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.
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.
Carl
