This is the mail archive of the
gcc-patches@gcc.gnu.org
mailing list for the GCC project.
Re: CPU_NONE ix86_schedule cpu attribute for -march=nocona
On Tue, Apr 17, 2012 at 8:04 AM, Alexander Monakov <amonakov@ispras.ru> wrote:
>
>
> On Tue, 17 Apr 2012, H.J. Lu wrote:
>
>> On Tue, Apr 17, 2012 at 7:35 AM, Roman Zhuykov <zhroma@ispras.ru> wrote:
>> > Hello,
>> >
>> > I found the following problem while investigating SMS on x86-64.
>> > When I run gcc with -march=nocona (on pentium-4 with EM64T extension), all
>> > latencies in data dependency graph become zeros. The global pointer
>> > "insn_default_latency" points to insn_default_latency_none, which
>> > returns zero for any instruction.
>> > This happens because ix86_schedule cpu attribute is set to CPU_NONE for nocona.
>> >
>> > CPU_NONE was introduced by this patch:
>> > http://gcc.gnu.org/ml/gcc-patches/2008-10/msg00179.html
>> >
>> > I think we don't want any scheduler to work with zero latencies on
>> > such processors (with such -march).
>> > The following patch fixes the problem for my case with -march=nocona.
>> > Is it correct to fix the problem like this?
>> > What to do with 32bit architectures (i386, i486, pentium4, pentium4m,
>> > prescott) ?
>> >
>> > diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
>> > index af4af7c..38d64e9 100644
>> > --- a/gcc/config/i386/i386.c
>> > +++ b/gcc/config/i386/i386.c
>> > @@ -2989,7 +2989,7 @@ ix86_option_override_internal (bool main_args_p)
>> > ? ? ? PTA_MMX | PTA_SSE | PTA_SSE2},
>> > ? ? ?{"prescott", PROCESSOR_NOCONA, CPU_NONE,
>> > ? ? ? PTA_MMX | PTA_SSE | PTA_SSE2 | PTA_SSE3},
>> > - ? ? ?{"nocona", PROCESSOR_NOCONA, CPU_NONE,
>> > + ? ? ?{"nocona", PROCESSOR_NOCONA, CPU_GENERIC64,
>> > ? ? ? PTA_64BIT | PTA_MMX | PTA_SSE | PTA_SSE2 | PTA_SSE3
>> > ? ? ? | PTA_CX16 | PTA_NO_SAHF},
>> > ? ? ?{"core2", PROCESSOR_CORE2_64, CPU_CORE2,
>> > --
>>
>> Should we replace all CPU_NONE with CPU_GENERIC32/CPU_GENERIC64?
>
> CPU_GENERIC32 had been removed by the 2008 patch Roman was referring to. ?Did
> you mean CPU_PENTIUMPRO?
Yes.
--
H.J.