Add ==, !=, <= and >= operators

main.c

@@ -89,6 +89,19 @@ static Token *new_token(TokenKind kind, char *start, char *end) {
   return tok;
 }
 
+static bool startswith(char *p, char *q) {
+  return strncmp(p, q, strlen(q)) == 0;
+}
+
+// Read a punctuator token from p and returns its length.
+static int read_punct(char *p) {
+  if (startswith(p, "==") || startswith(p, "!=") ||
+      startswith(p, "<=") || startswith(p, ">="))
+    return 2;
+
+  return ispunct(*p) ? 1 : 0;
+}
+
 // Tokenize `current_input` and returns new tokens.
 static Token *tokenize(void) {
   char *p = current_input;
@@ -112,9 +125,10 @@ static Token *tokenize(void) {
     }
 
     // Punctuators
-    if (ispunct(*p)) {
-      cur = cur->next = new_token(TK_PUNCT, p, p + 1);
-      p++;
+    int punct_len = read_punct(p);
+    if (punct_len) {
+      cur = cur->next = new_token(TK_PUNCT, p, p + punct_len);
+      p += cur->len;
       continue;
     }
 
@@ -135,6 +149,10 @@ typedef enum {
   ND_MUL, // *
   ND_DIV, // /
   ND_NEG, // unary -
+  ND_EQ,  // ==
+  ND_NE,  // !=
+  ND_LT,  // <
+  ND_LE,  // <=
   ND_NUM, // Integer
 } NodeKind;
 
@@ -173,12 +191,70 @@ static Node *new_num(int val) {
 }
 
 static Node *expr(Token **rest, Token *tok);
+static Node *equality(Token **rest, Token *tok);
+static Node *relational(Token **rest, Token *tok);
+static Node *add(Token **rest, Token *tok);
 static Node *mul(Token **rest, Token *tok);
 static Node *unary(Token **rest, Token *tok);
 static Node *primary(Token **rest, Token *tok);
 
-// expr = mul ("+" mul | "-" mul)*
+// expr = equality
 static Node *expr(Token **rest, Token *tok) {
+  return equality(rest, tok);
+}
+
+// equality = relational ("==" relational | "!=" relational)*
+static Node *equality(Token **rest, Token *tok) {
+  Node *node = relational(&tok, tok);
+
+  for (;;) {
+    if (equal(tok, "==")) {
+      node = new_binary(ND_EQ, node, relational(&tok, tok->next));
+      continue;
+    }
+
+    if (equal(tok, "!=")) {
+      node = new_binary(ND_NE, node, relational(&tok, tok->next));
+      continue;
+    }
+
+    *rest = tok;
+    return node;
+  }
+}
+
+// relational = add ("<" add | "<=" add | ">" add | ">=" add)*
+static Node *relational(Token **rest, Token *tok) {
+  Node *node = add(&tok, tok);
+
+  for (;;) {
+    if (equal(tok, "<")) {
+      node = new_binary(ND_LT, node, add(&tok, tok->next));
+      continue;
+    }
+
+    if (equal(tok, "<=")) {
+      node = new_binary(ND_LE, node, add(&tok, tok->next));
+      continue;
+    }
+
+    if (equal(tok, ">")) {
+      node = new_binary(ND_LT, add(&tok, tok->next), node);
+      continue;
+    }
+
+    if (equal(tok, ">=")) {
+      node = new_binary(ND_LE, add(&tok, tok->next), node);
+      continue;
+    }
+
+    *rest = tok;
+    return node;
+  }
+}
+
+// add = mul ("+" mul | "-" mul)*
+static Node *add(Token **rest, Token *tok) {
   Node *node = mul(&tok, tok);
 
   for (;;) {
@@ -292,6 +368,23 @@ static void gen_expr(Node *node) {
     printf("  cqo\n");
     printf("  idiv %%rdi\n");
     return;
+  case ND_EQ:
+  case ND_NE:
+  case ND_LT:
+  case ND_LE:
+    printf("  cmp %%rdi, %%rax\n");
+
+    if (node->kind == ND_EQ)
+      printf("  sete %%al\n");
+    else if (node->kind == ND_NE)
+      printf("  setne %%al\n");
+    else if (node->kind == ND_LT)
+      printf("  setl %%al\n");
+    else if (node->kind == ND_LE)
+      printf("  setle %%al\n");
+
+    printf("  movzb %%al, %%rax\n");
+    return;
   }
 
   error("invalid expression");

test.sh

@@ -27,4 +27,23 @@ assert 10 '-10+20'
 assert 10 '- -10'
 assert 10 '- - +10'
 
+assert 0 '0==1'
+assert 1 '42==42'
+assert 1 '0!=1'
+assert 0 '42!=42'
+
+assert 1 '0<1'
+assert 0 '1<1'
+assert 0 '2<1'
+assert 1 '0<=1'
+assert 1 '1<=1'
+assert 0 '2<=1'
+
+assert 1 '1>0'
+assert 0 '1>1'
+assert 0 '1>2'
+assert 1 '1>=0'
+assert 1 '1>=1'
+assert 0 '1>=2'
+
 echo OK