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Fix ConstProp/2005-01-28-SetCCGEP.ll: indexing over zero sized elements does

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not change the address.

llvm-svn: 19874
This commit is contained in:
Chris Lattner 2005-01-28 19:09:51 +00:00
parent 1d8c703bc9
commit f24ea9cf5e
1 changed files with 36 additions and 5 deletions
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41
lib/VMCore/ConstantFolding.cpp
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@ -623,6 +623,22 @@ Constant *llvm::ConstantFoldSelectInstruction(const Constant *Cond,
return 0;
}
/// isZeroSizedType - This type is zero sized if its an array or structure of
/// zero sized types. The only leaf zero sized type is an empty structure.
static bool isMaybeZeroSizedType(const Type *Ty) {
if (isa<OpaqueType>(Ty)) return true; // Can't say.
if (const StructType *STy = dyn_cast<StructType>(Ty)) {
// If all of elements have zero size, this does too.
for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
if (!isMaybeZeroSizedType(Ty)) return false;
return true;
} else if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
return isMaybeZeroSizedType(ATy->getElementType());
}
return false;
}
/// IdxCompare - Compare the two constants as though they were getelementptr
/// indices. This allows coersion of the types to be the same thing.
@ -631,7 +647,7 @@ Constant *llvm::ConstantFoldSelectInstruction(const Constant *Cond,
/// first is less than the second, return -1, if the second is less than the
/// first, return 1. If the constants are not integral, return -2.
///
static int IdxCompare(Constant *C1, Constant *C2) {
static int IdxCompare(Constant *C1, Constant *C2, const Type *ElTy) {
if (C1 == C2) return 0;
// Ok, we found a different index. Are either of the operands
@ -645,6 +661,11 @@ static int IdxCompare(Constant *C1, Constant *C2) {
C2 = ConstantExpr::getSignExtend(C2, Type::LongTy);
if (C1 == C2) return 0; // Are they just differing types?
// If the type being indexed over is really just a zero sized type, there is
// no pointer difference being made here.
if (isMaybeZeroSizedType(ElTy))
return -2; // dunno.
// If they are really different, now that they are the same type, then we
// found a difference!
if (cast<ConstantSInt>(C1)->getValue() < cast<ConstantSInt>(C2)->getValue())
@ -779,8 +800,11 @@ static Instruction::BinaryOps evaluateRelation(const Constant *V1,
unsigned i = 1;
// Compare all of the operands the GEP's have in common.
for (;i != CE1->getNumOperands() && i != CE2->getNumOperands(); ++i)
switch (IdxCompare(CE1->getOperand(i), CE2->getOperand(i))) {
gep_type_iterator GTI = gep_type_begin(CE1);
for (;i != CE1->getNumOperands() && i != CE2->getNumOperands();
++i, ++GTI)
switch (IdxCompare(CE1->getOperand(i), CE2->getOperand(i),
GTI.getIndexedType())) {
case -1: return Instruction::SetLT;
case 1: return Instruction::SetGT;
case -2: return Instruction::BinaryOpsEnd;
@ -790,10 +814,17 @@ static Instruction::BinaryOps evaluateRelation(const Constant *V1,
// are non-zero then we have a difference, otherwise we are equal.
for (; i < CE1->getNumOperands(); ++i)
if (!CE1->getOperand(i)->isNullValue())
return Instruction::SetGT;
if (isa<ConstantIntegral>(CE1->getOperand(i)))
return Instruction::SetGT;
else
return Instruction::BinaryOpsEnd; // Might be equal.
for (; i < CE2->getNumOperands(); ++i)
if (!CE2->getOperand(i)->isNullValue())
return Instruction::SetLT;
if (isa<ConstantIntegral>(CE2->getOperand(i)))
return Instruction::SetLT;
else
return Instruction::BinaryOpsEnd; // Might be equal.
return Instruction::SetEQ;
}
}