http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58662
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|ASSIGNED |NEW
Component|tree-optimization |rtl-optimization
Assignee|rguenth at gcc dot gnu.org |unassigned at gcc dot
gnu.org
Summary|wrong code at -O2 and -O3 |[4.9 Regression] wrong code
|on x86_64-linux-gnu (in |at -O2 and -O3 on
|64-bit mode) |x86_64-linux-gnu (in 64-bit
| |mode)
--- Comment #6 from Richard Biener <rguenth at gcc dot gnu.org> ---
Doesn't fail with -O2 -fno-tree-vrp.
The uncprop transform is correct.
_7 = _12 % 14;
if (_7 != 0)
goto <bb 3>;
else
goto <bb 7>;
<bb 7>:
goto <bb 4>;
<bb 3>:
c.4_9 = c;
_8 = c.4_9 != 0;
_13 = (int) _8;
<bb 4>:
iftmp.3_1 = PHI <_7(7), _13(3)>
we know that _7 is zero on the edge from BB 7.
What we now do is coalesce iftmp.3_1 with both _7 and _13 with also seems
correct. The initial RTL generated looks ok as well:
(insn 25 24 26 2 (parallel [
(set (reg:SI 83 [ D.1762 ])
(minus:SI (reg:SI 90 [ D.1762 ])
(reg:SI 106)))
(clobber (reg:CC 17 flags))
]) t.c:17 296 {*subsi_1}
(nil))
(insn 26 25 27 2 (set (reg:CCZ 17 flags)
(compare:CCZ (reg:SI 83 [ D.1762 ])
(const_int 0 [0]))) t.c:18 3 {*cmpsi_ccno_1}
(nil))
(jump_insn 27 26 28 2 (set (pc)
(if_then_else (eq (reg:CCZ 17 flags)
(const_int 0 [0]))
(label_ref 33)
(pc))) t.c:18 616 {*jcc_1}
(int_list:REG_BR_PROB 5000 (nil))
-> 33)
;; succ: 4 [50.0%] (FALLTHRU)
;; 5 [50.0%]
;; basic block 4, loop depth 0, count 0, freq 5000
;; prev block 2, next block 5, flags: (NEW, REACHABLE, RTL)
;; pred: 2 [50.0%] (FALLTHRU)
...
(insn 32 31 33 4 (set (reg:SI 83 [ D.1762 ])
(reg:SI 107 [ D.1763 ])) t.c:18 86 {*movsi_internal}
(nil))
;; succ: 5 [100.0%] (FALLTHRU)
;; basic block 5, loop depth 0, count 0, freq 10000, maybe hot
;; prev block 4, next block 6, flags: (NEW, REACHABLE, RTL)
;; pred: 2 [50.0%]
;; 4 [100.0%] (FALLTHRU)
(code_label 33 32 34 5 2 "" [1 uses])
(note 34 33 35 5 [bb 5] NOTE_INSN_BASIC_BLOCK)
(insn 35 34 36 5 (set (mem/v/c:SI (symbol_ref:DI ("b") <var_decl
0x7fc8088581c8 b>) [2 b+0 S4 A32])
(reg:SI 83 [ D.1762 ])) t.c:18 86 {*movsi_internal}
(nil))
it is combine where mysteriously all defining instructions for reg:SI 83
vanish. Not mine.
