[PATCH] D151098: [Clang][Docs] Add help test to `-march` and `-mcpu` to suggest `-mcpu=help`

Mon May 22 07:54:03 PDT 2023

aaron.ballman added a comment.

In D151098#4360758 <https://reviews.llvm.org/D151098#4360758>, @jhuber6 wrote:

> In D151098#4360750 <https://reviews.llvm.org/D151098#4360750>, @aaron.ballman wrote:
>
>> LGTM, though it's a bit jarring that `-march` suggests using `-mcpu=help` (should we ensure that `-march=help` works on all targets instead?)
>
> Using `-march=help` works inadvertently because it will list the targets when given an invalid one. We could probably map the `-mcpu=help` handling to `-march=help` but I'm not entirely sure what the semantics should be there. The distinction between `-march` and `-mcpu` is still not entirely clear to me, it's just a matter of whether or not the target decided to choose one or the other.

Oh, when I was trying it out, `-march=help` was not giving any useful information on some targets: https://godbolt.org/z/js4a64aTK -- FWIW, it's also unclear to me why and how these options differ.

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