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

["Stefan Kanthak" <stefan.kanthak@nexgo.de>]

"Jonathan Wakely" <jwakely.gcc@gmail.com> wrote:

> On Fri, 26 May 2023 at 15:34, Stefan Kanthak <stefan.kanthak@nexgo.de> wrote:
>>
>> "Jonathan Wakely" <jwakely.gcc@gmail.com> wrote:
>>
>> > On Fri, 26 May 2023 at 14:55, Stefan Kanthak <stefan.kanthak@nexgo.de> wrote:
>>
>> [...]
>>
>> >> NOT obvious is but that -m<feature> -march=<lowerISA> does not clear any
>> >> <feature> not supported in <lowerISA>, i.e the last one does NOT win here.
>> >
>> > The last -march option selects the base set of instructions. The -mISA
>> > options modify that base.
>>
>> You but missed the point, AGAIN: the modifications per -mISA and -mno-ISA
>> persist, i.e. they are NOT reset by the last -march= option.
> 
> Nobody said they are reset, and the docs don't say that, so assume they are not.

For the supported -march= the documentation EXPLICITLY enumerates (all?)
options!
Why should I assume that these options are "sticky" and override the
DOCUMENTED set?

Unless you document the behaviour in either way it is UB, so every user
of GCC can assume anything he wants!

> The last -march option selects a base and the -mISA options modify the
> base. Note *the* base. The one that was selected. By the last -march
> option. The base.
> 
>> Is this SOOOO hard to grok?
> 
> I understand your question. It's based on failing to read or
> understand what has been said.

Yes, silly!

[...]

>> Is this soooo hard to document?
> 
> I prefer arguing with trolls, it's even easier.

I don't like to argue with idiots: they beat me with experience!

Stefan