https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99881
H.J. Lu <hjl.tools at gmail dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Last reconfirmed| |2021-04-02
Ever confirmed|0 |1
Status|UNCONFIRMED |NEW
--- Comment #1 from H.J. Lu <hjl.tools at gmail dot com> ---
(In reply to Hongtao.liu from comment #0)
> testcase is extracted from 557.xz_r
>
> void
> foo (int* __restrict a, int n, int c)
> {
> a[0] = n;
> a[1] = c;
> }
>
> gcc -O2 -ftree-vectorize -fvect-cost-model=very-cheap
>
> foo(int*, int, int):
> movd xmm0, esi
> movd xmm1, edx
> punpckldq xmm0, xmm1
> movq QWORD PTR [rdi], xmm0
> ret
>
> without vectorization
>
> foo(int*, int, int):
> mov DWORD PTR [rdi], esi
> mov DWORD PTR [rdi+4], edx
> ret
>
> cost model:
> scalar: 2 times scalar_store costs 24,
> vector: 1 times unaligned_store costs 12, vec_contruct 8
How is vec_contruct cost computed today?
