Remove redundant calls of toString()
aph at redhat.com
Tue Apr 29 10:03:40 UTC 2014
On 04/29/2014 10:58 AM, David Holmes wrote:
> On 29/04/2014 7:40 PM, Andrew Haley wrote:
>> On 04/28/2014 07:57 AM, David Holmes wrote:
>>> On 28/04/2014 1:05 PM, Otávio Gonçalves de Santana wrote:
>>>> In my opinion not, because Objects.requireNonNull is more readable than
>>>> just string.toString. This way is more understandable which field is
>>>> required and doesn't impact on performance.
>>> An invocation of requireNonNull is potentially more expensive than the
>>> implicit null check that happens with foo.toString().
>> It's also potentially cheaper: a cbnz versus a fetch from memory with a
>> few cycles pipeline delay.
> Can you elaborate please? AFAIK implicit null checks have no overhead
> when the object reference is not null.
I'm sorry, that remark was too simplistic.
If you have to read the data at that time, I agree. And it might do
some useful prefetching. But if you're just checking the object is
non-null it may be cheaper to do (o != null) . I have noticed that
some Java code does (o.getClass()) or something similar to get an
implicit check rather than if (o != null)...
> Interpreted it is slower and the bytecode footprint is larger.
> IIRC the guidelines for use of requireNonNull in the JDK code was for
> replacing explicit null checks in precondition checking, not implicit ones.
> Anyway I don't find these changes compelling.
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