[PATCH] D84519: [llvm-objdump][AMDGPU] Detect subtarget

[Eric Christopher via llvm-commits]

On Mon, Jul 27, 2020 at 3:22 PM Fangrui Song via Phabricator <
reviews at reviews.llvm.org> wrote:

> MaskRay added a comment.
>
> In D84519#2176909 <https://reviews.llvm.org/D84519#2176909>,
> @scott.linder wrote:
>
> > In D84519#2174866 <https://reviews.llvm.org/D84519#2174866>, @MaskRay
> wrote:
> >
> > > Can we step back and think whether precise CPU selection is really
> necessary? For example, PowerPC has the needs for different ISA levels but
> it simply uses -mcpu=future.
> >
> >
> > I am a bit lost on what you mean; is there a significant cost to
> providing precise CPU selection? It doesn't make sense to require the user
> to e.g. run the dumper to inspect the binary in order to come up with the
> command-line to run the dumper in order to inspect the binary.
>
>
> -mcpu=pwr10 decodes more instructions than -mcpu=pwr9.
> -mcpu=pwr9 decodes more instructions than -mcpu=pwr8.
>
> I think GNU objdump just decodes all instructions it recognizes, not
> expecting a -mcpu option. It behaves as if the default recognized ISA level
> includes everything.
>
>
>
This works as long as there aren't conflicting changes per isa/cpu/etc
which can happen :)

-eric



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