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

[Kyrylo Tkachov <Kyrylo.Tkachov@arm.com>]

> -----Original Message-----
> From: Richard Earnshaw <Richard.Earnshaw@foss.arm.com>
> Sent: Monday, September 5, 2022 2:43 PM
> To: Kyrylo Tkachov <Kyrylo.Tkachov@arm.com>; gcc-patches@gcc.gnu.org
> Subject: Re: [PATCH][committed] aarch64: Suggest an -mcpu option when
> user passes CPU name to -march
> 
> 
> 
> 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?

It'd be good to warn for that too, though I think it's a somewhat less common error.
It can be a separate patch in any case.
Thanks,
Kyrill

> 
> R.