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, 2 deletions

diff --git a/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp b/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
index be2d72a5071..8530174bb6c 100644
--- a/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
@@ -1572,8 +1572,7 @@ bool AsmPrinter::doFinalization(Module &M) {
              "expected llvm.used to be an array type");
       if (const auto *A = cast<ConstantArray>(LU->getInitializer())) {
         for (const Value *Op : A->operands()) {
-          const auto *GV =
-              cast<GlobalValue>(Op->stripPointerCastsNoFollowAliases());
+          const auto *GV = cast<GlobalValue>(Op->stripPointerCasts());
           // Global symbols with internal or private linkage are not visible to
           // the linker, and thus would cause an error when the linker tried to
           // preserve the symbol due to the `/include:` directive.