Re: [PATCH] [PR target/97194] [AVX2] Support variable index vec_set.

[Hongtao Liu <crazylht@gmail.com>]

On Thu, Nov 12, 2020 at 5:15 PM Hongtao Liu <crazylht@gmail.com> wrote:
>
> On Thu, Nov 12, 2020 at 5:12 PM Hongtao Liu <crazylht@gmail.com> wrote:
> >
> > On Thu, Nov 12, 2020 at 4:21 PM Uros Bizjak <ubizjak@gmail.com> wrote:
> > >
> > > On Thu, Nov 12, 2020 at 3:04 AM Hongtao Liu <crazylht@gmail.com> wrote:
> > >
> > > > > > gcc/ChangeLog:
> > > > > >
> > > > > > PR target/97194
> > > > > > * config/i386/i386-expand.c (ix86_expand_vector_set_var): New function.
> > > > > > * config/i386/i386-protos.h (ix86_expand_vector_set_var): New Decl.
> > > > > > * config/i386/predicates.md (vec_setm_operand): New predicate,
> > > > > > true for const_int_operand or register_operand under TARGET_AVX2.
> > > > > > * config/i386/sse.md (vec_set<mode>): Support both constant
> > > > > > and variable index vec_set.
> > > > > >
> > > > > > gcc/testsuite/ChangeLog:
> > > > > >
> > > > > > * gcc.target/i386/avx2-vec-set-1.c: New test.
> > > > > > * gcc.target/i386/avx2-vec-set-2.c: New test.
> > > > > > * gcc.target/i386/avx512bw-vec-set-1.c: New test.
> > > > > > * gcc.target/i386/avx512bw-vec-set-2.c: New test.
> > > > > > * gcc.target/i386/avx512f-vec-set-2.c: New test.
> > > > > > * gcc.target/i386/avx512vl-vec-set-2.c: New test.
> > > > >
> > > > > +;; True for registers, or const_int_operand, used to vec_setm expander.
> > > > > +(define_predicate "vec_setm_operand"
> > > > > +  (ior (and (match_operand 0 "register_operand")
> > > > > +    (match_test "TARGET_AVX2"))
> > > > > +       (match_code "const_int")))
> > > > > +
> > > > >  ;; True for registers, or 1 or -1.  Used to optimize double-word shifts.
> > > > >  (define_predicate "reg_or_pm1_operand"
> > > > >    (ior (match_operand 0 "register_operand")
> > > > > diff --git a/gcc/config/i386/sse.md b/gcc/config/i386/sse.md
> > > > > index b153a87fb98..1798e5dea75 100644
> > > > > --- a/gcc/config/i386/sse.md
> > > > > +++ b/gcc/config/i386/sse.md
> > > > > @@ -8098,11 +8098,14 @@ (define_insn "vec_setv2df_0"
> > > > >  (define_expand "vec_set<mode>"
> > > > >    [(match_operand:V 0 "register_operand")
> > > > >     (match_operand:<ssescalarmode> 1 "register_operand")
> > > > > -   (match_operand 2 "const_int_operand")]
> > > > > +   (match_operand 2 "vec_setm_operand")]
> > > > >
> > > > > You need to specify a mode, otherwise a register of any mode can pass here.
> > > > >
> > > > Yes, theoretically, we only accept integer types. But in can_vec_set_var_idx_p
> > > > cut
> > > > ---
> > > > bool
> > > > can_vec_set_var_idx_p (machine_mode vec_mode)
> > > > {
> > > >   if (!VECTOR_MODE_P (vec_mode))
> > > >     return false;
> > > >
> > > >   machine_mode inner_mode = GET_MODE_INNER (vec_mode);
> > > >   rtx reg1 = alloca_raw_REG (vec_mode, LAST_VIRTUAL_REGISTER + 1);
> > > >   rtx reg2 = alloca_raw_REG (inner_mode, LAST_VIRTUAL_REGISTER + 2);
> > > >   rtx reg3 = alloca_raw_REG (VOIDmode, LAST_VIRTUAL_REGISTER + 3);
> > > >
> > > >   enum insn_code icode = optab_handler (vec_set_optab, vec_mode);
> > > >
> > > >   return icode != CODE_FOR_nothing && insn_operand_matches (icode, 0, reg1)
> > > >          && insn_operand_matches (icode, 1, reg2)
> > > >          && insn_operand_matches (icode, 2, reg3);
> > > > }
> > > > ---
> > > >
> > > > reg3 is assumed to be VOIDmode, set anymode in match_operand 2 will
> > > > fail insn_operand_matches (icode, 2, reg3)
> > > > ---
> > > > (gdb) p insn_operand_matches(icode,2,reg3)
> > > > $5 = false
> > > > (gdb)
> > > > ---
> > > >
> > > > Maybe we need to change
> > > >
> > > > rtx reg3 = alloca_raw_REG (VOIDmode, LAST_VIRTUAL_REGISTER + 3);
> > > >
> > > > to
> > > >
> > > > rtx reg3 = alloca_raw_REG (SImode, LAST_VIRTUAL_REGISTER + 3);
> > > >
> > > > cc Richard Biener, any thoughts?
> > >
> > > There are two targets (gcn in gcn-valu.md and s390 in vector.md) that
> > > specify SImode for operand 2 in vec_setM pattern and allow register
> > > operands. I wonder if and how they manage to generate the pattern.
> > >
> > > Uros.
> >
> > Variable index vec_set is enabled by r11-3486, about two months ago in
> > [1]. But for the upper two targets, the codes are already there since
> > GCC10(maybe earlier, i just looked at gcc10 branch), I don't think
> > those codes are for [1].
> >
> > [1] https://gcc.gnu.org/pipermail/gcc-patches/2020-October/555905.html
> >
> >
> > --
> > BR,
> > Hongtao
>
> Correct [1] https://gcc.gnu.org/pipermail/gcc-patches/2020-September/554240.html
>
> --
> BR,
> Hongtao

in https://gcc.gnu.org/pipermail/gcc-patches/2020-September/554592.html

It says

> >> +can_vec_set_var_idx_p (enum tree_code code, machine_mode vec_mode,
> >> +                      machine_mode value_mode, machine_mode idx_mode)
> >
> > toplevel comment missing
> >
> >> +{
> >> +  gcc_assert (code == VECTOR_TYPE);
> >
> > what's the point of pasing 'code' here then?  Since the optab only has a single
> > mode, the vector mode, the value_mode is redundant as well.  And I guess
> > we might want to handle "arbitrary" index modes?  That is, the .md expanders
> > should not restrict its mode - I guess it simply uses VOIDmode at the moment
> > (for integer constants).  Not sure how to best do this without an explicit mode
> > in the optab ...
>
> Yes, removed 'code' and value_mode by checking VECTOR_MODE_P and use GET_MODE_INNER
> for value_mode.  ".md expanders" shall support for integer constants index mode, but
> I guess they shouldn't be expanded by IFN as this function is for variable index
> insert only?  Anyway, the v3 patch used VOIDmode check...


-- 
BR,
Hongtao