[PATCH 08/16] cmp: canonicalize unsigned compare with UMAX or UMAX-1

[Luc Van Oostenryck <luc.vanoostenryck@gmail.com>]

Unsigned compares with UMAX (or UMAX-1) are equivalent to
equality tests. These are preferable since it's easier to reason
about them in other simplifications.

So canonicalize these compares to equality tests.

Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
---
 simplify.c                   | 8 ++++++++
 validation/optim/set-uimm2.c | 1 -
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/simplify.c b/simplify.c
index 160a6ab15e7f..7921300f7280 100644
--- a/simplify.c
+++ b/simplify.c
@@ -1090,6 +1090,8 @@ static int simplify_compare_constant(struct instruction *insn, long long value)
 			return replace_with_pseudo(insn, value_pseudo(0));
 		if (value == 1)			// (x < 1) --> (x == 0)
 			return replace_binop_value(insn, OP_SET_EQ, 0);
+		else if (value == bits)		// (x < ~0) --> (x != ~0)
+			return replace_binop_value(insn, OP_SET_NE, value);
 		else				// (x < y) --> (x <= (y-1))
 			changed |= replace_binop_value(insn, OP_SET_BE, value - 1);
 		break;
@@ -1098,6 +1100,8 @@ static int simplify_compare_constant(struct instruction *insn, long long value)
 			return replace_with_pseudo(insn, value_pseudo(1));
 		if (value == 1)			// (x >= 1) --> (x != 0)
 			return replace_binop_value(insn, OP_SET_NE, 0);
+		else if (value == bits)		// (x >= ~0) --> (x == ~0)
+			return replace_binop_value(insn, OP_SET_EQ, value);
 		else				// (x >= y) --> (x > (y-1)
 			changed |= replace_binop_value(insn, OP_SET_A, value - 1);
 		break;
@@ -1106,12 +1110,16 @@ static int simplify_compare_constant(struct instruction *insn, long long value)
 			return replace_opcode(insn, OP_SET_EQ);
 		if (value == bits)		// (x <= ~0) --> 1
 			return replace_with_pseudo(insn, value_pseudo(1));
+		if (value == (bits - 1))	// (x <= ~1) --> (x != ~0)
+			return replace_binop_value(insn, OP_SET_NE, bits);
 		break;
 	case OP_SET_A:
 		if (!value)			// (x > 0) --> (x != 0)
 			return replace_opcode(insn, OP_SET_NE);
 		if (value == bits)		// (x > ~0) --> 0
 			return replace_with_pseudo(insn, value_pseudo(0));
+		if (value == (bits - 1))	// (x > ~1) --> (x == ~0)
+			return replace_binop_value(insn, OP_SET_EQ, bits);
 		break;
 	}
 	return changed;
diff --git a/validation/optim/set-uimm2.c b/validation/optim/set-uimm2.c
index efa326f532ce..9138ae7276e7 100644
--- a/validation/optim/set-uimm2.c
+++ b/validation/optim/set-uimm2.c
@@ -6,7 +6,6 @@ static _Bool setgt_umax(unsigned int a) { return (a >  ~1) == (a == ~0); }
 /*
  * check-name: set-uimm2
  * check-command: test-linearize $file
- * check-known-to-fail
  *
  * check-output-ignore
  * check-output-returns: 1
-- 
2.29.2