[Bug target/23360] New: [4.1 regression] -ffast-math startup broken on i686 (maybe Athlon-xp)

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

$ cat hello.c
int main()
{
    return 0;
}
$ gcc -g -ffast-math hello.c
$ gdb ./a.out
GNU gdb 6.3-debian
Copyright 2004 Free Software Foundation, Inc.
GDB is free software, covered by the GNU General Public License, and you are
welcome to change it and/or distribute copies of it under certain conditions.
Type "show copying" to see the conditions.
There is absolutely no warranty for GDB.  Type "show warranty" for details.
This GDB was configured as "i386-linux"...Using host libthread_db library
"/lib/tls/libthread_db.so.1".

(gdb) r
Starting program: /home/ig25/Krempel/a.out

Program received signal SIGSEGV, Segmentation fault.
0x08048469 in set_fast_math ()
    at ../../gcc-4.1/gcc/config/i386/crtfastmath.c:70
70            __builtin_ia32_ldmxcsr (mxcsr);
(gdb) q
The program is running.  Exit anyway? (y or n) y
$ cat /proc/cpuinfo
processor       : 0
vendor_id       : AuthenticAMD
cpu family      : 6
model           : 8
model name      : AMD Athlon(TM) XP 2600+
stepping        : 1
cpu MHz         : 2083.203
cache size      : 256 KB
fdiv_bug        : no
hlt_bug         : no
f00f_bug        : no
coma_bug        : no
fpu             : yes
fpu_exception   : yes
cpuid level     : 1
wp              : yes
flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca
cmovpat pse36 mmx fxsr sse syscall mmxext 3dnowext 3dnow
bogomips        : 4128.76

$ gcc -v
Using built-in specs.
Target: i686-pc-linux-gnu
Configured with: ../gcc-4.1/configure --prefix=/home/ig25 --enable-languages=c,f95
Thread model: posix
gcc version 4.1.0 20050811 (experimental)


This shows up as a regression in the gfortran testsuite:

Running /home/ig25/gcc-4.1/gcc/testsuite/gfortran.dg/dg.exp ...
FAIL: gfortran.dg/g77/20010216-1.f  -O0  execution test
FAIL: gfortran.dg/g77/20010216-1.f  -O1  execution test
FAIL: gfortran.dg/g77/20010216-1.f  -O2  execution test
FAIL: gfortran.dg/g77/20010216-1.f  -O3 -fomit-frame-pointer  execution test
FAIL: gfortran.dg/g77/20010216-1.f  -O3 -fomit-frame-pointer -funroll-loops 
execution test
FAIL: gfortran.dg/g77/20010216-1.f  -O3 -fomit-frame-pointer
-funroll-all-loops-finline-functions  execution test
FAIL: gfortran.dg/g77/20010216-1.f  -O3 -g  execution test
FAIL: gfortran.dg/g77/20010216-1.f  -Os  execution test

-- 
           Summary: [4.1 regression] -ffast-math startup broken on i686
                    (maybe Athlon-xp)
           Product: gcc
           Version: 4.1.0
            Status: UNCONFIRMED
          Keywords: wrong-code
          Severity: normal
          Priority: P2
         Component: target
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: tkoenig at gcc dot gnu dot org
                CC: gcc-bugs at gcc dot gnu dot org
GCC target triplet: i686-pc-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23360