Bug 1511401 part 3. Inline the fast (no error) path of requireAtLeast. r=nbp

We don't want to pay the cost of a function call here in DOM bindings.

js/public/CallArgs.h

@@ -309,13 +309,28 @@ class MOZ_STACK_CLASS CallArgs
     return args;
   }
 
+  /*
+   * Helper for requireAtLeast to report the actual exception.
+   */
+  static JS_PUBLIC_API void reportMoreArgsNeeded(JSContext* cx,
+                                                 const char* fnname,
+                                                 unsigned required,
+                                                 unsigned actual);
+
  public:
   /*
    * Returns true if there are at least |required| arguments passed in. If
    * false, it reports an error message on the context.
    */
-  JS_PUBLIC_API bool requireAtLeast(JSContext* cx, const char* fnname,
-                                    unsigned required) const;
+  JS_PUBLIC_API inline bool requireAtLeast(JSContext* cx, const char* fnname,
+                                           unsigned required) const {
+    if (MOZ_LIKELY(required <= length())) {
+      return true;
+    }
+
+    reportMoreArgsNeeded(cx, fnname, required, length());
+    return false;
+  }
 };
 
 MOZ_ALWAYS_INLINE CallArgs CallArgsFromVp(unsigned argc, Value* vp) {

js/src/jsapi.cpp

@@ -124,21 +124,17 @@ using JS::SourceText;
 #define JS_ADDRESSOF_VA_LIST(ap) (&(ap))
 #endif
 
-JS_PUBLIC_API bool JS::CallArgs::requireAtLeast(JSContext* cx,
-                                                const char* fnname,
-                                                unsigned required) const {
-  if (length() < required) {
-    char requiredArgsStr[40];
-    SprintfLiteral(requiredArgsStr, "%u", required);
-    char actualArgsStr[40];
-    SprintfLiteral(actualArgsStr, "%u", length());
-    JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
-                              JSMSG_MORE_ARGS_NEEDED, fnname, requiredArgsStr,
-                              required == 1 ? "" : "s", actualArgsStr);
-    return false;
-  }
-
-  return true;
+JS_PUBLIC_API void JS::CallArgs::reportMoreArgsNeeded(JSContext* cx,
+                                                      const char* fnname,
+                                                      unsigned required,
+                                                      unsigned actual) {
+  char requiredArgsStr[40];
+  SprintfLiteral(requiredArgsStr, "%u", required);
+  char actualArgsStr[40];
+  SprintfLiteral(actualArgsStr, "%u", actual);
+  JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
+                            JSMSG_MORE_ARGS_NEEDED, fnname, requiredArgsStr,
+                            required == 1 ? "" : "s", actualArgsStr);
 }
 
 static bool ErrorTakesArguments(unsigned msg) {