linux-kernel - Re: [PATCH RFC 4/5] x86/alternative: Improve code generation readability

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Message-ID: <rvdkkywhaqcymcco3im4bmy2o35u2kpqxuqschjbuc3h7n2yzr@ikvofglh56gr>
Date: Wed, 9 Apr 2025 14:55:29 -0700
From: Josh Poimboeuf <jpoimboe@...nel.org>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>, x86@...nel.org, 
	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...nel.org>
Subject: Re: [PATCH RFC 4/5] x86/alternative: Improve code generation
 readability

On Wed, Apr 09, 2025 at 02:27:28PM -0700, Josh Poimboeuf wrote:
> On Wed, Apr 09, 2025 at 02:20:55PM -0700, Linus Torvalds wrote:
> > On Wed, 9 Apr 2025 at 12:51, Josh Poimboeuf <jpoimboe@...nel.org> wrote:
> > >
> > > What if we were to use a global asm() to define an alternative .macro
> > > whenever "alternative.h" gets included?
> > 
> > Yeah, I wouldn't mind that, but I have this dim memory of us having
> > tried it at some point and it didn't work.
> > 
> > I think the issue was that the in-compiler assembler was not as
> > complete as the external one (ie not doing macros at all or something
> > like that).
> 
> It seems to work with GCC 14 and Clang 18 at least.  I can try to find
> some old toolchains to test with.

Actually, Clang *compiled*, but on closer inspection it's actually
silently omitting the inline asm :-/

So yeah, that's not going to work.

-- 
Josh