[Bug tree-optimization/58532] [4.9 Regression] bootstrap failure with BOOT_CFLAGS="-g -O3"

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58532

--- Comment #6 from Richard Biener <rguenth at gcc dot gnu.org> ---
One difference happens in 057.cunrolli already, we create a preheader for a
loop depending on -g:

 ;; Function bool gfc_parse_file() (_Z14gfc_parse_filev, funcdef_no=257,
decl_ui
d=17369, symbol_order=156)

 Created preheader block for loop 4
-Created preheader block for loop 5
 ;; 10 loops found

...

@@ -18009,13 +19254,14 @@
   <bb 109>:
   st_228 = parse_spec (131);

-  # st_470 = PHI <st_228(109)>
-  # error_471 = PHI <0(109)>
+  # st_229 = PHI <st_228(109), st_232(124)>
+  # error_233 = PHI <0(109), 1(124)>
 loop:
-
-  <bb 205>:
-  # st_229 = PHI <st_470(110), st_232(207)>
-  # error_233 = PHI <error_471(110), 1(207)>
+  # DEBUG st => NULL
+  # DEBUG error => NULL
+  # DEBUG st => NULL
+  # DEBUG error => error_233
+  # DEBUG st => st_229
   st.280_230 = (int) st_229;
   switch (st.280_230) <default: <L61>, case 12: <L59>, case 33: <L60>, case
131: <L58>>

...

   <bb 124>:
   st_232 = next_statement ();
-
-  <bb 207>:
-  goto <bb 205>;
+  goto <bb 110> (loop);

(to investigate).