https://bugs.llvm.org/show_bug.cgi?id=43206
Bug ID: 43206
Summary: Loop idiom recognizer miscompiles a memcmp loop
Product: libraries
Version: trunk
Hardware: PC
OS: Linux
Status: NEW
Severity: normal
Priority: P
Component: Loop Optimizer
Assignee: unassignedb...@nondot.org
Reporter: malts...@gmail.com
CC: llvm-bugs@lists.llvm.org
Created attachment 22466
--> https://bugs.llvm.org/attachment.cgi?id=22466&action=edit
Source code
After a recent commit
commit 5c9f3cfec78f9e9ae013de9a0d092a68e3e79e00
Author: Roman Lebedev <lebedev...@gmail.com>
Date: Fri Aug 30 09:51:23 2019 +0000
[LoopIdiomRecognize] BCmp loop idiom recognition
...
some of our internal tests started failing on AArch64 and ARM targets.
When the attached reproducer test.c is compiled with the following options:
clang -c -O3 --target=aarch64-arm-none-eabi -march=armv8-a+simd+fp+nocrypto
-std=c99 test.c -o test.o
then linked and run on a model it outputs: "RESULT: FAILED". The same code
compiled with the previous LLVM commit outputs the expected string "RESULT:
PASSED"
Bugpoint points to the loop-idiom pass. The attached bitcode demonstrates the
problem (it produces the correct output, but when run through 'opt
-loop-idiom', the output becomes incorrect).
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