https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85375
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |NEW
Last reconfirmed| |2018-04-12
Blocks| |85316
Ever confirmed|0 |1
--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
.optimized shows
<bb 2> [local count: 114863532]:
_8 = __builtin_ffs (x_4(D));
if (_8 != 0)
goto <bb 3>; [94.50%]
else
goto <bb 7>; [5.50%]
<bb 3> [local count: 108546038]:
if (x_4(D) != 0)
goto <bb 4>; [94.50%]
else
goto <bb 7>; [5.50%]
missed jump-threading.
<bb 5> [local count: 958878293]:
# x_10 = PHI <x_4(D)(4), x_6(6)>
x_6 = x_10 - a.0_1;
_2 = __builtin_ffs (x_6);
if (_2 != 0)
goto <bb 6>; [94.50%]
else
goto <bb 7>; [5.50%]
<bb 6> [local count: 906139986]:
if (x_6 != 0)
goto <bb 5>; [94.50%]
else
goto <bb 7>; [5.50%]
likewise. VRP needs to derive a range for x_6 from _2 != 0.
Referenced Bugs:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85316
[Bug 85316] [meta-bug] VRP range propagation missed cases
