https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80819
Jakub Jelinek <jakub at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |uros at gcc dot gnu.org,
| |vmakarov at gcc dot gnu.org
--- Comment #6 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
The dead stores are created during LRA, e.g. with -mtune=haswell we get:
(insn 3 5 4 2 (set (mem/c:DI (plus:DI (reg/f:DI 7 sp)
(const_int -16 [0xfffffffffffffff0])) [2 %sfp+-8 S8 A64])
(reg:DI 4 si [ b ])) "pr80819.c":2 85 {*movdi_internal}
(nil))
(note 4 3 17 2 NOTE_INSN_FUNCTION_BEG)
(insn 17 4 19 2 (set (reg:DI 21 xmm0 [91])
(reg/v:DI 5 di [orig:88 a ] [88])) "include/emmintrin.h":591 85
{*movdi_internal}
(nil))
(note 19 17 20 2 NOTE_INSN_DELETED)
(note 20 19 7 2 NOTE_INSN_DELETED)
(insn 7 20 12 2 (set (reg:V2DI 21 xmm0 [91])
(vec_concat:V2DI (reg:DI 21 xmm0 [91])
(mem/c:DI (plus:DI (reg/f:DI 7 sp)
(const_int -16 [0xfffffffffffffff0])) [2 %sfp+-8 S8 A64])))
"include/emmintrin.h":591 3738 {vec_concatv2di}
(nil))
That is weird, because vec_concatv2di has:
(define_insn "vec_concatv2di"
[(set (match_operand:V2DI 0 "register_operand"
"=Yr,*x,x ,v ,Yi,v ,x ,x,v ,x,x,v")
(vec_concat:V2DI
(match_operand:DI 1 "nonimmediate_operand"
" 0, 0,x ,Yv,r ,vm,?!*Yn,0,Yv,0,0,v")
(match_operand:DI 2 "vector_move_operand"
"*rm,rm,rm,rm,C ,C ,C ,x,Yv,x,m,m")))]
constraints, so if it is able to reload the first vec_concat operand into the
destination register, why doesn't it pick the alternative (=Yr,0,*rm) or
(=*x,0,rm)? Is that because of the asterisks?
Shouldn't we help RA and have an alternative with (=Yi,r,r) guarded with x64
isa that would be split into movd + pinsrq?
