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

Mon Jul 27 15:22:16 PDT 2020

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.

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