linux-kernel - Re: [PATCH -tip] x86/locking/atomic: Use asm

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Message-ID: <20250305212638.GC35526@noisy.programming.kicks-ass.net>
Date: Wed, 5 Mar 2025 22:26:38 +0100
From: Peter Zijlstra <peterz@...radead.org>
To: Borislav Petkov <bp@...en8.de>
Cc: Uros Bizjak <ubizjak@...il.com>, Dave Hansen <dave.hansen@...el.com>,
	x86@...nel.org, linux-kernel@...r.kernel.org,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...nel.org>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Linus Torvalds <torvalds@...uxfoundation.org>
Subject: Re: [PATCH -tip] x86/locking/atomic: Use asm_inline for atomic
 locking insns

On Wed, Mar 05, 2025 at 09:36:33PM +0100, Borislav Petkov wrote:
> On Wed, Mar 05, 2025 at 09:54:11AM +0100, Uros Bizjak wrote:
> > The -Os argument was to show the effect of the patch when the compiler
> > is instructed to take care of the overall size. Giving the compiler
> > -O2 and then looking at the overall size of the produced binary is
> > just wrong.
> 
> No one cares about -Os AFAICT. It might as well be non-existent. So the effect
> doesn't matter.

Well, more people would care if it didn't stand for -Ostupid I suppose.
That is, traditionally GCC made some very questionable choices with -Os,
quite horrendous code-gen.