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Re: -march prescott: GENERAL_REGS error; but -msseX Ok ?
- From: "Sam Lauber" <sam124 at operamail dot com>
- To: gcc at gcc dot gnu dot org
- Date: Sun, 30 Jan 2005 02:14:11 +0100
- Subject: Re: -march prescott: GENERAL_REGS error; but -msseX Ok ?
Is it possible to disable the register allocator completly?
IMO, GCC **should not** rely on any schedurling. Would it
be possible to, in a worst-case scenario, force GCC use the
stack or even use an extra linker symbol. _I_ don't know
of any processor modifications that can cause that to
fail.
Samuel Lauber
P.S. IMO, `can't find a register' should be an ICE.
>> i386/dsputil_mmx.c: In function `h263_h_loop_filter_mmx':
>> i386/dsputil_mmx.c:634: error: can't find a register in class `GENERAL_REGS'
>> while reloading `asm'
>> dmesg | less make[2]: *** [dsputil_mmx.o] Error 1
>> My cflags are -mtune=prescott -O3 -funit-at-a-time -ffast-math
>> -fomit-frame-pointer
>> But -O3 -funit-at-a-time -ffast-math -fomit-frame-pointer -mmmx -msse
>> -msse2 -msse3 works!
>>
>> config/i386.c has:
>> {"prescott", PROCESSOR_NOCONA, PTA_SSE | PTA_SSE2 | PTA_SSE3
>> | PTA_MMX | PTA_PREFETCH_SSE}
>> So is the only reason prescott doesn't work is prefetch-sse.
> No, that is a red herring. The different instruction scheduling causes
> the register allocator to randomly fail or not. There's no way for us
> to fix this reliably, the asm must be changed to constrain the
> register allocator less.
--
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