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[Bug tree-optimization/83651] [7/8 regression] 20% slowdown of linux kernel AES cipher
- From: "arnd at linaro dot org" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: Mon, 15 Jan 2018 10:50:47 +0000
- Subject: [Bug tree-optimization/83651] [7/8 regression] 20% slowdown of linux kernel AES cipher
- Auto-submitted: auto-generated
- References: <bug-83651-4@http.gcc.gnu.org/bugzilla/>
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83651
--- Comment #2 from Arnd Bergmann <arnd at linaro dot org> ---
My kernel patch to use -Os got merged, but caused a regression, so I kept
experimenting with the libressl implementation. Apparently, turning off
-fcode-hoisting is a better way address PR83356, and the performance is the
same as with -Os: New numbers with libressl, same method as before:
-O2 -Os -O2 -fno-code-hoisting
gcc-6.3.1 16.7 16.7 -
gcc-7.0.1 17.5 16.0 16.0
gcc-7.1.1 17.5 16.0 16.0
gcc-7.2.1 17.5 16.0 16.0
gcc-8.0.0 16.8 15.5 15.5