Thanks Richard for comments.
> I think you want to use nop_convert here, for sure a truncation or
> extension wouldn't be valid?
Oh, yes, should be nop_convert.
> I think you don't need :c on both the inner plus and the bit_xor here?
Sure, could you please help to explain more about when should I need to add :c?
Liker inner plus/and/or ... etc, sometimes got confused for similar scenarios.
> + integer_zerop)
> + (bit_xor:c (negate (convert (lt @0 integer_zerop))) max_value)
> The comment above quotes 'MIN' but that's not present here - that is,
> the comment quotes a source form while we match what we see on
> GIMPLE? I do expect the matching will be quite fragile when not
> being isolated.
Got it, will update the comments to gimple.
Pan
-----Original Message-----
From: Richard Biener <richard.guent...@gmail.com>
Sent: Monday, August 26, 2024 9:40 PM
To: Li, Pan2 <pan2...@intel.com>
Cc: gcc-patches@gcc.gnu.org; tamar.christ...@arm.com; juzhe.zh...@rivai.ai;
kito.ch...@gmail.com; jeffreya...@gmail.com; rdapp....@gmail.com
Subject: Re: [PATCH v3] Match: Support form 1 for scalar signed integer .SAT_ADD
On Mon, Aug 26, 2024 at 4:20 AM <pan2...@intel.com> wrote:
>
> From: Pan Li <pan2...@intel.com>
>
> This patch would like to support the form 1 of the scalar signed
> integer .SAT_ADD. Aka below example:
>
> Form 1:
> #define DEF_SAT_S_ADD_FMT_1(T, UT, MIN, MAX) \
> T __attribute__((noinline)) \
> sat_s_add_##T##_fmt_1 (T x, T y) \
> { \
> T sum = (UT)x + (UT)y; \
> return (x ^ y) < 0 \
> ? sum \
> : (sum ^ x) >= 0 \
> ? sum \
> : x < 0 ? MIN : MAX; \
> }
>
> DEF_SAT_S_ADD_FMT_1(int64_t, uint64_t, INT64_MIN, INT64_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 │ int64_t sat_s_add_int64_t_fmt_1 (int64_t x, int64_t y)
> 6 │ {
> 7 │ int64_t sum;
> 8 │ long unsigned int x.0_1;
> 9 │ long unsigned int y.1_2;
> 10 │ long unsigned int _3;
> 11 │ long int _4;
> 12 │ long int _5;
> 13 │ int64_t _6;
> 14 │ _Bool _11;
> 15 │ long int _12;
> 16 │ long int _13;
> 17 │ long int _14;
> 18 │ long int _16;
> 19 │ long int _17;
> 20 │
> 21 │ ;; basic block 2, loop depth 0
> 22 │ ;; pred: ENTRY
> 23 │ x.0_1 = (long unsigned int) x_7(D);
> 24 │ y.1_2 = (long unsigned int) y_8(D);
> 25 │ _3 = x.0_1 + y.1_2;
> 26 │ sum_9 = (int64_t) _3;
> 27 │ _4 = x_7(D) ^ y_8(D);
> 28 │ _5 = x_7(D) ^ sum_9;
> 29 │ _17 = ~_4;
> 30 │ _16 = _5 & _17;
> 31 │ if (_16 < 0)
> 32 │ goto <bb 3>; [41.00%]
> 33 │ else
> 34 │ goto <bb 4>; [59.00%]
> 35 │ ;; succ: 3
> 36 │ ;; 4
> 37 │
> 38 │ ;; basic block 3, loop depth 0
> 39 │ ;; pred: 2
> 40 │ _11 = x_7(D) < 0;
> 41 │ _12 = (long int) _11;
> 42 │ _13 = -_12;
> 43 │ _14 = _13 ^ 9223372036854775807;
> 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 │ int64_t sat_s_add_int64_t_fmt_1 (int64_t x, int64_t y)
> 6 │ {
> 7 │ int64_t _4;
> 8 │
> 9 │ ;; basic block 2, loop depth 0
> 10 │ ;; pred: ENTRY
> 11 │ _4 = .SAT_ADD (x_5(D), y_6(D)); [tail call]
> 12 │ return _4;
> 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 matching for signed .SAT_ADD.
> * tree-ssa-math-opts.cc (gimple_signed_integer_sat_add): Add new
> matching func decl.
> (match_unsigned_saturation_add): Try signed .SAT_ADD and rename
> to ...
> (match_saturation_add): ... here.
> (math_opts_dom_walker::after_dom_children): Update the above renamed
> func from caller.
>
> Signed-off-by: Pan Li <pan2...@intel.com>
> ---
> gcc/match.pd | 18 ++++++++++++++++++
> gcc/tree-ssa-math-opts.cc | 35 ++++++++++++++++++++++++++++++-----
> 2 files changed, 48 insertions(+), 5 deletions(-)
>
> diff --git a/gcc/match.pd b/gcc/match.pd
> index 78f1957e8c7..b059e313415 100644
> --- a/gcc/match.pd
> +++ b/gcc/match.pd
> @@ -3192,6 +3192,24 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
> (if (INTEGRAL_TYPE_P (type) && TYPE_UNSIGNED (type)
> && types_match (type, @0))))
>
> +/* Signed saturation add, case 1:
> + T sum = (UT)X + (UT)Y;
> + SAT_S_ADD = (X ^ Y) < 0
> + ? sum
> + : (sum ^ x) >= 0
> + ? sum
> + : x < 0 ? MIN : MAX;
> + T and UT are type pair like T=int8_t, UT=uint8_t. */
> +(match (signed_integer_sat_add @0 @1)
> + (cond^ (lt (bit_and:c (bit_xor:c @0 (convert@2 (plus:c (convert @0)
> + (convert @1))))
I think you want to use nop_convert here, for sure a truncation or
extension wouldn't be valid?
