https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100253
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |NEW
Component|rtl-optimization |tree-optimization
Last reconfirmed| |2021-04-25
Ever confirmed|0 |1
--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
The problem is right away in expand:
;; vect__36.383_12 = MEM <vector(1) __int128 unsigned> [(char * {ref-all})_10 +
16B];
(insn 23 22 0 (set (reg:V1TI 88 [ vect__36.383 ])
(mem:V1TI (plus:DI (reg/f:DI 86 [ _10 ])
(const_int 16 [0x10])) [0 MEM <vector(1) __int128 unsigned>
[(char * {ref-all})_10 + 16B]+0 S16 A128])) -1
(nil))
I think SLP did not mark the load as unaligned even though it knows it is one:
t.cc:7:8: note: Vectorizing an unaligned access.
t.cc:7:8: note: vect_model_load_cost: unaligned supported by hardware.
t.cc:7:8: note: vect_model_load_cost: inside_cost = 24, prologue_cost = 0 .
t.cc:7:8: note: ==> examining statement: MEM <__int128 unsigned> [(char *
{ref-all})&s + 25B] = _36;
t.cc:7:8: note: vect_is_simple_use: operand # VUSE <.MEM_30>
MEM <__int128 unsignedD.19> [(charD.10 * {ref-all})_10], type of def: internal
t.cc:7:8: note: vect_is_simple_use: operand # VUSE <.MEM_35>
MEM <__int128 unsignedD.19> [(charD.10 * {ref-all})_19], type of def: internal
t.cc:7:8: note: Vectorizing an unaligned access.
t.cc:7:8: note: vect_model_store_cost: unaligned supported by hardware.
Confirmed.
When -fno-tree-bit-ccp is turned off, the prop of the unalignedness does not
happen.
