On Tue, Sep 3, 2024 at 2:34 PM <pan2...@intel.com> wrote:
>
> From: Pan Li <pan2...@intel.com>
>
> This patch would like to support the form 2 of the scalar signed
> integer .SAT_ADD. Aka below example:
>
> Form 2:
> #define DEF_SAT_S_ADD_FMT_2(T, UT, MIN, MAX) \
> T __attribute__((noinline)) \
> sat_s_add_##T##_fmt_2 (T x, T y) \
> { \
> T sum = (UT)x + (UT)y; \
> \
> if ((x ^ y) < 0 || (sum ^ x) >= 0) \
> return sum; \
> \
> return x < 0 ? MIN : MAX; \
> }
>
> DEF_SAT_S_ADD_FMT_2(int8_t, uint8_t, INT8_MIN, INT8_MAX)
>
> We can tell the difference before and after this patch if backend
> implemented the ssadd<m>3 pattern similar as below.
>
> Before this patch:
> 4 │ __attribute__((noinline))
> 5 │ int8_t sat_s_add_int8_t_fmt_2 (int8_t x, int8_t y)
> 6 │ {
> 7 │ int8_t sum;
> 8 │ unsigned char x.0_1;
> 9 │ unsigned char y.1_2;
> 10 │ unsigned char _3;
> 11 │ signed char _4;
> 12 │ signed char _5;
> 13 │ int8_t _6;
> 14 │ _Bool _11;
> 15 │ signed char _12;
> 16 │ signed char _13;
> 17 │ signed char _14;
> 18 │ signed char _22;
> 19 │ signed char _23;
> 20 │
> 21 │ ;; basic block 2, loop depth 0
> 22 │ ;; pred: ENTRY
> 23 │ x.0_1 = (unsigned char) x_7(D);
> 24 │ y.1_2 = (unsigned char) y_8(D);
> 25 │ _3 = x.0_1 + y.1_2;
> 26 │ sum_9 = (int8_t) _3;
> 27 │ _4 = x_7(D) ^ y_8(D);
> 28 │ _5 = x_7(D) ^ sum_9;
> 29 │ _23 = ~_4;
> 30 │ _22 = _5 & _23;
> 31 │ if (_22 >= 0)
> 32 │ goto <bb 4>; [42.57%]
> 33 │ else
> 34 │ goto <bb 3>; [57.43%]
> 35 │ ;; succ: 4
> 36 │ ;; 3
> 37 │
> 38 │ ;; basic block 3, loop depth 0
> 39 │ ;; pred: 2
> 40 │ _11 = x_7(D) < 0;
> 41 │ _12 = (signed char) _11;
> 42 │ _13 = -_12;
> 43 │ _14 = _13 ^ 127;
> 44 │ ;; succ: 4
> 45 │
> 46 │ ;; basic block 4, loop depth 0
> 47 │ ;; pred: 2
> 48 │ ;; 3
> 49 │ # _6 = PHI <sum_9(2), _14(3)>
> 50 │ return _6;
> 51 │ ;; succ: EXIT
> 52 │
> 53 │ }
>
> After this patch:
> 4 │ __attribute__((noinline))
> 5 │ int8_t sat_s_add_int8_t_fmt_2 (int8_t x, int8_t y)
> 6 │ {
> 7 │ int8_t _6;
> 8 │
> 9 │ ;; basic block 2, loop depth 0
> 10 │ ;; pred: ENTRY
> 11 │ _6 = .SAT_ADD (x_7(D), y_8(D)); [tail call]
> 12 │ return _6;
> 13 │ ;; succ: EXIT
> 14 │
> 15 │ }
>
> The below test suites are passed for this patch.
> * The rv64gcv fully regression test.
> * The x86 bootstrap test.
> * The x86 fully regression test.
>
> gcc/ChangeLog:
>
> * match.pd: Add the form 2 of signed .SAT_ADD matching.
>
> Signed-off-by: Pan Li <pan2...@intel.com>
> ---
> gcc/match.pd | 15 +++++++++++++++
> 1 file changed, 15 insertions(+)
>
> diff --git a/gcc/match.pd b/gcc/match.pd
> index 4298e89dad6..1372f2ba377 100644
> --- a/gcc/match.pd
> +++ b/gcc/match.pd
> @@ -3207,6 +3207,21 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
> (if (INTEGRAL_TYPE_P (type) && !TYPE_UNSIGNED (type)
> && types_match (type, @0, @1))))
>
> +/* Signed saturation add, case 2:
> + T sum = (T)((UT)X + (UT)Y)
> + SAT_S_ADD = (X ^ sum) & !(X ^ Y) >= 0 ? sum : (-(T)(X < 0) ^ MAX);
> +
> + The T and UT are type pair like T=int8_t, UT=uint8_t. */
> +(match (signed_integer_sat_add @0 @1)
> + (cond^ (ge (bit_and:c (bit_xor:c @0 (nop_convert@2 (plus (nop_convert @0)
> + (nop_convert @1))))
> + (bit_not (bit_xor:c @0 @1)))
You only need one :c on either bit_xor.
> + integer_zerop)
> + @2
> + (bit_xor:c (negate (convert (lt @0 integer_zerop))) max_value))
> + (if (INTEGRAL_TYPE_P (type) && !TYPE_UNSIGNED (type)
> + && types_match (type, @0, @1))))
I think the types_match is redundant as you have the bit_xor combining both.
OK with those changes.
Richard.
> +
> /* Unsigned saturation sub, case 1 (branch with gt):
> SAT_U_SUB = X > Y ? X - Y : 0 */
> (match (unsigned_integer_sat_sub @0 @1)
> --
> 2.43.0
>
