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, 1 insertions, 1 deletions

diff --git a/llvm/lib/CodeGen/Analysis.cpp b/llvm/lib/CodeGen/Analysis.cpp
index f1bbb34..3ef90d3 100644
--- a/llvm/lib/CodeGen/Analysis.cpp
+++ b/llvm/lib/CodeGen/Analysis.cpp
@@ -156,7 +156,7 @@ void llvm::computeValueLLTs(const DataLayout &DL, Type &Ty,
 
 /// ExtractTypeInfo - Returns the type info, possibly bitcast, encoded in V.
 GlobalValue *llvm::ExtractTypeInfo(Value *V) {
-  V = V->stripPointerCastsNoFollowAliases();
+  V = V->stripPointerCasts();
   GlobalValue *GV = dyn_cast<GlobalValue>(V);
   GlobalVariable *Var = dyn_cast<GlobalVariable>(V);