Match: Support form 4 for unsigned integer .SAT_TRUNC

This patch would like to support the form 4 of the unsigned integer
.SAT_TRUNC. Aka below example:

Form 4:
  #define DEF_SAT_U_TRUC_FMT_4(NT, WT)           \
  NT __attribute__((noinline))                   \
  sat_u_truc_##WT##_to_##NT##_fmt_4 (WT x)       \
  {                                              \
    bool not_overflow = x <= (WT)(NT)(-1);       \
    return ((NT)x) | (NT)((NT)not_overflow - 1); \
  }

DEF_SAT_U_TRUC_FMT_4(uint32_t, uint64_t)

Before this patch:
   4   │ __attribute__((noinline))
   5   │ uint8_t sat_u_truc_uint32_t_to_uint8_t_fmt_4 (uint32_t x)
   6   │ {
   7   │   _Bool not_overflow;
   8   │   unsigned char _1;
   9   │   unsigned char _2;
  10   │   unsigned char _3;
  11   │   uint8_t _6;
  12   │
  13   │ ;;   basic block 2, loop depth 0
  14   │ ;;    pred:       ENTRY
  15   │   not_overflow_5 = x_4(D) <= 255;
  16   │   _1 = (unsigned char) x_4(D);
  17   │   _2 = (unsigned char) not_overflow_5;
  18   │   _3 = _2 + 255;
  19   │   _6 = _1 | _3;
  20   │   return _6;
  21   │ ;;    succ:       EXIT
  22   │
  23   │ }

After this patch:
   4   │ __attribute__((noinline))
   5   │ uint8_t sat_u_truc_uint32_t_to_uint8_t_fmt_4 (uint32_t x)
   6   │ {
   7   │   uint8_t _6;
   8   │
   9   │ ;;   basic block 2, loop depth 0
  10   │ ;;    pred:       ENTRY
  11   │   _6 = .SAT_TRUNC (x_4(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 form 4 for unsigned .SAT_TRUNC matching.

Signed-off-by: Pan Li <pan2.li@intel.com>

1 files changed, 18 insertions, 0 deletions

diff --git a/gcc/match.pd b/gcc/match.pd
index 65a3aae..78f1957 100644
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -3325,6 +3325,24 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
   }
   (if (otype_precision < itype_precision && wi::eq_p (trunc_max, int_cst))))))
 
+/* Unsigned saturation truncate, case 3, sizeof (WT) > sizeof (NT).
+   SAT_U_TRUNC = (NT)X | ((NT)(X <= (WT)-1) + (NT)-1).  */
+(match (unsigned_integer_sat_trunc @0)
+ (bit_ior:c (plus:c (convert (le @0 INTEGER_CST@1)) INTEGER_CST@2)
+	    (convert @0))
+ (if (INTEGRAL_TYPE_P (type) && TYPE_UNSIGNED (type)
+      && TYPE_UNSIGNED (TREE_TYPE (@0)))
+ (with
+  {
+   unsigned itype_precision = TYPE_PRECISION (TREE_TYPE (@0));
+   unsigned otype_precision = TYPE_PRECISION (type);
+   wide_int trunc_max = wi::mask (otype_precision, false, itype_precision);
+   wide_int max = wi::mask (otype_precision, false, otype_precision);
+   wide_int int_cst_1 = wi::to_wide (@1);
+   wide_int int_cst_2 = wi::to_wide (@2);
+  }
+  (if (wi::eq_p (trunc_max, int_cst_1) && wi::eq_p (max, int_cst_2))))))
+
 /* x >  y  &&  x != XXX_MIN  -->  x > y
    x >  y  &&  x == XXX_MIN  -->  false . */
 (for eqne (eq ne)