https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84646
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |aldyh at gcc dot gnu.org
--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
(In reply to Jeffrey A. Law from comment #2)
> The backwards threader discovers the threads, but refuses to optimize them
> because it thinks doing so will create an irreducible loop without enough
> benefit.
The reason is now:
Checking profitability of path (backwards): bb:3 (2 insns) bb:7 (4 insns) bb:6
(1 insns) (latch) bb:5
Control statement insns: 2
Overall: 5 insns
Registering value_relation (path_oracle) (j_17 < m_23(D)) (root: bb5)
path: 5->6->7->3->xx REJECTED (unreachable)
it seems the path oracle is confused here.
<bb 3> [local count: 955630225]:
if (running_14 != 0)
goto <bb 4>; [50.00%]
else
goto <bb 6>; [50.00%]
<bb 4> [local count: 477815112]:
_1 = (long unsigned int) i_16;
_2 = _1 * 4;
_3 = p_25(D) + _2;
_4 = *_3;
_5 = (long unsigned int) j_17;
_6 = _5 * 4;
_7 = q_26(D) + _6;
_8 = *_7;
_9 = _4 * _8;
sum_27 = _9 + sum_11;
if (sum_27 > 19999)
goto <bb 5>; [50.00%]
else
goto <bb 6>; [50.00%]
<bb 5> [local count: 238907556]:
<bb 6> [local count: 955630225]:
# sum_10 = PHI <sum_11(3), 20000(5), sum_27(4)>
# running_13 = PHI <0(3), 0(5), 1(4)>
j_28 = j_17 + 1;
<bb 7> [local count: 1073741824]:
# sum_11 = PHI <sum_12(11), sum_10(6)>
# running_14 = PHI <running_15(11), running_13(6)>
# j_17 = PHI <0(11), j_28(6)>
if (j_17 < m_23(D))
goto <bb 3>; [89.00%]
else
goto <bb 8>; [11.00%]
