[patch] Fixing ppc64 test failure after patch dealing with scratches in IRA

[Vladimir Makarov]

On 2020-10-30 7:36 p.m., Segher Boessenkool wrote:
> Thanks for the patch!  But it has a problem:
>
>> diff --git a/gcc/config/rs6000/vsx.md b/gcc/config/rs6000/vsx.md
>> index 67e4f2fd037..78de85ccbbb 100644
>> --- a/gcc/config/rs6000/vsx.md
>> +++ b/gcc/config/rs6000/vsx.md
>> @@ -3717,7 +3717,7 @@
>>   	(vec_select:<VS_scalar>
>>   	 (match_operand:VSX_EXTRACT_I 1 "gpc_reg_operand" "<VSX_EX>,v")
>>   	 (parallel [(match_operand:QI 2 "const_int_operand" "n,n")])))
>> -   (clobber (match_scratch:<VS_scalar> 3 "=<VSX_EX>,&r"))
>> +   (clobber (match_scratch:<VS_scalar> 3 "=*<VSX_EX>,&*r"))
>>      (clobber (match_scratch:SI 4 "=X,&r"))]
>>     "VECTOR_MEM_VSX_P (<MODE>mode) && TARGET_VEXTRACTUB"
>>     "#"
> You add * to both alternatives here?  I would expect adding it to only
> the second alternative, does it work better with both?
No.  It works the same.  When the both alternatives use the hint, the 
scratch pseudo got the class ALL_REGS.  When only the 2nd use the hint, 
the class is VSX_REGS.  As I understand now the preferable alternative 
is the 1st one (with <VSX> for the scratch).  In this case using the 
hint only for the 2nd alternative has more sense.
> That also avoids a different problem: *<VSX_EX> won't work as expected.
> '*' in IRA skips one constraint character, but <VSX_EX> can be "wa", a
> two-letter constraint (and we do have an "a" constraint as well,
> something wholly different: "wa" means a VSX register, while "a" is an
> indexed address).
>
>                  case '*':
>                    /* Ignore the next letter for this pass.  */
>                    c = *++p;
>                    break;
>
>
I see.  Thanks for pointing this out. Definitely it is better to use the 
hint only for the second alternative ("&*r") then.  Is this solution ok 
for you?