Re: [PATCH] RISC-V: Fix uninitialized and redundant use of which_alternative

[Kito Cheng <kito.cheng@gmail.com>]

My first impression is those emit_insn (gen_rtx_SET()) seems
necessary, but I got the point after I checked vector.md :P

Committed to trunk, thanks :)


On Thu, Jul 27, 2023 at 6:23 PM juzhe.zhong@rivai.ai
<juzhe.zhong@rivai.ai> wrote:
>
> Oh, YES.
>
> Thanks for fixing it. It makes sense since the ternary operations in "vector.md"
> generate "vmv.v.v" according to RA.
>
> Thanks for fixing it.
>
> @kito: Could you confirm it? If it's ok to you, commit it for Han (I am lazy to commit patches :).
>
>
>
> juzhe.zhong@rivai.ai
>
> From: demin.han
> Date: 2023-07-27 17:48
> To: gcc-patches@gcc.gnu.org
> CC: kito.cheng@gmail.com; juzhe.zhong@rivai.ai
> Subject: [PATCH] RISC-V: Fix uninitialized and redundant use of which_alternative
> When pass split2 starts, which_alternative is random depending on
> last set of certain pass.
>
> Even initialized, the generated movement is redundant.
> The movement can be generated by assembly output template.
>
> Signed-off-by: demin.han <demin.han@starfivetech.com>
>
> gcc/ChangeLog:
>
> * config/riscv/autovec.md: Delete which_alternative use in split
>
> gcc/testsuite/ChangeLog:
>
> * gcc.target/riscv/rvv/autovec/madd-split2-1.c: New test.
>
> ---
> gcc/config/riscv/autovec.md                         | 12 ------------
> .../gcc.target/riscv/rvv/autovec/madd-split2-1.c    | 13 +++++++++++++
> 2 files changed, 13 insertions(+), 12 deletions(-)
> create mode 100644 gcc/testsuite/gcc.target/riscv/rvv/autovec/madd-split2-1.c
>
> diff --git a/gcc/config/riscv/autovec.md b/gcc/config/riscv/autovec.md
> index d899922586a..b7ea3101f5a 100644
> --- a/gcc/config/riscv/autovec.md
> +++ b/gcc/config/riscv/autovec.md
> @@ -1012,8 +1012,6 @@ (define_insn_and_split "*fma<VI:mode><P:mode>"
>    [(const_int 0)]
>    {
>      riscv_vector::emit_vlmax_vsetvl (<VI:MODE>mode, operands[4]);
> -    if (which_alternative == 2)
> -      emit_insn (gen_rtx_SET (operands[0], operands[3]));
>      rtx ops[] = {operands[0], operands[1], operands[2], operands[3], operands[0]};
>      riscv_vector::emit_vlmax_ternary_insn (code_for_pred_mul_plus (<VI:MODE>mode),
>    riscv_vector::RVV_TERNOP, ops, operands[4]);
> @@ -1058,8 +1056,6 @@ (define_insn_and_split "*fnma<VI:mode><P:mode>"
>    [(const_int 0)]
>    {
>      riscv_vector::emit_vlmax_vsetvl (<VI:MODE>mode, operands[4]);
> -    if (which_alternative == 2)
> -      emit_insn (gen_rtx_SET (operands[0], operands[3]));
>      rtx ops[] = {operands[0], operands[1], operands[2], operands[3], operands[0]};
>      riscv_vector::emit_vlmax_ternary_insn (code_for_pred_minus_mul (<VI:MODE>mode),
>         riscv_vector::RVV_TERNOP, ops, operands[4]);
> @@ -1102,8 +1098,6 @@ (define_insn_and_split "*fma<VF:mode><P:mode>"
>    [(const_int 0)]
>    {
>      riscv_vector::emit_vlmax_vsetvl (<VF:MODE>mode, operands[4]);
> -    if (which_alternative == 2)
> -      emit_insn (gen_rtx_SET (operands[0], operands[3]));
>      rtx ops[] = {operands[0], operands[1], operands[2], operands[3], operands[0]};
>      riscv_vector::emit_vlmax_fp_ternary_insn (code_for_pred_mul (PLUS, <VF:MODE>mode),
>       riscv_vector::RVV_TERNOP, ops, operands[4]);
> @@ -1148,8 +1142,6 @@ (define_insn_and_split "*fnma<VF:mode><P:mode>"
>    [(const_int 0)]
>    {
>      riscv_vector::emit_vlmax_vsetvl (<VF:MODE>mode, operands[4]);
> -    if (which_alternative == 2)
> -      emit_insn (gen_rtx_SET (operands[0], operands[3]));
>      rtx ops[] = {operands[0], operands[1], operands[2], operands[3], operands[0]};
>      riscv_vector::emit_vlmax_fp_ternary_insn (code_for_pred_mul_neg (PLUS, <VF:MODE>mode),
>       riscv_vector::RVV_TERNOP, ops, operands[4]);
> @@ -1194,8 +1186,6 @@ (define_insn_and_split "*fms<VF:mode><P:mode>"
>    [(const_int 0)]
>    {
>      riscv_vector::emit_vlmax_vsetvl (<VF:MODE>mode, operands[4]);
> -    if (which_alternative == 2)
> -      emit_insn (gen_rtx_SET (operands[0], operands[3]));
>      rtx ops[] = {operands[0], operands[1], operands[2], operands[3], operands[0]};
>      riscv_vector::emit_vlmax_fp_ternary_insn (code_for_pred_mul (MINUS, <VF:MODE>mode),
>       riscv_vector::RVV_TERNOP, ops, operands[4]);
> @@ -1242,8 +1232,6 @@ (define_insn_and_split "*fnms<VF:mode><P:mode>"
>    [(const_int 0)]
>    {
>      riscv_vector::emit_vlmax_vsetvl (<VF:MODE>mode, operands[4]);
> -    if (which_alternative == 2)
> -      emit_insn (gen_rtx_SET (operands[0], operands[3]));
>      rtx ops[] = {operands[0], operands[1], operands[2], operands[3], operands[0]};
>      riscv_vector::emit_vlmax_fp_ternary_insn (code_for_pred_mul_neg (MINUS, <VF:MODE>mode),
>       riscv_vector::RVV_TERNOP, ops, operands[4]);
> diff --git a/gcc/testsuite/gcc.target/riscv/rvv/autovec/madd-split2-1.c b/gcc/testsuite/gcc.target/riscv/rvv/autovec/madd-split2-1.c
> new file mode 100644
> index 00000000000..14a9802667e
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/riscv/rvv/autovec/madd-split2-1.c
> @@ -0,0 +1,13 @@
> +/* { dg-do compile } */
> +/* { dg-options "-march=rv64gcv_zvl256b -O3 -fno-cprop-registers -fno-dce --param riscv-autovec-preference=scalable" } */
> +
> +long
> +foo (long *__restrict a, long *__restrict b, long n)
> +{
> +  long i;
> +  for (i = 0; i < n; ++i)
> +    a[i] = b[i] + i * 8;
> +  return a[1];
> +}
> +
> +/* { dg-final { scan-assembler-times {\tvmv1r\.v} 1 } } */
> --
> 2.41.0
>
>