[PATCH GCC 8] x86: Re-enable partial_reg_dependency and movx for Haswell

[Jan Hubicka]

> r254152 disabled partial_reg_dependency and movx for Haswell and newer
> Intel processors.  r258972 restored them for skylake-avx512.  For Haswell,
> movx improves performance.  But partial_reg_stall may be better than
> partial_reg_dependency in theory.  We will investigate performance impact
> of partial_reg_stall vs partial_reg_dependency on Haswell for GCC 9.  In
> the meantime, this patch restores both partial_reg_dependency and mox for
> Haswell in GCC 8.
> 
> OK for GCC 8?

I would still like to know in what situations/bechnarks it improves the performance.
The change was benchmarked on spec2000/2006 plus some additional benchmarks and, so
it would be nice to know where it hurts.

Honza
> 
> H.J.
> ---
> 	PR target/85829
> 	* config/i386/x86-tune.def: Re-enable partial_reg_dependency
> 	and movx for Haswell.
> ---
>  gcc/config/i386/x86-tune.def | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/gcc/config/i386/x86-tune.def b/gcc/config/i386/x86-tune.def
> index 5649fdcf416..60625668236 100644
> --- a/gcc/config/i386/x86-tune.def
> +++ b/gcc/config/i386/x86-tune.def
> @@ -48,7 +48,7 @@ DEF_TUNE (X86_TUNE_SCHEDULE, "schedule",
>     over partial stores.  For example preffer MOVZBL or MOVQ to load 8bit
>     value over movb.  */
>  DEF_TUNE (X86_TUNE_PARTIAL_REG_DEPENDENCY, "partial_reg_dependency",
> -          m_P4_NOCONA | m_CORE2 | m_NEHALEM  | m_SANDYBRIDGE
> +          m_P4_NOCONA | m_CORE2 | m_NEHALEM  | m_SANDYBRIDGE | m_HASWELL
>  	  | m_BONNELL | m_SILVERMONT | m_INTEL
>  	  | m_KNL | m_KNM | m_AMD_MULTIPLE | m_SKYLAKE_AVX512 | m_GENERIC)
>  
> @@ -84,7 +84,7 @@ DEF_TUNE (X86_TUNE_PARTIAL_FLAG_REG_STALL, "partial_flag_reg_stall",
>     partial dependencies.  */
>  DEF_TUNE (X86_TUNE_MOVX, "movx",
>            m_PPRO | m_P4_NOCONA | m_CORE2 | m_NEHALEM  | m_SANDYBRIDGE
> -	  | m_BONNELL | m_SILVERMONT | m_KNL | m_KNM | m_INTEL
> +	  | m_BONNELL | m_SILVERMONT | m_KNL | m_KNM | m_INTEL | m_HASWELL
>  	  | m_GEODE | m_AMD_MULTIPLE | m_SKYLAKE_AVX512 | m_GENERIC)
>  
>  /* X86_TUNE_MEMORY_MISMATCH_STALL: Avoid partial stores that are followed by
> -- 
> 2.17.0
>