linux-kernel - Re: [PATCH v4 15/18] static

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Message-ID: <20200506181005.GY3762@hirez.programming.kicks-ass.net>
Date:   Wed, 6 May 2020 20:10:05 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     x86@...nel.org
Cc:     linux-kernel@...r.kernel.org, rostedt@...dmis.org,
        mhiramat@...nel.org, bristot@...hat.com, jbaron@...mai.com,
        torvalds@...ux-foundation.org, tglx@...utronix.de,
        mingo@...nel.org, namit@...are.com, hpa@...or.com, luto@...nel.org,
        ard.biesheuvel@...aro.org, jpoimboe@...hat.com,
        pbonzini@...hat.com, mathieu.desnoyers@...icios.com
Subject: Re: [PATCH v4 15/18] static_call: Handle tail-calls

On Fri, May 01, 2020 at 10:29:04PM +0200, Peter Zijlstra wrote:
>  	if (IS_ENABLED(CONFIG_HAVE_STATIC_CALL_INLINE) && site)
> -		__static_call_transform(site, !func, func);
> +		__static_call_transform(site, 2*tail + !func, func);

I'm having trouble making that more readable though... that !func can be
exanded like proposed in 14 without code-gen changes, but:

	__static_call_transform(site, tail ? (func ? JMP : RET)
					   : (func ? CALL : NOP), func);

generates a right old mess.