Peter Collingbourne 2452d7030b 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
2019-08-22 19:56:14 +00:00

16 lines
660 B
LLVM

; RUN: opt -S -instcombine -o - %s | FileCheck %s
target datalayout = "e-m:e-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128"
target triple = "aarch64-unknown-linux-android10000"
@x.hwasan = private global { [3 x i32], [4 x i8] } { [3 x i32] [i32 42, i32 57, i32 10], [4 x i8] c"\00\00\00\87" }, align 16
@x = alias [3 x i32], inttoptr (i64 add (i64 ptrtoint ({ [3 x i32], [4 x i8] }* @x.hwasan to i64), i64 -8718968878589280256) to [3 x i32]*)
define i32 @f(i64 %i) {
entry:
; CHECK: getelementptr inbounds [3 x i32], [3 x i32]* @x
%arrayidx = getelementptr inbounds [3 x i32], [3 x i32]* @x, i64 0, i64 %i
%0 = load i32, i32* %arrayidx
ret i32 %0
}