[gcc r17-1261] Match: Support unsigned scalar SAT_MUL form 11

[Pan Li]

https://gcc.gnu.org/g:1385e403f29fc65719c022a9e58f01a4876750f5

commit r17-1261-g1385e403f29fc65719c022a9e58f01a4876750f5
Author: Pan Li <pan2.li@intel.com>
Date:   Mon May 18 17:43:19 2026 +0800

    Match: Support unsigned scalar SAT_MUL form 11
    
    This patch would like to try to match the the unsigned
    SAT_MUL form 11, aka below
    
      #define DEF_SAT_U_MUL_FMT_11(NT, WT)             \
      NT __attribute__((noinline))                     \
      sat_u_mul_##NT##_from_##WT##_fmt_11 (NT a, NT b) \
      {                                                \
        WT x = (WT)a * (WT)b;                          \
        NT max = -1;                                   \
        bool overflow_p = x >= (WT)(max);              \
        return -(NT)(overflow_p) | (NT)x;              \
      }
    
    while WT is uint128_t, uint64_t, uint32_t and uint16_t, and
    NT is uint64_t, uint32_t, uint16_t or uint8_t.
    
    gcc/ChangeLog:
    
            * match-sat-alu.pd: Add pattern for unsigned scalar
            SAT_MUL form 11.
    
    Signed-off-by: Pan Li <pan2.li@intel.com>

Diff:
---
 gcc/match-sat-alu.pd | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/gcc/match-sat-alu.pd b/gcc/match-sat-alu.pd
index 483c37b6d9f6..6145a0c99484 100644
--- a/gcc/match-sat-alu.pd
+++ b/gcc/match-sat-alu.pd
@@ -548,7 +548,7 @@ along with GCC; see the file COPYING3.  If not see
    /* SAT_U_MUL (X, Y) = {
 	WT x = (WT)a * (WT)b;
 	NT max = -1;
-	bool overflow_p = x > (WT)max;
+	bool overflow_p = x > (WT)max || x > (WT)(max - 1);
 	return -(NT)(overflow_p) | (NT)x;
       } while WT is uint128_t, uint64_t, uint32_t, uint16_t,
 	and T is uint64_t, uint32_t, uint16_t, uint8_t.  */
@@ -560,7 +560,12 @@ along with GCC; see the file COPYING3.  If not see
       unsigned prec = TYPE_PRECISION (type);
       unsigned widen_prec = TYPE_PRECISION (TREE_TYPE (@3));
       wide_int max = wi::mask (prec, false, widen_prec);
-      bool c2_is_max_p = wi::eq_p (wi::to_wide (@2), max);
+
+      wide_int c2 = wi::to_wide (@2);
+      bool c2_is_max_p = wi::eq_p (c2, max);
+
+      wide_int c2_plus_one = wi::add (c2, wi::uhwi (1, widen_prec));
+      bool c2_plus_one_is_max_p = wi::eq_p (c2_plus_one, max);
      }
-     (if (c2_is_max_p)))))
+     (if (c2_is_max_p || c2_plus_one_is_max_p)))))
 )