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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@29925 91177308-0d34-0410-b5e6-96231b3b80d8
459 lines
16 KiB
C++
459 lines
16 KiB
C++
//===- LevelRaise.cpp - Code to change LLVM to higher level ---------------===//
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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 'raising' part of the LevelChange API. This is
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// useful because, in general, it makes the LLVM code terser and easier to
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// analyze.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Transforms/Scalar.h"
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#include "llvm/Transforms/Utils/Local.h"
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#include "TransformInternals.h"
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#include "llvm/Instructions.h"
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#include "llvm/Pass.h"
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#include "llvm/Transforms/Utils/BasicBlockUtils.h"
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#include "llvm/Support/CommandLine.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/ADT/Statistic.h"
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#include "llvm/ADT/STLExtras.h"
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#include <algorithm>
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#include <iostream>
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using namespace llvm;
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// StartInst - This enables the -raise-start-inst=foo option to cause the level
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// raising pass to start at instruction "foo", which is immensely useful for
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// debugging!
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//
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static cl::opt<std::string>
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StartInst("raise-start-inst", cl::Hidden, cl::value_desc("inst name"),
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cl::desc("Start raise pass at the instruction with the specified name"));
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static Statistic<>
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NumLoadStorePeepholes("raise", "Number of load/store peepholes");
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static Statistic<>
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NumGEPInstFormed("raise", "Number of other getelementptr's formed");
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static Statistic<>
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NumExprTreesConv("raise", "Number of expression trees converted");
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static Statistic<>
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NumCastOfCast("raise", "Number of cast-of-self removed");
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static Statistic<>
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NumDCEorCP("raise", "Number of insts DCEd or constprop'd");
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static Statistic<>
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NumVarargCallChanges("raise", "Number of vararg call peepholes");
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#define PRINT_PEEPHOLE(ID, NUM, I) \
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DEBUG(std::cerr << "Inst P/H " << ID << "[" << NUM << "] " << I)
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#define PRINT_PEEPHOLE1(ID, I1) do { PRINT_PEEPHOLE(ID, 0, I1); } while (0)
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#define PRINT_PEEPHOLE2(ID, I1, I2) \
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do { PRINT_PEEPHOLE(ID, 0, I1); PRINT_PEEPHOLE(ID, 1, I2); } while (0)
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#define PRINT_PEEPHOLE3(ID, I1, I2, I3) \
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do { PRINT_PEEPHOLE(ID, 0, I1); PRINT_PEEPHOLE(ID, 1, I2); \
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PRINT_PEEPHOLE(ID, 2, I3); } while (0)
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#define PRINT_PEEPHOLE4(ID, I1, I2, I3, I4) \
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do { PRINT_PEEPHOLE(ID, 0, I1); PRINT_PEEPHOLE(ID, 1, I2); \
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PRINT_PEEPHOLE(ID, 2, I3); PRINT_PEEPHOLE(ID, 3, I4); } while (0)
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namespace {
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struct RPR : public FunctionPass {
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virtual bool runOnFunction(Function &F);
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virtual void getAnalysisUsage(AnalysisUsage &AU) const {
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AU.setPreservesCFG();
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AU.addRequired<TargetData>();
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}
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private:
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bool DoRaisePass(Function &F);
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bool PeepholeOptimize(BasicBlock *BB, BasicBlock::iterator &BI);
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};
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RegisterPass<RPR> X("raise", "Raise Pointer References");
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}
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FunctionPass *llvm::createRaisePointerReferencesPass() {
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return new RPR();
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}
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// isReinterpretingCast - Return true if the cast instruction specified will
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// cause the operand to be "reinterpreted". A value is reinterpreted if the
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// cast instruction would cause the underlying bits to change.
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//
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static inline bool isReinterpretingCast(const CastInst *CI) {
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return!CI->getOperand(0)->getType()->isLosslesslyConvertibleTo(CI->getType());
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}
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bool RPR::PeepholeOptimize(BasicBlock *BB, BasicBlock::iterator &BI) {
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Instruction *I = BI;
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const TargetData &TD = getAnalysis<TargetData>();
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if (CastInst *CI = dyn_cast<CastInst>(I)) {
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Value *Src = CI->getOperand(0);
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const Type *DestTy = CI->getType();
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// Peephole optimize the following instruction:
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// %V2 = cast <ty> %V to <ty>
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//
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// Into: <nothing>
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//
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if (DestTy == Src->getType()) { // Check for a cast to same type as src!!
