ReturnInst*> Returns; // Ignore returns cloned...
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CloneFunctionInto(NewF, F, ValueMap, Returns, "", CodeInfo);
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return NewF;
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}
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namespace {
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/// PruningFunctionCloner - This class is a private class used to implement
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/// the CloneAndPruneFunctionInto method.
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struct PruningFunctionCloner {
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Function *NewFunc;
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const Function *OldFunc;
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std::map<const Value*, Value*> &ValueMap;
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std::vector<ReturnInst*> &Returns;
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const char *NameSuffix;
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ClonedCodeInfo *CodeInfo;
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public:
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PruningFunctionCloner(Function *newFunc, const Function *oldFunc,
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std::map<const Value*, Value*> &valueMap,
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std::vector<ReturnInst*> &returns,
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const char *nameSuffix,
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ClonedCodeInfo *codeInfo)
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: NewFunc(newFunc), OldFunc(oldFunc), ValueMap(valueMap), Returns(returns),
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NameSuffix(nameSuffix), CodeInfo(codeInfo) {
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}
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/// CloneBlock - The specified block is found to be reachable, clone it and
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/// anything that it can reach.
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void CloneBlock(const BasicBlock *BB);
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public:
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/// ConstantFoldMappedInstruction - Constant fold the specified instruction,
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/// mapping its operands through ValueMap if they are available.
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Constant *ConstantFoldMappedInstruction(const Instruction *I);
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};
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}
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/// CloneBlock - The specified block is found to be reachable, clone it and
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/// anything that it can reach.
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void PruningFunctionCloner::CloneBlock(const BasicBlock *BB) {
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Value *&BBEntry = ValueMap[BB];
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// Have we already cloned this block?
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if (BBEntry) return;
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// Nope, clone it now.
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BasicBlock *NewBB;
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BBEntry = NewBB = new BasicBlock();
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if (BB->hasName()) NewBB->setName(BB->getName()+NameSuffix);
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bool hasCalls = false, hasDynamicAllocas = false, hasStaticAllocas = false;
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// Loop over all instructions, and copy them over, DCE'ing as we go. This
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// loop doesn't include the terminator.
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for (BasicBlock::const_iterator II = BB->begin(), IE = --BB->end();
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II != IE; ++II) {
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// If this instruction constant folds, don't bother cloning the instruction,
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// instead, just add the constant to the value map.
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if (Constant *C = ConstantFoldMappedInstruction(II)) {
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ValueMap[II] = C;
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continue;
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}
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Instruction *NewInst = II->clone();
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if (II->hasName())
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NewInst->setName(II->getName()+NameSuffix);
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NewBB->getInstList().push_back(NewInst);
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ValueMap[II] = NewInst; // Add instruction map to value.
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hasCalls |= isa<CallInst>(II);
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if (const AllocaInst *AI = dyn_cast<AllocaInst>(II)) {
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if (isa<ConstantInt>(AI->getArraySize()))
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hasStaticAllocas = true;
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else
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hasDynamicAllocas = true;
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}
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}
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// Finally, clone over the terminator.
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const TerminatorInst *OldTI = BB->getTerminator();
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bool TerminatorDone = false;
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if (const BranchInst *BI = dyn_cast<BranchInst>(OldTI)) {
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if (BI->isConditional()) {
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// If the condition was a known constant in the callee...
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ConstantBool *Cond = dyn_cast<ConstantBool>(BI->getCondition());
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if (Cond == 0) // Or is a known constant in the caller...
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Cond = dyn_cast_or_null<ConstantBool>(ValueMap[BI->getCondition()]);
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if (Cond) { // Constant fold to uncond branch!
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BasicBlock *Dest = BI->getSuccessor(!Cond->getValue());
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ValueMap[OldTI] = new BranchInst(Dest, NewBB);
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CloneBlock(Dest);
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TerminatorDone = true;
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}
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}
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} else if (const SwitchInst *SI = dyn_cast<SwitchInst>(OldTI)) {
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// If switching on a value known constant in the caller.
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ConstantInt *Cond = dyn_cast<ConstantInt>(SI->getCondition());
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if (Cond == 0) // Or known constant after constant prop in the callee...
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Cond = dyn_cast_or_null<ConstantInt>(ValueMap[SI->getCondition()]);
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if (Cond) { // Constant fold to uncond branch!
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BasicBlock *Dest = SI->getSuccessor(SI->findCaseValue(Cond));
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ValueMap[OldTI] = new BranchInst(Dest, NewBB);
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CloneBlock(Dest);
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TerminatorDone = true;
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}
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}
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if (!TerminatorDone) {
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Instruction *NewInst = OldTI->clone();
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if (OldTI->hasName())
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NewInst->setName(OldTI->getName()+NameSuffix);
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NewBB->getInstList().push_back(NewInst);
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ValueMap[OldTI] = NewInst; // Add instruction map to value.
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// Recursively clone any reachable successor blocks.
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const TerminatorInst *TI = BB->getTerminator();
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for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i)
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CloneBlock(TI->getSuccessor(i));
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}
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if (CodeInfo) {
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CodeInfo->ContainsCalls |= hasCalls;
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CodeInfo->ContainsUnwinds |= isa<UnwindInst>(OldTI);
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CodeInfo->ContainsDynamicAllocas |= hasDynamicAllocas;
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CodeInfo->ContainsDynamicAllocas |= hasStaticAllocas &&
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BB != &BB->getParent()->front();
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}
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if (ReturnInst *RI = dyn_cast<ReturnInst>(NewBB->getTerminator()))
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Returns.push_back(RI);
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}
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/// ConstantFoldMappedInstruction - Constant fold the specified instruction,
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/// mapping its operands through ValueMap if they are available.
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Constant *PruningFunctionCloner::
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ConstantFoldMappedInstruction(const Instruction *I) {
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if (isa<BinaryOperator>(I) || isa<ShiftInst>(I)) {
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if (Constant *Op0 = dyn_cast_or_null<Constant>(MapValue(I->getOperand(0),
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ValueMap)))
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if (Constant *Op1 = dyn_cast_or_null<Constant>(MapValue(I->getOperand(1),
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ValueMap)))
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return ConstantExpr::get(I->getOpcode(), Op0, Op1);
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return 0;
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}
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std::vector<Constant*> Ops;
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for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
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if (Constant *Op = dyn_cast_or_null<Constant>(MapValue(I->getOperand(i),
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ValueMap)))
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Ops.push_back(Op);
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else
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return 0; // All operands not constant!
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return ConstantFoldInstOperands(I->getOpcode(), I->getType(), Ops);
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}
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/// CloneAndPruneFunctionInto - This works exactly like CloneFunctionInto,
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/// except that it does some simple constant prop and DCE on the fly. The
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/// effect of this is to copy significantly less code in cases where (for
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/// example) a function call with constant arguments is inlined, and those
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/// constant arguments cause a significant amount of code in the callee to be
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/// dead. Since this doesn't produce an exactly copy of the input, it can't be
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/// used for things like CloneFunction or CloneModule.
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void llvm::CloneAndPruneFunctionInto(Function *NewFunc, const Function *OldFunc,
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std::map<const Value*, Value*> &ValueMap,
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std::vector<ReturnInst*> &Returns,
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const char *NameSuffix,
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ClonedCodeInfo *CodeInfo) {
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assert(NameSuffix && "NameSuffix cannot be null!");
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#ifndef NDEBUG
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for (Function::const_arg_iterator I = OldFunc->arg_begin(),
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E = OldFunc->arg_end(); I != E; ++I)
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assert(ValueMap.count(I) && "No mapping from source argument specified!");
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#endif
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PruningFunctionCloner PFC(NewFunc, OldFunc, ValueMap, Returns,
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NameSuffix, CodeInfo);
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// Clone the entry block, and anything recursively reachable from it.
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PFC.CloneBlock(&OldFunc->getEntryBlock());
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// Loop over all of the basic blocks in the old function. If the block was
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// reachable, we have cloned it and the old block is now in the value map:
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// insert it into the new function in the right order. If not, ignore it.
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//
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// Defer PHI resolution until rest of function is resolved.
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std::vector<const PHINode*> PHIToResolve;
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for (Function::const_iterator BI = OldFunc->begin(), BE = OldFunc->end();
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BI != BE; ++BI) {
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BasicBlock *NewBB = cast_or_null<BasicBlock>(ValueMap[BI]);
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if (NewBB == 0) continue; // Dead block.
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// Add the new block to the new function.
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NewFunc->getBasicBlockList().push_back(NewBB);
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// Loop over all of the instructions in the block, fixing up operand
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// references as we go. This uses ValueMap to do all the hard work.
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//
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BasicBlock::iterator I = NewBB->begin();
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// Handle PHI nodes specially, as we have to remove references to dead
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// blocks.
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if (PHINode *PN = dyn_cast<PHINode>(I)) {
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// Skip over all PHI nodes, remembering them for later.
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BasicBlock::const_iterator OldI = BI->begin();
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for (; (PN = dyn_cast<PHINode>(I)); ++I, ++OldI)
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PHIToResolve.push_back(cast<PHINode>(OldI));
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}
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// Otherwise, remap the rest of the instructions normally.
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for (; I != NewBB->end(); ++I)
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RemapInstruction(I, ValueMap);
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}
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// Defer PHI resolution until rest of function is resolved, PHI resolution
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// requires the CFG to be up-to-date.
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for (unsigned phino = 0, e = PHIToResolve.size(); phino != e; ) {
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const PHINode *OPN = PHIToResolve[phino];
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unsigned NumPreds = OPN->getNumIncomingValues();
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unsigned BBPHIStart = phino;
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const BasicBlock *OldBB = OPN->getParent();
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BasicBlock *NewBB = cast<BasicBlock>(ValueMap[OldBB]);
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// Map operands for blocks that are live and remove operands for blocks
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// that are dead.
