feat: add while loops

1 files changed, 73 insertions, 32 deletions

diff --git a/src/nasm.c b/src/nasm.c
index 15f5f01..7a7d1e6 100644
--- a/src/nasm.c
+++ b/src/nasm.c
@@ -999,51 +999,64 @@ static void emit_float_operand(struct Emitter* emitter, const struct Expr* expr)
 	fprintf(emitter->out, "%.*s", (int)token.length, token.start);
 }
 
-static void emit_if(struct Emitter* emitter, struct IfStatement* branch)
+// Emits the comparison for `left cmp right` and a jump to `target` taken when
+// the condition is false, so the code that follows runs when it is true. Both
+// if and while build on this. Returns false (after a TODO note) for a form that
+// isn't supported yet.
+static bool emit_branch_test(struct Emitter* emitter, struct Expr* left,
+	struct Token comparison, struct Expr* right, const char* target)
 {
-	bool is_float = value_is_float(emitter, branch->left) || value_is_float(emitter, branch->right);
-	bool has_else = branch->else_count > 0;
-
-	uint32_t id = emitter->label_id;
-	emitter->label_id += 1;
-
-	const char* target = has_else ? ".if_else_" : ".if_end_";
+	bool is_float = value_is_float(emitter, left) || value_is_float(emitter, right);
 
 	if (is_float)
 	{
-		const char* jump = float_jump_if_false(branch->comparison.type);
-		bool left_reg = branch->left->kind == EXPR_PRIMARY
-			&& is_float_register(resolve_register(emitter, branch->left->primary.token));
-		if (jump == NULL || !left_reg || !value_is_float(emitter, branch->right))
+		const char* jump = float_jump_if_false(comparison.type);
+		bool left_reg = left->kind == EXPR_PRIMARY
+			&& is_float_register(resolve_register(emitter, left->primary.token));
+		if (jump == NULL || !left_reg || !value_is_float(emitter, right))
 		{
-			fprintf(emitter->out, "\t; TODO: unsupported if\n");
-			return;
+			fprintf(emitter->out, "\t; TODO: unsupported condition\n");
+			return false;
 		}
 
 		fprintf(emitter->out, "\tucomisd ");
-		emit_float_operand(emitter, branch->left);
+		emit_float_operand(emitter, left);
 		fprintf(emitter->out, ", ");
-		emit_float_operand(emitter, branch->right);
-		fprintf(emitter->out, "\n\t%s %s%u\n", jump, target, id);
+		emit_float_operand(emitter, right);
+		fprintf(emitter->out, "\n\t%s %s\n", jump, target);
+		return true;
 	}
-	else
-	{
-		const char* jump = jump_if_false(branch->comparison.type);
-		if (jump == NULL
-			|| branch->left->kind == EXPR_BINARY || branch->left->kind == EXPR_DEREF
-			|| branch->right->kind == EXPR_BINARY || branch->right->kind == EXPR_DEREF)
-		{
-			fprintf(emitter->out, "\t; TODO: unsupported if\n");
-			return;
-		}
 
-		fprintf(emitter->out, "\tcmp ");
-		emit_operand(emitter, branch->left);
-		fprintf(emitter->out, ", ");
-		emit_operand(emitter, branch->right);
-		fprintf(emitter->out, "\n\t%s %s%u\n", jump, target, id);
+	const char* jump = jump_if_false(comparison.type);
+	if (jump == NULL
+		|| left->kind == EXPR_BINARY || left->kind == EXPR_DEREF
+		|| right->kind == EXPR_BINARY || right->kind == EXPR_DEREF)
+	{
+		fprintf(emitter->out, "\t; TODO: unsupported condition\n");
+		return false;
 	}
 
+	fprintf(emitter->out, "\tcmp ");
+	emit_operand(emitter, left);
+	fprintf(emitter->out, ", ");
+	emit_operand(emitter, right);
+	fprintf(emitter->out, "\n\t%s %s\n", jump, target);
+	return true;
+}
+
+static void emit_if(struct Emitter* emitter, struct IfStatement* branch)
+{
+	bool has_else = branch->else_count > 0;
+
+	uint32_t id = emitter->label_id;
+	emitter->label_id += 1;
+
+	char target[32];
+	snprintf(target, sizeof(target), ".if_%s_%u", has_else ? "else" : "end", id);
+
+	if (!emit_branch_test(emitter, branch->left, branch->comparison, branch->right, target))
+		return;
+
 	emit_block(emitter, branch->body, branch->body_count);
 
 	if (has_else)
@@ -1056,6 +1069,25 @@ static void emit_if(struct Emitter* emitter, struct IfStatement* branch)
 	fprintf(emitter->out, ".if_end_%u:\n", id);
 }
 
+static void emit_while(struct Emitter* emitter, struct WhileStatement* loop)
+{
+	uint32_t id = emitter->label_id;
+	emitter->label_id += 1;
+
+	char target[32];
+	snprintf(target, sizeof(target), ".while_end_%u", id);
+
+	fprintf(emitter->out, ".while_%u:\n", id);
+
+	if (!emit_branch_test(emitter, loop->left, loop->comparison, loop->right, target))
+		return;
+
+	emit_block(emitter, loop->body, loop->body_count);
+
+	fprintf(emitter->out, "\tjmp .while_%u\n", id);
+	fprintf(emitter->out, ".while_end_%u:\n", id);
+}
+
 static void emit_statement(struct Emitter* emitter, struct Statement* statement)
 {
 	FILE* out = emitter->out;
@@ -1076,6 +1108,9 @@ static void emit_statement(struct Emitter* emitter, struct Statement* statement)
 		case STATEMENT_IF:
 			emit_if(emitter, &statement->branch);
 			break;
+		case STATEMENT_WHILE:
+			emit_while(emitter, &statement->loop);
+			break;
 		case STATEMENT_CALL:
 			emit_call(emitter, &statement->call);
 			break;
@@ -1161,6 +1196,12 @@ static void collect_floats_statement(struct FloatTable* floats, struct Statement
 			for (size_t i = 0; i < statement->branch.else_count; i += 1)
 				collect_floats_statement(floats, &statement->branch.else_body[i]);
 			break;
+		case STATEMENT_WHILE:
+			collect_floats_expr(floats, statement->loop.left);
+			collect_floats_expr(floats, statement->loop.right);
+			for (size_t i = 0; i < statement->loop.body_count; i += 1)
+				collect_floats_statement(floats, &statement->loop.body[i]);
+			break;
 		case STATEMENT_CALL:
 			for (size_t i = 0; i < statement->call.arg_count; i += 1)
 				collect_floats_expr(floats, statement->call.args[i]);