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

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//===- LevelRaise.cpp - Code to change LLVM to higher level -----------------=//
//
// 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/LevelChange.h"
#include "TransformInternals.h"
#include "llvm/Function.h"
#include "llvm/iOther.h"
#include "llvm/iMemory.h"
#include "llvm/ConstantVals.h"
#include "llvm/Pass.h"
#include "llvm/ConstantHandling.h"
#include "llvm/Transforms/Scalar/DCE.h"
#include "llvm/Transforms/Scalar/ConstantProp.h"
#include "llvm/Analysis/Expressions.h"
#include "Support/STLExtras.h"
#include <algorithm>
#include "llvm/Assembly/Writer.h"
//#define DEBUG_PEEPHOLE_INSTS 1
#ifdef DEBUG_PEEPHOLE_INSTS
#define PRINT_PEEPHOLE(ID, NUM, I) \
std::cerr << "Inst P/H " << ID << "[" << NUM << "] " << I;
#else
#define PRINT_PEEPHOLE(ID, NUM, I)
#endif
#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)
// isReinterpretingCast - Return true if the cast instruction specified will
// cause the operand to be "reinterpreted". A value is reinterpreted if the
// cast instruction would cause the underlying bits to change.
//
static inline bool isReinterpretingCast(const CastInst *CI) {
return!CI->getOperand(0)->getType()->isLosslesslyConvertableTo(CI->getType());
}
// Peephole optimize the following instructions:
// %t1 = cast ? to x *
// %t2 = add x * %SP, %t1 ;; Constant must be 2nd operand
//
// Into: %t3 = getelementptr {<...>} * %SP, <element indices>
// %t2 = cast <eltype> * %t3 to {<...>}*
//
static bool HandleCastToPointer(BasicBlock::iterator BI,
const PointerType *DestPTy) {
CastInst *CI = cast<CastInst>(*BI);
if (CI->use_empty()) return false;
// Scan all of the uses, looking for any uses that are not add
// instructions. If we have non-adds, do not make this transformation.
//
for (Value::use_iterator I = CI->use_begin(), E = CI->use_end();
I != E; ++I) {
if (BinaryOperator *BO = dyn_cast<BinaryOperator>(*I)) {
if (BO->getOpcode() != Instruction::Add)
return false;
} else {
return false;
}
}
std::vector<Value*> Indices;
Value *Src = CI->getOperand(0);
const Type *Result = ConvertableToGEP(DestPTy, Src, Indices, &BI);
if (Result == 0) return false; // Not convertable...
PRINT_PEEPHOLE2("cast-add-to-gep:in", Src, CI);
// If we have a getelementptr capability... transform all of the
// add instruction uses into getelementptr's.
while (!CI->use_empty()) {
BinaryOperator *I = cast<BinaryOperator>(*CI->use_begin());
assert(I->getOpcode() == Instruction::Add && I->getNumOperands() == 2 &&
"Use is not a valid add instruction!");
// Get the value added to the cast result pointer...
Value *OtherPtr = I->getOperand((I->getOperand(0) == CI) ? 1 : 0);
Instruction *GEP = new GetElementPtrInst(OtherPtr, Indices, I->getName());
PRINT_PEEPHOLE1("cast-add-to-gep:i", I);
if (GEP->getType() == I->getType()) {
// Replace the old add instruction with the shiny new GEP inst
ReplaceInstWithInst(I, GEP);
} else {
// If the type produced by the gep instruction differs from the original
// add instruction type, insert a cast now.
//
// Insert the GEP instruction before the old add instruction... and get an
// iterator to point at the add instruction...
BasicBlock::iterator GEPI = InsertInstBeforeInst(GEP, I)+1;
PRINT_PEEPHOLE1("cast-add-to-gep:o", GEP);
CastInst *CI = new CastInst(GEP, I->getType());
GEP = CI;
// Replace the old add instruction with the shiny new GEP inst
ReplaceInstWithInst(I->getParent()->getInstList(), GEPI, GEP);
}
PRINT_PEEPHOLE1("cast-add-to-gep:o", GEP);
}
return true;
}
// Peephole optimize the following instructions:
// %t1 = cast ulong <const int> to {<...>} *
// %t2 = add {<...>} * %SP, %t1 ;; Constant must be 2nd operand
//
// or
// %t1 = cast {<...>}* %SP to int*
// %t5 = cast ulong <const int> to int*
// %t2 = add int* %t1, %t5 ;; int is same size as field
//
// Into: %t3 = getelementptr {<...>} * %SP, <element indices>
// %t2 = cast <eltype> * %t3 to {<...>}*
//
static bool PeepholeOptimizeAddCast(BasicBlock *BB, BasicBlock::iterator &BI,
Value *AddOp1, CastInst *AddOp2) {
const CompositeType *CompTy;
Value *OffsetVal = AddOp2->getOperand(0);
Value *SrcPtr; // Of type pointer to struct...
if ((CompTy = getPointedToComposite(AddOp1->getType()))) {
SrcPtr = AddOp1; // Handle the first case...
