https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107916
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Version|unknown |13.0
--- Comment #5 from Richard Biener <rguenth at gcc dot gnu.org> ---
Vector lowering does only lower "operations", it doesn't touch data transfer
which means {reg,mem} <-> {mem,reg} copies, even if performed as part of
PHI node copies. In the end this means unsupported vector modes will be
expanded to the stack variables. Note there's later forwprop which will
deal with the loads/stores in most cases (but that's really an
afterthought), nothing handles the (loop) PHI node case so we end up with
<bb 4> [local count: 955630225]:
# c_15 = PHI <c_12(4), { 0, 0, 0, 0, 0, 0, 0, 0 }(3)>
# i_17 = PHI <i_13(4), 0(3)>
_4 = BIT_FIELD_REF <c_15, 128, 0>;
_6 = _4 + _5;
_18 = BIT_FIELD_REF <c_15, 128, 128>;
_19 = _14 + _18;
c_12 = {_6, _19};
i_13 = i_17 + 1;
if (n_7(D) != i_13)
goto <bb 4>; [89.00%]
else
goto <bb 5>; [11.00%]
<bb 5> [local count: 118111600]:
# c_16 = PHI <c_12(4), { 0, 0, 0, 0, 0, 0, 0, 0 }(2)>
Vector lowering would need to work more like Complex lowering to improve
things here. I'm not sure if stmt-by-stmt lowering of PHIs and
other reg-reg copies will give the desired results (esp. when backedges
are involved).
