[PATCH 08/10] cmps: canonicalize signed compares with constant

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

Modify the constants to canonicalize (x < C) to (x <= (C-1)) and
(x <= C) to (x > (C-1)). This choice is partially arbitrary but
1) it's the one with the smallest positive constants,
2) it eliminates all OP_SET_LT & OP_SET_GE with a constant.
A disadvantage of this choice is that we lost some compares with 0:
(x < 0) is now canonicalized into (x <= -1).

Note: Another good choice would be to canonicalize using the
      smallest absolute constants. This would keep compares with 0
      but would also keep the 4 kinds of comparison.

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

diff --git a/simplify.c b/simplify.c
index ad3adb11595e..b29f5d5b2444 100644
--- a/simplify.c
+++ b/simplify.c
@@ -1177,6 +1177,7 @@ static int simplify_compare_constant(struct instruction *insn, long long value)
 			return replace_opcode(insn, OP_SET_NE);
 		if (value == sign_bit(size) + 1)// (x < SMIN + 1) --> (x == SMIN)
 			return replace_binop_value(insn, OP_SET_EQ, sign_bit(size));
+		changed |= replace_binop_value(insn, OP_SET_LE, (value - 1) & bits);
 		break;
 	case OP_SET_LE:
 		if (value == sign_mask(size))	// (x <= SMAX) --> 1
@@ -1193,6 +1194,7 @@ static int simplify_compare_constant(struct instruction *insn, long long value)
 			return replace_opcode(insn, OP_SET_EQ);
 		if (value == sign_bit(size) + 1)// (x >= SMIN + 1) --> (x != SMIN)
 			return replace_binop_value(insn, OP_SET_NE, sign_bit(size));
+		changed |= replace_binop_value(insn, OP_SET_GT, (value - 1) & bits);
 		break;
 	case OP_SET_GT:
 		if (value == sign_mask(size))	// (x >  SMAX) --> 0
diff --git a/validation/optim/canonical-cmps.c b/validation/optim/canonical-cmps.c
index f42664b21e04..42801cdce520 100644
--- a/validation/optim/canonical-cmps.c
+++ b/validation/optim/canonical-cmps.c
@@ -10,7 +10,6 @@ _Bool ge_x(int a) { return (a >= 1234) == (a > 1233); }
 /*
  * check-name: canonical-cmps
  * check-command: test-linearize -Wno-decl $file
- * check-known-to-fail
  *
  * check-output-ignore
  * check-output-returns: 1
-- 
2.30.0