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[Bug tree-optimization/85416] New: Massive performance regression when switching on "-march=native"
- From: "martin at mpa-garching dot mpg dot de" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: Mon, 16 Apr 2018 11:41:56 +0000
- Subject: [Bug tree-optimization/85416] New: Massive performance regression when switching on "-march=native"
- Auto-submitted: auto-generated
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85416
Bug ID: 85416
Summary: Massive performance regression when switching on
"-march=native"
Product: gcc
Version: 8.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: martin@mpa-garching.mpg.de
Target Milestone: ---
Created attachment 43945
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=43945&action=edit
Test case
When compiling the attached test case with
g++ -O3 -std=c++14 testcase.cc
and measuring the runtime via
time ./a.out
I get a CPU time of roughly 1.3 seconds
Recompiling with
g++ -O3 -std=c++14 -march=native testcase.cc
increases run time to over 8 seconds.
CPU: Intel Core i5-5300U
This was measured on trunk (gcc version 8.0.1 20180411), but I see similar
performance degradations already in gcc 5.4.