4 files changed, 52 insertions, 2 deletions

diff --git a/src/ast.c b/src/ast.c
index 84fe38e..d698543 100644
--- a/src/ast.c
+++ b/src/ast.c
@@ -282,6 +282,13 @@ AstNode* ast_new_member_access_expr(AstNode* obj, const char* name) {
     return e;
 }
 
+AstNode* ast_new_cast_expr(AstNode* operand, Type* result_ty) {
+    AstNode* e = ast_new(AstNodeKind_cast_expr);
+    e->node_operand = operand;
+    e->ty = result_ty;
+    return e;
+}
+
 int type_sizeof_struct(Type* ty) {
     int next_offset = 0;
     int struct_align = 0;
diff --git a/src/ast.h b/src/ast.h
index e0d8410..ce84739 100644
--- a/src/ast.h
+++ b/src/ast.h
@@ -89,6 +89,7 @@ typedef enum {
     AstNodeKind_assign_expr,
     AstNodeKind_binary_expr,
     AstNodeKind_break_stmt,
+    AstNodeKind_cast_expr,
     AstNodeKind_cond_expr,
     AstNodeKind_continue_stmt,
     AstNodeKind_deref_expr,
@@ -178,5 +179,6 @@ AstNode* ast_new_assign_sub_expr(AstNode* lhs, AstNode* rhs);
 AstNode* ast_new_ref_expr(AstNode* operand);
 AstNode* ast_new_deref_expr(AstNode* operand);
 AstNode* ast_new_member_access_expr(AstNode* obj, const char* name);
+AstNode* ast_new_cast_expr(AstNode* operand, Type* result_ty);
 
 #endif
diff --git a/src/codegen.c b/src/codegen.c
index 000126b..dccabe4 100644
--- a/src/codegen.c
+++ b/src/codegen.c
@@ -134,6 +134,46 @@ static void codegen_deref_expr(CodeGen* g, AstNode* ast, GenMode gen_mode) {
     }
 }
 
+static void codegen_cast_expr(CodeGen* g, AstNode* ast) {
+    codegen_expr(g, ast->node_operand, GenMode_rval);
+
+    int src_size = type_sizeof(ast->node_operand->ty);
+    int dst_size = type_sizeof(ast->ty);
+
+    if (src_size == dst_size)
+        return;
+
+    fprintf(g->out, "  pop rax\n");
+
+    if (dst_size == 1) {
+        fprintf(g->out, "  movsx rax, al\n");
+    } else if (dst_size == 2) {
+        if (src_size == 1) {
+            fprintf(g->out, "  movsx rax, al\n");
+        } else {
+            fprintf(g->out, "  movsx rax, ax\n");
+        }
+    } else if (dst_size == 4) {
+        if (src_size == 1) {
+            fprintf(g->out, "  movsx rax, al\n");
+        } else if (src_size == 2) {
+            fprintf(g->out, "  movsx rax, ax\n");
+        } else {
+            fprintf(g->out, "  movsxd rax, eax\n");
+        }
+    } else if (dst_size == 8) {
+        if (src_size == 1) {
+            fprintf(g->out, "  movsx rax, al\n");
+        } else if (src_size == 2) {
+            fprintf(g->out, "  movsx rax, ax\n");
+        } else if (src_size == 4) {
+            fprintf(g->out, "  movsxd rax, eax\n");
+        }
+    }
+
+    fprintf(g->out, "  push rax\n");
+}
+
 static void codegen_logical_expr(CodeGen* g, AstNode* ast) {
     int label = codegen_new_label(g);
 
@@ -406,6 +446,8 @@ static void codegen_expr(CodeGen* g, AstNode* ast, GenMode gen_mode) {
         codegen_ref_expr(g, ast, gen_mode);
     } else if (ast->kind == AstNodeKind_deref_expr) {
         codegen_deref_expr(g, ast, gen_mode);
+    } else if (ast->kind == AstNodeKind_cast_expr) {
+        codegen_cast_expr(g, ast);
     } else if (ast->kind == AstNodeKind_binary_expr) {
         codegen_binary_expr(g, ast, gen_mode);
     } else if (ast->kind == AstNodeKind_cond_expr) {
diff --git a/src/parse.c b/src/parse.c
index b6fa043..b65a6b3 100644
--- a/src/parse.c
+++ b/src/parse.c
@@ -577,8 +577,7 @@ static AstNode* parse_cast_expr(Parser* p) {
 
         // TODO: check whether the original type can be casted to the result type.
         AstNode* e = parse_cast_expr(p);
-        e->ty = ty;
-        return e;
+        return ast_new_cast_expr(e, ty);
     }
     return parse_prefix_expr(p);
 }