IR. Change strip* family of functions to not look through aliases.

I noticed another instance of the issue where references to aliases were
being replaced with aliasees, this time in InstCombine. In the instance that
I saw it turned out to be only a QoI issue (a symbol ended up being missing
from the symbol table due to the last reference to the alias being removed,
preventing HWASAN from symbolizing a global reference), but it could easily
have manifested as incorrect behaviour.

Since this is the third such issue encountered (previously: D65118, D65314)
it seems to be time to address this common error/QoI issue once and for all
and make the strip* family of functions not look through aliases.

Includes a test for the specific issue that I saw, but no doubt there are
other similar bugs fixed here.

As with D65118 this has been tested to make sure that the optimization isn't
load bearing. I built Clang, Chromium for Linux, Android and Windows as well
as the test-suite and there were no size regressions.

Differential Revision: https://reviews.llvm.org/D66606

llvm-svn: 369697

1 files changed, 2 insertions, 2 deletions

diff --git a/llvm/lib/Analysis/StackSafetyAnalysis.cpp b/llvm/lib/Analysis/StackSafetyAnalysis.cpp
index 4cf235db86e..1b363869895 100644
--- a/llvm/lib/Analysis/StackSafetyAnalysis.cpp
+++ b/llvm/lib/Analysis/StackSafetyAnalysis.cpp
@@ -333,8 +333,8 @@ bool StackSafetyLocalAnalysis::analyzeAllUses(const Value *Ptr, UseInfo &US) {
         // FIXME: consult devirt?
         // Do not follow aliases, otherwise we could inadvertently follow
         // dso_preemptable aliases or aliases with interposable linkage.
-        const GlobalValue *Callee = dyn_cast<GlobalValue>(
-            CS.getCalledValue()->stripPointerCastsNoFollowAliases());
+        const GlobalValue *Callee =
+            dyn_cast<GlobalValue>(CS.getCalledValue()->stripPointerCasts());
         if (!Callee) {
           US.updateRange(UnknownRange);
           return false;