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8e7f409169
llvm-6502/lib/Transforms/LevelRaise.cpp
Chris Lattner 8e7f409169 Minor method rename 
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@1119 91177308-0d34-0410-b5e6-96231b3b80d8
2001-11-04 08:08:34 +00:00

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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. Note that it is good to run DCE after doing this transformation.
//
// Eliminate silly things in the source that do not effect the level, but do
// clean up the code:
// * Casts of casts
// - getelementptr/load & getelementptr/store are folded into a direct
// load or store
// - Convert this code (for both alloca and malloc):
// %reg110 = shl uint %n, ubyte 2 ;;<uint>
// %reg108 = alloca ubyte, uint %reg110 ;;<ubyte*>
// %cast76 = cast ubyte* %reg108 to uint* ;;<uint*>
// To: %cast76 = alloca uint, uint %n
// Convert explicit addressing to use getelementptr instruction where possible
// - ...
//
// Convert explicit addressing on pointers to use getelementptr instruction.
// - If a pointer is used by arithmetic operation, insert an array casted
// version into the source program, only for the following pointer types:
// * Method argument pointers
// - Pointers returned by alloca or malloc
// - Pointers returned by function calls
// - If a pointer is indexed with a value scaled by a constant size equal
// to the element size of the array, the expression is replaced with a
// getelementptr instruction.
//
//===----------------------------------------------------------------------===//
#include "llvm/Transforms/LevelChange.h"
#include "llvm/Method.h"
#include "llvm/Support/STLExtras.h"
#include "llvm/iOther.h"
#include "llvm/iMemory.h"
#include "llvm/ConstPoolVals.h"
#include "llvm/Target/TargetData.h"
#include "llvm/Optimizations/ConstantHandling.h"
#include "llvm/Optimizations/DCE.h"
#include <map>
#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)
// TargetData Hack: Eventually we will have annotations given to us by the
// backend so that we know stuff about type size and alignments. For now
// though, just use this, because it happens to match the model that GCC uses.
//
const TargetData TD("LevelRaise: Should be GCC though!");
// losslessCastableTypes - Return true if the types are bitwise equivalent.
// This predicate returns true if it is possible to cast from one type to
// another without gaining or losing precision, or altering the bits in any way.
//
static bool losslessCastableTypes(const Type *T1, const Type *T2) {
if (!T1->isPrimitiveType() && !isa<PointerType>(T1)) return false;
if (!T2->isPrimitiveType() && !isa<PointerType>(T2)) return false;
if (T1->getPrimitiveID() == T2->getPrimitiveID())
return true; // Handles identity cast, and cast of differing pointer types
// Now we know that they are two differing primitive or pointer types
switch (T1->getPrimitiveID()) {
case Type::UByteTyID: return T2 == Type::SByteTy;
case Type::SByteTyID: return T2 == Type::UByteTy;
case Type::UShortTyID: return T2 == Type::ShortTy;
case Type::ShortTyID: return T2 == Type::UShortTy;
case Type::UIntTyID: return T2 == Type::IntTy;
case Type::IntTyID: return T2 == Type::UIntTy;
case Type::ULongTyID:
case Type::LongTyID:
case Type::PointerTyID:
return T2 == Type::ULongTy || T2 == Type::LongTy ||
T2->getPrimitiveID() == Type::PointerTyID;
default:
return false; // Other types have no identity values
}
}
// 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 !losslessCastableTypes(CI->getOperand(0)->getType(), CI->getType());
}
// getPointedToStruct - If the argument is a pointer type, and the pointed to
// value is a struct type, return the struct type, else return null.
//
static const StructType *getPointedToStruct(const Type *Ty) {
const PointerType *PT = dyn_cast<PointerType>(Ty);
return PT ? dyn_cast<StructType>(PT->getValueType()) : 0;
}
// getStructOffsetType - Return a vector of offsets that are to be used to index
// into the specified struct type to get as close as possible to index as we
// can. Note that it is possible that we cannot get exactly to Offset, in which
// case we update offset to be the offset we actually obtained. The resultant
// leaf type is returned.
//
static const Type *getStructOffsetType(const Type *Ty, unsigned &Offset,
vector<ConstPoolVal*> &Offsets) {
if (!isa<StructType>(Ty)) {
Offset = 0; // Return the offset that we were able to acheive
return Ty; // Return the leaf type
}
assert(Offset < TD.getTypeSize(Ty) && "Offset not in struct!");
const StructType *STy = cast<StructType>(Ty);
const StructLayout *SL = TD.getStructLayout(STy);
// This loop terminates always on a 0 <= i < MemberOffsets.size()
unsigned i;
for (i = 0; i < SL->MemberOffsets.size()-1; ++i)
if (Offset >= SL->MemberOffsets[i] && Offset < SL->MemberOffsets[i+1])
break;
assert(Offset >= SL->MemberOffsets[i] &&
(i == SL->MemberOffsets.size()-1 || Offset < SL->MemberOffsets[i+1]));
// Make sure to save the current index...
Offsets.push_back(ConstPoolUInt::get(Type::UByteTy, i));
unsigned SubOffs = Offset - SL->MemberOffsets[i];
const Type *LeafTy = getStructOffsetType(STy->getElementTypes()[i], SubOffs,
Offsets);
Offset = SL->MemberOffsets[i] + SubOffs;
return LeafTy;
}
// ReplaceInstWithValue - Replace all uses of an instruction (specified by BI)
// with a value, then remove and delete the original instruction.
//
static void ReplaceInstWithValue(BasicBlock::InstListType &BIL,
BasicBlock::iterator &BI, Value *V) {
Instruction *I = *BI;
// Replaces all of the uses of the instruction with uses of the value
I->replaceAllUsesWith(V);
// Remove the unneccesary instruction now...
BIL.remove(BI);
// Make sure to propogate a name if there is one already...
if (I->hasName() && !V->hasName())
V->setName(I->getName(), BIL.getParent()->getSymbolTable());
// Remove the dead instruction now...
delete I;
}
// ReplaceInstWithInst - Replace the instruction specified by BI with the
// instruction specified by I. The original instruction is deleted and BI is
// updated to point to the new instruction.
//
static void ReplaceInstWithInst(BasicBlock::InstListType &BIL,
BasicBlock::iterator &BI, Instruction *I) {
assert(I->getParent() == 0 &&
"ReplaceInstWithInst: Instruction already inserted into basic block!");
// Insert the new instruction into the basic block...
BI = BIL.insert(BI, I)+1;
// Replace all uses of the old instruction, and delete it.
ReplaceInstWithValue(BIL, BI, I);
// Reexamine the instruction just inserted next time around the cleanup pass
// loop.
--BI;
}
// ExpressionConvertableToType - Return true if it is possible
static bool ExpressionConvertableToType(Value *V, const Type *Ty) {
Instruction *I = dyn_cast<Instruction>(V);
if (I == 0) {
// It's not an instruction, check to see if it's a constant... all constants
// can be converted to an equivalent value (except pointers, they can't be
// const prop'd in general).
//
if (isa<ConstPoolVal>(V) &&
!isa<PointerType>(V->getType()) && !isa<PointerType>(Ty)) return true;
return false; // Otherwise, we can't convert!
}
if (I->getType() == Ty) return false; // Expression already correct type!
switch (I->getOpcode()) {
case Instruction::Cast:
// We can convert the expr if the cast destination type is losslessly
// convertable to the requested type.
return losslessCastableTypes(Ty, I->getType());
case Instruction::Add:
case Instruction::Sub:
return ExpressionConvertableToType(I->getOperand(0), Ty) &&
ExpressionConvertableToType(I->getOperand(1), Ty);
case Instruction::Shl:
return ExpressionConvertableToType(I->getOperand(0), Ty);
case Instruction::Shr:
if (Ty->isSigned() != V->getType()->isSigned()) return false;
return ExpressionConvertableToType(I->getOperand(0), Ty);
case Instruction::Load: {
LoadInst *LI = cast<LoadInst>(I);
if (LI->hasIndices()) return false;
return ExpressionConvertableToType(LI->getPtrOperand(),
PointerType::get(Ty));
}
case Instruction::GetElementPtr: {
// GetElementPtr's are directly convertable to a pointer type if they have
// a number of zeros at the end. Because removing these values does not
// change the logical offset of the GEP, it is okay and fair to remove them.
