Preliminary RFR (L): 8001107: @Stable annotation for constant folding of lazily evaluated variables

[Vladimir Ivanov]

John,

I'm fine with both options (add an assert or use 
element_value(index).as_char() in product).

Vladimir K., what do you prefer?

Best regards,
Vladimir Ivanov

On 9/3/13 10:40 AM, John Rose wrote:
> On Aug 29, 2013, at 4:57 PM, Vladimir Kozlov <vladimir.kozlov at oracle.com
> <mailto:vladimir.kozlov at oracle.com>> wrote:
>
>>>> ciTypeArray.cpp: why we need these changes?
>>> I consider this as a cleanup. element_value(index).as_char() performs
>>> additional checks and it looks better (IMO, of course :-) ) than
>>> get_typeArrayOop()->char_at(index).
>>
>> But element_value() is much more expensive! I don't like this change.
>
> The old char_at function works fine, but I think it needs an assert that
> the array being referenced is truly a char[] array.  The more expensive
> element_value function performs this check, so it is safer.  It is also
> helpful to prove (at least via an assert) that element_value is a true
> extension of char_at.
>
> If we don't like making char_at slightly more expensive (it doesn't make
> much difference!) then I suggest putting the call to element_value into
> the #ifdef ASSERT, as follows:
>
>      assert(index >= 0 && index < length(), "out of range");
> !   jchar c = get_typeArrayOop()->char_at(index);
> ! #ifdef ASSERT
> !   jchar d = element_value(index).as_char();
> !   assert(c == d, "");
> ! #endif //ASSERT
> !   return c;
>    }
>
> — John