Re: [PATCH] [ARC] Recognise add_n and sub_n in combine again

[Claudiu Zissulescu <claziss@gmail.com>]

Hi Graham,

May I ask if you tested this with gcc's dejagnu?

Thanks,
Claudiu

On Fri, May 12, 2017 at 9:14 PM, Graham Markall
<graham.markall@embecosm.com> wrote:
> Since the combine pass canonicalises shift-add insns using plus and
> ashift (as opposed to plus and mult which it previously used to do), it
> no longer creates *add_n or *sub_n insns, as the patterns match plus and
> mult only. The outcome of this is that some opportunities to generate
> add{1,2,3} and sub{1,2,3} instructions are missed.
>
> This change adds additional *add_n and *sub_n insns that match the
> plus-ashift pattern. The original *add_n and *sub_n insns are still left
> in, as they are sometimes generated later on by constant propagation.
> The idea of adding these insns is modelled on the changes in:
>
>   https://gcc.gnu.org/ml/gcc-patches/2015-05/msg01882.html
>
> which addresses a similar issue for the PA target.
>
> For the small test cases that are added, even if the combine pass misses
> the opportunity to generate addN or subN, constant propagation manages
> to do so, so the rtl of the combine pass is checked.
>
> gcc/ChangeLog:
>
>         * config/arc/arc.c (arc_print_operand): Handle constant operands.
>         (arc_rtx_costs): Add costs for new patterns.
>         * config/arc/arc.md: Additional *add_n and *sub_n patterns.
>         * config/arc/predicates.md: Add _1_2_3_operand predicate.
>
> gcc/testsuite/ChangeLog:
>
>         * gcc.target/arc/add_n-combine.c: New.
>         * gcc.target/arc/sub_n-combine.c: New.
> ---
>  gcc/ChangeLog                                |  7 ++++
>  gcc/config/arc/arc.c                         | 20 +++++++++---
>  gcc/config/arc/arc.md                        | 26 +++++++++++++++
>  gcc/config/arc/predicates.md                 |  5 +++
>  gcc/testsuite/ChangeLog                      |  5 +++
>  gcc/testsuite/gcc.target/arc/add_n-combine.c | 48 ++++++++++++++++++++++++++++
>  gcc/testsuite/gcc.target/arc/sub_n-combine.c | 21 ++++++++++++
>  7 files changed, 128 insertions(+), 4 deletions(-)
>  create mode 100644 gcc/testsuite/gcc.target/arc/add_n-combine.c
>  create mode 100644 gcc/testsuite/gcc.target/arc/sub_n-combine.c
>
> diff --git a/gcc/config/arc/arc.c b/gcc/config/arc/arc.c
> index 91c28e7..42730d5 100644
> --- a/gcc/config/arc/arc.c
> +++ b/gcc/config/arc/arc.c
> @@ -3483,6 +3483,14 @@ arc_print_operand (FILE *file, rtx x, int code)
>
>        return;
>
> +    case 'c':
> +      if (GET_CODE (x) == CONST_INT)
> +        fprintf (file, "%d", INTVAL (x) );
> +      else
> +        output_operand_lossage ("invalid operands to %%c code");
> +
> +      return;
> +
>      case 'M':
>        if (GET_CODE (x) == CONST_INT)
>         fprintf (file, "%d",exact_log2(~INTVAL (x)) );
> @@ -4895,8 +4903,10 @@ arc_rtx_costs (rtx x, machine_mode mode, int outer_code,
>         *total = COSTS_N_INSNS (2);
>        return false;
>      case PLUS:
> -      if (GET_CODE (XEXP (x, 0)) == MULT
> -         && _2_4_8_operand (XEXP (XEXP (x, 0), 1), VOIDmode))
> +      if ((GET_CODE (XEXP (x, 0)) == ASHIFT
> +          && _1_2_3_operand (XEXP (XEXP (x, 0), 1), VOIDmode))
> +          || (GET_CODE (XEXP (x, 0)) == MULT
> +              && _2_4_8_operand (XEXP (XEXP (x, 0), 1), VOIDmode)))
>         {
>           *total += (rtx_cost (XEXP (x, 1), mode, PLUS, 0, speed)
>                      + rtx_cost (XEXP (XEXP (x, 0), 0), mode, PLUS, 1, speed));
> @@ -4904,8 +4914,10 @@ arc_rtx_costs (rtx x, machine_mode mode, int outer_code,
>         }
>        return false;
>      case MINUS:
> -      if (GET_CODE (XEXP (x, 1)) == MULT
> -         && _2_4_8_operand (XEXP (XEXP (x, 1), 1), VOIDmode))
> +      if ((GET_CODE (XEXP (x, 1)) == ASHIFT
> +          && _1_2_3_operand (XEXP (XEXP (x, 1), 1), VOIDmode))
> +          || (GET_CODE (XEXP (x, 1)) == MULT
> +              && _2_4_8_operand (XEXP (XEXP (x, 1), 1), VOIDmode)))
>         {
>           *total += (rtx_cost (XEXP (x, 0), mode, PLUS, 0, speed)
>                      + rtx_cost (XEXP (XEXP (x, 1), 0), mode, PLUS, 1, speed));
