Changes in directory llvm/lib/VMCore:
ConstantFolding.cpp updated: 1.109 -> 1.110 --- Log message: Fix constant folding to deal with external weak global values. --- Diffs of the changes: (+22 -14) ConstantFolding.cpp | 36 ++++++++++++++++++++++-------------- 1 files changed, 22 insertions(+), 14 deletions(-) Index: llvm/lib/VMCore/ConstantFolding.cpp diff -u llvm/lib/VMCore/ConstantFolding.cpp:1.109 llvm/lib/VMCore/ConstantFolding.cpp:1.110 --- llvm/lib/VMCore/ConstantFolding.cpp:1.109 Tue Dec 5 01:18:07 2006 +++ llvm/lib/VMCore/ConstantFolding.cpp Tue Dec 5 18:25:09 2006 @@ -1202,17 +1202,14 @@ // 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 @@ 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 @@ // 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 _______________________________________________ llvm-commits mailing list llvm-commits@cs.uiuc.edu http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits