https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91355
Jakub Jelinek <jakub at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |ebotcazou at gcc dot gnu.org,
| |rth at gcc dot gnu.org
--- Comment #5 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
I'm afraid I don't know enough of the EH rules on what's wrong, so will just
try to describe what happens:
;; basic block 3, loop depth 0
;; pred: 2
_10 = __cxa_allocate_exception (4);
MEM[(int *)_10] = 3;
__cxa_throw (_10, &_ZTIi, 0B);
;; succ: 6
;; basic block 4, loop depth 0
;; pred: 2
d.0_14 = d;
_15 = d.0_14 + 1;
d = _15;
_6 = __cxa_allocate_exception (4);
MEM[(int *)_6] = 3;
__cxa_throw (_6, &_ZTIi, 0B);
;; succ: 5
;; basic block 5, loop depth 0
;; pred: 4
<L2>:
d.1_16 = d;
_17 = d.1_16 + 4294967295;
d = _17;
resx 4
;; succ: 6
;; basic block 6, loop depth 0
;; pred: 3
;; 5
<L3>:
_20 = __builtin_eh_filter (1);
if (_20 == -1)
goto <bb 8>; [0.00%]
else
goto <bb 7>; [0.00%]
;; succ: 8
;; 7
Now, if not -fno-tree-sink or Honza's change is in, sink changes that to:
;; basic block 5, loop depth 0, count 0 (precise), probably never executed
;; prev block 4, next block 10, flags: (NEW, REACHABLE, VISITED)
;; pred: 4 [never] count:0 (precise) (EH,EXECUTABLE)
<L2>:
resx 4
;; succ: 10 [never] count:0 (precise) (EH,EXECUTABLE)
;; basic block 10, loop depth 0, count 0 (precise), probably never executed
;; prev block 5, next block 9, flags: (NEW)
;; pred: 5 [never] count:0 (precise) (EH,EXECUTABLE)
<L7>:
d.1_16 = d;
_17 = d.1_16 + 4294967295;
d = _17;
goto <bb 6>; [100.00%]
;; succ: 6 [always] count:0 (precise) (FALLTHRU)
;; basic block 9, loop depth 0, count 0 (precise), probably never executed
;; prev block 10, next block 6, flags: (NEW)
;; pred: 3 [never] count:0 (precise) (EH,EXECUTABLE)
<L6>:
;; succ: 6 [always] count:0 (precise) (FALLTHRU)
;; basic block 6, loop depth 0, count 0 (precise), probably never executed
;; prev block 9, next block 7, flags: (NEW, REACHABLE, VISITED)
;; pred: 9 [always] count:0 (precise) (FALLTHRU)
;; 10 [always] count:0 (precise) (FALLTHRU)
<L3>:
_20 = __builtin_eh_filter (1);
if (_20 == -1)
goto <bb 8>; [0.00%]
else
goto <bb 7>; [0.00%]
;; succ: 8 [never] count:0 (precise) (TRUE_VALUE,EXECUTABLE)
;; 7 [never] count:0 (precise) (FALSE_VALUE,EXECUTABLE)
Before ehcleanup2 the difference is then (-fno-tree-sink -O1 vs. -ftree-sink
-O1):
;; basic block 5, loop depth 0
;; pred: 4
<L2>:
- d.1_16 = d;
- _17 = d.1_16 + 4294967295;
- d = _17;
resx 4
;; succ: 6
;; basic block 6, loop depth 0
+;; pred: 5
+<L7>:
+ d.1_16 = d;
+ _17 = d.1_16 + 4294967295;
+ d = _17;
+ goto <bb 8>; [100.00%]
+;; succ: 8
+
+;; basic block 7, loop depth 0
;; pred: 3
-;; 5
+<L6>:
+;; succ: 8
+
+;; basic block 8, loop depth 0
+;; pred: 7
+;; 6
<L3>:
_20 = __builtin_eh_filter (1);
Now, ehcleanup2 removes resx 4; for some reason:
Before removal of unreachable regions:
Eh tree:
- 1 allowed_exceptions land:{1,<L3>},{3,} filter :-1 types:int
+ 1 allowed_exceptions land:{4,<L6>},{1,<L7>},{3,} filter :-1 types:int
4 cleanup land:{2,<L2>}
Reachable regions: n_bits = 8, set = {1 4 }
-Reachable landing pads: n_bits = 4, set = {1 2 }
+Reachable landing pads: n_bits = 5, set = {1 2 4 }
Removing unreachable landing pad 3
After removal of unreachable regions:
Eh tree:
- 1 allowed_exceptions land:{1,<L3>} filter :-1 types:int
+ 1 allowed_exceptions land:{4,<L6>},{1,<L7>} filter :-1 types:int
4 cleanup land:{2,<L2>}
+Removing basic block 7
+Removing basic block 5
+Removing unreachable region 4
...
;; basic block 5, loop depth 0
;; pred: 4
-<L2>:
+<L7>:
d.1_16 = d;
_17 = d.1_16 + 4294967295;
d = _17;
- resx 4
;; succ: 6
and in *.optimized dump that means:
;; basic block 5, loop depth 0
;; pred: 4
-<L2>:
+<L7>:
d.1_16 = d;
_17 = d.1_16 + 4294967295;
d = _17;
- __builtin_eh_copy_values (1, 4);
;; succ: 6
change and abort.
