[PATCH v4 1/3] Internal-fn: Support new IFN SAT_ADD for unsigned scalar int

[pan2.li@intel.com]

From: Pan Li <pan2.li@intel.com>

This patch would like to add the middle-end presentation for the
saturation add.  Aka set the result of add to the max when overflow.
It will take the pattern similar as below.

SAT_ADD (x, y) => (x + y) | (-(TYPE)((TYPE)(x + y) < x))

Take uint8_t as example, we will have:

* SAT_ADD (1, 254)   => 255.
* SAT_ADD (1, 255)   => 255.
* SAT_ADD (2, 255)   => 255.
* SAT_ADD (255, 255) => 255.

Given below example for the unsigned scalar integer uint64_t:

uint64_t sat_add_u64 (uint64_t x, uint64_t y)
{
  return (x + y) | (- (uint64_t)((uint64_t)(x + y) < x));
}

Before this patch:
uint64_t sat_add_uint64_t (uint64_t x, uint64_t y)
{
  long unsigned int _1;
  _Bool _2;
  long unsigned int _3;
  long unsigned int _4;
  uint64_t _7;
  long unsigned int _10;
  __complex__ long unsigned int _11;

;;   basic block 2, loop depth 0
;;    pred:       ENTRY
  _11 = .ADD_OVERFLOW (x_5(D), y_6(D));
  _1 = REALPART_EXPR <_11>;
  _10 = IMAGPART_EXPR <_11>;
  _2 = _10 != 0;
  _3 = (long unsigned int) _2;
  _4 = -_3;
  _7 = _1 | _4;
  return _7;
;;    succ:       EXIT

}

After this patch:
uint64_t sat_add_uint64_t (uint64_t x, uint64_t y)
{
  uint64_t _7;

;;   basic block 2, loop depth 0
;;    pred:       ENTRY
  _7 = .SAT_ADD (x_5(D), y_6(D)); [tail call]
  return _7;
;;    succ:       EXIT
}

We perform the tranform during widen_mult because that the sub-expr of
SAT_ADD will be optimized to .ADD_OVERFLOW.  We need to try the .SAT_ADD
pattern first and then .ADD_OVERFLOW,  or we may never catch the pattern
.SAT_ADD.  Meanwhile, the isel pass is after widen_mult and then we
cannot perform the .SAT_ADD pattern match as the sub-expr will be
optmized to .ADD_OVERFLOW first.

The below tests are passed for this patch:
1. The riscv fully regression tests.
2. The aarch64 fully regression tests.
3. The x86 bootstrap tests.
4. The x86 fully regression tests.

	PR target/51492
	PR target/112600

gcc/ChangeLog:

	* internal-fn.cc (commutative_binary_fn_p): Add type IFN_SAT_ADD
	to the return true switch case(s).
	* internal-fn.def (SAT_ADD):  Add new signed optab SAT_ADD.
	* match.pd: Add unsigned SAT_ADD match.
	* optabs.def (OPTAB_NL): Remove fixed-point limitation for us/ssadd.
	* tree-ssa-math-opts.cc (gimple_unsigned_integer_sat_add): New extern
	func decl generated in match.pd match.
	(match_saturation_arith): New func impl to match the saturation arith.
	(math_opts_dom_walker::after_dom_children): Try match saturation
	arith.

Signed-off-by: Pan Li <pan2.li@intel.com>
---
 gcc/internal-fn.cc        |  1 +
 gcc/internal-fn.def       |  2 ++
 gcc/match.pd              | 28 ++++++++++++++++++++++++
 gcc/optabs.def            |  4 ++--
 gcc/tree-ssa-math-opts.cc | 46 +++++++++++++++++++++++++++++++++++++++
 5 files changed, 79 insertions(+), 2 deletions(-)

diff --git a/gcc/internal-fn.cc b/gcc/internal-fn.cc
index 0a7053c2286..73045ca8c8c 100644
--- a/gcc/internal-fn.cc
+++ b/gcc/internal-fn.cc
@@ -4202,6 +4202,7 @@ commutative_binary_fn_p (internal_fn fn)
     case IFN_UBSAN_CHECK_MUL:
     case IFN_ADD_OVERFLOW:
     case IFN_MUL_OVERFLOW:
+    case IFN_SAT_ADD:
     case IFN_VEC_WIDEN_PLUS:
     case IFN_VEC_WIDEN_PLUS_LO:
     case IFN_VEC_WIDEN_PLUS_HI:
diff --git a/gcc/internal-fn.def b/gcc/internal-fn.def
index 848bb9dbff3..25badbb86e5 100644
--- a/gcc/internal-fn.def
+++ b/gcc/internal-fn.def
@@ -275,6 +275,8 @@ DEF_INTERNAL_SIGNED_OPTAB_FN (MULHS, ECF_CONST | ECF_NOTHROW, first,
 DEF_INTERNAL_SIGNED_OPTAB_FN (MULHRS, ECF_CONST | ECF_NOTHROW, first,
 			      smulhrs, umulhrs, binary)
 
+DEF_INTERNAL_SIGNED_OPTAB_FN (SAT_ADD, ECF_CONST, first, ssadd, usadd, binary)
+
 DEF_INTERNAL_COND_FN (ADD, ECF_CONST, add, binary)
 DEF_INTERNAL_COND_FN (SUB, ECF_CONST, sub, binary)
 DEF_INTERNAL_COND_FN (MUL, ECF_CONST, smul, binary)
diff --git a/gcc/match.pd b/gcc/match.pd
index d401e7503e6..7058e4cbe29 100644
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -3043,6 +3043,34 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
        || POINTER_TYPE_P (itype))
       && wi::eq_p (wi::to_wide (int_cst), wi::max_value (itype))))))
 
