Fix ConstantFold's folding of icmp instructions to recognize that,
for example, a one-past-the-end pointer from one global variable may
be equal to the base pointer of another global variable.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@173995 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/IR/ConstantFold.cpp b/lib/IR/ConstantFold.cpp
index 417e0d1..587b7ce 100644
--- a/lib/IR/ConstantFold.cpp
+++ b/lib/IR/ConstantFold.cpp
@@ -1495,9 +1495,8 @@
"Surprising getelementptr!");
return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
} else {
- // If they are different globals, we don't know what the value is,
- // but they can't be equal.
- return ICmpInst::ICMP_NE;
+ // If they are different globals, we don't know what the value is.
+ return ICmpInst::BAD_ICMP_PREDICATE;
}
}
} else {
@@ -1510,10 +1509,10 @@
default: break;
case Instruction::GetElementPtr:
// By far the most common case to handle is when the base pointers are
- // obviously to the same or different globals.
+ // obviously to the same global.
if (isa<GlobalValue>(CE1Op0) && isa<GlobalValue>(CE2Op0)) {
- if (CE1Op0 != CE2Op0) // Don't know relative ordering, but not equal
- return ICmpInst::ICMP_NE;
+ if (CE1Op0 != CE2Op0) // Don't know relative ordering.
+ return ICmpInst::BAD_ICMP_PREDICATE;
// Ok, we know that both getelementptr instructions are based on the
// same global. From this, we can precisely determine the relative
// ordering of the resultant pointers.