// This can change this:
// %t1 = getelementptr %Hosp * %hosp, ubyte 4, ubyte 0 ; <%List **>
// %t2 = cast %List * * %t1 to %List *
// into
// %t2 = getelementptr %Hosp * %hosp, ubyte 4 ; <%List *>
//
GetElementPtrInst *GEP = cast<GetElementPtrInst>(I);
const PointerType *PTy = dyn_cast<PointerType>(Ty);
if (!PTy) return false;
// Check to see if there are zero elements that we can remove from the
// index array. If there are, check to see if removing them causes us to
// get to the right type...
//
vector<ConstPoolVal*> Indices = GEP->getIndices();
const Type *BaseType = GEP->getPtrOperand()->getType();
while (Indices.size() &&
cast<ConstPoolUInt>(Indices.back())->getValue() == 0) {
Indices.pop_back();
const Type *ElTy = GetElementPtrInst::getIndexedType(BaseType, Indices,
true);
if (ElTy == PTy->getValueType())
return true; // Found a match!!
}
break; // No match, maybe next time.
}
}
return false;
}
static Value *ConvertExpressionToType(Value *V, const Type *Ty) {
assert(ExpressionConvertableToType(V, Ty) && "Value is not convertable!");
Instruction *I = dyn_cast<Instruction>(V);
if (I == 0)
if (ConstPoolVal *CPV = cast<ConstPoolVal>(V)) {
// Constants are converted by constant folding the cast that is required.
// We assume here that all casts are implemented for constant prop.
Value *Result = opt::ConstantFoldCastInstruction(CPV, Ty);
if (!Result) cerr << "Couldn't fold " << CPV << " to " << Ty << endl;
assert(Result && "ConstantFoldCastInstruction Failed!!!");
return Result;
}
BasicBlock *BB = I->getParent();
BasicBlock::InstListType &BIL = BB->getInstList();
string Name = I->getName(); if (!Name.empty()) I->setName("");
Instruction *Res; // Result of conversion
//cerr << endl << endl << "Type:\t" << Ty << "\nInst: " << I << "BB Before: " << BB << endl;
switch (I->getOpcode()) {
case Instruction::Cast:
Res = new CastInst(I->getOperand(0), Ty, Name);
break;
case Instruction::Add:
case Instruction::Sub:
Res = BinaryOperator::create(cast<BinaryOperator>(I)->getOpcode(),
ConvertExpressionToType(I->getOperand(0), Ty),
ConvertExpressionToType(I->getOperand(1), Ty),
Name);
break;
case Instruction::Shl:
case Instruction::Shr:
Res = new ShiftInst(cast<ShiftInst>(I)->getOpcode(),
ConvertExpressionToType(I->getOperand(0), Ty),
I->getOperand(1), Name);
break;
case Instruction::Load: {
LoadInst *LI = cast<LoadInst>(I);
assert(!LI->hasIndices());
Res = new LoadInst(ConvertExpressionToType(LI->getPtrOperand(),
PointerType::get(Ty)), Name);
break;
}
case Instruction::GetElementPtr: {
// GetElementPtr's are directly convertable to a pointer type if they have
// a number of zeros at the end. Because removing these values does not
// change the logical offset of the GEP, it is okay and fair to remove them.
// This can change this:
// %t1 = getelementptr %Hosp * %hosp, ubyte 4, ubyte 0 ; <%List **>
// %t2 = cast %List * * %t1 to %List *
// into
// %t2 = getelementptr %Hosp * %hosp, ubyte 4 ; <%List *>
//
GetElementPtrInst *GEP = cast<GetElementPtrInst>(I);
// Check to see if there are zero elements that we can remove from the
// index array. If there are, check to see if removing them causes us to
// get to the right type...