> diff --git a/gcc/config/arc/arc.md b/gcc/config/arc/arc.md
> index edb983f..ec783a0 100644
> --- a/gcc/config/arc/arc.md
> +++ b/gcc/config/arc/arc.md
> @@ -2995,6 +2995,19 @@
>
>  (define_insn "*add_n"
>    [(set (match_operand:SI 0 "dest_reg_operand" "=Rcqq,Rcw,W,W,w,w")
> +       (plus:SI (ashift:SI (match_operand:SI 1 "register_operand" "Rcqq,c,c,c,c,c")
> +                           (match_operand:SI 2 "_1_2_3_operand" ""))
> +                (match_operand:SI 3 "nonmemory_operand" "0,0,c,?Cal,?c,??Cal")))]
> +  ""
> +  "add%c2%? %0,%3,%1%&"
> +  [(set_attr "type" "shift")
> +   (set_attr "length" "*,4,4,8,4,8")
> +   (set_attr "predicable" "yes,yes,no,no,no,no")
> +   (set_attr "cond" "canuse,canuse,nocond,nocond,nocond,nocond")
> +   (set_attr "iscompact" "maybe,false,false,false,false,false")])
> +
> +(define_insn "*add_n"
> +  [(set (match_operand:SI 0 "dest_reg_operand" "=Rcqq,Rcw,W,W,w,w")
>         (plus:SI (mult:SI (match_operand:SI 1 "register_operand" "Rcqq,c,c,c,c,c")
>                           (match_operand:SI 2 "_2_4_8_operand" ""))
>                  (match_operand:SI 3 "nonmemory_operand" "0,0,c,?Cal,?c,??Cal")))]
> @@ -3011,6 +3024,19 @@
>  (define_insn "*sub_n"
>    [(set (match_operand:SI 0 "dest_reg_operand" "=Rcw,w,w")
>         (minus:SI (match_operand:SI 1 "nonmemory_operand" "0,c,?Cal")
> +                 (ashift:SI (match_operand:SI 2 "register_operand" "c,c,c")
> +                            (match_operand:SI 3 "_1_2_3_operand" ""))))]
> +  ""
> +  "sub%c3%? %0,%1,%2"
> +  [(set_attr "type" "shift")
> +   (set_attr "length" "4,4,8")
> +   (set_attr "predicable" "yes,no,no")
> +   (set_attr "cond" "canuse,nocond,nocond")
> +   (set_attr "iscompact" "false")])
> +
> +(define_insn "*sub_n"
> +  [(set (match_operand:SI 0 "dest_reg_operand" "=Rcw,w,w")
> +       (minus:SI (match_operand:SI 1 "nonmemory_operand" "0,c,?Cal")
>                   (mult:SI (match_operand:SI 2 "register_operand" "c,c,c")
>                            (match_operand:SI 3 "_2_4_8_operand" ""))))]
>    ""
> diff --git a/gcc/config/arc/predicates.md b/gcc/config/arc/predicates.md
> index 7ddec91..1f66438 100644
> --- a/gcc/config/arc/predicates.md
> +++ b/gcc/config/arc/predicates.md
> @@ -615,6 +615,11 @@
>             (match_test "TARGET_ARC700 || TARGET_EA_SET")))
>  )
>
> +(define_predicate "_1_2_3_operand"
> +  (and (match_code "const_int")
> +       (match_test "INTVAL (op) == 1 || INTVAL (op) == 2 || INTVAL (op) == 3"))
> +)
> +
>  (define_predicate "_2_4_8_operand"
>    (and (match_code "const_int")
>         (match_test "INTVAL (op) == 2 || INTVAL (op) == 4 || INTVAL (op) == 8"))
> diff --git a/gcc/testsuite/gcc.target/arc/add_n-combine.c b/gcc/testsuite/gcc.target/arc/add_n-combine.c
> new file mode 100644
> index 0000000..db6454f
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/arc/add_n-combine.c
> @@ -0,0 +1,48 @@
> +/* { dg-do compile }  */
> +/* { dg-options "-O2 -fdump-rtl-combine" }  */
> +
> +struct b1 {
> +      char c;
> +      char bg;
> +};
> +
> +struct bj1 {
> +  char bk;
> +  struct b1 bn[];
> +};
> +
> +struct b2 {
> +      short c;
> +      char bg;
> +};
> +
> +struct bj2 {
> +  short bk;
> +  struct b2 bn[];
> +};
> +
> +struct b3 {
> +      int c;
> +      char bg;
> +};
> +
> +struct bj3 {
> +  int bk;
> +  struct b3 bn[];
> +};
> +
> +
> +struct bj1 at1;
> +struct bj2 at2;
> +struct bj3 at3;
> +
> +int bu;
> +void a();
> +
> +void f() {
> +  a(at1.bn[bu]);
> +  a(at2.bn[bu]);
> +  a(at3.bn[bu]);
> +}
> +
> +/* { dg-final { scan-rtl-dump-times "\\*add_n" 3 "combine" } } */
> diff --git a/gcc/testsuite/gcc.target/arc/sub_n-combine.c b/gcc/testsuite/gcc.target/arc/sub_n-combine.c
> new file mode 100644
> index 0000000..4e227e4
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/arc/sub_n-combine.c
> @@ -0,0 +1,21 @@
> +/* { dg-do compile }  */
> +/* { dg-options "-O2 -fdump-rtl-combine" }  */
> +
> +int a;
> +
> +double b1() {
> +  int c = a << 1;
> +  return 1 - c;
> +}
> +
> +double b2() {
> +  int c = a << 2;
> +  return 1 - c;
> +}
> +
> +double b3() {
> +  int c = a << 3;
> +  return 1 - c;
> +}
> +
> +/* { dg-final { scan-rtl-dump-times "\\*sub_n" 3 "combine" } } */
> --
> 2.9.3
>