Re: Will GCC eventually support SSE2 or SSE4.1?

[Jonathan Wakely <jwakely.gcc@gmail.com>]

On Fri, 26 May 2023 at 15:48, Stefan Kanthak <stefan.kanthak@nexgo.de> wrote:
>
> "Jakub Jelinek" <jakub@redhat.com> wrote:
>
> [...]
>
> > And for -m32 it is also the last option that wins, but as with
> > many other cases just last one from certain set of options. [...]
> > The -mISA options are processed left to right after
>
> as well as BEFORE

No. You seem to be interpreting "after" to mean "later in the command
line" but Jakub means *at a later time*. He used "left to right" to
describe position in the command line, and "after" means "at a later
time".

Any -march options are processed first, from left to right. After
that, there is a base arch in effect.
Then, after that, the -mISA options are processed, and take effect
relative to the base arch.

What Jakub wrote is correct. If you try a bit harder to understand
what has been said repeatedly, you might get it.

>
> > setting base from -march=.
>
> In other words: although -march= selects a (documented sub)set of
> -mISA options, it does NEITHER reset any -mISA option set NOR any
> -mno-ISA option reset BEFORE or AFTER itself, i.e. all -m[no-]ISA
> options have precedence even if they preceed -march=.
>
> Just document that!

That is not far from unreadable.