Re: [RFC] gcc feature request: Moving blocks into sections

From: "H. Peter Anvin" <hpa@linux.intel.com>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: LKML <linux-kernel@vger.kernel.org>, gcc <gcc@gcc.gnu.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Ingo Molnar <mingo@kernel.org>,
	Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	David Daney <ddaney.cavm@gmail.com>,
	Behan Webster <behanw@converseincode.com>,
	Peter Zijlstra <peterz@infradead.org>
Subject: Re: [RFC] gcc feature request: Moving blocks into sections
Date: Mon, 05 Aug 2013 10:02:24 -0700	[thread overview]
Message-ID: <51FFDAA0.6020107@linux.intel.com> (raw)
In-Reply-To: <1375721715.22073.80.camel@gandalf.local.home>

On 08/05/2013 09:55 AM, Steven Rostedt wrote:
> 
> Almost a full year ago, Mathieu suggested something like:
> 
> if (unlikely(x)) __attribute__((section(".unlikely"))) {
>         ...
> } else __attribute__((section(".likely"))) {
>         ...
> }
> 
> https://lkml.org/lkml/2012/8/9/658
> 
> Which got me thinking. How hard would it be to set a block in its own
> section. Like what Mathieu suggested, but it doesn't have to be
> ".unlikely".
> 
> if (x) __attibute__((section(".foo"))) {
> 	/* do something */
> }
> 

One concern I have is how this kind of code would work when embedded
inside a function which already has a section attribute.  This could
easily cause really weird bugs when someone "optimizes" an inline or
macro and breaks a single call site...

	-hpa