From 2069733522922fc45cc87da0327e6dfcda74f1b2 Mon Sep 17 00:00:00 2001
From: WormHeamer
Date: Tue, 5 Aug 2025 01:44:20 -0400
Subject: correction!  equality is communative, but not _associative_

so constants can still be shuffled from left to right, not(X) from
right to left, but the regrouping optimizations don't apply
---
 ir.c | 22 ++++++++++++++++------
 1 file changed, 16 insertions(+), 6 deletions(-)

diff --git a/ir.c b/ir.c
index e1b86c6..c0de33c 100644
--- a/ir.c
+++ b/ir.c
@@ -245,6 +245,14 @@ Node *node_new_lit_bool(Proc *p, int b) {
 }
 
 static inline int node_op_communative(NodeType t) {
+	NodeType ops[] = { N_OP_ADD, N_OP_MUL, N_OP_AND, N_OP_XOR, N_OP_OR, N_CMP_EQL, N_CMP_NEQ };
+	for (unsigned i = 0; i < sizeof ops / sizeof *ops; i++) {
+		if (ops[i] == t) return 1;
+	}
+	return 0;
+}
+
+static inline int node_op_associative(NodeType t) {
 	NodeType ops[] = { N_OP_ADD, N_OP_MUL, N_OP_AND, N_OP_XOR, N_OP_OR };
 	for (unsigned i = 0; i < sizeof ops / sizeof *ops; i++) {
 		if (ops[i] == t) return 1;
@@ -487,6 +495,14 @@ Node *node_idealize(Node *n, Proc *p, Lexer *l) {
 		/* op(lit, X) -> op(X, lit) */
 		if (T(CAR(n), N_LIT) && !T(CDR(n), N_LIT)) return OP(CDR(n), CAR(n));
 
+		/* op(X, not(Y)) -> op(not(Y), X) */
+		/* shuffle not left to avoid conflict w/ literals */
+		if (T(CDR(n), N_OP_NOT) && !T(CAR(n), N_OP_NOT)) {
+			return NODE(n->type, CDR(n), CAR(n));
+		}
+	}
+
+	if (node_op_associative(n->type)) {
 		/* op(X, op(Y,Z)) -> op(op(Y,Z), X) */
 		/*if (!T(CAR(n), n->type) && T(CDR(n), n->type)
 				&& C(CAR(n), CDAR(n))) return OP(CDR(n), CAR(n));*/
@@ -510,12 +526,6 @@ Node *node_idealize(Node *n, Proc *p, Lexer *l) {
 				&& C(CADR(n), CDR(n))) {
 			return OP(OP(CAAR(n), CDR(n)), CADR(n));
 		}
-
-		/* op(X, not(Y)) -> op(not(Y), X) */
-		/* shuffle not left to avoid conflict w/ literals */
-		if (T(CDR(n), N_OP_NOT) && !T(CAR(n), N_OP_NOT)) {
-			return NODE(n->type, CDR(n), CAR(n));
-		}
 	}
 
 	/* optimize based on situations where the input is partly known (e.g.
-- 
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