[PATCH 06/16] cmp: canonicalize unsigned (x {<,>=} C) --> (x {<=,>} C-1)

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

An unsigned comparison like (x < 3) is equivalent to (x <= 2).
Canonicalize '<' & '>=' to '<=' & '>', such that the smallest
constant is used.

Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
---
 simplify.c                        | 8 +++++++-
 validation/optim/canonical-cmpu.c | 1 -
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/simplify.c b/simplify.c
index 59e6d1eee291..b8dfbad1f077 100644
--- a/simplify.c
+++ b/simplify.c
@@ -1081,18 +1081,24 @@ static int simplify_seteq_setne(struct instruction *insn, long long value)
 
 static int simplify_compare_constant(struct instruction *insn, long long value)
 {
+	int changed = 0;
+
 	switch (insn->opcode) {
 	case OP_SET_B:
 		if (!value)			// (x < 0) --> 0
 			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				// (x < y) --> (x <= (y-1))
+			changed |= replace_binop_value(insn, OP_SET_BE, value - 1);
 		break;
 	case OP_SET_AE:
 		if (!value)			// (x >= 0) --> 1
 			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				// (x >= y) --> (x > (y-1)
+			changed |= replace_binop_value(insn, OP_SET_A, value - 1);
 		break;
 	case OP_SET_BE:
 		if (!value)			// (x <= 0) --> (x == 0)
@@ -1103,7 +1109,7 @@ static int simplify_compare_constant(struct instruction *insn, long long value)
 			return replace_opcode(insn, OP_SET_NE);
 		break;
 	}
-	return 0;
+	return changed;
 }
 
 static int simplify_constant_mask(struct instruction *insn, unsigned long long mask)
diff --git a/validation/optim/canonical-cmpu.c b/validation/optim/canonical-cmpu.c
index 482408aa90c1..29bbd0a8690a 100644
--- a/validation/optim/canonical-cmpu.c
+++ b/validation/optim/canonical-cmpu.c
@@ -9,7 +9,6 @@ int cmp_geu(unsigned int x) { return (x >= 256) == (x >  255); }
 /*
  * check-name: canonical-cmpu
  * check-command: test-linearize -Wno-decl $file
- * check-known-to-fail
  *
  * check-output-ignore
  * check-output-returns: 1
-- 
2.29.2