From 8c0a2fa3efdaf100b7119649863ecc173236153a Mon Sep 17 00:00:00 2001
From: WormHeamer
Date: Fri, 22 Aug 2025 04:08:17 -0400
Subject: bitshift zero peepholes, recognize known (a = b) <> (a <> b) etc

---
 peephole.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/peephole.c b/peephole.c
index d8846f5..b30a052 100644
--- a/peephole.c
+++ b/peephole.c
@@ -196,6 +196,7 @@ static inline int node_sub_add_equiv(Node *a, Node *b) {
 
 static int node_equiv_input(Node *a, Node *b);
 
+/* TODO: separate out equivalence as in complete identity vs. just same value */
 static int node_equiv(Node *a, Node *b) {
 	/* will doing this recursively be too slow? */
 	if (a == b) return 1;
@@ -217,6 +218,7 @@ static inline int node_known_not_equiv_ord(Node *a, Node *b) {
 	return 0;
 }
 static inline int node_known_not_equiv(Node *a, Node *b) {
+	if (node_cmp_incompat(a->op, b->op) && node_equiv_input(a, b)) return 1;
 	return node_known_not_equiv_ord(a, b) || node_known_not_equiv_ord(b, a);
 }
 
@@ -486,6 +488,10 @@ zero_no_effect:	if (node_eql_i64(CAR(n), 0)) return CDR(n);
 		if (BOOL_EQ(CDR(n), 1)) return CAR(n);
 		if (BOOL_EQ(CDR(n), 0)) return NODE(N_OP_NOT, CAR(n));
 		if (T(CAR(n), N_OP_NOT) && node_equiv(CDR(n), CAAR(n))) return node_new_lit_bool(p, 0);
+		if (((T(CAR(n), N_CMP_LTE) && T(CDR(n), N_CMP_GTE)) || (T(CAR(n), N_CMP_GTE) && T(CDR(n), N_CMP_LTE)))
+				&& node_equiv_input(CAR(n), CDR(n))) {
+			return NODE(N_CMP_EQL, CAAR(n), CADR(n));
+		}
 		break;
 	case N_CMP_NEQ:
 		if (same) return node_new_lit_bool(p, 0);
@@ -560,6 +566,13 @@ zero_no_effect:	if (node_eql_i64(CAR(n), 0)) return CDR(n);
 		}
 	} break;
 
+	case N_OP_SHL:
+	case N_OP_SHR:
+		/* a (<< | >>) 0 -> a */
+		/* 0 (<< | >>) a -> 0 */
+		if (node_eql_i64(CDR(n), 0) || node_eql_i64(CAR(n), 0)) return CAR(n);
+		break;
+
 	default:
 		break;
 	}
-- 
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