[Bug tree-optimization/104156] [12 Regression] -fcompare-debug failure with -O3

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104156

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |12.0
   Last reconfirmed|                            |2022-01-21
            Version|unknown                     |12.0
     Ever confirmed|0                           |1
           Keywords|                            |needs-bisection
             Status|UNCONFIRMED                 |NEW
          Component|middle-end                  |tree-optimization

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Confirmed. -O2 -funswitch-loops is enough to produce the failure. and yes the
first difference in the IR (minus the debug statements) between -g and -g0 is
150t.unswitch .

--- t.gk.c.150t.unswitch        2022-01-21 07:55:45.860933512 +0000
+++ t.c.150t.unswitch   2022-01-21 07:55:45.623933488 +0000
@@ -1,6 +1,30 @@

 ;; Function main (main, funcdef_no=1, decl_uid=2004, cgraph_uid=2,
symbol_order=5) (executed once)

+
+SSA replacement table
+N_i -> { O_1 ... O_j } means that N_i replaces O_1, ..., O_j
+
+.MEM_24 -> { .MEM_42 }
+Incremental SSA update started at block: 2
+Number of blocks in CFG: 36
+Number of blocks to update: 5 ( 14%)

Without the debug statements unswitch does something.