lkml.org 
[lkml]   [2007]   [Dec]   [3]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: Fedora's latest gcc produces unbootable kernels
On Mon, Dec 03, 2007 at 09:17:22AM +0100, Thomas Gleixner wrote:
> I looked at the disassembly but I can not spot the problem.
>
> I think the real problem is somewhere else. Likely candidates are
> hrtimer_forward() or hrtimer_start() - in that order.

Should be hopefully fixed in latest Fedora gcc. The problem was in code like
typedef union { long long int s; } U;
typedef struct { U u; } S;

void foo (S *s, long long int x, unsigned long int y)
{
s->u = ({ (U) { .s = s->u.s + x * y }; });
}

where a backport of a recent optimization of mine, without which gcc handles
terribly initializers from compound literals (which is something hrtimer
uses just everywhere - why can't ktime.h for #if BITS_PER_LONG == 64 || defined(CONFIG_KTIME_SCALAR)
just use a scalar rather than union with a scalar in it??), sets the LHS
object to the compound literal's initializer rather than forcing creation of
a temporary object (the compound literal). Unfortunately the gimplifier
had some bugs in case the initializer references (or at least might
reference) parts of LHS object. Fixed by backporting 2 Ada bugfixes for the
gimplifier from GCC trunk (Ada was hitting those bugs even without this
compound literal optimization).

Jakub


\
 
 \ /
  Last update: 2007-12-03 10:01    [W:0.057 / U:0.084 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site