On 7/27/2022 2:34 PM, Swinney, Jonathan wrote:
I recognize that this patch is going to be somewhat controversial. I'm
submitting it mostly to see what the opinions are and evaluate options. I am
working on improving performance for aarch64. On that architecture, there are
fewer hand written assembly implementations of hot functions than there are for
x86_64 and allowing gcc to auto-vectorize yields noticeable improvements.
Gcc vectorization has improved recently and it hasn't been evaluated on the
mailing list for a few years. This is the latest discussion I found in my
searches: http://ffmpeg.org/pipermail/ffmpeg-devel/2016-May/193977.html
Every time this was done, it was inevitably reverted after complains and
crash reports started piling up because gcc can't really handle all the
inline code our codebase has, among other things.
If the community is not comfortable accepting a patch like this outright, would
you be willing to accept a new option to the configure script, something like
--enable-auto-vectorization?
--extra-cflags can be used for this.
Thanks!
Signed-off-by: Jonathan Swinney <jswin...@amazon.com>
---
configure | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/configure b/configure
index 6629d14099..c63c9348ad 100755
--- a/configure
+++ b/configure
@@ -7173,7 +7173,9 @@ if enabled icc; then
disable aligned_stack
fi
elif enabled gcc; then
- check_optflags -fno-tree-vectorize
+ case $gcc_basever in
+ 2|2.*|3.*|4.*|5.*|6.*) check_optflags -fno-tree-vectorize ;;
+ esac
check_cflags -Werror=format-security
check_cflags -Werror=implicit-function-declaration
check_cflags -Werror=missing-prototypes
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