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Add a simple xform to simplify array accesses with casts in the way.

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This is useful for 178.galgel where resolution of dope vectors (by the
optimizer) causes the scales to become apparent.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@23328 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2005-09-13 18:36:04 +00:00
parent 396b2baf3c
commit 7835cdde40
1 changed files with 62 additions and 2 deletions
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64
lib/Transforms/Scalar/InstructionCombining.cpp
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@ -4718,8 +4718,8 @@ Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst &GEP) {
}
} else if (GEP.getNumOperands() == 2) {
// Transform things like:
// %t = getelementptr ubyte* cast ([2 x sbyte]* %str to ubyte*), uint %V
// into: %t1 = getelementptr [2 x sbyte*]* %str, int 0, uint %V; cast
// %t = getelementptr ubyte* cast ([2 x int]* %str to uint*), uint %V
// into: %t1 = getelementptr [2 x int*]* %str, int 0, uint %V; cast
const Type *SrcElTy = cast<PointerType>(X->getType())->getElementType();
const Type *ResElTy=cast<PointerType>(PtrOp->getType())->getElementType();
if (isa<ArrayType>(SrcElTy) &&
@ -4730,6 +4730,66 @@ Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst &GEP) {
GEP.getOperand(1), GEP.getName()), GEP);
return new CastInst(V, GEP.getType());
}
// Transform things like:
// getelementptr sbyte* cast ([100 x double]* X to sbyte*), int %tmp
// (where tmp = 8*tmp2) into:
// getelementptr [100 x double]* %arr, int 0, int %tmp.2
if (isa<ArrayType>(SrcElTy) &&
(ResElTy == Type::SByteTy || ResElTy == Type::UByteTy)) {
uint64_t ArrayEltSize =
TD->getTypeSize(cast<ArrayType>(SrcElTy)->getElementType());
// Check to see if "tmp" is a scale by a multiple of ArrayEltSize. We
// allow either a mul, shift, or constant here.
Value *NewIdx = 0;
ConstantInt *Scale = 0;
if (ArrayEltSize == 1) {
NewIdx = GEP.getOperand(1);
Scale = ConstantInt::get(NewIdx->getType(), 1);
} else if (ConstantInt *CI = dyn_cast<ConstantInt>(GEP.getOperand(1))) {
NewIdx = ConstantInt::get(NewIdx->getType(), 1);
Scale = CI;
} else if (Instruction *Inst =dyn_cast<Instruction>(GEP.getOperand(1))){
if (Inst->getOpcode() == Instruction::Shl &&
isa<ConstantInt>(Inst->getOperand(1))) {
unsigned ShAmt =cast<ConstantUInt>(Inst->getOperand(1))->getValue();
if (Inst->getType()->isSigned())
Scale = ConstantSInt::get(Inst->getType(), 1ULL << ShAmt);
else
Scale = ConstantUInt::get(Inst->getType(), 1ULL << ShAmt);
NewIdx = Inst->getOperand(0);
} else if (Inst->getOpcode() == Instruction::Mul &&
isa<ConstantInt>(Inst->getOperand(1))) {
Scale = cast<ConstantInt>(Inst->getOperand(1));
NewIdx = Inst->getOperand(0);
}
}
// If the index will be to exactly the right offset with the scale taken
// out, perform the transformation.
if (Scale && Scale->getRawValue() % ArrayEltSize == 0) {
if (ConstantSInt *C = dyn_cast<ConstantSInt>(Scale))
Scale = ConstantSInt::get(C->getType(),
C->getRawValue()/(int64_t)ArrayEltSize);
else
Scale = ConstantUInt::get(Scale->getType(),
Scale->getRawValue() / ArrayEltSize);
if (Scale->getRawValue() != 1) {
Constant *C = ConstantExpr::getCast(Scale, NewIdx->getType());
Instruction *Sc = BinaryOperator::createMul(NewIdx, C, "idxscale");
NewIdx = InsertNewInstBefore(Sc, GEP);
}
// Insert the new GEP instruction.
Instruction *Idx =
new GetElementPtrInst(X, Constant::getNullValue(Type::IntTy),
NewIdx, GEP.getName());
Idx = InsertNewInstBefore(Idx, GEP);
return new CastInst(Idx, GEP.getType());
}
}
}
}