------- Comment #1 from hjl dot tools at gmail dot com 2008-10-29 05:44 -------
It looks like the cost of loading/storing FP values aren't appropriate for
Core 2. With this patch:
[EMAIL PROTECTED] i386]$ diff -up i386.c.foo i386.c
--- i386.c.foo 2008-10-28 21:56:19.000000000 -0700
+++ i386.c 2008-10-28 22:01:53.000000000 -0700
@@ -990,9 +990,9 @@ struct processor_costs core2_cost = {
Relative to reg-reg move (2). */
{4, 4, 4}, /* cost of storing integer registers */
2, /* cost of reg,reg fld/fst */
- {6, 6, 6}, /* cost of loading fp registers
+ {12, 12, 12}, /* cost of loading fp registers
in SFmode, DFmode and XFmode */
- {4, 4, 4}, /* cost of storing fp registers
+ {6, 6, 8}, /* cost of storing fp registers
in SFmode, DFmode and XFmode */
2, /* cost of moving MMX register */
{6, 6}, /* cost of loading MMX registers
@@ -1000,9 +1000,9 @@ struct processor_costs core2_cost = {
{4, 4}, /* cost of storing MMX registers
in SImode and DImode */
2, /* cost of moving SSE register */
- {6, 6, 6}, /* cost of loading SSE registers
+ {8, 8, 8}, /* cost of loading SSE registers
in SImode, DImode and TImode */
- {4, 4, 4}, /* cost of storing SSE registers
+ {8, 8, 8}, /* cost of storing SSE registers
in SImode, DImode and TImode */
2, /* MMX or SSE register to integer */
32, /* size of l1 cache. */
[EMAIL PROTECTED] i386]$
I got
[EMAIL PROTECTED] gcc]$ ./xgcc -B./ -m32 -O2 /tmp/foo.c -o core2.sse
-mtune=core2
-msse3 -mfpmath=sse
[EMAIL PROTECTED] gcc]$ ./xgcc -B./ -m32 -O2 /tmp/foo.c -o core2 -mtune=core2
[EMAIL PROTECTED] gcc]$ ./xgcc -B./ -m32 -O2 /tmp/foo.c -o o2 -msse3
-mfpmath=sse
[EMAIL PROTECTED] gcc]$ ./xgcc -B./ -m32 -O2 /tmp/foo.c -o o2.sse
[EMAIL PROTECTED] gcc]$ time ./o2
real 0m7.163s
user 0m7.161s
sys 0m0.001s
[EMAIL PROTECTED] gcc]$ time ./core2
real 0m7.833s
user 0m7.829s
sys 0m0.001s
[EMAIL PROTECTED] gcc]$ time ./o2.sse
real 0m7.795s
user 0m7.794s
sys 0m0.000s
[EMAIL PROTECTED] gcc]$ time ./core2.sse
real 0m7.339s
user 0m7.337s
sys 0m0.001s
[EMAIL PROTECTED] gcc]$
But even with this patch, IRA still generates slower codes:
[EMAIL PROTECTED] gcc]$ ./xgcc -B./ -m32 -O2 /tmp/foo.c -o core2.noira
-mtune=core2
-fno-ira
[EMAIL PROTECTED] gcc]$ time ./core2.noira
real 0m7.444s
user 0m7.441s
sys 0m0.001s
[EMAIL PROTECTED] gcc]$ ./xgcc -B./ -m32 -O2 /tmp/foo.c -o core2.sse.noira
-mtune=core2 -fno-ira -msse3 -mfpmath=sse
[EMAIL PROTECTED] gcc]$ time ./core2.sse.noira
real 0m7.229s
user 0m7.224s
sys 0m0.000s
[EMAIL PROTECTED] gcc]$
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37948
