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

From: Jason Baron
Date: Mon Aug 05 2013 - 15:58:08 EST

On 08/05/2013 03:40 PM, Marek Polacek wrote:
On Mon, Aug 05, 2013 at 11:34:55AM -0700, Linus Torvalds wrote:
On Mon, Aug 5, 2013 at 11:24 AM, Linus Torvalds
<torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:
Ugh. I can see the attraction of your section thing for that case, I
just get the feeling that we should be able to do better somehow.
Hmm.. Quite frankly, Steven, for your use case I think you actually
want the C goto *labels* associated with a section. Which sounds like
it might be a cleaner syntax than making it about the basic block
FWIW, we also support hot/cold attributes for labels, thus e.g.

if (bar ())
goto A;
/* ... */
A: __attribute__((cold))
/* ... */

I don't know whether that might be useful for what you want or not though...


It certainly would be.

That was how I wanted to the 'static_key' stuff to work, but unfortunately the last time I tried it, it didn't move the text out-of-line any further than it was already doing. Would that be expected? The change for us, if it worked would be quite simple. Something like:

--- a/arch/x86/include/asm/jump_label.h
+++ b/arch/x86/include/asm/jump_label.h
@@ -21,7 +21,7 @@ static __always_inline bool arch_static_branch(struct static_key *key)
".popsection \n\t"
: : "i" (key) : : l_yes);
return false;
+l_yes: __attribute__((cold))
return true;

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