Request for Reviews (S): JDK-8003585 strength reduce or eliminate range checks for power-of-two sized arrays

[Vladimir Kozlov]

I know it is duplication but CmpU creation should be under conditions otherwise you are creating and transforming dead node.

+     Node* ncmp = phase->transform(new CmpUNode(cmp1, cmp2));
+     if (_test._test == BoolTest::le || _test._test == BoolTest::eq) {

The test does not cover next conversions:

+   // Change (arraylength <= 0) or (arraylength == 0)
+   //   into (arraylength u<= 0)
+   // Also change (arraylength != 0) into (arraylength u> 0)

Thanks,
Vladimir

On 1/7/16 1:29 AM, Roland Westrelin wrote:
> Can I get a review for this?
>
> Roland.
>
>> On Oct 5, 2015, at 12:51 PM, Roland Westrelin <roland.westrelin at oracle.com> wrote:
>>
>> Here is a new webrev:
>>
>> http://cr.openjdk.java.net/~roland/8003585/webrev.01/
>>
>> Roland.
>>
>>> On Oct 2, 2015, at 3:30 PM, Roland Westrelin <roland.westrelin at oracle.com> wrote:
>>>
>>> Hi Chris,
>>>
>>>> Thanks for picking it up! It mostly looks good to me. (Not a Reviewer)
>>>
>>> Thanks for looking at this again.
>>>
>>>> What I really needed with my earlier webrev was some instructions as to what test to write -- since the Java corelibs can come across this optimization a lot (e.g. HashMap), I didn't have a good idea of what kind of test really needs to be written.
>>>>
>>>> A couple of issues with this webrev:
>>>>
>>>> 1. In subnode.cpp, line 1346:
>>>>
>>>> 1344     } else if (_test._test == BoolTest::lt &&
>>>> 1345                cmp2->Opcode() == Op_AddI &&
>>>> 1346                cmp2->in(2)->find_int_con(1)) {
>>>> 1347       bound = cmp2->in(1);
>>>> 1348     }
>>>>
>>>> I think it should be
>>>> cmp2->in(2)->find_int_con(0) == 1
>>>> instead, because the value passed into this function is actually for a "fallback when no int constant is found". Passing the expected value (1) to it defeats the purpose.
>>>
>>> You’re right. Thanks for spotting that.
>>>
>>>> jint find_int_con(jint value_if_unknown) const {
>>>>    const TypeInt* t = find_int_type();
>>>>    return (t != NULL && t->is_con()) ? t->get_con() : value_if_unknown;
>>>> }
>>>>
>>>> 2. Formattign nitpick: could you please trim the spaces before the new's on lines 1368, 1369 and 1387
>>>
>>> Sure.
>>>
>>> I’ll send an updated webrev.
>>>
>>> Roland.
>>>
>>>>
>>>> Thanks,
>>>> Kris (OpenJDK username: krismo)
>>>>
>>>> On Wed, Sep 30, 2015 at 1:34 AM, Roland Westrelin <roland.westrelin at oracle.com> wrote:
>>>> I’m picking that one up. Here is a new webrev:
>>>>
>>>> http://cr.openjdk.java.net/~roland/8003585/webrev.00/
>>>>
>>>> The only change to c2 compared to the previous webrev is that ((x & m) u< m+1) is optimized the same way ((x & m) u<= m) is. Actually, I don’t think that C2 currently produces the ((x & m) u<= m) shape. The IfNode::fold_compares() logic produces the ((x & m) u< m+1) variant. I also added a test case to check the validity of the transformations and ran usual testing on the change.
>>>>
>>>> Roland.
>>
>