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i686 g77 optimization regressions, egcs-20000619
- To: <gcc-bugs at gcc dot gnu dot org>
- Subject: i686 g77 optimization regressions, egcs-20000619
- From: "Tim Prince" <tprince at computer dot org>
- Date: Thu, 22 Jun 2000 16:22:15 -0700
The following anomalies occur with the attached Livermore Kernel source
code, both on linux-glibc and cygwin:
erroneous result in kernel 18 at -Os -funroll-loops, correct with all
other option combinations tested
At -Os, the first loop of kernel 18, where the error appears to occur,
is unrolled by 2.
At -O2, this loop is unrolled by 4, with several pointer spills.
Tests with previous 2.96 versions showed an error in the first loop also
with the original LFK code.
Kernel 1 performance drops 20% from -O to -Os, even more from -Os
to -O2. This is the largest contributor to a 10% overall reduction in
performance at -O2 from version 2.95.2.
Kernels 8 and 21 have lost performance at -Os from 2.95.2, but perform
well at -O2.
Kernel 13 has lost performance from 2.95.2 at all levels of
optimization.
Tim Prince
lfk537g.f.gz