linux-kernel - Re: [PATCH 2/2] jump label: disable due to compiler bug

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Date:	Fri, 29 Oct 2010 11:13:52 -0700
From:	Richard Henderson <rth@...hat.com>
To:	David Daney <ddaney@...iumnetworks.com>
CC:	Steven Rostedt <rostedt@...dmis.org>,
	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>,
	Ingo Molnar <mingo@...e.hu>, Jason Baron <jbaron@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, tglx@...utronix.de,
	andi@...stfloor.org, roland@...hat.com,
	masami.hiramatsu.pt@...achi.com, fweisbec@...il.com,
	avi@...hat.com, davem@...emloft.net, vgoyal@...hat.com,
	sam@...nborg.org, tony@...eyournoodle.com, dsd@...top.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] jump label: disable due to compiler bug

On 10/29/2010 10:48 AM, David Daney wrote:
> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46226
> 
> Perhaps it could be integrated with the current checks for the presence of 'asm goto'

If you're looking for a cross-compile-able test, you can strip the
testcase down to 

extern void abort(void);
void g(int x, ...);
void f(int x)
{
  if (x == 0)
    g(0);
  g(1, 2, 3, 4, 5, 6, 7);
  asm goto ("XYZZY" : : : : label);
  abort ();
 label:
  return;
}

and use perl to notice the adjustment to esp before or after XYZZY.
It should be fairly obvious looking at the assembly before and after
the patch.

I don't know what sort of embedded processors supported by linux
actually use ACCUMULATE_OUTGOING_ARGS.  Almost all ports don't, so
I'd be pretty comfortable making this a 32-bit x86 only test, and
let other targets just check that the test compiles.


r~
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