Add ?: operator

Author: rui314

chibicc.h

@@ -101,6 +101,7 @@ typedef enum {
   ND_LT,        // <
   ND_LE,        // <=
   ND_ASSIGN,    // =
+  ND_COND,      // ?:
   ND_COMMA,     // ,
   ND_MEMBER,    // . (struct member access)
   ND_ADDR,      // unary &

codegen.c

@@ -209,6 +209,18 @@ static void gen_expr(Node *node) {
     gen_expr(node->lhs);
     cast(node->lhs->ty, node->ty);
     return;
+  case ND_COND: {
+    int c = count();
+    gen_expr(node->cond);
+    println("  cmp $0, %%rax");
+    println("  je .L.else.%d", c);
+    gen_expr(node->then);
+    println("  jmp .L.end.%d", c);
+    println(".L.else.%d:", c);
+    gen_expr(node->els);
+    println(".L.end.%d:", c);
+    return;
+  }
   case ND_NOT:
     gen_expr(node->lhs);
     println("  cmp $0, %%rax");

parse.c

@@ -97,6 +97,7 @@ static Node *expr_stmt(Token **rest, Token *tok);
 static Node *expr(Token **rest, Token *tok);
 static Node *assign(Token **rest, Token *tok);
 static Node *logor(Token **rest, Token *tok);
+static Node *conditional(Token **rest, Token *tok);
 static Node *logand(Token **rest, Token *tok);
 static Node *bitor(Token **rest, Token *tok);
 static Node *bitxor(Token **rest, Token *tok);
@@ -856,11 +857,11 @@ static Node *to_assign(Node *binary) {
   return new_binary(ND_COMMA, expr1, expr2, tok);
 }
 
-// assign    = logor (assign-op assign)?
+// assign    = conditional (assign-op assign)?
 // assign-op = "=" | "+=" | "-=" | "*=" | "/=" | "%=" | "&=" | "|=" | "^="
 //           | "<<=" | ">>="
 static Node *assign(Token **rest, Token *tok) {
-  Node *node = logor(&tok, tok);
+  Node *node = conditional(&tok, tok);
 
   if (equal(tok, "="))
     return new_binary(ND_ASSIGN, node, assign(rest, tok->next), tok);
@@ -899,6 +900,23 @@ static Node *assign(Token **rest, Token *tok) {
   return node;
 }
 
+// conditional = logor ("?" expr ":" conditional)?
+static Node *conditional(Token **rest, Token *tok) {
+  Node *cond = logor(&tok, tok);
+
+  if (!equal(tok, "?")) {
+    *rest = tok;
+    return cond;
+  }
+
+  Node *node = new_node(ND_COND, tok);
+  node->cond = cond;
+  node->then = expr(&tok, tok->next);
+  tok = skip(tok, ":");
+  node->els = conditional(rest, tok);
+  return node;
+}
+
 // logor = logand ("||" logand)*
 static Node *logor(Token **rest, Token *tok) {
   Node *node = logand(&tok, tok);

test/arith.c

@@ -108,6 +108,19 @@ int main() {
   ASSERT(-1, ({ int i=-1; i; }));
   ASSERT(-1, ({ int i=-1; i>>=1; i; }));
 
+  ASSERT(2, 0?1:2);
+  ASSERT(1, 1?1:2);
+  ASSERT(-1, 0?-2:-1);
+  ASSERT(-2, 1?-2:-1);
+  ASSERT(4, sizeof(0?1:2));
+  ASSERT(8, sizeof(0?(long)1:(long)2));
+  ASSERT(-1, 0?(long)-2:-1);
+  ASSERT(-1, 0?-2:(long)-1);
+  ASSERT(-2, 1?(long)-2:-1);
+  ASSERT(-2, 1?-2:(long)-1);
+
+  1 ? -2 : (void)-1;
+
   printf("OK\n");
   return 0;
 }

type.c

@@ -145,6 +145,14 @@ void add_type(Node *node) {
   case ND_VAR:
     node->ty = node->var->ty;
     return;
+  case ND_COND:
+    if (node->then->ty->kind == TY_VOID || node->els->ty->kind == TY_VOID) {
+      node->ty = ty_void;
+    } else {
+      usual_arith_conv(&node->then, &node->els);
+      node->ty = node->then->ty;
+    }
+    return;
   case ND_COMMA:
     node->ty = node->rhs->ty;
     return;