+/* Unsigned Saturation Add */
+(match (usadd_left_part @0 @1)
+ (plus:c @0 @1)
+ (if (INTEGRAL_TYPE_P (type)
+      && TYPE_UNSIGNED (TREE_TYPE (@0))
+      && types_match (type, TREE_TYPE (@0))
+      && types_match (type, TREE_TYPE (@1)))))
+
+(match (usadd_right_part @0 @1)
+ (negate (convert (lt (plus:c @0 @1) @0)))
+ (if (INTEGRAL_TYPE_P (type)
+      && TYPE_UNSIGNED (TREE_TYPE (@0))
+      && types_match (type, TREE_TYPE (@0))
+      && types_match (type, TREE_TYPE (@1)))))
+
+(match (usadd_right_part @0 @1)
+ (negate (convert (gt @0 (plus:c @0 @1))))
+ (if (INTEGRAL_TYPE_P (type)
+      && TYPE_UNSIGNED (TREE_TYPE (@0))
+      && types_match (type, TREE_TYPE (@0))
+      && types_match (type, TREE_TYPE (@1)))))
+
+/* Unsigned saturation add, case 1 (branchless):
+   SAT_U_ADD = (X + Y) | - ((X + Y) < X) or
+   SAT_U_ADD = (X + Y) | - (X > (X + Y)).  */
+(match (unsigned_integer_sat_add @0 @1)
+ (bit_ior:c (usadd_left_part @0 @1) (usadd_right_part @0 @1)))
+
 /* x >  y  &&  x != XXX_MIN  -->  x > y
    x >  y  &&  x == XXX_MIN  -->  false . */
 (for eqne (eq ne)
diff --git a/gcc/optabs.def b/gcc/optabs.def
index ad14f9328b9..3f2cb46aff8 100644
--- a/gcc/optabs.def
+++ b/gcc/optabs.def
@@ -111,8 +111,8 @@ OPTAB_NX(add_optab, "add$F$a3")
 OPTAB_NX(add_optab, "add$Q$a3")
 OPTAB_VL(addv_optab, "addv$I$a3", PLUS, "add", '3', gen_intv_fp_libfunc)
 OPTAB_VX(addv_optab, "add$F$a3")
-OPTAB_NL(ssadd_optab, "ssadd$Q$a3", SS_PLUS, "ssadd", '3', gen_signed_fixed_libfunc)
-OPTAB_NL(usadd_optab, "usadd$Q$a3", US_PLUS, "usadd", '3', gen_unsigned_fixed_libfunc)
+OPTAB_NL(ssadd_optab, "ssadd$a3", SS_PLUS, "ssadd", '3', gen_signed_fixed_libfunc)
+OPTAB_NL(usadd_optab, "usadd$a3", US_PLUS, "usadd", '3', gen_unsigned_fixed_libfunc)
 OPTAB_NL(sub_optab, "sub$P$a3", MINUS, "sub", '3', gen_int_fp_fixed_libfunc)
 OPTAB_NX(sub_optab, "sub$F$a3")
 OPTAB_NX(sub_optab, "sub$Q$a3")
diff --git a/gcc/tree-ssa-math-opts.cc b/gcc/tree-ssa-math-opts.cc
index 705f4a4695a..35a46edc9f6 100644
--- a/gcc/tree-ssa-math-opts.cc
+++ b/gcc/tree-ssa-math-opts.cc
@@ -4026,6 +4026,44 @@ arith_overflow_check_p (gimple *stmt, gimple *cast_stmt, gimple *&use_stmt,
   return 0;
 }
 
+extern bool gimple_unsigned_integer_sat_add (tree, tree*, tree (*)(tree));
+
+/*
+ * Try to match saturation arith pattern(s).
+ *   1. SAT_ADD (unsigned)
+ *      _7 = _4 + _6;
+ *      _8 = _4 > _7;
+ *      _9 = (long unsigned int) _8;
+ *      _10 = -_9;
+ *      _12 = _7 | _10;
+ *      =>
+ *      _12 = .SAT_ADD (_4, _6);  */
+static bool
+match_saturation_arith (gimple_stmt_iterator *gsi, gimple *stmt,
+			bool *cfg_changed_p)
+{
+  gcall *call = NULL;
+  bool changed_p = false;
+
+  gcc_assert (is_gimple_assign (stmt));
+
+  tree ops[2];
+  tree lhs = gimple_assign_lhs (stmt);
+
+  if (gimple_unsigned_integer_sat_add (lhs, ops, NULL)
+      && direct_internal_fn_supported_p (IFN_SAT_ADD, TREE_TYPE (lhs),
+					OPTIMIZE_FOR_SPEED))
+    {
+      call = gimple_build_call_internal (IFN_SAT_ADD, 2, ops[0], ops[1]);
+      gimple_call_set_lhs (call, lhs);
+      gsi_replace (gsi, call, true);
+      changed_p = true;
+      *cfg_changed_p = changed_p;
+    }
+
+  return changed_p;
+}
+
 /* Recognize for unsigned x
    x = y - z;
    if (x > y)
@@ -5886,6 +5924,14 @@ math_opts_dom_walker::after_dom_children (basic_block bb)
 
   fma_deferring_state fma_state (param_avoid_fma_max_bits > 0);
 
+  for (gsi = gsi_after_labels (bb); !gsi_end_p (gsi); gsi_next (&gsi))
+    {
+      gimple *stmt = gsi_stmt (gsi);
+
+      if (is_gimple_assign (stmt))
+	match_saturation_arith (&gsi, stmt, m_cfg_changed_p);
+    }
+
   for (gsi = gsi_after_labels (bb); !gsi_end_p (gsi);)
     {
       gimple *stmt = gsi_stmt (gsi);
-- 
2.34.1