[Bug tree-optimization/32328] [4.2/4.3 Regression] -fstrict-aliasing causes skipped code

[rguenth at gcc dot gnu dot org]

------- Comment #19 from rguenth at gcc dot gnu dot org  2007-07-16 15:51 -------
The backported patch causes 

FAIL: gcc.c-torture/execute/pr28778.c execution,  -O2 
FAIL: gcc.c-torture/execute/pr28778.c execution,  -Os 

DCE removes

-
-<L1>:;
-  list[3] = 42;

we have one added constraint:

 blist.0_7 = blist_1
+*blist.0_7 = &ANYTHING
 ESCAPED_VARS = blist.0_7

IL differences after alias1 are

@@ -251,12 +247,11 @@
   list[3] = 42;
   blist_6 = &list;

-  # list_8 = PHI <list_4(3), list_5(4)>;
   # blist_1 = PHI <blist_3(3), blist_6(4)>;
 <L2>:;
   blist.0_7 = (const GLint *) blist_1;
-  #   list_10 = V_MAY_DEF <list_8>;
-  #   NONLOCAL.44_11 = V_MAY_DEF <NONLOCAL.44_9>;
+  #   NONLOCAL.44_10 = V_MAY_DEF <NONLOCAL.44_8>;
+  #   SMT.45_11 = V_MAY_DEF <SMT.45_9>;
   aglChoosePixelFormat (blist.0_7);
   return;

we also have

+NULL = &ANYTHING

but this doesn't result in IL differences.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=32328