On Wed, Jul 2, 2025 at 7:31 AM <pan2...@intel.com> wrote:
>
> From: Pan Li <pan2...@intel.com>
>
> This patch would like to try to match the SAT_MUL during
> widening-mul pass, aka below pattern.
>
> NT __attribute__((noinline))
> sat_u_mul_##NT##_fmt_1 (NT a, NT b)
> {
> uint128_t x = (uint128_t)a * (uint128_t)b;
> NT max = -1;
> if (x > (uint128_t)(max))
> return max;
> else
> return (NT)x;
> }
>
> while the NT can be uint8_t, uint16_t, uint32_t and uint64_t.
OK.
Richard.
> gcc/ChangeLog:
>
> * match.pd: Add new match pattern for unsigned SAT_MUL.
> * tree-ssa-math-opts.cc (gimple_unsigned_integer_sat_mul):
> new decl for pattern match func.
> (match_unsigned_saturation_mul): Add new func to match unsigned
> SAT_MUL.
> (math_opts_dom_walker::after_dom_children): Try to match
> unsigned SAT_MUL on NOP.
>
> Signed-off-by: Pan Li <pan2...@intel.com>
> ---
> gcc/match.pd | 31 +++++++++++++++++++++++++++++++
> gcc/tree-ssa-math-opts.cc | 26 ++++++++++++++++++++++++++
> 2 files changed, 57 insertions(+)
>
> diff --git a/gcc/match.pd b/gcc/match.pd
> index f4416d9172c..c8addf9b421 100644
> --- a/gcc/match.pd
> +++ b/gcc/match.pd
> @@ -3572,6 +3572,37 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
> || (wi::eq_p (int_cst_1, itype_max) && wi::eq_p (int_cst_2,
> limit_1)))
> && wi::eq_p (int_cst_3, otype_max)))))))
>
> +/* Saturation mult for unsigned integer. */
> +(if (INTEGRAL_TYPE_P (type) && TYPE_UNSIGNED (type))
> + (match (unsigned_integer_sat_mul @0 @1)
> + /* SAT_U_MUL (X, Y) = {
> + WT x = (WT)a * (WT)b;
> + T max = -1;
> + if (x > (WT)(max))
> + return max;
> + else
> + return (T)x;
> + }
> + while WT is uint128_t, T is uint8_t, uint16_t, uint32_t or uint64_t.
> */
> + (convert@4 (min (widen_mult:c@3 (convert@5 (convert @0))
> + (convert@6 (convert @1)))
> + INTEGER_CST@2))
> + (if (types_match (type, @0, @1) && types_match (type, @4))
> + (with
> + {
> + unsigned prec = TYPE_PRECISION (type);
> + unsigned widen_prec = TYPE_PRECISION (TREE_TYPE (@3));
> + unsigned cvt5_prec = TYPE_PRECISION (TREE_TYPE (@5));
> + unsigned cvt6_prec = TYPE_PRECISION (TREE_TYPE (@6));
> + unsigned hw_int_prec = sizeof (HOST_WIDE_INT) * 8;
> + wide_int c2 = wi::to_wide (@2);
> + wide_int max = wi::mask (prec, false, widen_prec);
> + bool c2_is_max_p = wi::eq_p (c2, max);
> + bool widen_mult_p = cvt5_prec == cvt6_prec && hw_int_prec == cvt5_prec;
> + }
> + (if (widen_prec > prec && c2_is_max_p && widen_mult_p)))))
> +)
> +
> /* The boundary condition for case 10: IMM = 1:
> SAT_U_SUB = X >= IMM ? (X - IMM) : 0.
> simplify (X != 0 ? X + ~0 : 0) to X - (X != 0). */
> diff --git a/gcc/tree-ssa-math-opts.cc b/gcc/tree-ssa-math-opts.cc
> index 4cfcc420fea..ca98205d58f 100644
> --- a/gcc/tree-ssa-math-opts.cc
> +++ b/gcc/tree-ssa-math-opts.cc
> @@ -4064,6 +4064,7 @@ arith_overflow_check_p (gimple *stmt, gimple
> *cast_stmt, gimple *&use_stmt,
> 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_unsigned_integer_sat_mul (tree, tree*, tree (*)(tree));
>
> extern bool gimple_signed_integer_sat_add (tree, tree*, tree (*)(tree));
> extern bool gimple_signed_integer_sat_sub (tree, tree*, tree (*)(tree));
> @@ -4216,6 +4217,30 @@ match_unsigned_saturation_sub (gimple_stmt_iterator
> *gsi, gassign *stmt)
> ops[0], ops[1]);
> }
>
> +/*
> + * Try to match saturation unsigned mul.
> + * _1 = (unsigned int) a_6(D);
> + * _2 = (unsigned int) b_7(D);
> + * x_8 = _1 * _2;
> + * overflow_9 = x_8 > 255;
> + * _3 = (unsigned char) overflow_9;
> + * _4 = -_3;
> + * _5 = (unsigned char) x_8;
> + * _10 = _4 | _5;
> + * =>
> + * _10 = .SAT_SUB (a_6, b_7); */
> +
> +static void
> +match_unsigned_saturation_mul (gimple_stmt_iterator *gsi, gassign *stmt)
> +{
> + tree ops[2];
> + tree lhs = gimple_assign_lhs (stmt);
> +
> + if (gimple_unsigned_integer_sat_mul (lhs, ops, NULL))
> + build_saturation_binary_arith_call_and_replace (gsi, IFN_SAT_MUL, lhs,
> + ops[0], ops[1]);
> +}
> +
> /*
> * Try to match saturation unsigned sub.
> * <bb 2> [local count: 1073741824]:
> @@ -6469,6 +6494,7 @@ math_opts_dom_walker::after_dom_children (basic_block
> bb)
> break;
>
> case NOP_EXPR:
> + match_unsigned_saturation_mul (&gsi, as_a<gassign *> (stmt));
> match_unsigned_saturation_trunc (&gsi, as_a<gassign *> (stmt));
> match_saturation_add_with_assign (&gsi, as_a<gassign *> (stmt));
> break;
> --
> 2.43.0
>
