[Bug target/84481] New: 429.mcf with -O2 regresses by ~6% and ~4%, depending on tuning, on Zen compared to GCC 7.2
jamborm at gcc dot gnu.org
gcc-bugzilla@gcc.gnu.org
Tue Feb 20 13:56:00 GMT 2018
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84481
Bug ID: 84481
Summary: 429.mcf with -O2 regresses by ~6% and ~4%, depending
on tuning, on Zen compared to GCC 7.2
Product: gcc
Version: 8.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: target
Assignee: unassigned at gcc dot gnu.org
Reporter: jamborm at gcc dot gnu.org
Target Milestone: ---
Our friends at AMD reported that, compared to gcc 7.2, 429.mcf is
about 6% slower when compiled with just -O2 with trunk and run on Zen
CPU, which I can confirm. I have managed to bisect this to Honza's
r255395.
The benchmark also regresses compared to gcc 7.2 with -O2
-march=native -mtune=native, by over 4% but I was not able to pin this
down to a single commit.
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