[PATCH olang v1 1/2] codegen: x86_64: extract function to emit expression

[Johnny Richard <johnny@johnnyrichard.com>]

We want to generalize how we emit expressions since we could have
different ast_node types.  Today we are expecting integer literal but we
want to make room for emitting binary operations as well.

Signed-off-by: Johnny Richard <johnny@johnnyrichard.com>
---
 src/codegen_linux_x86_64.c | 29 ++++++++++++++++++++++-------
 1 file changed, 22 insertions(+), 7 deletions(-)

diff --git a/src/codegen_linux_x86_64.c b/src/codegen_linux_x86_64.c
index d4f8222..72db1c6 100644
--- a/src/codegen_linux_x86_64.c
+++ b/src/codegen_linux_x86_64.c
@@ -56,6 +56,24 @@ codegen_linux_x86_64_emit_start_entrypoint(FILE *out)
     fprintf(out, "    syscall\n");
 }
 
+static void
+codegen_linux_x86_64_emit_expression(FILE *out, ast_node_t *expr_node)
+{
+    switch (expr_node->kind) {
+        case AST_NODE_LITERAL: {
+            ast_literal_t literal_u32 = expr_node->data.as_literal;
+            assert(literal_u32.kind == AST_LITERAL_U32);
+            uint32_t exit_code = literal_u32.value.as_u32;
+
+            fprintf(out, "    mov $%d, %%eax\n", exit_code);
+            return;
+        }
+        case AST_NODE_BINARY_OP:
+        default:
+            assert(0 && "NOT IMPLEMENTED");
+    }
+}
+
 static void
 codegen_linux_x86_64_emit_function(FILE *out, ast_fn_definition_t *fn)
 {
@@ -70,14 +88,11 @@ codegen_linux_x86_64_emit_function(FILE *out, ast_fn_definition_t *fn)
     assert(return_node->kind == AST_NODE_RETURN_STMT);
     ast_return_stmt_t return_stmt = return_node->data.as_return_stmt;
 
-    ast_node_t *literal_node = return_stmt.data;
-    assert(literal_node->kind == AST_NODE_LITERAL);
-    ast_literal_t literal_u32 = literal_node->data.as_literal;
-
-    assert(literal_u32.kind == AST_LITERAL_U32);
-    uint32_t exit_code = literal_u32.value.as_u32;
+    ast_node_t *expr = return_stmt.data;
 
     fprintf(out, "" SV_FMT ":\n", SV_ARG(fn->identifier));
-    fprintf(out, "    mov $%d, %%eax\n", exit_code);
+
+    codegen_linux_x86_64_emit_expression(out, expr);
+
     fprintf(out, "    ret\n");
 }
-- 
2.44.0