From c85e4b4d2411e60af7387dec663ea62b03743eab Mon Sep 17 00:00:00 2001
From: Kimplul <kimi.h.kuparinen@gmail.com>
Date: Sun, 19 Nov 2023 20:25:45 +0200
Subject: add implicit ret to void functions

---
 include/ek/ast.h |  1 +
 include/ek/ops.h |  1 +
 src/actualize.c  |  5 +++++
 src/asm.c        | 22 +++++++++++++++++-----
 src/ops.c        | 17 +++++++++++++++++
 5 files changed, 41 insertions(+), 5 deletions(-)

diff --git a/include/ek/ast.h b/include/ek/ast.h
index d36860f..e078f59 100644
--- a/include/ek/ast.h
+++ b/include/ek/ast.h
@@ -22,6 +22,7 @@
 #define AST_CAST(x) x->_cast
 #define AST_PROC(x) x->_proc
 #define AST_VAR(x) x->_var
+#define AST_RETURN(x) x->_return
 #define AST_STRUCT(x) x->_struct
 #define AST_ENUM(x) x->_enum
 #define AST_CALL(x) x->_call
diff --git a/include/ek/ops.h b/include/ek/ops.h
index e913d37..0d9d433 100644
--- a/include/ek/ops.h
+++ b/include/ek/ops.h
@@ -27,6 +27,7 @@ enum opcode {
 	OP_LDT,
 	OP_STW,
 	OP_LDW,
+	OP_RET,
 	OP_MV, /* kind of meta op, will be realized as either load/store or register move */
 	OP_LABEL,
 	OP_COMMENT,
diff --git a/src/actualize.c b/src/actualize.c
index ab72589..694eca9 100644
--- a/src/actualize.c
+++ b/src/actualize.c
@@ -683,6 +683,11 @@ static int actualize_proc(struct act_state *state,
 			               "no return with non-void return type");
 			ret = -1;
 		}
+		/* add 'implicit' return */
+		struct ast_node *body = AST_PROC(actual).body;
+		struct ast_node *r = gen_return(NULL);
+		r->scope = body->scope;
+		ast_append(AST_BLOCK(body).body, r);
 	}
 	else if (ast_block_last(actual->_proc.body)->node_type != AST_RETURN) {
 		/* TODO: something more sophisticated than this */
diff --git a/src/asm.c b/src/asm.c
index 4102265..e2076f5 100644
--- a/src/asm.c
+++ b/src/asm.c
@@ -57,6 +57,17 @@ static int print_stt(struct op *op, FILE *f)
 	return 0;
 }
 
+static int print_ret(struct op *op, FILE *f)
+{
+	/* technically speaking ret takes a number of inputs, but they should be
+	 * marshaled into registers with moves etc. so don't worry about them
+	 * here */
+	fprintf(f, "jalr x0, 0(x21)\n");
+	/* eventually add in proper ret alias to assembly language once I go
+	 * through calling conventions etc. */
+	return 0;
+}
+
 static int print_op(struct op *op, FILE *f)
 {
 	int ret = 0;
@@ -66,6 +77,7 @@ static int print_op(struct op *op, FILE *f)
 	case OP_LI: ret = print_li(op, f); break;
 	case OP_MV: ret = print_mv(op, f); break;
 	case OP_STT: ret = print_stt(op, f); break;
+	case OP_RET: ret = print_ret(op, f); break;
 	default: abort();
 	}
 
@@ -77,7 +89,11 @@ int print_asm(struct ops *ops, const char *output)
 	FILE *f = fopen(output, "w");
 
 	/* main should probably be mangled here as well */
-	fprintf(f, "jal x0, main\n");
+	fprintf(f, "jal x21, main\n");
+	/* tell simulator to turn off (very much temp) */
+	fprintf(f, "li x1, 3\n");
+	fprintf(f, "csrrw mpower, x0, x1\n");
+
 	int ret = 0;
 	struct op *op = ops->base;
 	while (op) {
@@ -87,10 +103,6 @@ int print_asm(struct ops *ops, const char *output)
 		op = op->next;
 	}
 
-	/* tell simulator to turn off (very much temp) */
-	fprintf(f, "li x1, 3\n");
-	fprintf(f, "csrrw mpower, x0, x1\n");
-
 	fclose(f);
 	return ret;
 }
diff --git a/src/ops.c b/src/ops.c
index 625f0cf..9562035 100644
--- a/src/ops.c
+++ b/src/ops.c
@@ -252,6 +252,21 @@ static int lower_id(struct ast_node *n, struct ops *ops)
 	return 0;
 }
 
+static int lower_ret(struct ast_node *n, struct ops *ops)
+{
+	if (AST_RETURN(n).expr) {
+		int ret = lower_op(AST_RETURN(n).expr, ops);
+		if (ret)
+			return ret;
+	}
+
+	struct op *op = append_op(ops, OP_RET);
+	if (AST_RETURN(n).expr)
+		set_reg(&op->inputs, HEAD_OUTPUTS(ops).reg);
+
+	return 0;
+}
+
 static int lower_op(struct ast_node *n, struct ops *ops)
 {
 	int ret = 0;
@@ -264,6 +279,7 @@ static int lower_op(struct ast_node *n, struct ops *ops)
 	case AST_ASSIGN: ret = lower_assign(n, ops); break;
 	case AST_UNOP: ret = lower_unop(n, ops); break;
 	case AST_ID: ret = lower_id(n, ops); break;
+	case AST_RETURN: ret = lower_ret(n, ops); break;
 	default:
 		       semantic_error(n->scope->fctx, n, "unimplemented lowering");
 		       return -1;
@@ -316,6 +332,7 @@ static void print_op(struct op *op)
 	case OP_LDT: printf("ldt"); break;
 	case OP_STW: printf("stw"); break;
 	case OP_LDW: printf("ldw"); break;
+	case OP_RET: printf("ret"); break;
 	case OP_MV: printf("mv"); break;
 	default: printf("unimp"); break;
 	}
-- 
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