Address Richard's comment. Thanks Jim
Richard Sandiford <richard.sandif...@arm.com> 於 2024年12月30日 週一 下午7:50寫道：
>
> Tsung Chun Lin <tclin...@gmail.com> writes:
> > From ddb7852c92dc0222af9eeec1deafce753b3a7067 Mon Sep 17 00:00:00 2001
> > From: Jim Tsung-Chun Lin <j...@andestech.com>
> > Date: Mon, 30 Dec 2024 15:32:12 +0800
> > Subject: [PATCH] Prefer scalar_int_mode if the size - 1 is equal to
> > UNITS_PER_WORD.
> >
> > Don't use the QI vector if its size is equal to UNITS_PER_WORD for
> > better code generation.
>
> That makes sense, but...
>
> > Before patch:
> >
> > vsetivli zero,4,e8,mf4,ta,ma
> > vmv.v.i v1,0
> > addi a4,sp,12
> > vse8.v v1,0(a4)
> >
> > After patch:
> >
> > sw zero,12(sp)
> > ---
> > gcc/expr.cc | 2 +-
> > gcc/testsuite/gcc.target/riscv/rvv/autovec/pr113469.c | 1 -
> > 2 files changed, 1 insertion(+), 2 deletions(-)
> >
> > diff --git a/gcc/expr.cc b/gcc/expr.cc
> > index babf00f34dc..e2abef1f544 100644
> > --- a/gcc/expr.cc
> > +++ b/gcc/expr.cc
> > @@ -1062,7 +1062,7 @@ widest_fixed_size_mode_for_size (unsigned int size,
> > by_pieces_operation op)
> > gcc_checking_assert (size > 1);
> >
> > /* Use QI vector only if size is wider than a WORD. */
> > - if (can_use_qi_vectors (op) && size > UNITS_PER_WORD)
> > + if (can_use_qi_vectors (op) && (size - 1) > UNITS_PER_WORD)
>
> ...it looks like this will still use UNITS_PER_WORD QI vectors for
> size == UNITS_PER_WORD + 2.
>
> How about instead removing the size > UNITS_PER_WORD check above and
> instead checking:
>
> if (is_a<fixed_size_mode> (mode, &candidate)
> && GET_MODE_SIZE (candidate) > UNITS_PER_WORD
> && GET_MODE_INNER (candidate) == QImode)
>
> in the loop (with the second line being new)?
>
> Thanks,
> Richard
>
> > {
> > machine_mode mode;
> > fixed_size_mode candidate;
> > diff --git a/gcc/testsuite/gcc.target/riscv/rvv/autovec/pr113469.c
> > b/gcc/testsuite/gcc.target/riscv/rvv/autovec/pr113469.c
> > index 52e2580c53e..6549ae61c67 100644
> > --- a/gcc/testsuite/gcc.target/riscv/rvv/autovec/pr113469.c
> > +++ b/gcc/testsuite/gcc.target/riscv/rvv/autovec/pr113469.c
> > @@ -51,5 +51,4 @@ void p(int buf, __builtin_va_list ab, int q) {
> > } while (k);
> > }
> >
> > -/* { dg-final { scan-assembler-times
> > {vsetivli\tzero,\s*4,\s*e8,\s*mf4,\s*t[au],\s*m[au]} 1 } } */
> > /* { dg-final { scan-assembler-times
> > {vsetivli\tzero,\s*8,\s*e8,\s*mf2,\s*t[au],\s*m[au]} 1 } } */
0001-Prefer-scalar_int_mode-if-the-size-of-QI-vector-is-e.patch
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