[Bug c/54149] write introduction incorrect wrt the C11 memory model

[aldyh at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54149

Aldy Hernandez aldyh at gcc dot gnu.org changed:

   What|Removed |Added

 Status|UNCONFIRMED |NEW
   Last reconfirmed||2012-09-07
 CC||amacleod at redhat dot com
 AssignedTo|unassigned at gcc dot   |aldyh at gcc dot gnu.org
   |gnu.org |
 Ever Confirmed|0   |1

--- Comment #2 from Aldy Hernandez aldyh at gcc dot gnu.org 2012-09-07 
19:45:29 UTC ---
This looks like a data race introduced by LIM.  Ughh, I thought I had this pass
all fixed... I'll take a look.

[Bug c/54149] write introduction incorrect wrt the C11 memory model

[francesco.zappa.nardelli at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54149

--- Comment #1 from Francesco Zappa Nardelli francesco.zappa.nardelli at gmail 
dot com 2012-08-23 16:34:38 UTC ---
Here is another C program that hits a similar write-introduction problem:

int g_7, g_372;

char func_10 () {
  for (; g_7  0; ++g_7) {
  }
  return 0;
}

void main () {
  int l_8;
lbl_914:
  (l_8 = g_7) = func_10 ();
  if (l_8)
if (g_372) {
} else
  goto lbl_914;
}

The reference trace is:

*** unoptimised trace: gcc --param allow-store-data-races=0 8-min.c -o
8-min_unopt

  g_70  4Init
g_3720  4Init
  g_70  4Load
  g_70  4Load

while the optimised trace (requires -O2 or -O3 to be observable) is

*** optimised trace: gcc --param allow-store-data-races=0 -O3 8-min.c -o
8-min_opt

  g_70  4Init
g_3720  4Init
g_3720  4Load
  g_70  4Load
  g_70  4   Store

[ gcc version 4.8.0 20120627 (experimental) (GCC) ]