An alloca can be equal to an argument. It can't *alias* an alloca, but it could
be equal, since there's nothing preventing a caller from correctly predicting
the stack location of an alloca.
llvm-svn: 174119
diff --git a/llvm/lib/Analysis/InstructionSimplify.cpp b/llvm/lib/Analysis/InstructionSimplify.cpp
index d5e38e5..f8e76ca 100644
--- a/llvm/lib/Analysis/InstructionSimplify.cpp
+++ b/llvm/lib/Analysis/InstructionSimplify.cpp
@@ -1828,18 +1828,6 @@
else if (Pred == CmpInst::ICMP_NE)
return ConstantInt::get(ITy, true);
}
- } else if (Argument *LHSArg = dyn_cast<Argument>(LHSPtr)) {
- RHSPtr = RHSPtr->stripInBoundsOffsets();
- // An alloca can't be equal to an argument unless they come from separate
- // functions via inlining.
- if (AllocaInst *RHSInst = dyn_cast<AllocaInst>(RHSPtr)) {
- if (LHSArg->getParent() == RHSInst->getParent()->getParent()) {
- if (Pred == CmpInst::ICMP_EQ)
- return ConstantInt::get(ITy, false);
- else if (Pred == CmpInst::ICMP_NE)
- return ConstantInt::get(ITy, true);
- }
- }
}
// If we are comparing with zero then try hard since this is a common case.
diff --git a/llvm/test/Transforms/InstSimplify/compare.ll b/llvm/test/Transforms/InstSimplify/compare.ll
index 56627b9..a6d7a64 100644
--- a/llvm/test/Transforms/InstSimplify/compare.ll
+++ b/llvm/test/Transforms/InstSimplify/compare.ll
@@ -647,3 +647,16 @@
%Y = icmp eq i32* %X, null
ret i1 %Y
}
+
+; It's not valid to fold a comparison of an argument with an alloca, even though
+; that's tempting. An argument can't *alias* an alloca, however the aliasing rule
+; relies on restrictions against guessing an object's address and dereferencing.
+; There are no restrictions against guessing an object's address and comparing.
+
+define i1 @alloca_argument_compare(i64* %arg) {
+ %alloc = alloca i64
+ %cmp = icmp eq i64* %arg, %alloc
+ ret i1 %cmp
+ ; CHECK: alloca_argument_compare
+ ; CHECK: ret i1 %cmp
+}