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for (; phino != PHIToResolve.size() &&
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PHIToResolve[phino]->getParent() == OldBB; ++phino) {
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OPN = PHIToResolve[phino];
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PHINode *PN = cast<PHINode>(ValueMap[OPN]);
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for (unsigned pred = 0, e = NumPreds; pred != e; ++pred) {
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if (BasicBlock *MappedBlock =
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cast_or_null<BasicBlock>(ValueMap[PN->getIncomingBlock(pred)])) {
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Value *InVal = MapValue(PN->getIncomingValue(pred), ValueMap);
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assert(InVal && "Unknown input value?");
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PN->setIncomingValue(pred, InVal);
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PN->setIncomingBlock(pred, MappedBlock);
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} else {
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PN->removeIncomingValue(pred, false);
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--pred, --e; // Revisit the next entry.
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}
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}
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}
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// The loop above has removed PHI entries for those blocks that are dead
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// and has updated others. However, if a block is live (i.e. copied over)
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// but its terminator has been changed to not go to this block, then our
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// phi nodes will have invalid entries. Update the PHI nodes in this
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// case.
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PHINode *PN = cast<PHINode>(NewBB->begin());
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NumPreds = std::distance(pred_begin(NewBB), pred_end(NewBB));
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if (NumPreds != PN->getNumIncomingValues()) {
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assert(NumPreds < PN->getNumIncomingValues());
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// Count how many times each predecessor comes to this block.
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std::map<BasicBlock*, unsigned> PredCount;
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for (pred_iterator PI = pred_begin(NewBB), E = pred_end(NewBB);
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PI != E; ++PI)
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--PredCount[*PI];
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// Figure out how many entries to remove from each PHI.
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for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
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++PredCount[PN->getIncomingBlock(i)];
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// At this point, the excess predecessor entries are positive in the
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// map. Loop over all of the PHIs and remove excess predecessor
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// entries.
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BasicBlock::iterator I = NewBB->begin();
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for (; (PN = dyn_cast<PHINode>(I)); ++I) {
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for (std::map<BasicBlock*, unsigned>::iterator PCI =PredCount.begin(),
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E = PredCount.end(); PCI != E; ++PCI) {
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BasicBlock *Pred = PCI->first;
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for (unsigned NumToRemove = PCI->second; NumToRemove; --NumToRemove)
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PN->removeIncomingValue(Pred, false);
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}
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}
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}
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// If the loops above have made these phi nodes have 0 or 1 operand,
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// replace them with undef or the input value. We must do this for
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// correctness, because 0-operand phis are not valid.
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PN = cast<PHINode>(NewBB->begin());
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if (PN->getNumIncomingValues() == 0) {
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BasicBlock::iterator I = NewBB->begin();
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BasicBlock::const_iterator OldI = OldBB->begin();
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while ((PN = dyn_cast<PHINode>(I++))) {
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Value *NV = UndefValue::get(PN->getType());
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PN->replaceAllUsesWith(NV);
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assert(ValueMap[OldI] == PN && "ValueMap mismatch");
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ValueMap[OldI] = NV;
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PN->eraseFromParent();
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++OldI;
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}
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} else if (PN->getNumIncomingValues() == 1) {
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BasicBlock::iterator I = NewBB->begin();
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BasicBlock::const_iterator OldI = OldBB->begin();
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while ((PN = dyn_cast<PHINode>(I++))) {
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Value *NV = PN->getIncomingValue(0);
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PN->replaceAllUsesWith(NV);
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assert(ValueMap[OldI] == PN && "ValueMap mismatch");
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|
ValueMap[OldI] = NV;
|
|
PN->eraseFromParent();
|
|
++OldI;
|
|
}
|
|
}
|
|
}
|
|
|
|
// Now that the inlined function body has been fully constructed, go through
|
|
// and zap unconditional fall-through branches. This happen all the time when
|
|
// specializing code: code specialization turns conditional branches into
|
|
// uncond branches, and this code folds them.
|
|
Function::iterator I = cast<BasicBlock>(ValueMap[&OldFunc->getEntryBlock()]);
|
|
while (I != NewFunc->end()) {
|
|
BranchInst *BI = dyn_cast<BranchInst>(I->getTerminator());
|
|
if (!BI || BI->isConditional()) { ++I; continue; }
|
|
|
|
BasicBlock *Dest = BI->getSuccessor(0);
|
|
if (!Dest->getSinglePredecessor()) { ++I; continue; }
|
|
|
|
// We know all single-entry PHI nodes in the inlined function have been
|
|
// removed, so we just need to splice the blocks.
|
|
BI->eraseFromParent();
|
|
|
|
// Move all the instructions in the succ to the pred.
|
|
I->getInstList().splice(I->end(), Dest->getInstList());
|
|
|
|
// Make all PHI nodes that referred to Dest now refer to I as their source.
|
|
Dest->replaceAllUsesWith(I);
|
|
|
|
// Remove the dest block.
|
|
Dest->eraseFromParent();
|
|
|
|
// Do not increment I, iteratively merge all things this block branches to.
|
|
}
|
|
}
|