------- Comment #24 from rguenth at gcc dot gnu dot org 2007-05-13 13:02
-------
That leaves aliasing and DCE.
The following statement connects to the initializing of the function pointer.
# SFT.78D.2952_55 = V_MAY_DEF <SFT.78D.2952_31>;
# VUSE <D.2838_29>;
thisD.2828_22->functor_D.2399 = D.2838;
but,
D.2839_30 = 0B;
# SFT.78D.2952_32 = V_MUST_DEF <SFT.78D.2952_55>;
D.2831.bound1_D.2423 = D.2839_30;
kills it. Still they look like they are accessing different fields
(propagating pointers for the first expression):
# SFT.78D.2952_55 = V_MAY_DEF <SFT.78D.2952_31>;
# VUSE <D.2838_29>;
D.2831.D.2432.functor_D.2382.functor_D.2399 = D.2838;
so my hint at a frontend problem with type-layout. Scheduling some more
early cleanup passes before the first DCE shows this (and fixes the
segfault!?):
# SFT.79D.2951_66 = V_MUST_DEF <SFT.79D.2951_49>;
# VUSE <D.2836_27>;
D.2435.D.2432.functor_D.2382.functor_D.2399 = D.2836;
D.2837_28 = 0B;
# SFT.78D.2950_30 = V_MUST_DEF <SFT.78D.2950_29>;
D.2435.bound1_D.2423 = D.2837_28;
note how we no longer thing the second store kills the first one. Which
makes it look like an aliasing problem again. Scheduling another may_alias
pass before the first DCE also fixes the problem, as we then have
# SFT.88D.2960_48 = V_MAY_DEF <SFT.88D.2960_29>;
# SFT.89D.2961_61 = V_MAY_DEF <SFT.89D.2961_49>;
# VUSE <D.2836_27>;
thisD.2827_20->functor_D.2399 = D.2836;
D.2837_28 = 0B;
# SFT.88D.2960_30 = V_MUST_DEF <SFT.88D.2960_48>;
D.2435.bound1_D.2423 = D.2837_28;
aliasing is fixed as long as the extra may_alias pass is after CCP, but that
CCP pass doesn't do too much interesting stuff to the above stmts:
# SFT.88D.2960_48 = V_MAY_DEF <SFT.88D.2960_29>;
# VUSE <D.2836_27>;
thisD.2827_20->functor_D.2399 = D.2836;
# VUSE <_A_b1D.2819_9>;
- D.2837_28 = *_A_bound1D.2820_11;
+ D.2837_28 = _A_b1D.2819;
# SFT.88D.2960_30 = V_MUST_DEF <SFT.88D.2960_48>;
D.2435.bound1_D.2423 = D.2837_28;
and if you diff a may_alias pass before and after CCP you get
@@ -487,20 +489,20 @@
_A_bound1_11 = { _A_b1 }
this_12 = { D.2435 D.2435.bound1_ }
D.2435 = { }
-D.2435.bound1_ = { NULL }
+D.2435.bound1_ = { NULL foo }
this_13 = { D.2435 D.2435.bound1_ }
_A_functor_14 = { D.2328 }
this_15 = { D.2435 D.2435.bound1_ }
this_16 = { D.2435 D.2435.bound1_ }
this_17 = { D.2435 D.2435.bound1_ }
this_18 = { D.2435 D.2435.bound1_ }
-this_19 = { D.2435.bound1_ }
-this_20 = { D.2435.bound1_ }
+this_19 = { D.2435 D.2435.bound1_ }
+this_20 = { D.2435 D.2435.bound1_ }
_A_functor_21 = { D.2328 }
-this_22 = { D.2435.bound1_ }
-this_23 = { D.2435.bound1_ }
-this_24 = { D.2435.bound1_ }
-this_25 = { D.2435.bound1_ }
+this_22 = { D.2435 D.2435.bound1_ }
+this_23 = { D.2435 D.2435.bound1_ }
+this_24 = { D.2435 D.2435.bound1_ }
+this_25 = { D.2435 D.2435.bound1_ }
D.2836 = { foo }
D.2837_28 = { NULL }
functor_31 = { D.2435 D.2435.bound1_ }
@@ -510,8 +512,6 @@
functor_35 = { D.2435 D.2435.bound1_ }
this_36 = { NULL NONLOCAL.105 foo call_it }
this_37 = { NULL NONLOCAL.105 foo call_it }
-structcopydereftmp.127 = { NULL }
-structcopydereftmp.127.bound1_ = { NULL }
rep_38 = { NULL NONLOCAL.105 foo call_it }
this_39 = { D.2301 }
D.2301 = { NULL NONLOCAL.105 foo call_it }
@@ -524,7 +524,7 @@
call_it = { NULL NONLOCAL.105 foo call_it }
D.2967_47 = { call_it }
which should be the most interesting parts of the diff (apart from the
extra vops that prevent the DCE).
Danny? Any hints on what can go wrong here?
--
rguenth at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |dberlin at gcc dot gnu dot
| |org
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=30252