> + (bit_not (bit_xor:c @0 @1)))
I think you don't need :c on both the inner plus and the bit_xor here?
> + integer_zerop)
> + (bit_xor:c (negate (convert (lt @0 integer_zerop))) max_value)
The comment above quotes 'MIN' but that's not present here - that is,
the comment quotes a source form while we match what we see on
GIMPLE? I do expect the matching will be quite fragile when not
being isolated.
How do you select the cases you want to support?
> + @2)
> + (if (INTEGRAL_TYPE_P (type) && !TYPE_UNSIGNED (type)
> + && types_match (type, @0, @1))))
> +
> /* Unsigned saturation sub, case 1 (branch with gt):
> SAT_U_SUB = X > Y ? X - Y : 0 */
> (match (unsigned_integer_sat_sub @0 @1)
> diff --git a/gcc/tree-ssa-math-opts.cc b/gcc/tree-ssa-math-opts.cc
> index 8d96a4c964b..3c93fca5b53 100644
> --- a/gcc/tree-ssa-math-opts.cc
> +++ b/gcc/tree-ssa-math-opts.cc
> @@ -4023,6 +4023,8 @@ extern bool gimple_unsigned_integer_sat_add (tree,
> tree*, tree (*)(tree));
> extern bool gimple_unsigned_integer_sat_sub (tree, tree*, tree (*)(tree));
> extern bool gimple_unsigned_integer_sat_trunc (tree, tree*, tree (*)(tree));
>
> +extern bool gimple_signed_integer_sat_add (tree, tree*, tree (*)(tree));
> +
> static void
> build_saturation_binary_arith_call (gimple_stmt_iterator *gsi, internal_fn
> fn,
> tree lhs, tree op_0, tree op_1)
> @@ -4072,7 +4074,8 @@ match_unsigned_saturation_add (gimple_stmt_iterator
> *gsi, gassign *stmt)
> }
>
> /*
> - * Try to match saturation unsigned add with PHI.
> + * Try to match saturation add with PHI.
> + * For unsigned integer:
> * <bb 2> :
> * _1 = x_3(D) + y_4(D);
> * if (_1 >= x_3(D))
> @@ -4086,10 +4089,31 @@ match_unsigned_saturation_add (gimple_stmt_iterator
> *gsi, gassign *stmt)
> * # _2 = PHI <255(2), _1(3)>
> * =>
> * <bb 4> [local count: 1073741824]:
> - * _2 = .SAT_ADD (x_4(D), y_5(D)); */
> + * _2 = .SAT_ADD (x_4(D), y_5(D));
> + *
> + * For signed integer:
> + * x.0_1 = (long unsigned int) x_7(D);
> + * y.1_2 = (long unsigned int) y_8(D);
> + * _3 = x.0_1 + y.1_2;
> + * sum_9 = (int64_t) _3;
> + * _4 = x_7(D) ^ y_8(D);
> + * _5 = x_7(D) ^ sum_9;
> + * _15 = ~_4;
> + * _16 = _5 & _15;
> + * if (_16 < 0)
> + * goto <bb 3>; [41.00%]
> + * else
> + * goto <bb 4>; [59.00%]
> + * _11 = x_7(D) < 0;
> + * _12 = (long int) _11;
> + * _13 = -_12;
> + * _14 = _13 ^ 9223372036854775807;
> + * # _6 = PHI <_14(3), sum_9(2)>
> + * =>
> + * _6 = .SAT_ADD (x_5(D), y_6(D)); [tail call] */
>
> static void
> -match_unsigned_saturation_add (gimple_stmt_iterator *gsi, gphi *phi)
> +match_saturation_add (gimple_stmt_iterator *gsi, gphi *phi)
> {
> if (gimple_phi_num_args (phi) != 2)
> return;
> @@ -4097,7 +4121,8 @@ match_unsigned_saturation_add (gimple_stmt_iterator
> *gsi, gphi *phi)
> tree ops[2];
> tree phi_result = gimple_phi_result (phi);
>
> - if (gimple_unsigned_integer_sat_add (phi_result, ops, NULL))
> + if (gimple_unsigned_integer_sat_add (phi_result, ops, NULL)
> + || gimple_signed_integer_sat_add (phi_result, ops, NULL))
> build_saturation_binary_arith_call (gsi, phi, IFN_SAT_ADD, phi_result,
> ops[0], ops[1]);
> }
> @@ -6097,7 +6122,7 @@ math_opts_dom_walker::after_dom_children (basic_block
> bb)
> gsi_next (&psi))
> {
> gimple_stmt_iterator gsi = gsi_after_labels (bb);
> - match_unsigned_saturation_add (&gsi, psi.phi ());
> + match_saturation_add (&gsi, psi.phi ());
> match_unsigned_saturation_sub (&gsi, psi.phi ());
> }
>
> --
> 2.43.0
>
