[Bug optimization/8126] [3.3/3.4 regression] Floating point computation far slower in 3.2 than in 2.95

["pinskia at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>]

------- Additional Comments From pinskia at gcc dot gnu dot org  2004-01-01 04:11 -------
What is weird is that -march=i386 is faster than -march=i686 on a pentium3:
grendel:~/src/gnu/gcctest>gcc -O3 -ffast-math -fomit-frame-pointer pr8126.c -march=i386
grendel:~/src/gnu/gcctest>time ./a.out
Start?
Stop!
Result = 0.000000, 0.000000, 1.000000
2.726u 0.000s 0:02.74 99.2%     0+0k 0+0io 2pf+0w
grendel:~/src/gnu/gcctest>time ./a.out
Start?
Stop!
Result = 0.000000, 0.000000, 1.000000
2.710u 0.000s 0:02.74 98.9%     0+0k 0+0io 0pf+0w
grendel:~/src/gnu/gcctest>gcc -O3 -ffast-math -fomit-frame-pointer pr8126.c -march=i686
grendel:~/src/gnu/gcctest>time ./a.out
Start?
Stop!
Result = 0.000000, 0.000000, 1.000000
2.843u 0.007s 0:02.87 98.9%     0+0k 0+0io 2pf+0w
grendel:~/src/gnu/gcctest>gcc -O3 -ffast-math -fomit-frame-pointer pr8126.c -march=i586
grendel:~/src/gnu/gcctest>time ./a.out
Start?
Stop!
Result = 0.000000, 0.000000, 1.000000
2.703u 0.000s 0:02.72 99.2%     0+0k 0+0io 2pf+0w
grendel:~/src/gnu/gcctest>gcc -O3 -ffast-math -fomit-frame-pointer pr8126.c -march=
pentium3
grendel:~/src/gnu/gcctest>time ./a.out
Start?
Stop!
Result = 0.000000, 0.000000, 1.000000
2.843u 0.007s 0:02.87 98.9%     0+0k 0+0io 2pf+0w

Is it looks like a choosing the wrong instruction for pentium3. (pentium4 is different and 
does not matter that mcuh).

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|0000-00-00 00:00:00         |2004-01-01 04:11:34
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=8126