[Patch, i386] Support BMI and BMI2 targets in multiversioning

[Allan Sandfeld Jensen]

On Monday 26 January 2015, H.J. Lu wrote:
> On Sun, Jan 25, 2015 at 10:37 AM, Uros Bizjak <ubizjak@gmail.com> wrote:
> > On Sun, Jan 25, 2015 at 7:23 PM, Uros Bizjak <ubizjak@gmail.com> wrote:
> >> On Sat, Jan 24, 2015 at 11:49 AM, Allan Sandfeld Jensen
> >> 
> >> <allan@carewolf.com> wrote:
> >>> On Saturday 24 January 2015, Uros Bizjak wrote:
> >>>> On Mon, Jan 12, 2015 at 6:02 PM, Uros Bizjak <ubizjak@gmail.com> wrote:
> >>>> > Hello!
> >>>> > 
> >>>> >>> On Wed, Dec 31, 2014 at 01:28:47PM +0100, Allan Sandfeld Jensen 
wrote:
> >>>> >>> > I recently wanted to use multiversioning for BMI2 specific
> >>>> >>> > extensions PDEP/PEXT, and noticed it wasn't there. So I wrote
> >>>> >>> > this patch to add it, and also added AES, F16C and BMI1 for
> >>>> >>> > completeness.
> >>>> >>> 
> >>>> >>> AES nor F16C doesn't make any sense IMHO for multiversioning, you
> >>>> >>> need special intrinsics for that anyway and when you use them,
> >>>> >>> the function will fail to compile without those features.
> >>>> >>> Multiversioning only makes sense for ISA features the compiler
> >>>> >>> uses for normal C/C++ code without any intrinsics.
> >>>> >> 
> >>>> >> Patch reduced to just adding BMI and BMI2 multiversioning:
> >>>> > +2014-12-29  Allan Sandfeld Jensen  <sandfeld@kde.org>
> >>>> > +
> >>>> > + * config/i386/i386.c (get_builtin_code_for_version): Add
> >>>> > + support for BMI and BMI2 multiversion functions.
> >>>> > 
> >>>> > +2014-12-29  Allan Sandfeld Jensen  <sandfeld@kde.org>
> >>>> > +
> >>>> > + * gcc.target/i386/funcspec-5.c: Test new multiversion targets.
> >>>> > + * g++.dg/ext/mv17.C: Test BMI/BMI2 multiversion dispatcher.
> >>>> > 
> >>>> > +2014-12-29  Allan Sandfeld Jensen  <sandfeld@kde.org>
> >>>> > +
> >>>> > + * config/i386/cpuinfo.c (enum processor_features): Add FEATURE_BMI
> >>>> > and + FEATURE_BMI2.
> >>>> > + (get_available_features): Detect FEATURE_BMI and FEATURE_BMI2.
> >>>> > 
> >>>> > OK for mainline
> >>>> 
> >>>> Allan, did you commit the patch to mainline? I don't see it in SVN
> >>>> logs.
> >>>> 
> >>>> (If you don't have SVN commit access, please mention it in the patch
> >>>> submission, so someone will commit the patch for you).
> >>> 
> >>> Sorry. I don't have SVN commit access.
> >> 
> >> Committed with a bunch of fixes (e.g. missing fold_builtin_cpu part in
> >> gcc/config/i386/i386.c, and mv17.C test didn't compile at all due to
> >> missing parenthesis).
> > 
> > ... and now with committed ChangeLog and patch.
> > 
> > gcc/ChangeLog:
> >     * config/i386/i386.c (get_builtin_code_for_version): Add
> >     support for BMI and BMI2 multiversion functions.
> >     (fold_builtin_cpu): Add F_BMI and F_BMI2.
> > 
> > libgcc/ChangeLog:
> >     * config/i386/cpuinfo.c (enum processor_features): Add FEATURE_BMI
> >     and FEATURE_BMI2.
> >     (get_available_features): Detect FEATURE_BMI and FEATURE_BMI2.
> > 
> > testsuite/ChangeLog:
> >     * gcc.target/i386/funcspec-5.c: Test new multiversion targets.
> >     * g++.dg/ext/mv17.C: Test BMI/BMI2 multiversion dispatcher.
> 
> diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
> index 9ec40cb..441911d 100644
> --- a/gcc/config/i386/i386.c
> +++ b/gcc/config/i386/i386.c
> @@ -34289,15 +34289,18 @@ get_builtin_code_for_version (tree decl, tree
> *predica te_list)
>      P_PROC_SSE4_A,
>      P_SSE4_1,
>      P_SSE4_2,
> -    P_PROC_SSE4_2,
>      P_POPCNT,
> +    P_PROC_SSE4_2,
>      P_AVX,
>      P_PROC_AVX,
> +    P_BMI,
> +    P_PROC_BMI,
>      P_FMA4,
>      P_XOP,
>      P_PROC_XOP,
>      P_FMA,
>      P_PROC_FMA,
> +    P_BMI2,
>      P_AVX2,
>      P_PROC_AVX2,
>      P_AVX512F,
> 
> This changed the priority of P_POPCNT and caused
> 
> FAIL: g++.dg/ext/mv1.C  -std=gnu++98 execution test
> FAIL: g++.dg/ext/mv1.C  -std=gnu++11 execution test
> FAIL: g++.dg/ext/mv1.C  -std=gnu++14 execution test
> 
> on Nehalem and Westmere machines:
> 
> mv1.exe:
> /export/gnu/import/git/sources/gcc/gcc/testsuite/g++.dg/ext/mv1.C:51: int
> main(): Assertion `val == 5' failed.
> 
> since "val" is 6 now.

Right. I am not sure why popcnt was prioritized below arch=corei7. The logic 
is supposed to be that any target that includes an extension is prioritized 
above that extension. I included the change in the order in i386.c, but not 
the updated test. It is probably better to not change the order in i386.c, or 
at least change that in a separate commit.

`Allan