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PRINT_PEEPHOLE1("cast-of-self-ty", *CI);
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CI->replaceAllUsesWith(Src);
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if (!Src->hasName() && CI->hasName()) {
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std::string Name = CI->getName();
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CI->setName("");
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Src->setName(Name);
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}
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// DCE the instruction now, to avoid having the iterative version of DCE
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// have to worry about it.
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//
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BI = BB->getInstList().erase(BI);
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++NumCastOfCast;
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return true;
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}
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// Check to see if it's a cast of an instruction that does not depend on the
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// specific type of the operands to do it's job.
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if (!isReinterpretingCast(CI)) {
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ValueTypeCache ConvertedTypes;
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// Check to see if we can convert the source of the cast to match the
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// destination type of the cast...
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//
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ConvertedTypes[CI] = CI->getType(); // Make sure the cast doesn't change
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if (ExpressionConvertibleToType(Src, DestTy, ConvertedTypes, TD)) {
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PRINT_PEEPHOLE3("CAST-SRC-EXPR-CONV:in ", *Src, *CI, *BB->getParent());
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DEBUG(std::cerr << "\nCONVERTING SRC EXPR TYPE:\n");
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{ // ValueMap must be destroyed before function verified!
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ValueMapCache ValueMap;
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Value *E = ConvertExpressionToType(Src, DestTy, ValueMap, TD);
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if (Constant *CPV = dyn_cast<Constant>(E))
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CI->replaceAllUsesWith(CPV);
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PRINT_PEEPHOLE1("CAST-SRC-EXPR-CONV:out", *E);
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DEBUG(std::cerr << "DONE CONVERTING SRC EXPR TYPE: \n"
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<< *BB->getParent());
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}
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BI = BB->begin(); // Rescan basic block. BI might be invalidated.
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++NumExprTreesConv;
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return true;
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}
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// Check to see if we can convert the users of the cast value to match the
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// source type of the cast...
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//
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ConvertedTypes.clear();
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// Make sure the source doesn't change type
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ConvertedTypes[Src] = Src->getType();
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if (ValueConvertibleToType(CI, Src->getType(), ConvertedTypes, TD)) {
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//PRINT_PEEPHOLE3("CAST-DEST-EXPR-CONV:in ", *Src, *CI,
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// *BB->getParent());
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DEBUG(std::cerr << "\nCONVERTING EXPR TYPE:\n");
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{ // ValueMap must be destroyed before function verified!
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ValueMapCache ValueMap;
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ConvertValueToNewType(CI, Src, ValueMap, TD); // This will delete CI!
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}
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PRINT_PEEPHOLE1("CAST-DEST-EXPR-CONV:out", *Src);
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DEBUG(std::cerr << "DONE CONVERTING EXPR TYPE: \n\n" <<
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*BB->getParent());
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BI = BB->begin(); // Rescan basic block. BI might be invalidated.
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++NumExprTreesConv;
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return true;
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}
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}
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// Check to see if we are casting from a structure pointer to a pointer to
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// the first element of the structure... to avoid munching other peepholes,
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// we only let this happen if there are no add uses of the cast.
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//
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// Peephole optimize the following instructions:
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// %t1 = cast {<...>} * %StructPtr to <ty> *
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//
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// Into: %t2 = getelementptr {<...>} * %StructPtr, <0, 0, 0, ...>
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// %t1 = cast <eltype> * %t1 to <ty> *
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//
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if (const CompositeType *CTy = getPointedToComposite(Src->getType()))
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if (const PointerType *DestPTy = dyn_cast<PointerType>(DestTy)) {
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// Loop over uses of the cast, checking for add instructions. If an add
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// exists, this is probably a part of a more complex GEP, so we don't
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// want to mess around with the cast.
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//
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bool HasAddUse = false;
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for (Value::use_iterator I = CI->use_begin(), E = CI->use_end();
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I != E; ++I)
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if (isa<Instruction>(*I) &&
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cast<Instruction>(*I)->getOpcode() == Instruction::Add) {
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HasAddUse = true; break;
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}
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// If it doesn't have an add use, check to see if the dest type is
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// losslessly convertible to one of the types in the start of the struct
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// type.