} else if (CastInst *AddOp1c = dyn_cast<CastInst>(AddOp1)) {
SrcPtr = AddOp1c->getOperand(0); // Handle the second case...
CompTy = getPointedToComposite(SrcPtr->getType());
}
// Only proceed if we have detected all of our conditions successfully...
if (!CompTy || !SrcPtr || !OffsetVal->getType()->isIntegral())
return false;
std::vector<Value*> Indices;
if (!ConvertableToGEP(SrcPtr->getType(), OffsetVal, Indices, &BI))
return false; // Not convertable... perhaps next time
if (getPointedToComposite(AddOp1->getType())) { // case 1
PRINT_PEEPHOLE2("add-to-gep1:in", AddOp2, *BI);
} else {
PRINT_PEEPHOLE3("add-to-gep2:in", AddOp1, AddOp2, *BI);
}
GetElementPtrInst *GEP = new GetElementPtrInst(SrcPtr, Indices,
AddOp2->getName());
BI = BB->getInstList().insert(BI, GEP)+1;
Instruction *NCI = new CastInst(GEP, AddOp1->getType());
ReplaceInstWithInst(BB->getInstList(), BI, NCI);
PRINT_PEEPHOLE2("add-to-gep:out", GEP, NCI);
return true;
}
static bool PeepholeOptimize(BasicBlock *BB, BasicBlock::iterator &BI) {
Instruction *I = *BI;
if (CastInst *CI = dyn_cast<CastInst>(I)) {
Value *Src = CI->getOperand(0);
Instruction *SrcI = dyn_cast<Instruction>(Src); // Nonnull if instr source
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, BB->getParent()->getSymbolTable());
}
return true;
}
// Peephole optimize the following instructions:
// %tmp = cast <ty> %V to <ty2>
// %V = cast <ty2> %tmp to <ty3> ; Where ty & ty2 are same size
//
// Into: cast <ty> %V to <ty3>
//
if (SrcI)
if (CastInst *CSrc = dyn_cast<CastInst>(SrcI))
if (isReinterpretingCast(CI) + isReinterpretingCast(CSrc) < 2) {
// We can only do c-c elimination if, at most, one cast does a
// reinterpretation of the input data.
//
// If legal, make this cast refer the the original casts argument!
//
PRINT_PEEPHOLE2("cast-cast:in ", CI, CSrc);
CI->setOperand(0, CSrc->getOperand(0));
PRINT_PEEPHOLE1("cast-cast:out", CI);
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 (!isReinterpretingCast(CI)) {
ValueTypeCache ConvertedTypes;
// Check to see if we can convert the users of the cast value to match the
// source type of the cast...
//
ConvertedTypes[CI] = CI->getType(); // Make sure the cast doesn't change
if (ExpressionConvertableToType(Src, DestTy, ConvertedTypes)) {
PRINT_PEEPHOLE3("CAST-SRC-EXPR-CONV:in ", Src, CI, BB->getParent());
#ifdef DEBUG_PEEPHOLE_INSTS
cerr << "\nCONVERTING SRC EXPR TYPE:\n";
#endif
ValueMapCache ValueMap;
Value *E = ConvertExpressionToType(Src, DestTy, ValueMap);
if (Constant *CPV = dyn_cast<Constant>(E))
CI->replaceAllUsesWith(CPV);
BI = BB->begin(); // Rescan basic block. BI might be invalidated.
PRINT_PEEPHOLE1("CAST-SRC-EXPR-CONV:out", E);
#ifdef DEBUG_PEEPHOLE_INSTS
cerr << "DONE CONVERTING SRC EXPR TYPE: \n" << BB->getParent();
#endif
return true;
}
// Check to see if we can convert the source of the cast to match the
// destination type of the cast...
//
ConvertedTypes.clear();
if (ValueConvertableToType(CI, Src->getType(), ConvertedTypes)) {
PRINT_PEEPHOLE3("CAST-DEST-EXPR-CONV:in ", Src, CI, BB->getParent());
#ifdef DEBUG_PEEPHOLE_INSTS
cerr << "\nCONVERTING EXPR TYPE:\n";
#endif
ValueMapCache ValueMap;
ConvertValueToNewType(CI, Src, ValueMap); // This will delete CI!
