PING^3: [PATCH V4, rs6000] Disable generation of scalar modulo instructions

[Pat Haugen <pthaugen@linux.ibm.com>]

Ping.

On 6/30/23 2:26 PM, Pat Haugen via Gcc-patches wrote:
> Updated from prior version to address latest review comment (simplify
> umod<mode>3).
> 
> Disable generation of scalar modulo instructions.
> 
> It was recently discovered that the scalar modulo instructions can suffer
> noticeable performance issues for certain input values. This patch disables
> their generation since the equivalent div/mul/sub sequence does not suffer
> the same problem.
> 
> Bootstrapped and regression tested on powerpc64/powerpc64le.
> Ok for master and backports after burn in?
> 
> -Pat
> 
> 
> 2023-06-30  Pat Haugen  <pthaugen@linux.ibm.com>
> 
> gcc/
>      * config/rs6000/rs6000.cc (rs6000_rtx_costs): Check if disabling
>      scalar modulo.
>      * config/rs6000/rs6000.h (RS6000_DISABLE_SCALAR_MODULO): New.
>      * config/rs6000/rs6000.md (mod<mode>3, *mod<mode>3): Disable.
>      (define_expand umod<mode>3): New.
>      (define_insn umod<mode>3): Rename to *umod<mode>3 and disable.
>      (umodti3, modti3): Disable.
> 
> gcc/testsuite/
>      * gcc.target/powerpc/clone1.c: Add xfails.
>      * gcc.target/powerpc/clone3.c: Likewise.
>      * gcc.target/powerpc/mod-1.c: Update scan strings and add xfails.
>      * gcc.target/powerpc/mod-2.c: Likewise.
>      * gcc.target/powerpc/p10-vdivq-vmodq.c: Add xfails.