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Make InstructionCombining::getBitCastOperand() recognize GEP instructions and

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constant expression with all zero indices as being the same as a bitcast.

llvm-svn: 57442
This commit is contained in:
Matthijs Kooijman 2008-10-13 15:17:01 +00:00
parent 5d8f1a58b3
commit b86d48c717
1 changed files with 23 additions and 3 deletions
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26
lib/Transforms/Scalar/InstructionCombining.cpp
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@ -436,14 +436,34 @@ static const Type *getPromotedType(const Type *Ty) {
return Ty;
}
/// getBitCastOperand - If the specified operand is a CastInst or a constant
/// expression bitcast, return the operand value, otherwise return null.
/// getBitCastOperand - If the specified operand is a CastInst, a constant
/// expression bitcast, or a GetElementPtrInst with all zero indices, return the
/// operand value, otherwise return null.
static Value *getBitCastOperand(Value *V) {
if (BitCastInst *I = dyn_cast<BitCastInst>(V))
// BitCastInst?
return I->getOperand(0);
else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V))
else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(V)) {
// GetElementPtrInst?
if (GEP->hasAllZeroIndices())
return GEP->getOperand(0);
} else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) {
if (CE->getOpcode() == Instruction::BitCast)
// BitCast ConstantExp?
return CE->getOperand(0);
else if (CE->getOpcode() == Instruction::GetElementPtr) {
// GetElementPtr ConstantExp?
for (User::op_iterator I = CE->op_begin() + 1, E = CE->op_end();
I != E; ++I) {
ConstantInt *CI = dyn_cast<ConstantInt>(I);
if (!CI || !CI->isZero())
// Any non-zero indices? Not cast-like.
return 0;
}
// All-zero indices? This is just like casting.
return CE->getOperand(0);
}
}
return 0;
}