https://gcc.gnu.org/bugzilla/show_bug.cgi?id=39612
Aldy Hernandez <aldyh at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |aldyh at gcc dot gnu.org
--- Comment #29 from Aldy Hernandez <aldyh at gcc dot gnu.org> ---
(In reply to Richard Biener from comment #11)
> Re-confirmed on trunk with the testcase in comment #4 and -Os:
>
> > ./cc1 -quiet t.c -Os -Wall -fdump-tree-all
> t.c: In function 'f2':
> t.c:4:11: warning: 'inter[0]' is used uninitialized in this function
> [-Wuninitialized]
> t.c:4:11: warning: 'inter[1]' is used uninitialized in this function
> [-Wuninitialized]
>
> There is also a store data-race introduced by LIM when the loop header
> is not copied. I suppose the real fix is to disable SM if the loop
> header is not copied.
The warning is gone for the testcase in comment #4:
abulafia:/build/t/gcc$ ./cc1 b.c -Os -Wall -quiet -fdump-tree-all
abulafia:/build/t/gcc$ ./cc1 b.c -O2 -Wall -quiet -fdump-tree-all
But the load from maybe-uninitialized memory is still there. This is lim2:
f2 (int * dst, int R)
{
_Bool inter_I_lsm.3;
int inter_I_lsm.2;
_Bool inter_I_lsm.1;
int inter_I_lsm.0;
int inter[2];
int i;
<bb 2> [local count: 118111601]:
inter_I_lsm.0_16 = inter[0]; // unconditional load outside loop
inter_I_lsm.1_17 = 0;
inter_I_lsm.2_18 = inter[1]; // unconditional load outside loop
inter_I_lsm.3_19 = 0;
goto <bb 4>; [100.00%]
Reconfirmed, I guess?
