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llvm-project/llvm/lib/Transforms/LevelRaise.cpp

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