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[Bug rtl-optimization/19780] Floating point computation far slower for -mfpmath=sse
- From: "uros at kss-loka dot si" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: 25 Oct 2006 12:04:59 -0000
- Subject: [Bug rtl-optimization/19780] Floating point computation far slower for -mfpmath=sse
- References: <bug-19780-1649@http.gcc.gnu.org/bugzilla/>
- Reply-to: gcc-bugzilla at gcc dot gnu dot org
------- Comment #6 from uros at kss-loka dot si 2006-10-25 12:04 -------
(In reply to comment #5)
> With more registers (x86_64) the stack moves are gone, but: (!)
> (testing done on AMD Athlon fam 15 model 35 stepping 2)
On Xeon 3.6, SSE is now faster:
gcc -O2 -march=pentium4 -mfpmath=387 pr19780.c
time ./a.out
Start?
Stop!
Result = 0.000000, 0.000000, 1.000000
real 0m0.805s
user 0m0.804s
sys 0m0.000s
gcc -O2 -march=pentium4 -mfpmath=sse pr19780.c
time ./a.out
Start?
Stop!
Result = 0.000000, 0.000000, 1.000000
real 0m0.707s
user 0m0.704s
sys 0m0.004s
vendor_id : GenuineIntel
cpu family : 15
model : 4
model name : Intel(R) Xeon(TM) CPU 3.60GHz
stepping : 10
cpu MHz : 3600.970
cache size : 2048 KB
The question is now, why is Athlon so slow with SFmode SSE?
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19780