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Re: [PATCH PR62011]


Jakub,

Is it important to have correct value for length attribute for Big Cores?
As I new this attribute is used for code layout alignment.

2014-08-15 15:54 GMT+04:00 Jakub Jelinek <jakub@redhat.com>:
> On Fri, Aug 15, 2014 at 03:45:33PM +0400, Yuri Rumyantsev wrote:
>> gcc/ChangeLog
>> 2014-08-15  Yuri Rumyantsev  <ysrumyan@gmail.com>
>>
>> PR target/62011
>> * config/i386/i386-protos.h (ix86_avoid_false_dep_for_bm): New function
>>  prototype.
>> * config/i386/i386.c (ix86_avoid_false_dep_for_bm): New function.
>> * config/i386/i386.h (TARGET_AVOID_FALSE_DEP_FOR_BM) New macros.
>> * config/i386/i386.md (ctz<mode>2, clz<mode>2_lzcnt, popcount<mode>2,
>>  *popcount<mode>2_cmp, *popcountsi2_cmp_zext): Output zeroing
>>  destination register for unary bit-manipulation instructions
>>  if required.
>> * config/i386/x86-tune.def (X86_TUNE_AVOID_FALSE_DEP_FOR_BM): New.
>
> --- config/i386/i386.md (revision 213842)
> +++ config/i386/i386.md (working copy)
> @@ -12111,7 +12111,13 @@
>    ""
>  {
>    if (TARGET_BMI)
> -    return "tzcnt{<imodesuffix>}\t{%1, %0|%0, %1}";
> +    {
> +      if (ix86_avoid_false_dep_for_bm (insn, operands))
> +       return "xor{<imodesuffix>}\t%0, %0\n\t"
> +               "tzcnt{<imodesuffix>}\t{%1, %0|%0, %1}";
> +      else
> +        return "tzcnt{<imodesuffix>}\t{%1, %0|%0, %1}";
> +    }
>    else if (optimize_function_for_size_p (cfun))
>      ;
>    else if (TARGET_GENERIC)
>
> etc., this will make lenght attribute incorrect though.
>
>         Jakub


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