Re: [PATCH] oops_in_progress is unlikely()

[Pavel Machek <pavel@ucw.cz>]

Hi!

> > > 		cmpl	$1, %eax
> > > 		jz	1f
> > > 		jc	2f
> > > 		call	do_default
> > > 		jmp	more_code
> > > 	1:	call	do_something_if_equal
> > > 		jmp	more_code
> > > 	2:	call	do_something_if_less
> > > 	more_code:
> > >
> > > In every case, one has to jump around code for other execution paths
> > > except the last, where you have to jump on condition anyway. There
> > > is no free liunch, and the straight-through route, do_default
> > > uas just as many jumps as the last.
> >
> > Here is your code optimised for no jumps in the "do_default" case:
> >
> > 		cmpl	$1,%eax
> > 		jbe	1f
> > 		call	do_default
> > 	more_code:
> > 		.subsection 1
> > 	1:	jnz	2f
> > 		call	do_something_if_equal
> > 		jmp	more_code
> > 	2:	call	do_something_if_less
> > 		jmp	more_code
> > 		.previous
> >
> 
> You are a magician! Putting in a .subsection to hide the jump
> is absolute bullshit. The built-in macros, ".subsection", and
> ".previous" just made the damn linker do the fixup. You just
> did a long jump, out of the current code-stream, into some

He's right. Even without subsections you can move code somewhere
outside the function. And gcc should be smart enough to do that.

							Pavel

-- 
When do you have a heart between your knees?
[Johanka's followup: and *two* hearts?]