Hi Carl,
on 2023/7/3 23:57, Carl Love wrote:
> Kewen:
>
> On Fri, 2023-06-30 at 15:20 -0700, Carl Love wrote:
>> Segher never liked the above way of looking at the assembly. He
>> prefers:
>> gcc -S -g -mcpu=power8 -o vsx-vector-6-func-2lop.s vsx-vector-6-
>> func-
>> 2lop.c
>>
>> grep xxlor vsx-vector-6-func-2lop.s | wc
>> 34 68 516
>>
>> So, again, I get the same count of 34 on both makalu and genoa. But
>> again, that doesn't agree with what make script/scan-assembler thinks
>> the counts should be.
>>
>> When I looked at the vsx-vector-6-func-2lop.s I see on BE:
>>
>> ....
>> lxvd2x 0,10,9
>> xxlor 0,12,0
>> xxlnor 0,0,0
>> ...
>>
>> I was guessing that it was adjusting the data layout from the load.
>> But looking again more carefully versus LE:
>>
>> ....
>> lxvd2x 0,31,9
>> xxpermdi 0,0,0,2
>> xxlor 0,12,0
>> xxlnor 0,0,0
>> xxpermdi 0,0,0,2
>> ....
>>
>> the xxpermdi is probably what is really doing the data layout change.
>>
>> So, we have the issue that looking at the assembly gives different
>> instruction counts then what
>>
>> dg-final { scan-assembler-times {\mxxlor\M} }
>>
>> comes up with??? Now I am really confused. I don't know how the
>> scan-
>> assembler-times works but I will go see if I can find it and see if I
>> can figure out what the issue is. I would expect that the scan-
>> assembler is working off the --save-temp files, which get deleted as
>> part of the run. I would guess that scan-assembler does a grep to
>> find
>> the instructions and then maybe uses wc to count them??? I will go
>> see
>> if I can figure out how scan-assembler-times works.
>
> OK, I figured out why I was getting 34 xxlor instructions instead of
> the 22 that the scan-assembler-times was getting. The difference was
> when I compiled the program I forgot to use -O2. So with -O2 I get the
> same number of xxlor instructins as scan-assembler-instructions. I get
> 34 if I do not specify optimization.
OK, thanks for looking into it. When you run a test case with RUNTESTFLAGS,
you can add the "-v" (and even more times) to RUNTESTFLAGS, then you can find
the exact compiling commands in the dumping, I usually used this way for
reproducing and I hope it can avoid some inconsistency for reproduction.
>
> So, I think the scan-assembler-times are all correct.
>
> As Peter says, counting xxlor is a bit problematic in general. We
> could just drop counting xxlor or have the LE/BE count qualifier for
> the instructions. Your call.
Yeah, I agree that counting xxlor in the checking code (from function main)
is fragile, but as you said we still want to check expected xxlor generated
for bif vec_or, so I'd prefer to separate the existing case into the
compiling part and run part, I'll reply with more details to your latest v3.
Thanks,
Kewen
