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Fix constant folding to deal with external weak global values.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@32247 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Reid Spencer 2006-12-06 00:25:09 +00:00
parent b25389c67d
commit 87d5f6c29f
1 changed files with 22 additions and 14 deletions
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36
lib/VMCore/ConstantFold.cpp
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@ -1202,17 +1202,14 @@ static Instruction::BinaryOps evaluateRelation(Constant *V1, Constant *V2) {
// Now we know that the RHS is a GlobalValue or simple constant,
// which (since the types must match) means that it's a ConstantPointerNull.
if (const GlobalValue *CPR2 = dyn_cast<GlobalValue>(V2)) {
assert(CPR1 != CPR2 &&
"GVs for the same value exist at different addresses??");
// FIXME: If both globals are external weak, they might both be null!
return Instruction::SetNE;
if (!CPR1->hasExternalWeakLinkage() || !CPR2->hasExternalWeakLinkage())
return Instruction::SetNE;
} else {
// GlobalVals can never be null.
assert(isa<ConstantPointerNull>(V2) && "Canonicalization guarantee!");
// Global can never be null. FIXME: if we implement external weak
// linkage, this is not necessarily true!
return Instruction::SetNE;
if (!CPR1->hasExternalWeakLinkage())
return Instruction::SetNE;
}
} else {
// Ok, the LHS is known to be a constantexpr. The RHS can be any of a
// constantexpr, a CPR, or a simple constant.
@ -1258,10 +1255,15 @@ static Instruction::BinaryOps evaluateRelation(Constant *V1, Constant *V2) {
if (isa<ConstantPointerNull>(V2)) {
// If we are comparing a GEP to a null pointer, check to see if the base
// of the GEP equals the null pointer.
if (isa<GlobalValue>(CE1Op0)) {
// FIXME: this is not true when we have external weak references!
// No offset can go from a global to a null pointer.
return Instruction::SetGT;
if (GlobalValue *GV = dyn_cast<GlobalValue>(CE1Op0)) {
if (GV->hasExternalWeakLinkage())
// Weak linkage GVals could be zero or not. We're comparing that
// to null pointer so its greater-or-equal
return Instruction::SetGE;
else
// If its not weak linkage, the GVal must have a non-zero address
// so the result is greater-than
return Instruction::SetGT;
} else if (isa<ConstantPointerNull>(CE1Op0)) {
// If we are indexing from a null pointer, check to see if we have any
// non-zero indices.
@ -1275,8 +1277,14 @@ static Instruction::BinaryOps evaluateRelation(Constant *V1, Constant *V2) {
// Otherwise, we can't really say if the first operand is null or not.
} else if (const GlobalValue *CPR2 = dyn_cast<GlobalValue>(V2)) {
if (isa<ConstantPointerNull>(CE1Op0)) {
// FIXME: This is not true with external weak references.
return Instruction::SetLT;
if (CPR2->hasExternalWeakLinkage())
// Weak linkage GVals could be zero or not. We're comparing it to
// a null pointer, so its less-or-equal
return Instruction::SetLE;
else
// If its not weak linkage, the GVal must have a non-zero address
// so the result is less-than
return Instruction::SetLT;
} else if (const GlobalValue *CPR1 = dyn_cast<GlobalValue>(CE1Op0)) {
if (CPR1 == CPR2) {
// If this is a getelementptr of the same global, then it must be