[Bug middle-end/33199] [4.3 Regression] tr1/2_general_utilities/shared_ptr/assign/auto_ptr.cc

["rguenth at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>]

------- Comment #20 from rguenth at gcc dot gnu dot org  2007-08-29 11:58 -------
Due to the alias differences with -g compared to without -g we have the
following
difference after tree-level optimization:

--- -   2007-08-29 13:52:02.567822000 +0200
+++ b/auto_ptr.min.ii.116t.optimized    2007-08-29 13:51:05.000000000 +0200
@@ -505,6 +505,7 @@ int test01() ()
   D.8890 = (struct _Sp_counted_base_impl *) D.8889;
   __d = __d.79;
   D.8891 = &D.8890->D.8307;
+  D.8890->D.8307._vptr._Sp_counted_base =
&_ZTVNSt3tr116_Sp_counted_baseILN9__gnu_cxx12_Lock_policyE1EEE[2];
   D.8890->D.8307._M_use_count = 1;
   D.8890->D.8307._M_weak_count = 1;
   D.8890->D.8307._vptr._Sp_counted_base =
&_ZTVNSt3tr121_Sp_counted_base_implIP1BNS_11_Sp_deleterIS1_EELN9__gnu_cxx12_Lock_policyE1EEE[2];
@@ -529,9 +530,9 @@ Invalid sum of incoming frequencies 8500
   goto <bb 9>;

 <bb 8>:
-  D.8898 = D.8890->D.8307._M_use_count + 1;
-  *D.8895 ={v} D.8898;
   __result = D.8890->D.8307._M_use_count;
+  D.8898 = __result + 1;
+  *D.8895 ={v} D.8898;
   D.9413 = __result + -1;
   *D.8895 ={v} D.9413;
   goto <bb 11>;

that is, we have one dead store removed by DSE and PRE removes one load of
_M_use_count:

 int test01() ()
 {
+  _Atomic_word prephitmp.476;
+  _Atomic_word pretmp.475;
   int storetmp.473;
   volatile _Atomic_word * __mem.22;
   _Atomic_word __result;
@@ -3806,9 +3836,11 @@ Invalid sum of incoming frequencies 8415
   goto <bb 13>;

 <bb 29>:
+  pretmp.475_164 = D.8890_24->D.8307._M_use_count;

 <bb 12>:
-  __result_86 = D.8890_24->D.8307._M_use_count;
+  # prephitmp.476_144 = PHI <pretmp.475_164(29), D.8897_31(8)>
+  __result_86 = prephitmp.476_144;
   D.9413_88 = __result_86 + -1;
   *D.8895_29 ={v} D.9413_88;

before PRE this looks like

<bb 6>:
Invalid sum of incoming frequencies 8500, should be 7225
  D.8895_29 = &D.8890_24->D.8307._M_use_count;
...

<bb 8>:
  # VUSE <SMT.465_361, SMT.466_362>
  D.8897_31 = D.8890_24->D.8307._M_use_count;
  D.8898_32 = D.8897_31 + 1;
  # ctor_count_373 = VDEF <ctor_count_344(ab)>
  # ctor_count_374 = VDEF <ctor_count_345(ab)>
  # dtor_count_375 = VDEF <dtor_count_346(ab)>
  *D.8895_29 ={v} D.8898_32;
  goto <bb 12>;

...

<bb 29>:

<bb 12>:
  # MPT.471_203 = PHI <MPT.471_280(29), MPT.471_351(ab)(8)>
  # SMT.470_61 = PHI <SMT.470_260(29), SMT.470_350(ab)(8)>
  # SMT.467_59 = PHI <SMT.467_240(29), SMT.467_349(ab)(8)>
  # SMT.466_58 = PHI <SMT.466_220(29), SMT.466_362(8)>
  # SMT.465_54 = PHI <SMT.465_200(29), SMT.465_361(8)>
  # dtor_count_53 = PHI <dtor_count_180(29), dtor_count_375(8)>
  # ctor_count_52 = PHI <ctor_count_160(29), ctor_count_374(8)>
  # ctor_count_48 = PHI <ctor_count_140(29), ctor_count_373(8)>
  # VUSE <SMT.465_54, SMT.466_58>
  __result_86 = D.8890_24->D.8307._M_use_count;
  D.9413_88 = __result_86 + -1;
  # ctor_count_449 = VDEF <ctor_count_48>
  # ctor_count_450 = VDEF <ctor_count_52>
  # dtor_count_451 = VDEF <dtor_count_53>
  *D.8895_29 ={v} D.9413_88;


forwprop doesn't propagate the address expr &D.8890_24->D.8307._M_use_count
to the dereference because the dereference site has volatile ops.  But
you can see from <bb 8> that we have wrong alias info there - the load
does not use the ctor_count and dtor_count syms and the store does not
def the two SMTs.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33199