Re: [PATCH] rs6000: Fix condition of define_expand vec_shr_<mode> [PR100645]

["Kewen.Lin" <linkw@linux.ibm.com>]

Hi Segher,

Thanks for the comments!

on 2022/9/23 05:39, Segher Boessenkool wrote:
> Hi!
> 
> Heh, I first thought I had mistyped thgew PR #, but it is this one after
> all :-)
> 
> On Thu, Sep 22, 2022 at 09:41:34AM +0800, Kewen.Lin wrote:
>> PR100645 exposes one latent bug in define_expand vec_shr_<mode>
>> that the current condition TARGET_ALTIVEC is too loose.  The
>> mode iterator VEC_L contains a few modes, they are not always
>> supported as vector mode, VECTOR_UNIT_ALTIVEC_OR_VSX_P should
>> be used like some other VEC_L usages.
> 
>> --- a/gcc/config/rs6000/vector.md
>> +++ b/gcc/config/rs6000/vector.md
>> @@ -1475,7 +1475,7 @@ (define_expand "vec_shr_<mode>"
>>    [(match_operand:VEC_L 0 "vlogical_operand")
>>     (match_operand:VEC_L 1 "vlogical_operand")
>>     (match_operand:QI 2 "reg_or_short_operand")]
>> -  "TARGET_ALTIVEC"
>> +  "VECTOR_UNIT_ALTIVEC_OR_VSX_P (<MODE>mode)"
> 
>> --- /dev/null
>> +++ b/gcc/testsuite/gcc.target/powerpc/pr100645.c
>> @@ -0,0 +1,13 @@
>> +/* { dg-require-effective-target powerpc_altivec_ok } */
>> +/* { dg-options "-mdejagnu-cpu=power6 -maltivec" } */
> 
> This is a strange choice: we normally do not enable VMX on p6.  Just use
> p7 instead?  There is no need for altivec_ok in any case, the -mcpu=
> guarantees it is satisfied.

Unfortunately a single power7 doesn't work for this case, since it (VSX) makes
rs6000_vector_mem[TImode] not VECTOR_NONE any more, we need one extra -mno-vsx
to reproduce this.

As you mentioned above, power6 doesn't enable altivec by default, I noticed
altivec_ok excludes some envs like aix 5.3 etc., and also ensures it's fine
to have an explicit maltivec there, so I added it for robustness.

> 
>> +/* It's to verify no ICE here.  */
> 
> "This used to ICE."?

Updated.

> 
> Please commit this now, looks good.  Thanks!
> 

Committed in r13-2844.  Thanks!

BR,
Kewen