llvm-6502/lib/Transforms/LevelRaise.cpp
2001-11-26 16:58:14 +00:00

574 lines
20 KiB
C++

//===- 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/Method.h"
#include "llvm/Support/STLExtras.h"
#include "llvm/iOther.h"
#include "llvm/iMemory.h"
#include "llvm/ConstPoolVals.h"
#include "llvm/Optimizations/ConstantHandling.h"
#include "llvm/Optimizations/DCE.h"
#include "llvm/Analysis/Expressions.h"
#include <algorithm>
#include "llvm/Assembly/Writer.h"
#define DEBUG_PEEPHOLE_INSTS 1
#ifdef DEBUG_PEEPHOLE_INSTS
#define PRINT_PEEPHOLE(ID, NUM, I) \
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 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;
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()) {
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;
if (ValueConvertableToType(CI, Src->getType(), ConvertedTypes)) {
PRINT_PEEPHOLE2("CAST-DEST-EXPR-CONV:in ", Src, CI);
#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;
} else {
ConvertedTypes.clear();
if (ExpressionConvertableToType(Src, DestTy, ConvertedTypes)) {
PRINT_PEEPHOLE2("CAST-SRC-EXPR-CONV:in ", Src, CI);
#ifdef DEBUG_PEEPHOLE_INSTS
cerr << "\nCONVERTING SRC EXPR TYPE:\n";
#endif
ValueMapCache ValueMap;
Value *E = ConvertExpressionToType(Src, DestTy, ValueMap);
if (ConstPoolVal *CPV = dyn_cast<ConstPoolVal>(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\n";// << BB->getParent();
#endif
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->getValueType();
unsigned Depth = 1;
const CompositeType *CurCTy = CTy;
const Type *ElTy = 0;
// Build the index vector, full of all zeros
vector<Value*> Indices;
while (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(ConstPoolUInt::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:
// %t1 = getelementptr {<...>} * %StructPtr, <element indices>
// store <elementty> %v, <elementty> * %t1
//
// Into: store <elementty> %v, {<...>} * %StructPtr, <element indices>
//
if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Pointer)) {
// Append any indices that the store instruction has onto the end of the
// ones that the GEP is carrying...
//
vector<Value*> Indices(GEP->copyIndices());
Indices.insert(Indices.end(), SI->idx_begin(), SI->idx_end());
PRINT_PEEPHOLE2("gep-store:in", GEP, SI);
ReplaceInstWithInst(BB->getInstList(), BI,
SI = new StoreInst(Val, GEP->getPointerOperand(),
Indices));
PRINT_PEEPHOLE1("gep-store:out", SI);
return true;
}
// 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
//
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->getValueType()) &&
!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->getValueType(),
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 (LoadInst *LI = dyn_cast<LoadInst>(I)) {
Value *Pointer = LI->getPointerOperand();
// Peephole optimize the following instructions:
// %t1 = getelementptr {<...>} * %StructPtr, <element indices>
// %V = load <elementty> * %t1
//
// Into: load {<...>} * %StructPtr, <element indices>
//
if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Pointer)) {
// Append any indices that the load instruction has onto the end of the
// ones that the GEP is carrying...
//
vector<Value*> Indices(GEP->copyIndices());
Indices.insert(Indices.end(), LI->idx_begin(), LI->idx_end());
PRINT_PEEPHOLE2("gep-load:in", GEP, LI);
ReplaceInstWithInst(BB->getInstList(), BI,
LI = new LoadInst(GEP->getPointerOperand(),
Indices));
PRINT_PEEPHOLE1("gep-load:out", LI);
return true;
}
// Peephole optimize the following instructions:
// %t1 = cast <ty> * %t0 to <ty2> *
// %V = load <ty2> * %t1
//
// Into: %t1 = load <ty> * %t0
// %V = cast <ty> %t1 to <ty2>
//
// The idea behind this transformation is that if the expression type
// conversion engine could not convert the cast into some other nice form,
// that there is something fundementally wrong with the current shape of
// the program. Move the cast through the load and try again. This will
// leave the original cast instruction, to presumably become dead.
//
if (CastInst *CI = dyn_cast<CastInst>(Pointer)) {
Value *SrcVal = CI->getOperand(0);
const PointerType *SrcTy = dyn_cast<PointerType>(SrcVal->getType());
const Type *ElTy = SrcTy ? SrcTy->getValueType() : 0;
// Make sure that nothing will be lost in the new cast...
if (!LI->hasIndices() && SrcTy &&
ElTy->isLosslesslyConvertableTo(LI->getType())) {
PRINT_PEEPHOLE2("CL-LoadCast:in ", CI, LI);
string CName = CI->getName(); CI->setName("");
LoadInst *NLI = new LoadInst(SrcVal, LI->getName());
LI->setName(""); // Take over the old load's name
// Insert the load before the old load
BI = BB->getInstList().insert(BI, NLI)+1;
// Replace the old load with a new cast...