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//
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if (!HasAddUse) {
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const Type *DestPointedTy = DestPTy->getElementType();
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unsigned Depth = 1;
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const CompositeType *CurCTy = CTy;
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const Type *ElTy = 0;
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// Build the index vector, full of all zeros
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std::vector<Value*> Indices;
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Indices.push_back(Constant::getNullValue(Type::UIntTy));
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while (CurCTy && !isa<PointerType>(CurCTy)) {
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if (const StructType *CurSTy = dyn_cast<StructType>(CurCTy)) {
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// Check for a zero element struct type... if we have one, bail.
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if (CurSTy->getNumElements() == 0) break;
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// Grab the first element of the struct type, which must lie at
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// offset zero in the struct.
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//
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ElTy = CurSTy->getElementType(0);
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} else {
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ElTy = cast<SequentialType>(CurCTy)->getElementType();
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}
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// Insert a zero to index through this type...
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Indices.push_back(Constant::getNullValue(Type::UIntTy));
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// Did we find what we're looking for?
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if (ElTy->isLosslesslyConvertibleTo(DestPointedTy)) break;
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// Nope, go a level deeper.
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++Depth;
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CurCTy = dyn_cast<CompositeType>(ElTy);
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ElTy = 0;
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}
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// Did we find what we were looking for? If so, do the transformation
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if (ElTy) {
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PRINT_PEEPHOLE1("cast-for-first:in", *CI);
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std::string Name = CI->getName(); CI->setName("");
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// Insert the new T cast instruction... stealing old T's name
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GetElementPtrInst *GEP = new GetElementPtrInst(Src, Indices,
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Name, BI);
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// Make the old cast instruction reference the new GEP instead of
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// the old src value.
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//
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CI->setOperand(0, GEP);
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PRINT_PEEPHOLE2("cast-for-first:out", *GEP, *CI);
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++NumGEPInstFormed;
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return true;
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}
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}
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}
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} else if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
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Value *Val = SI->getOperand(0);
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Value *Pointer = SI->getPointerOperand();
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// Peephole optimize the following instructions:
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// %t = cast <T1>* %P to <T2> * ;; If T1 is losslessly convertible to T2
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// store <T2> %V, <T2>* %t
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//
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// Into:
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// %t = cast <T2> %V to <T1>
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// store <T1> %t2, <T1>* %P
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//
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// Note: This is not taken care of by expr conversion because there might
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// not be a cast available for the store to convert the incoming value of.
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// This code is basically here to make sure that pointers don't have casts
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// if possible.
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//
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if (CastInst *CI = dyn_cast<CastInst>(Pointer))
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if (Value *CastSrc = CI->getOperand(0)) // CSPT = CastSrcPointerType
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if (const PointerType *CSPT = dyn_cast<PointerType>(CastSrc->getType()))
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// convertible types?
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if (Val->getType()->isLosslesslyConvertibleTo(CSPT->getElementType())) {
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PRINT_PEEPHOLE3("st-src-cast:in ", *Pointer, *Val, *SI);
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// Insert the new T cast instruction... stealing old T's name
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std::string Name(CI->getName()); CI->setName("");
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CastInst *NCI = new CastInst(Val, CSPT->getElementType(),
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Name, BI);
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// Replace the old store with a new one!
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ReplaceInstWithInst(BB->getInstList(), BI,
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SI = new StoreInst(NCI, CastSrc));
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PRINT_PEEPHOLE3("st-src-cast:out", *NCI, *CastSrc, *SI);
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++NumLoadStorePeepholes;
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return true;
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}
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} else if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
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Value *Pointer = LI->getOperand(0);
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const Type *PtrElType =
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cast<PointerType>(Pointer->getType())->getElementType();
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// Peephole optimize the following instructions:
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// %Val = cast <T1>* to <T2>* ;; If T1 is losslessly convertible to T2
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// %t = load <T2>* %P
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//
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// Into:
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// %t = load <T1>* %P
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// %Val = cast <T1> to <T2>
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//
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// Note: This is not taken care of by expr conversion because there might
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// not be a cast available for the store to convert the incoming value of.
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// This code is basically here to make sure that pointers don't have casts
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// if possible.
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//
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if (CastInst *CI = dyn_cast<CastInst>(Pointer))
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if (Value *CastSrc = CI->getOperand(0)) // CSPT = CastSrcPointerType
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if (const PointerType *CSPT = dyn_cast<PointerType>(CastSrc->getType()))
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// convertible types?
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if (PtrElType->isLosslesslyConvertibleTo(CSPT->getElementType())) {
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PRINT_PEEPHOLE2("load-src-cast:in ", *Pointer, *LI);
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// Create the new load instruction... loading the pre-casted value
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LoadInst *NewLI = new LoadInst(CastSrc, LI->getName(), BI);
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// Insert the new T cast instruction... stealing old T's name
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CastInst *NCI = new CastInst(NewLI, LI->getType(), CI->getName());
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// Replace the old store with a new one!
