[GNU] Support case ranges

chibicc.h

@@ -259,10 +259,14 @@ struct Node {
   char *unique_label;
   Node *goto_next;
 
-  // Switch-cases
+  // Switch
   Node *case_next;
   Node *default_case;
 
+  // Case
+  long begin;
+  long end;
+
   // "asm" string literal
   char *asm_str;
 

codegen.c

@@ -1160,9 +1160,20 @@ static void gen_stmt(Node *node) {
     gen_expr(node->cond);
 
     for (Node *n = node->case_next; n; n = n->case_next) {
-      char *reg = (node->cond->ty->size == 8) ? "%rax" : "%eax";
-      println("  cmp $%ld, %s", n->val, reg);
-      println("  je %s", n->label);
+      char *ax = (node->cond->ty->size == 8) ? "%rax" : "%eax";
+      char *di = (node->cond->ty->size == 8) ? "%rdi" : "%edi";
+
+      if (n->begin == n->end) {
+        println("  cmp $%ld, %s", n->begin, ax);
+        println("  je %s", n->label);
+        continue;
+      }
+
+      // [GNU] Case ranges
+      println("  mov %s, %s", ax, di);
+      println("  sub $%ld, %s", n->begin, di);
+      println("  cmp $%ld, %s", n->end - n->begin, di);
+      println("  jbe %s", n->label);
     }
 
     if (node->default_case)

parse.c

@@ -1507,7 +1507,7 @@ static Node *asm_stmt(Token **rest, Token *tok) {
 // stmt = "return" expr? ";"
 //      | "if" "(" expr ")" stmt ("else" stmt)?
 //      | "switch" "(" expr ")" stmt
-//      | "case" const-expr ":" stmt
+//      | "case" const-expr ("..." const-expr)? ":" stmt
 //      | "default" ":" stmt
 //      | "for" "(" expr-stmt expr? ";" expr? ")" stmt
 //      | "while" "(" expr ")" stmt
@@ -1573,11 +1573,23 @@ static Node *stmt(Token **rest, Token *tok) {
       error_tok(tok, "stray case");
 
     Node *node = new_node(ND_CASE, tok);
-    int val = const_expr(&tok, tok->next);
+    int begin = const_expr(&tok, tok->next);
+    int end;
+
+    if (equal(tok, "...")) {
+      // [GNU] Case ranges, e.g. "case 1 ... 5:"
+      end = const_expr(&tok, tok->next);
+      if (end < begin)
+        error_tok(tok, "empty case range specified");
+    } else {
+      end = begin;
+    }
+
     tok = skip(tok, ":");
     node->label = new_unique_name();
     node->lhs = stmt(rest, tok);
-    node->val = val;
+    node->begin = begin;
+    node->end = end;
     node->case_next = current_switch->case_next;
     current_switch->case_next = node;
     return node;

test/control.c

@@ -83,6 +83,10 @@ int main() {
   ASSERT(10, ({ double i=10.0; int j=0; for (; i; i--, j++); j; }));
   ASSERT(10, ({ double i=10.0; int j=0; do j++; while(--i); j; }));
 
+  ASSERT(2, ({ int i=0; switch(7) { case 0 ... 5: i=1; break; case 6 ... 20: i=2; break; } i; }));
+  ASSERT(1, ({ int i=0; switch(7) { case 0 ... 7: i=1; break; case 8 ... 10: i=2; break; } i; }));
+  ASSERT(1, ({ int i=0; switch(7) { case 0: i=1; break; case 7 ... 7: i=1; break; } i; }));
+
   printf("OK\n");
   return 0;
 }