//
vector<ConstPoolVal*> Indices = GEP->getIndices();
const Type *BaseType = GEP->getPtrOperand()->getType();
const Type *PVTy = cast<PointerType>(Ty)->getValueType();
Res = 0;
while (Indices.size() &&
cast<ConstPoolUInt>(Indices.back())->getValue() == 0) {
Indices.pop_back();
if (GetElementPtrInst::getIndexedType(BaseType, Indices, true) == PVTy) {
if (Indices.size() == 0) {
Res = new CastInst(GEP->getPtrOperand(), BaseType); // NOOP
} else {
Res = new GetElementPtrInst(GEP->getPtrOperand(), Indices, Name);
}
break;
}
}
assert(Res && "Didn't find match!");
break; // No match, maybe next time.
}
default:
assert(0 && "Expression convertable, but don't know how to convert?");
return 0;
}
BasicBlock::iterator It = find(BIL.begin(), BIL.end(), I);
assert(It != BIL.end() && "Instruction not in own basic block??");
BIL.insert(It, Res);
//cerr << "RInst: " << Res << "BB After: " << BB << endl << endl;
return Res;
}
// 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(Method *CurMeth, Value *V, BasicBlock *BB,
BasicBlock::iterator &InsertBefore,
CastInst *&CastResult) {
const PointerType *ThePtrType = dyn_cast<PointerType>(V->getType());
if (!ThePtrType) return false;
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()) {
default: break; // Not an interesting use...
case Instruction::Add: // It's being used as an array index!
//case Instruction::Sub:
InsertCast = true;
break;
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! Return the existing one!
CastResult = cast<CastInst>(Inst);
return false; // No changes made to program though...
}
break;
}
}
if (!InsertCast) return false; // There is no reason to insert a cast!
// Insert a cast!
const Type *ElTy = ThePtrType->getValueType();
const PointerType *DestTy = PointerType::get(ArrayType::get(ElTy));
CastResult = new CastInst(V, DestTy);
BB->getInstList().insert(InsertBefore, CastResult);
//cerr << "Inserted cast: " << CastResult;
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, a value created by alloca or malloc, or a value
// returned from a function call. All casts are kept attached to their original
// values through the PtrCasts map.
//
static bool DoInsertArrayCasts(Method *M, map<Value*, CastInst*> &PtrCasts) {
assert(!M->isExternal() && "Can't handle external methods!");
// Insert casts for all arguments to the function...
bool Changed = false;
BasicBlock *CurBB = M->front();
BasicBlock::iterator It = CurBB->begin();
for (Method::ArgumentListType::iterator AI = M->getArgumentList().begin(),
AE = M->getArgumentList().end(); AI != AE; ++AI) {
CastInst *TheCast = 0;
if (DoInsertArrayCast(M, *AI, CurBB, It, TheCast)) {
It = CurBB->begin(); // We might have just invalidated the iterator!
Changed = true; // Yes we made a change
++It; // Insert next cast AFTER this one...
}
if (TheCast) // Is there a cast associated with this value?
PtrCasts[*AI] = TheCast; // Yes, add it to the map...
}
// 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;
}
// DoElminatePointerArithmetic - Loop over each incoming pointer variable,
// replacing indexing arithmetic with getelementptr calls.
//
static bool DoEliminatePointerArithmetic(const pair<Value*, CastInst*> &Val) {
Value *V = Val.first; // The original pointer
CastInst *CV = Val.second; // The array casted version of the pointer...
for (Value::use_iterator I = V->use_begin(), E = V->use_end(); I != E; ++I) {
Instruction *Inst = cast<Instruction>(*I);
if (Inst->getOpcode() != Instruction::Add)
continue; // We only care about add instructions
BinaryOperator *Add = cast<BinaryOperator>(Inst);
// Make sure the array is the first operand of the add expression...
if (Add->getOperand(0) != V)
Add->swapOperands();
// Get the amount added to the pointer value...
