http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51497
Bug #: 51497
Summary: [4.7 Regression] The run time for the polyhedron test
nf.f90 is ~10% slower with -flto after revision 182107
Classification: Unclassified
Product: gcc
Version: 4.7.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: lto
AssignedTo: [email protected]
ReportedBy: [email protected]
CC: [email protected]
Host: x86_64-apple-darwin10
Target: x86_64-apple-darwin10
Build: x86_64-apple-darwin10
After revision 182107 the run time for the polyhedron test nf.f90 is ~10%
slower with -flto:
[macbook] lin/test% gfc -Ofast -funroll-loops nf.f90
[macbook] lin/test% time a.out > /dev/null
18.795u 0.202s 0:19.00 99.9% 0+0k 0+0io 0pf+0w
[macbook] lin/test% gfc -Ofast -funroll-loops nf.f90 -flto
[macbook] lin/test% time a.out > /dev/null
20.640u 0.173s 0:20.82 99.9% 0+0k 0+0io 0pf+0w
This slowdown disappears if I revert the first 'else if' added block:
[macbook] lin/test% gfcp -Ofast -funroll-loops nf.f90
[macbook] lin/test% time a.out > /dev/null
18.820u 0.198s 0:19.02 99.9% 0+0k 0+0io 0pf+0w
[macbook] lin/test% gfcp -Ofast -funroll-loops nf.f90 -flto
[macbook] lin/test% time a.out > /dev/null
18.821u 0.202s 0:19.02 100.0% 0+0k 0+0io 0pf+0w
but not if I revert the second one:
[macbook] lin/test% /opt/gcc/gcc4.7p-182107r1a/bin/gfortran -Ofast
-funroll-loops nf.f90
[macbook] lin/test% time a.out > /dev/null
18.809u 0.199s 0:19.01 99.8% 0+0k 0+0io 0pf+0w
[macbook] lin/test% /opt/gcc/gcc4.7p-182107r1a/bin/gfortran -Ofast
-funroll-loops nf.f90 -flto
[macbook] lin/test% time a.out > /dev/null
20.601u 0.177s 0:20.78 99.9% 0+0k 0+0io 0pf+0w
