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* Implement expression type conversion for constant values

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* Fix a problem setting a name on a constant value that died because no symbol table was passed in
* Add some comments describing the passes
* Implement a new peephole:
     // 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


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@1080 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2001-11-01 05:57:59 +00:00
parent edefaa1196
commit dedee7bf15
1 changed files with 76 additions and 11 deletions
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87
lib/Transforms/LevelRaise.cpp
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@ -36,6 +36,7 @@
#include "llvm/iMemory.h"
#include "llvm/ConstPoolVals.h"
#include "llvm/Target/TargetData.h"
#include "llvm/Optimizations/ConstantHandling.h"
#include <map>
#include <algorithm>
@ -70,8 +71,8 @@ const TargetData TD("LevelRaise: Should be GCC though!");
// another without gaining or losing precision, or altering the bits in any way.
//
static bool losslessCastableTypes(const Type *T1, const Type *T2) {
assert(T1->isPrimitiveType() || isa<PointerType>(T1));
assert(T2->isPrimitiveType() || isa<PointerType>(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
@ -195,7 +196,16 @@ static void ReplaceInstWithInst(BasicBlock::InstListType &BIL,
// ExpressionConvertableToType - Return true if it is possible
static bool ExpressionConvertableToType(Value *V, const Type *Ty) {
Instruction *I = dyn_cast<Instruction>(V);
if (I == 0) return false; // Noninstructions can't convert
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()) {
@ -216,9 +226,20 @@ static bool ExpressionConvertableToType(Value *V, const Type *Ty) {
}
static Instruction *ConvertExpressionToType(Value *V, const Type *Ty) {
Instruction *I = cast<Instruction>(V);
assert(ExpressionConvertableToType(I, Ty) && "Inst is not convertable!");
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("");
@ -438,6 +459,7 @@ static bool PeepholeMallocInst(BasicBlock *BB, BasicBlock::iterator &BI) {
static bool PeepholeOptimize(BasicBlock *BB, BasicBlock::iterator &BI) {
Instruction *I = *BI;
// TODO: replace this with a DCE call
if (I->use_size() == 0 && I->getType() != Type::VoidTy) return false;
if (CastInst *CI = dyn_cast<CastInst>(I)) {
@ -451,7 +473,8 @@ static bool PeepholeOptimize(BasicBlock *BB, BasicBlock::iterator &BI) {
CI->replaceAllUsesWith(Src);
if (!Src->hasName() && CI->hasName()) {
string Name = CI->getName();
CI->setName(""); Src->setName(Name);
CI->setName(""); Src->setName(Name,
BB->getParent()->getSymbolTable());
}
return true;
}
@ -473,10 +496,10 @@ static bool PeepholeOptimize(BasicBlock *BB, BasicBlock::iterator &BI) {
// 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 (SrcI && !isReinterpretingCast(CI) &&
ExpressionConvertableToType(SrcI, DestTy)) {
PRINT_PEEPHOLE2("EXPR-CONV:in ", CI, SrcI);
CI->setOperand(0, ConvertExpressionToType(SrcI, DestTy));
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;
@ -489,6 +512,12 @@ static bool PeepholeOptimize(BasicBlock *BB, BasicBlock::iterator &BI) {
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,
@ -497,10 +526,46 @@ static bool PeepholeOptimize(BasicBlock *BB, BasicBlock::iterator &BI) {
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,