highly speculative peephole stuff

1 files changed, 55 insertions, 22 deletions

diff --git a/main.c b/main.c
index 12e43bd..2642fac 100644
--- a/main.c
+++ b/main.c
@@ -217,35 +217,68 @@ Node *node_new_lit_i64(Proc *p, int64_t i) {
 	return n;
 }
 
+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 };
+	for (unsigned i = 0; i < sizeof ops / sizeof *ops; i++) {
+		if (ops[i] == t) return 1;
+	}
+	return 0;
+}
+
 /* needs lexer for error reporting */
 Node *node_peephole(Node *n, Proc *p, Lexer *l) {
 	return n;
-	for (int i = 0; i < n->in.len; i++) {
-		if (n->in.data[i]->type != N_LIT) return n;
-	}
+	/*
+	 * Is there a method to convey these transformations a little more nicely?
+	 *
+	 * add(lit, lit) -> lit
+	 * add(lit, add(N, lit)) -> add(N, add(lit, lit))
+	 *
+	 */
+
 	Node **in = n->in.data;
 	Node *r = n;
-	switch (n->type) {
-	case N_OP_NEG: r = node_new_lit_i64(p, -in[0]->lit.i); break;
-	case N_OP_NOT: r = node_new_lit_i64(p, ~in[0]->lit.i); break;
-	case N_OP_ADD: r = node_new_lit_i64(p, in[0]->lit.i + in[1]->lit.i); break;
-	case N_OP_SUB: r = node_new_lit_i64(p, in[0]->lit.i - in[1]->lit.i); break;
-	case N_OP_MUL: r = node_new_lit_i64(p, in[0]->lit.i * in[1]->lit.i); break;
-	case N_OP_DIV:
-		if (in[1]->lit.i == 0) {
-			lex_error_at(l, n->src_pos, LE_ERROR, S("Division by zero"));
+
+	int all_lit = 1;
+	for (int i = 0; i < n->in.len; i++) {
+		if (n->in.data[i]->type != N_LIT) all_lit = 0;
+	}
+
+	if (all_lit) {
+		switch (n->type) {
+		case N_OP_NEG: r = node_new_lit_i64(p, -in[0]->lit.i); break;
+		case N_OP_NOT: r = node_new_lit_i64(p, ~in[0]->lit.i); break;
+		case N_OP_ADD: r = node_new_lit_i64(p, in[0]->lit.i + in[1]->lit.i); break;
+		case N_OP_SUB: r = node_new_lit_i64(p, in[0]->lit.i - in[1]->lit.i); break;
+		case N_OP_MUL: r = node_new_lit_i64(p, in[0]->lit.i * in[1]->lit.i); break;
+		case N_OP_DIV:
+		       if (in[1]->lit.i == 0) {
+			       lex_error_at(l, n->src_pos, LE_ERROR, S("Division by zero"));
+		       }
+		       r = node_new_lit_i64(p, in[0]->lit.i / in[1]->lit.i);
+		       break;
+		case N_OP_AND: r = node_new_lit_i64(p, in[0]->lit.i & in[1]->lit.i); break;
+		case N_OP_OR: r = node_new_lit_i64(p, in[0]->lit.i | in[1]->lit.i); break;
+		case N_OP_XOR: r = node_new_lit_i64(p, in[0]->lit.i ^ in[1]->lit.i); break;
+		default: break;
 		}
-		r = node_new_lit_i64(p, in[0]->lit.i / in[1]->lit.i);
-		break;
-	case N_OP_AND: r = node_new_lit_i64(p, in[0]->lit.i & in[1]->lit.i); break;
-	case N_OP_OR: r = node_new_lit_i64(p, in[0]->lit.i | in[1]->lit.i); break;
-	case N_OP_XOR: r = node_new_lit_i64(p, in[0]->lit.i ^ in[1]->lit.i); break;
-	default:
-		return n;
-		break;
+	} else {
+		if (node_op_communative(n->type)
+				&& in[0]->type == N_LIT
+				&& in[1]->type == n->type
+				&& in[1]->in.data[0]->type != N_LIT
+				&& in[1]->in.data[1]->type == N_LIT) {
+			/* op(lit, op(X, lit)) -> op(X, op(lit, lit)) */
+			Node *tmp = in[1]->in.data[0];
+			in[1]->in.data[0] = in[0];
+			in[0] = tmp;
+		}
+	}
+
+	if (r != n) {
+		r->src_pos = n->src_pos;
+		if (n->out.len == 0) node_kill(n, p);
 	}
-	r->src_pos = n->src_pos;
-	if (n->out.len == 0) node_kill(n, p);
 	return r;
 }