[Bug tree-optimization/116156] [14/15 regression] -fcompare-debug -gno-statement-frontiers failure with -O2 when building gdk-pixbuf

[pinskia at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116156

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2024-07-31
     Ever confirmed|0                           |1

--- Comment #6 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Confirmed.

The first difference in the IR is in forwprop3:
Removing dead stmt:x_density_8(ab) = x_density_17;

is removed with -g while not removed without -g.

In the case of it was used with:
  x_density_8(ab) = x_density_17;
  # DEBUG x_densityD.4428 => x_density_8(ab)


I am 99% sure this was introduced by r14-3982-g9ea74d235c7e78 .
I have not checked if it is a bug in simple_dce_from_worklist or this loop is
missing a check to see if the statement was a debug statement and not do it:
+                 /* Queue old uses for simple DCE.  */
+                 for (tree use : uses)
+                   if (TREE_CODE (use) == SSA_NAME
+                       && !SSA_NAME_IS_DEFAULT_DEF (use))
+                     bitmap_set_bit (simple_dce_worklist,
+                                     SSA_NAME_VERSION (use));