[bindings] Split toUInt32 into faster inline and non-inline slower path.

Source/bindings/core/v8/V8Binding.h

Index: Source/bindings/core/v8/V8Binding.h
diff --git a/Source/bindings/core/v8/V8Binding.h b/Source/bindings/core/v8/V8Binding.h
index abbd3fdcb5e710b26fa3e970e9fbc827d746710e..b705e352af6da2c6f64ec52952bacede1be60b82 100644
--- a/Source/bindings/core/v8/V8Binding.h
+++ b/Source/bindings/core/v8/V8Binding.h
@@ -432,7 +432,29 @@ int32_t toInt32(v8::Handle<v8::Value>);
 // Convert a value to a 32-bit unsigned integer. The conversion fails if the
 // value cannot be converted to a number or the range violated per WebIDL:
 // http://www.w3.org/TR/WebIDL/#es-unsigned-long
-uint32_t toUInt32(v8::Handle<v8::Value>, IntegerConversionConfiguration, ExceptionState&);
+uint32_t toUInt32Slow(v8::Handle<v8::Value>, IntegerConversionConfiguration, ExceptionState&);
+inline uint32_t toUInt32(v8::Handle<v8::Value> value, IntegerConversionConfiguration configuration, ExceptionState& exceptionState)
+{
+    // Fast case. The value is already a 32-bit unsigned integer.
+    if (value->IsUint32())
+        return value->Uint32Value();
+
+    // Fast case. The value is a 32-bit signed integer - possibly positive?
+    if (value->IsInt32()) {
+        int32_t result = value->Int32Value();
+        if (result >= 0)
+            return result;
+        if (configuration == EnforceRange) {

[Jens Widell, 2015/02/23 11:41:56]

I think in principle that we're inlining too much here. As a rule of thumb,
optimizing error handling code is never meaningful.

It's probably fine here since 'configuration' will be known (it's a constant at
all call sites) meaning the compiler ought to have no trouble eliminating this
clause (and the next) in every instance where it's inlined.

But still, I think it would look better if you make the outer if-statement

  if (value->IsInt32() && configuration == NormalConversion) {
    ...
  }

and skip these two if-statements (move them to toUInt32Slow()).

+            exceptionState.throwTypeError("Value is outside the 'unsigned long' value range.");
+            return 0;
+        }
+        if (configuration == Clamp)
+            return clampTo<uint32_t>(result);
+        return result;
+    }
+    return toUInt32Slow(value, configuration, exceptionState);
+}
+
 inline uint32_t toUInt32(v8::Handle<v8::Value> value, ExceptionState& exceptionState)
 {
     return toUInt32(value, NormalConversion, exceptionState);