https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103723
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Last reconfirmed| |2021-12-15
Summary|Loop invariant motion pass |zero extend not moved out
|failed to remove unused |of the loop after IV-OPTS
|code from loop |
Ever confirmed|0 |1
Status|UNCONFIRMED |NEW
Severity|normal |enhancement
--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
>For this case, the instruction `mov ecx, eax` in bb `.L3` could remove
>from loop body and could sink to '.L8' and '.L1'.
Right the problem is not what you referenced in the comment #0 though, it is
the following instead:
_4 = (unsigned int) ivtmp.7_15;
That is a truncate from 64bit to 32bit.
There is no pass after IV-OPTS that sinks the zero extend out of the loop
though. LIM on the gimple level is not doing it for some reason ...
At Lim4 we have:
<bb 4> [local count: 1014686026]:
# ivtmp.7_15 = PHI <ivtmp.7_7(7), 2(6)>
_4 = (unsigned int) ivtmp.7_15;
len_test_13 = _4;
_3 = MEM[(const uint8_t *)buf_9(D) + ivtmp.7_15 * 1];
_6 = MEM[(const uint8_t *)buf_back_11(D) + ivtmp.7_15 * 1];
if (_3 == _6)
goto <bb 3>; [94.50%]
else
goto <bb 10>; [5.50%]
<bb 10> [local count: 55807731]:
# len_test_16 = PHI <len_test_13(4)>
I don't know enough about LIM if it was designed to handle non stores to sink
but maybe it should.