Value *AddAmount = Add->getOperand(1);
}
return false;
}
// Peephole Malloc instructions: we take a look at the use chain of the
// malloc instruction, and try to find out if the following conditions hold:
// 1. The malloc is of the form: 'malloc [sbyte], uint <constant>'
// 2. The only users of the malloc are cast instructions
// 3. Of the cast instructions, there is only one destination pointer type
// [RTy] where the size of the pointed to object is equal to the number
// of bytes allocated.
//
// If these conditions hold, we convert the malloc to allocate an [RTy]
// element. This should be extended in the future to handle arrays. TODO
//
static bool PeepholeMallocInst(BasicBlock *BB, BasicBlock::iterator &BI) {
MallocInst *MI = cast<MallocInst>(*BI);
if (!MI->isArrayAllocation()) return false; // No array allocation?
ConstPoolUInt *Amt = dyn_cast<ConstPoolUInt>(MI->getArraySize());
if (Amt == 0 || MI->getAllocatedType() != ArrayType::get(Type::SByteTy))
return false;
// Get the number of bytes allocated...
unsigned Size = Amt->getValue();
const Type *ResultTy = 0;
// Loop over all of the uses of the malloc instruction, inspecting casts.
for (Value::use_iterator I = MI->use_begin(), E = MI->use_end();
I != E; ++I) {
if (!isa<CastInst>(*I)) {
//cerr << "\tnon" << *I;
return false; // A non cast user?
}
CastInst *CI = cast<CastInst>(*I);
//cerr << "\t" << CI;
// We only work on casts to pointer types for sure, be conservative
if (!isa<PointerType>(CI->getType())) {
cerr << "Found cast of malloc value to non pointer type:\n" << CI;
return false;
}
const Type *DestTy = cast<PointerType>(CI->getType())->getValueType();
if (TD.getTypeSize(DestTy) == Size && DestTy != ResultTy) {
// Does the size of the allocated type match the number of bytes
// allocated?
//
if (ResultTy == 0) {
ResultTy = DestTy; // Keep note of this for future uses...
} else {
// It's overdefined! We don't know which type to convert to!
return false;
}
}
}
// If we get this far, we have either found, or not, a type that is cast to
// that is of the same size as the malloc instruction.
if (!ResultTy) return false;
PRINT_PEEPHOLE1("mall-refine:in ", MI);
ReplaceInstWithInst(BB->getInstList(), BI,
MI = new MallocInst(PointerType::get(ResultTy)));
PRINT_PEEPHOLE1("mall-refine:out", MI);
return true;
}
// Peephole optimize the following instructions:
// %t1 = cast int (uint) * %reg111 to uint (...) *
// %t2 = call uint (...) * %cast111( uint %key )
//
// Into: %t3 = call int (uint) * %reg111( uint %key )
// %t2 = cast int %t3 to uint
//
static bool PeepholeCallInst(BasicBlock *BB, BasicBlock::iterator &BI) {
CallInst *CI = cast<CallInst>(*BI);
return false;
}
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) &&
ExpressionConvertableToType(Src, DestTy)) {
PRINT_PEEPHOLE2("EXPR-CONV:in ", CI, Src);
CI->setOperand(0, ConvertExpressionToType(Src, DestTy));
BI = BB->begin(); // Rescan basic block. BI might be invalidated.
PRINT_PEEPHOLE2("EXPR-CONV:out", CI, CI->getOperand(0));
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 StructType *STy = getPointedToStruct(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 StructType *CurSTy = STy;
const Type *ElTy = 0;
while (CurSTy) {
// 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];
// Did we find what we're looking for?
if (losslessCastableTypes(ElTy, DestPointedTy)) break;
// Nope, go a level deeper.
++Depth;
CurSTy = dyn_cast<StructType>(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);
// Build the index vector, full of all zeros
vector<ConstPoolVal *> Indices(Depth,
ConstPoolUInt::get(Type::UByteTy,0));
// 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;
}
}
}
} else if (MallocInst *MI = dyn_cast<MallocInst>(I)) {
if (PeepholeMallocInst(BB, BI)) return true;
} else if (CallInst *CI = dyn_cast<CallInst>(I)) {
if (PeepholeCallInst(BB, BI)) return true;
} else if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
Value *Val = SI->getOperand(0);
Value *Pointer = SI->getPtrOperand();
// 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)) {
PRINT_PEEPHOLE2("gep-store:in", GEP, SI);
ReplaceInstWithInst(BB->getInstList(), BI,
SI = new StoreInst(Val, GEP->getPtrOperand(),
GEP->getIndices()));
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()))
if (losslessCastableTypes(Val->getType(), // convertable types!