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ReplaceInstWithInst(BB->getInstList(), BI, NCI);
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PRINT_PEEPHOLE3("load-src-cast:out", *NCI, *CastSrc, *NewLI);
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++NumLoadStorePeepholes;
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return true;
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}
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} else if (CallInst *CI = dyn_cast<CallInst>(I)) {
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// If we have a call with all varargs arguments, convert the call to use the
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// actual argument types present...
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//
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const PointerType *PTy = cast<PointerType>(CI->getCalledValue()->getType());
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const FunctionType *FTy = cast<FunctionType>(PTy->getElementType());
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// Is the call to a vararg variable with no real parameters?
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if (FTy->isVarArg() && FTy->getNumParams() == 0 &&
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!CI->getCalledFunction()) {
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// If so, insert a new cast instruction, casting it to a function type
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// that matches the current arguments...
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//
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std::vector<const Type *> Params; // Parameter types...
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for (unsigned i = 1, e = CI->getNumOperands(); i != e; ++i)
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Params.push_back(CI->getOperand(i)->getType());
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FunctionType *NewFT = FunctionType::get(FTy->getReturnType(),
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Params, false);
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PointerType *NewPFunTy = PointerType::get(NewFT);
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// Create a new cast, inserting it right before the function call...
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Value *NewCast;
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Constant *ConstantCallSrc = 0;
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if (Constant *CS = dyn_cast<Constant>(CI->getCalledValue()))
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ConstantCallSrc = CS;
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if (ConstantCallSrc)
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NewCast = ConstantExpr::getCast(ConstantCallSrc, NewPFunTy);
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else
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NewCast = new CastInst(CI->getCalledValue(), NewPFunTy,
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CI->getCalledValue()->getName()+"_c",CI);
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// Create a new call instruction...
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CallInst *NewCall = new CallInst(NewCast,
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std::vector<Value*>(CI->op_begin()+1, CI->op_end()));
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if (CI->isTailCall()) NewCall->setTailCall();
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NewCall->setCallingConv(CI->getCallingConv());
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++BI;
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ReplaceInstWithInst(CI, NewCall);
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++NumVarargCallChanges;
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return true;
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}
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}
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return false;
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}
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bool RPR::DoRaisePass(Function &F) {
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bool Changed = false;
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for (Function::iterator BB = F.begin(), BBE = F.end(); BB != BBE; ++BB)
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for (BasicBlock::iterator BI = BB->begin(); BI != BB->end();) {
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DEBUG(std::cerr << "LevelRaising: " << *BI);
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if (dceInstruction(BI) || doConstantPropagation(BI)) {
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Changed = true;
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++NumDCEorCP;
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DEBUG(std::cerr << "***\t\t^^-- Dead code eliminated!\n");
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} else if (PeepholeOptimize(BB, BI)) {
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Changed = true;
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} else {
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++BI;
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}
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}
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return Changed;
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}
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// runOnFunction - Raise a function representation to a higher level.
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bool RPR::runOnFunction(Function &F) {
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DEBUG(std::cerr << "\n\n\nStarting to work on Function '" << F.getName()
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<< "'\n");
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// Insert casts for all incoming pointer pointer values that are treated as
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// arrays...
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//
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bool Changed = false, LocalChange;
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// If the StartInst option was specified, then Peephole optimize that
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// instruction first if it occurs in this function.
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//
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if (!StartInst.empty()) {
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for (Function::iterator BB = F.begin(), BBE = F.end(); BB != BBE; ++BB)
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for (BasicBlock::iterator BI = BB->begin(); BI != BB->end(); ++BI)
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if (BI->getName() == StartInst) {
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bool SavedDebug = DebugFlag; // Save the DEBUG() controlling flag.
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DebugFlag = true; // Turn on DEBUG's
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Changed |= PeepholeOptimize(BB, BI);
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DebugFlag = SavedDebug; // Restore DebugFlag to previous state
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}
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}
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do {
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DEBUG(std::cerr << "Looping: \n" << F);
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// Iterate over the function, refining it, until it converges on a stable
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// state
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LocalChange = false;
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while (DoRaisePass(F)) LocalChange = true;
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Changed |= LocalChange;
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} while (LocalChange);
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return Changed;
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}
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