Add "for" statement

chibicc.h

@@ -73,6 +73,7 @@ typedef enum {
   ND_ASSIGN,    // =
   ND_RETURN,    // "return"
   ND_IF,        // "if"
+  ND_FOR,       // "for"
   ND_BLOCK,     // { ... }
   ND_EXPR_STMT, // Expression statement
   ND_VAR,       // Variable
@@ -87,10 +88,12 @@ struct Node {
   Node *lhs;     // Left-hand side
   Node *rhs;     // Right-hand side
 
-  // "if" statement
+  // "if" or "for" statement
   Node *cond;
   Node *then;
   Node *els;
+  Node *init;
+  Node *inc;
 
   // Block
   Node *body;

codegen.c

@@ -113,6 +113,22 @@ static void gen_stmt(Node *node) {
     printf(".L.end.%d:\n", c);
     return;
   }
+  case ND_FOR: {
+    int c = count();
+    gen_stmt(node->init);
+    printf(".L.begin.%d:\n", c);
+    if (node->cond) {
+      gen_expr(node->cond);
+      printf("  cmp $0, %%rax\n");
+      printf("  je  .L.end.%d\n", c);
+    }
+    gen_stmt(node->then);
+    if (node->inc)
+      gen_expr(node->inc);
+    printf("  jmp .L.begin.%d\n", c);
+    printf(".L.end.%d:\n", c);
+    return;
+  }
   case ND_BLOCK:
     for (Node *n = node->body; n; n = n->next)
       gen_stmt(n);

parse.c

@@ -64,6 +64,7 @@ static Obj *new_lvar(char *name) {
 
 // stmt = "return" expr ";"
 //      | "if" "(" expr ")" stmt ("else" stmt)?
+//      | "for" "(" expr-stmt expr? ";" expr? ")" stmt
 //      | "{" compound-stmt
 //      | expr-stmt
 static Node *stmt(Token **rest, Token *tok) {
@@ -85,6 +86,24 @@ static Node *stmt(Token **rest, Token *tok) {
     return node;
   }
 
+  if (equal(tok, "for")) {
+    Node *node = new_node(ND_FOR);
+    tok = skip(tok->next, "(");
+
+    node->init = expr_stmt(&tok, tok);
+
+    if (!equal(tok, ";"))
+      node->cond = expr(&tok, tok);
+    tok = skip(tok, ";");
+
+    if (!equal(tok, ")"))
+      node->inc = expr(&tok, tok);
+    tok = skip(tok, ")");
+
+    node->then = stmt(rest, tok);
+    return node;
+  }
+
   if (equal(tok, "{"))
     return compound_stmt(rest, tok->next);
 

test.sh

@@ -69,4 +69,7 @@ assert 2 '{ if (2-1) return 2; return 3; }'
 assert 4 '{ if (0) { 1; 2; return 3; } else { return 4; } }'
 assert 3 '{ if (1) { 1; 2; return 3; } else { return 4; } }'
 
+assert 55 '{ i=0; j=0; for (i=0; i<=10; i=i+1) j=i+j; return j; }'
+assert 3 '{ for (;;) {return 3;} return 5; }'
+
 echo OK

tokenize.c

@@ -80,7 +80,7 @@ static int read_punct(char *p) {
 }
 
 static bool is_keyword(Token *tok) {
-  static char *kw[] = {"return", "if", "else"};
+  static char *kw[] = {"return", "if", "else", "for"};
 
   for (int i = 0; i < sizeof(kw) / sizeof(*kw); i++)
     if (equal(tok, kw[i]))