BI = BB->begin(); // Rescan basic block. BI might be invalidated.
PRINT_PEEPHOLE1("CAST-DEST-EXPR-CONV:out", Src);
#ifdef DEBUG_PEEPHOLE_INSTS
cerr << "DONE CONVERTING EXPR TYPE: \n\n" << BB->getParent();
#endif
return true;
}
}
// Otherwise find out it this cast is a cast to a pointer type, which is
// then added to some other pointer, then loaded or stored through. If
// so, convert the add into a getelementptr instruction...
//
if (const PointerType *DestPTy = dyn_cast<PointerType>(DestTy)) {
if (HandleCastToPointer(BI, DestPTy)) {
BI = BB->begin(); // Rescan basic block. BI might be invalidated.
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 1
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 convertable 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(ConstantUInt::get(Type::UIntTy, 0));
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->getElementTypes().size() == 0) break;
// Grab the first element of the struct type, which must lie at
// offset zero in the struct.
//
ElTy = CurSTy->getElementTypes()[0];
} else {
ElTy = cast<ArrayType>(CurCTy)->getElementType();
}
// Insert a zero to index through this type...
Indices.push_back(ConstantUInt::get(CurCTy->getIndexType(), 0));
// Did we find what we're looking for?
if (ElTy->isLosslesslyConvertableTo(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);
// Insert the new T cast instruction... stealing old T's name
GetElementPtrInst *GEP = new GetElementPtrInst(Src, Indices,
CI->getName());
CI->setName("");
BI = BB->getInstList().insert(BI, GEP)+1;
// Make the old cast instruction reference the new GEP instead of
// the old src value.
//
CI->setOperand(0, GEP);
PRINT_PEEPHOLE2("cast-for-first:out", GEP, CI);
return true;
}
}
}
#endif
#if 1
} 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 convertable 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 (PointerType *CSPT = dyn_cast<PointerType>(CastSrc->getType()))
// convertable types?
if (Val->getType()->isLosslesslyConvertableTo(CSPT->getElementType()) &&
!SI->hasIndices()) { // No subscripts yet!
PRINT_PEEPHOLE3("st-src-cast:in ", Pointer, Val, SI);
// Insert the new T cast instruction... stealing old T's name
CastInst *NCI = new CastInst(Val, CSPT->getElementType(),
CI->getName());
CI->setName("");
BI = BB->getInstList().insert(BI, NCI)+1;
// 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);
return true;
}
} else if (I->getOpcode() == Instruction::Add &&
isa<CastInst>(I->getOperand(1))) {
if (PeepholeOptimizeAddCast(BB, BI, I->getOperand(0),
cast<CastInst>(I->getOperand(1))))
return true;
#endif
}
return false;
}
static bool DoRaisePass(Function *F) {
bool Changed = false;
for (Method::iterator MI = F->begin(), ME = F->end(); MI != ME; ++MI) {
BasicBlock *BB = *MI;
BasicBlock::InstListType &BIL = BB->getInstList();
for (BasicBlock::iterator BI = BB->begin(); BI != BB->end();) {
#if DEBUG_PEEPHOLE_INSTS
cerr << "Processing: " << *BI;
#endif
if (dceInstruction(BIL, BI) || doConstantPropogation(BB, BI)) {
Changed = true;
#ifdef DEBUG_PEEPHOLE_INSTS
cerr << "***\t\t^^-- DeadCode Elinated!\n";
#endif
} else if (PeepholeOptimize(BB, BI))
Changed = true;
else
++BI;
}
}
return Changed;
}
// RaisePointerReferences::doit - Raise a method representation to a higher
// level.
//
static bool doRPR(Function *F) {
#ifdef DEBUG_PEEPHOLE_INSTS
cerr << "\n\n\nStarting to work on Function '" << F->getName() << "'\n";
#endif
// Insert casts for all incoming pointer pointer values that are treated as
// arrays...
//
bool Changed = false, LocalChange;
do {
#ifdef DEBUG_PEEPHOLE_INSTS
cerr << "Looping: \n" << F;
#endif
// Iterate over the method, refining it, until it converges on a stable
// state
LocalChange = false;
while (DoRaisePass(F)) LocalChange = true;
Changed |= LocalChange;
} while (LocalChange);
return Changed;
}
namespace {
struct RaisePointerReferences : public MethodPass {
virtual bool runOnMethod(Function *F) { return doRPR(F); }
};
}
Pass *createRaisePointerReferencesPass() {
return new RaisePointerReferences();
}
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