https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112616
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Priority|P3 |P2
CC| |hubicka at gcc dot gnu.org,
| |jamborm at gcc dot gnu.org
Version|unknown |13.2.1
--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
IPA-SRA at work. With -fno-inline added you see
-long int p ()
+void p.isra ()
{
...
@@ -106,13 +82,13 @@
i.2_2 = i;
h.3_3 = h;
*i.2_2 = h.3_3;
- _4 = o ();
+ o.isra ();
<bb 4> [local count: 1073741824]:
- # q_11 = PHI <0B(2), _4(3)>
- _5 = *q_11;
- _10 = (long int) _5;
- return _10;
+ # q_5 = PHI <0B(2), removed_return.17_12(D)(3)>
+ _6 = *q_5;
+ _7 = (long int) _6;
+ return;
Note the issue is that we end up with the following after inlining:
<bb 5> [local count: 1073741824]:
# q_11 = PHI <0B(2), removed_return.14_14(D)(4), removed_return.14_14(D)(3)>
_12 = *q_11;
and CCP will optimistically simplify q_11 to 0B because accessing the
removed_return.14_14(D) would be undefined behavior.
That means substituting a default-def isn't correct - it exposes undefined
behavior on valid paths of the program.
