On Mon, May 31, 2021 at 11:13 AM H.J. Lu <hjl.to...@gmail.com> wrote:
>
> On Mon, May 31, 2021 at 11:07 AM Jeff Law <jeffreya...@gmail.com> wrote:
> >
> >
> >
> > On 5/31/2021 6:04 AM, H.J. Lu wrote:
> > > On Sun, May 30, 2021 at 11:49 AM Jeff Law <jeffreya...@gmail.com> wrote:
> > >>
> > >>
> > >> On 5/11/2021 5:35 PM, H.J. Lu via Gcc-patches wrote:
> > >>> Add TARGET_READ_MEMSET_VALUE and TARGET_GEN_MEMSET_VALUE to support
> > >>> target instructions to duplicate QImode value to TImode/OImode/XImode
> > >>> value for memmset. Define SCRATCH_SSE_REG as a scratch register for
> > >>> ix86_gen_memset_value.
> > >>>
> > >>> gcc/
> > >>>
> > >>> PR middle-end/90773
> > >>> * builtins.c (builtin_memset_read_str): Call
> > >>> targetm.read_memset_value.
> > >>> (builtin_memset_gen_str): Call targetm.gen_memset_value.
> > >>> * target.def (read_memset_value): New hook.
> > >>> (gen_memset_value): Likewise.
> > >>> * targhooks.c: Inclue "builtins.h".
> > >>> (default_read_memset_value): New function.
> > >>> (default_gen_memset_value): Likewise.
> > >>> * targhooks.h (default_read_memset_value): New prototype.
> > >>> (default_gen_memset_value): Likewise.
> > >>> * config/i386/i386-expand.c (ix86_expand_vector_init_duplicate):
> > >>> Make it global.
> > >>> * config/i386/i386-protos.h
> > >>> (ix86_minimum_incoming_stack_boundary):
> > >>> New.
> > >>> (ix86_expand_vector_init_duplicate): Likewise.
> > >>> * config/i386/i386.c (ix86_minimum_incoming_stack_boundary): Add
> > >>> an argument to ignore stack_alignment_estimated. It is passed
> > >>> as false by default.
> > >>> (ix86_gen_memset_value_from_prev): New function.
> > >>> (ix86_gen_memset_value): Likewise.
> > >>> (ix86_read_memset_value): Likewise.
> > >>> (TARGET_GEN_MEMSET_VALUE): New.
> > >>> (TARGET_READ_MEMSET_VALUE): Likewise.
> > >>> * config/i386/i386.h (SCRATCH_SSE_REG): New.
> > >>> * doc/tm.texi.in: Add TARGET_READ_MEMSET_VALUE and
> > >>> TARGET_GEN_MEMSET_VALUE hooks.
> > >>> * doc/tm.texi: Regenerated.
> > >>>
> > >>> gcc/testsuite/
> > >>>
> > >>> PR middle-end/90773
> > >>> * gcc.target/i386/pr90773-15.c: New test.
> > >>> * gcc.target/i386/pr90773-16.c: Likewise.
> > >>> * gcc.target/i386/pr90773-17.c: Likewise.
> > >>> * gcc.target/i386/pr90773-18.c: Likewise.
> > >>> * gcc.target/i386/pr90773-19.c: Likewise.
> > >> Why does this need target hooks? ISTM the right way to go here is to
> > >> just emit the constant load to the target register and let the target
> > >> figure out how best to construct the constant into the register. If
> > >> that means load it via QImode and broadcast, that's fine, but I'm not
> > >> sure why that's not all implemented in the target files.
> > >>
> > > I will submit a patch to add optabs instead.
> > I may be missing something, but I'm not even sure why we need special
> > optabs.
> >
> > Aren't you just trying to efficiently get a constant element broadcast
> > across an entire vector?
>
> Since vec_duplicate must not fail and for broadcast from a constant QImode
> value, vec_duplicate may not be faster than a compile-time constant, I am
> adding vec_const_duplicate. If vec_duplicate can fail, I don't need
> vec_const_duplicate.
>
> --
> H.J.
For
extern void *ops;
void
foo (int c)
{
__builtin_memset (ops, 4, 32);
}
without vec_const_duplicate, I got
movl $4, %eax
movq ops(%rip), %rdx
movd %eax, %xmm0
punpcklbw %xmm0, %xmm0
punpcklwd %xmm0, %xmm0
pshufd $0, %xmm0, %xmm0
movups %xmm0, (%rdx)
movups %xmm0, 16(%rdx)
ret
with vec_const_duplicate, I got
movq ops(%rip), %rax
movdqa .LC0(%rip), %xmm0
movups %xmm0, (%rax)
movups %xmm0, 16(%rax)
ret
--
H.J.
