https://bugs.llvm.org/show_bug.cgi?id=40976
Bug ID: 40976
Summary: arm tree vectorizer fails to optimize kernel raid/xor
code
Product: clang
Version: 8.0
Hardware: PC
OS: Linux
Status: NEW
Severity: enhancement
Priority: P
Component: -New Bugs
Assignee: unassignedclangb...@nondot.org
Reporter: a...@linaro.org
CC: htmldevelo...@gmail.com, llvm-bugs@lists.llvm.org,
neeil...@live.com, richard-l...@metafoo.co.uk
Created attachment 21569
--> https://bugs.llvm.org/attachment.cgi?id=21569&action=edit
preprocessed arch/arm/lib/xor-neon.c
The RAID code in the Linux kernel is written in a way that should let the
compiler autovectorize it with good results. When compiling the kernel with
clang-8, this does not happen, only scalar code is emitted.
I have reproduced this with the attached file, also for comparison the same
file at https://godbolt.org/z/7bMthX, which shows the difference between the
gcc and the clang output.
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