http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56415
Bug #: 56415
Summary: Performance regression after fix for 56273
Classification: Unclassified
Product: gcc
Version: 4.8.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
AssignedTo: unassig...@gcc.gnu.org
ReportedBy: ysrum...@gmail.com
In process of testing x86 platforms we found out that the fix for 56273 caused
-30% regression for one important benchmark. This regression can be
illustraated by attache test (it must be compiled with "-O3 -funroll-loops"
options:
before fix
time ./t_before.exe
19
real 0m4.324s
user 0m4.262s
sys 0m0.000s
after fix
time ./t_after.exe
19
real 0m10.530s
user 0m10.400s
sys 0m0.000s
Note that for 32-bit mode timing is worse.
Test is attached.
