feat: implement conditional expression

4 files changed, 53 insertions, 4 deletions

diff --git a/ast.c b/ast.c
index 8562088..6473d46 100644
--- a/ast.c
+++ b/ast.c
@@ -163,6 +163,7 @@ enum AstNodeKind {
     AstNodeKind_assign_expr,
     AstNodeKind_binary_expr,
     AstNodeKind_break_stmt,
+    AstNodeKind_cond_expr,
     AstNodeKind_continue_stmt,
     AstNodeKind_deref_expr,
     AstNodeKind_do_while_stmt,
diff --git a/codegen.c b/codegen.c
index f717c25..d6f320a 100644
--- a/codegen.c
+++ b/codegen.c
@@ -203,6 +203,20 @@ void codegen_binary_expr(CodeGen* g, AstNode* ast, GenMode gen_mode) {
     printf("  push rax\n");
 }
 
+void codegen_cond_expr(CodeGen* g, AstNode* ast, GenMode gen_mode) {
+    int label = codegen_new_label(g);
+
+    codegen_expr(g, ast->node_cond, GenMode_rval);
+    printf("  pop rax\n");
+    printf("  cmp rax, 0\n");
+    printf("  je .Lelse%d\n", label);
+    codegen_expr(g, ast->node_then, gen_mode);
+    printf("  jmp .Lend%d\n", label);
+    printf(".Lelse%d:\n", label);
+    codegen_expr(g, ast->node_else, gen_mode);
+    printf(".Lend%d:\n", label);
+}
+
 void codegen_assign_expr_helper(CodeGen* g, AstNode* ast) {
     if (ast->node_op == TokenKind_assign) {
         return;
@@ -379,6 +393,8 @@ void codegen_expr(CodeGen* g, AstNode* ast, GenMode gen_mode) {
         codegen_deref_expr(g, ast, gen_mode);
     } else if (ast->kind == AstNodeKind_binary_expr) {
         codegen_binary_expr(g, ast, gen_mode);
+    } else if (ast->kind == AstNodeKind_cond_expr) {
+        codegen_cond_expr(g, ast, gen_mode);
     } else if (ast->kind == AstNodeKind_logical_expr) {
         codegen_logical_expr(g, ast);
     } else if (ast->kind == AstNodeKind_assign_expr) {
diff --git a/parse.c b/parse.c
index c9b2886..a185241 100644
--- a/parse.c
+++ b/parse.c
@@ -707,22 +707,41 @@ AstNode* parse_logical_or_expr(Parser* p) {
     return lhs;
 }
 
+AstNode* parse_conditional_expr(Parser* p) {
+    AstNode* e = parse_logical_or_expr(p);
+    if (peek_token(p)->kind == TokenKind_question) {
+        next_token(p);
+        AstNode* then_expr = parse_expr(p);
+        expect(p, TokenKind_colon);
+        AstNode* else_expr = parse_assignment_expr(p);
+        AstNode* ret = ast_new(AstNodeKind_cond_expr);
+        ret->node_cond = e;
+        ret->node_then = then_expr;
+        ret->node_else = else_expr;
+        ret->ty = then_expr->ty;
+        return ret;
+    } else {
+        return e;
+    }
+}
+
 AstNode* parse_assignment_expr(Parser* p) {
-    AstNode* lhs = parse_logical_or_expr(p);
+    AstNode* lhs = parse_conditional_expr(p);
     while (1) {
         TokenKind op = peek_token(p)->kind;
+        // TODO: check if the lhs is unary expression.
         if (op == TokenKind_assign || op == TokenKind_assign_mul || op == TokenKind_assign_div ||
             op == TokenKind_assign_mod) {
             next_token(p);
-            AstNode* rhs = parse_logical_or_expr(p);
+            AstNode* rhs = parse_assignment_expr(p);
             lhs = ast_new_assign_expr(op, lhs, rhs);
         } else if (op == TokenKind_assign_add) {
             next_token(p);
-            AstNode* rhs = parse_logical_or_expr(p);
+            AstNode* rhs = parse_assignment_expr(p);
             lhs = ast_new_assign_add_expr(lhs, rhs);
         } else if (op == TokenKind_assign_sub) {
             next_token(p);
-            AstNode* rhs = parse_logical_or_expr(p);
+            AstNode* rhs = parse_assignment_expr(p);
             lhs = ast_new_assign_sub_expr(lhs, rhs);
         } else {
             break;
diff --git a/tests/091.sh b/tests/091.sh
new file mode 100644
index 0000000..9281811
--- /dev/null
+++ b/tests/091.sh
@@ -0,0 +1,13 @@
+set -e
+
+cat <<'EOF' > expected
+2 5
+EOF
+
+bash ../../test_diff.sh <<'EOF'
+int printf();
+
+int main() {
+    printf("%d %d\n", 1 ? 2 : 3, 0 ? 4 : 5);
+}
+EOF