https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111157
Martin Jambor <jamborm at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Ever confirmed|0 |1
Assignee|unassigned at gcc dot gnu.org |jamborm at gcc dot
gnu.org
Status|UNCONFIRMED |ASSIGNED
Last reconfirmed| |2023-08-25
--- Comment #2 from Martin Jambor <jamborm at gcc dot gnu.org> ---
With the propagation, PRE performs the following:
void point.constprop.isra (double ISRA.1740, int & restrict ipoint, double &
restrict x, double & restrict y, double & restrict z, int & restrict istat)
{
int iy;
int ix;
double & restrict prploc;
int _5;
- int _9;
int _11;
int _12;
long int _13;
@@ -13284,7 +15377,6 @@
<bb 2> [local count: 1073741824]:
# DEBUG D#556 s=> prploc
# DEBUG prploc => D#556
- *istat_1(D) = 0;
if (ISRA.1740_70(D) !=
6.08805302369215843745180305174265706886482420102590225625e-154)
goto <bb 7>; [50.00%]
else
@@ -13301,8 +15393,7 @@
calcom (x_6(D), y_7(D), z_8(D));
<bb 5> [local count: 536870912]:
- _9 = *ipoint_4(D);
- if (_9 > 1)
+ if (_5 > 1)
goto <bb 6>; [59.00%]
else
goto <bb 25>; [41.00%]
The write of zero to where we know there is already zero is however
problematic because all callers expect the pointed to value to be
overwritten and dse2 pass does:
@@ -20229,7 +14076,6 @@
xpt = 0.0;
ypt = 0.0;
zpt = 0.0;
- istat = 0;
point.constprop.isra (_73, &ipoint, &xpt, &ypt, &zpt, &istat);
_77 = istat;
if (_77 < 0)
So I guess this is a nasty interaction with IPA-modref, and indeed
-fno-ipa-modref avoids the issue.
I'll discuss with Honza whether IPA-modref can be modified to kill the
known values in summaries in such cases or whether it is IPA-CP that
should avoid "knowing" the value.