ReplaceInstWithInst(BB->getInstList(), BI,
CI = new CastInst(NLI, LI->getType(), CName));
PRINT_PEEPHOLE2("CL-LoadCast:out", NLI, CI);
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(Method *M) {
bool Changed = false;
for (Method::iterator MI = M->begin(), ME = M->end(); MI != ME; ++MI) {
BasicBlock *BB = *MI;
BasicBlock::InstListType &BIL = BB->getInstList();
for (BasicBlock::iterator BI = BB->begin(); BI != BB->end();) {
if (opt::DeadCodeElimination::dceInstruction(BIL, BI)) {
Changed = true;
#ifdef DEBUG_PEEPHOLE_INSTS
cerr << "DeadCode Elinated!\n";
#endif
} else if (PeepholeOptimize(BB, BI))
Changed = true;
else
++BI;
}
}
return Changed;
}
// DoInsertArrayCast - If the argument value has a pointer type, and if the
// argument value is used as an array, insert a cast before the specified
// basic block iterator that casts the value to an array pointer. Return the
// new cast instruction (in the CastResult var), or null if no cast is inserted.
//
static bool DoInsertArrayCast(Value *V, BasicBlock *BB,
BasicBlock::iterator InsertBefore) {
const PointerType *ThePtrType = dyn_cast<PointerType>(V->getType());
if (!ThePtrType) return false;
const Type *ElTy = ThePtrType->getValueType();
if (isa<MethodType>(ElTy) || isa<ArrayType>(ElTy)) return false;
unsigned ElementSize = TD.getTypeSize(ElTy);
bool InsertCast = false;
for (Value::use_iterator I = V->use_begin(), E = V->use_end(); I != E; ++I) {
Instruction *Inst = cast<Instruction>(*I);
switch (Inst->getOpcode()) {
case Instruction::Cast: // There is already a cast instruction!
if (const PointerType *PT = dyn_cast<const PointerType>(Inst->getType()))
if (const ArrayType *AT = dyn_cast<const ArrayType>(PT->getValueType()))
if (AT->getElementType() == ThePtrType->getValueType()) {
// Cast already exists! Don't mess around with it.
return false; // No changes made to program though...
}
break;
case Instruction::Add: { // Analyze pointer arithmetic...
Value *OtherOp = Inst->getOperand(Inst->getOperand(0) == V);
analysis::ExprType Expr = analysis::ClassifyExpression(OtherOp);
// This looks like array addressing iff:
// A. The constant of the index is larger than the size of the element
// type.
// B. The scale factor is >= the size of the type.
//
if (Expr.Offset && getConstantValue(Expr.Offset) >= (int)ElementSize) // A
InsertCast = true;
if (Expr.Scale && getConstantValue(Expr.Scale) >= (int)ElementSize) // B
InsertCast = true;
break;
}
default: break; // Not an interesting use...
}
}
if (!InsertCast) return false; // There is no reason to insert a cast!
// Calculate the destination pointer type
const PointerType *DestTy = PointerType::get(ArrayType::get(ElTy));
// Check to make sure that all uses of the value can be converted over to use
// the newly typed value.
//
ValueTypeCache ConvertedTypes;
if (!ValueConvertableToType(V, DestTy, ConvertedTypes)) {
cerr << "FAILED to convert types of values for " << V << "\n";
ConvertedTypes.clear();
ValueConvertableToType(V, DestTy, ConvertedTypes);
return false;
}
ConvertedTypes.clear();
// Insert a cast!
CastInst *TheCast =
new CastInst(ConstPoolVal::getNullConstant(V->getType()), DestTy,
V->getName());
BB->getInstList().insert(InsertBefore, TheCast);
cerr << "Inserting cast for " << V << endl;
// Convert users of the old value over to use the cast result...
ValueMapCache VMC;
ConvertValueToNewType(V, TheCast, VMC);
// The cast is the only thing that is allowed to reference the value...
TheCast->setOperand(0, V);
cerr << "Inserted ptr-array cast: " << TheCast;
return true; // Made a change!
}
// DoInsertArrayCasts - Loop over all "incoming" values in the specified method,
// inserting a cast for pointer values that are used as arrays. For our
// purposes, an incoming value is considered to be either a value that is
// either a method parameter, or a pointer returned from a function call.
//
static bool DoInsertArrayCasts(Method *M) {
assert(!M->isExternal() && "Can't handle external methods!");
// Insert casts for all arguments to the function...
bool Changed = false;
BasicBlock *CurBB = M->front();
for (Method::ArgumentListType::iterator AI = M->getArgumentList().begin(),
AE = M->getArgumentList().end(); AI != AE; ++AI) {
Changed |= DoInsertArrayCast(*AI, CurBB, CurBB->begin());
}
// TODO: insert casts for alloca, malloc, and function call results. Also,
// look for pointers that already have casts, to add to the map.
return Changed;
}
// RaisePointerReferences::doit - Raise a method representation to a higher
// level.
//
bool RaisePointerReferences::doit(Method *M) {
if (M->isExternal()) return false;
#ifdef DEBUG_PEEPHOLE_INSTS
cerr << "\n\n\nStarting to work on Method '" << M->getName() << "'\n";
#endif
// Insert casts for all incoming pointer pointer values that are treated as
// arrays...
//
bool Changed = false, LocalChange;
do {
LocalChange = DoInsertArrayCasts(M);
// Iterate over the method, refining it, until it converges on a stable
// state
while (DoRaisePass(M)) LocalChange = true;
Changed |= LocalChange;
} while (LocalChange);
return Changed;
}