https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112384
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Target|aarch64 |aarch64, x86_64-*-*
Ever confirmed|0 |1
Status|UNCONFIRMED |NEW
Last reconfirmed| |2023-11-06
--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> ---
Confirmed. Note for f2 the target needs to support .VEC_EXTRACT with variable
index.
OTOH we miss to transform
i_4 = VIEW_CONVERT_EXPR<int[4]>(t)[i_2];
tt_5 = {i_4, i_4, i_4, i_4};
into
tt_3 = {i_2, i_2, i_2, i_2};
r_6 = VEC_PERM_EXPR <t_4(D), t_4(D), tt_3>;
but the complication is that 't' isn't in SSA form (which is also why
it goes through memory here).
On x86_64 with SSE4.1 we get
f1:
.LFB0:
.cfi_startproc
andl $3, %edi
movd %edi, %xmm2
pshufd $0, %xmm2, %xmm1
pslld $2, %xmm1
pshufb .LC1(%rip), %xmm1
paddb .LC2(%rip), %xmm1
pshufb %xmm1, %xmm0
ret
f2:
.LFB1:
.cfi_startproc
andl $3, %edi
movaps %xmm0, -24(%rsp)
movd -24(%rsp,%rdi,4), %xmm1
pshufd $0, %xmm1, %xmm0
ret
I suspect the memory case is actually faster. With AVX512VL this
improves to
f1:
.LFB0:
.cfi_startproc
andl $3, %edi
vmovdqa %xmm0, %xmm1
vpbroadcastd %edi, %xmm0
vpermi2d %xmm1, %xmm1, %xmm0
ret
f2:
.LFB1:
.cfi_startproc
andl $3, %edi
vmovdqa %xmm0, -24(%rsp)
vpbroadcastd -24(%rsp,%rdi,4), %xmm0
ret
AVX2 has the odd
f1:
.LFB0:
.cfi_startproc
andl $3, %edi
vinserti128 $1, %xmm0, %ymm0, %ymm0
vmovd %edi, %xmm2
vpbroadcastd %xmm2, %xmm1
vinserti128 $1, %xmm1, %ymm1, %ymm1
vpermd %ymm0, %ymm1, %ymm0
vzeroupper
ret
where sth feels wrong - f2 is similar to AVX512. It's not clear whether
the f1 IL is better in the end.
