Re: [PATCH][committed] aarch64: Suggest an -mcpu option when user passes CPU name to -march

[Richard Earnshaw <Richard.Earnshaw@foss.arm.com>]

On 05/09/2022 14:35, Kyrylo Tkachov via Gcc-patches wrote:
> Hi all,
> 
> This small patch helps users who confuse -march and -mcpu on AArch64.
> Sometimes users pass -march with a CPU name, where they most likely wanted to
> use -mcpu, which would select the right architecture features *and* tune for
> their desired CPU. Currently we'll just error out with an unkown architecture
> message and list the valid architecture options.
> With this patch we check if their string matches a known CPU and suggest they
> use an -mcpu option instead.
> 
> So compiling with -march=neoverse-n1 will now give the error:
> cc1: error: unknown value 'neoverse-n1' for '-march'
> cc1: note: valid arguments are: armv8-a armv8.1-a armv8.2-a armv8.3-a armv8.4-a armv8.5-a armv8.6-a armv8.7-a armv8.8-a armv8-r armv9-a
> cc1: note: did you mean '-mcpu=neoverse-n1'?
> 
> Bootstrapped and tested on aarch64-none-linux-gnu.
> Pushing to trunk.
> Thanks,
> Kyrill
> 
> gcc/ChangeLog:
> 
> 	* config/aarch64/aarch64.cc (aarch64_validate_march): Check if invalid arch
> 	string is a valid -mcpu string and emit hint.
> 
> gcc/testsuite/ChangeLog:
> 
> 	* gcc.target/aarch64/spellcheck_10.c: New test.

What about the reverse case, passing an architecture to -mcpu?

R.