[dart2wasm] Use Function.prototype.call.bind(Number.prototype.toString) for small ints and doubles

This increases `{int,double}.toString()` speed when switching to JS
strings (for `int`) and generally for `double`.

Change-Id: I5a3be41220f35c5226b63f09f5a7f9c25e262eb4
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/403981
Commit-Queue: Martin Kustermann <[email protected]>
Reviewed-by: Slava Egorov <[email protected]>

Author: mkustermann

sdk/lib/_internal/wasm/lib/boxed_double.dart

@@ -341,7 +341,12 @@ final class BoxedDouble implements double {
       }
     }
     String result = jsStringToDartString(
-      JSStringImpl(JS<WasmExternRef>("v => v.toString()", value)),
+      JSStringImpl(
+        JS<WasmExternRef?>(
+          'Function.prototype.call.bind(Number.prototype.toString)',
+          WasmF64.fromDouble(value),
+        ),
+      ),
     );
     if (this % 1.0 == 0.0 && result.indexOf('e') == -1) {
       result = '$result.0';

sdk/lib/_internal/wasm_js_compatibility/lib/boxed_int_to_string.dart

@@ -25,10 +25,19 @@ class BoxedInt {
 }
 
 @pragma("wasm:prefer-inline")
-String _jsBigIntToString(int i, int radix) => JSStringImpl(
-  JS<WasmExternRef?>(
-    'Function.prototype.call.bind(BigInt.prototype.toString)',
-    WasmI64.fromInt(i),
-    WasmI32.fromInt(radix),
-  ),
-);
+String _jsBigIntToString(int i, int radix) {
+  final upperBits = (i >> 31);
+  final result =
+      (upperBits == -1 || upperBits == 0)
+          ? JS<WasmExternRef?>(
+            'Function.prototype.call.bind(Number.prototype.toString)',
+            WasmI32.fromInt(i),
+            WasmI32.fromInt(radix),
+          )
+          : JS<WasmExternRef?>(
+            'Function.prototype.call.bind(BigInt.prototype.toString)',
+            WasmI64.fromInt(i),
+            WasmI32.fromInt(radix),
+          );
+  return JSStringImpl(result);
+}