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->getPtrOperand();
// 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)) {
PRINT_PEEPHOLE2("gep-load:in", GEP, LI);
ReplaceInstWithInst(BB->getInstList(), BI,
LI = new LoadInst(GEP->getPtrOperand(),
GEP->getIndices()));
PRINT_PEEPHOLE1("gep-load:out", LI);
return true;
}
} else if (I->getOpcode() == Instruction::Add &&
isa<CastInst>(I->getOperand(1))) {
// 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 {<...>}*
//
Value *AddOp1 = I->getOperand(0);
CastInst *AddOp2 = cast<CastInst>(I->getOperand(1));
ConstPoolUInt *OffsetV = dyn_cast<ConstPoolUInt>(AddOp2->getOperand(0));
unsigned Offset = OffsetV ? OffsetV->getValue() : 0;
Value *SrcPtr; // Of type pointer to struct...
const StructType *StructTy;
if ((StructTy = getPointedToStruct(AddOp1->getType()))) {
SrcPtr = AddOp1; // Handle the first case...
} else if (CastInst *AddOp1c = dyn_cast<CastInst>(AddOp1)) {
SrcPtr = AddOp1c->getOperand(0); // Handle the second case...
StructTy = getPointedToStruct(SrcPtr->getType());
}
// Only proceed if we have detected all of our conditions successfully...
if (Offset && StructTy && SrcPtr && Offset < TD.getTypeSize(StructTy)) {
const StructLayout *SL = TD.getStructLayout(StructTy);
vector<ConstPoolVal*> Offsets;
unsigned ActualOffset = Offset;
const Type *ElTy = getStructOffsetType(StructTy, ActualOffset, Offsets);
if (getPointedToStruct(AddOp1->getType())) { // case 1
PRINT_PEEPHOLE2("add-to-gep1:in", AddOp2, I);
} else {
PRINT_PEEPHOLE3("add-to-gep2:in", AddOp1, AddOp2, I);
}
GetElementPtrInst *GEP = new GetElementPtrInst(SrcPtr, Offsets);
BI = BB->getInstList().insert(BI, GEP)+1;
assert(Offset-ActualOffset == 0 &&
"GEP to middle of element not implemented yet!");
ReplaceInstWithInst(BB->getInstList(), BI,
I = new CastInst(GEP, I->getType()));
PRINT_PEEPHOLE2("add-to-gep:out", GEP, I);
return true;
}
}
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) ||
PeepholeOptimize(BB, BI))
Changed = true;
else
++BI;
}
}
return Changed;
}
// RaisePointerReferences::doit - Raise a method representation to a higher
// level.
//
bool RaisePointerReferences::doit(Method *M) {
if (M->isExternal()) return false;
bool Changed = false;
#ifdef DEBUG_PEEPHOLE_INSTS
cerr << "\n\n\nStarting to work on Method '" << M->getName() << "'\n";
#endif
while (DoRaisePass(M)) Changed = true;
// PtrCasts - Keep a mapping between the pointer values (the key of the
// map), and the cast to array pointer (the value) in this map. This is
// used when converting pointer math into array addressing.
//
map<Value*, CastInst*> PtrCasts;
// Insert casts for all incoming pointer values. Keep track of those casts
// and the identified incoming values in the PtrCasts map.
//
Changed |= DoInsertArrayCasts(M, PtrCasts);
// Loop over each incoming pointer variable, replacing indexing arithmetic
// with getelementptr calls.
//
Changed |= reduce_apply_bool(PtrCasts.begin(), PtrCasts.end(),
ptr_fun(DoEliminatePointerArithmetic));
return Changed;
}
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