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

[Graham Markall <graham.markall@embecosm.com>]

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Hi Claudiu,

I ran the gcc testsuite with EZsim for NPS-400:

$ ./EZsim_linux_x86_64 --version
NPS-400 EZsim      - Version 1.9a ( 35b02d7, Nov  3 2015, 20:14:04 )

both with and without the patch, and it did not introduce any new failures.


Best regards,
Graham.

On 15/05/17 17:48, Claudiu Zissulescu wrote:
> 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
>>



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