RFR(M): 8137168: Replace IfNode with a new RangeCheckNode for range checks

[Roland Westrelin]

Thanks for the review, Tobias. I’ll make the suggested changes.

Roland.

> On Nov 3, 2015, at 11:10 AM, Tobias Hartmann <tobias.hartmann at oracle.com> wrote:
> 
> Hi Roland,
> 
> I think this is a really nice feature allowing the compiler to optimize custom range checks in the library code.
> 
> The code looks good to me. Here are some minor comments (you don't need to send another webrev):
> 
> loopUnswitch.cpp: Please add brackets (for readability) here 
> 239   IfNode* iff = opcode == Op_RangeCheck ?
> 
> loopopts.cpp: Please add brackets here
> 1947   IfNode* new_if = opcode == Op_If ?
> 
> multnode.cpp: Please add spaces here:
> (which_proj?Op_IfTrue:Op_IfFalse)
> 
> In general: Not sure if there is an official rule for this but I prefer 'Node* ' over 'Node * '. At least we should be consistent for the newly added code.
> 
> Best,
> Tobias
> 
> On 25.09.2015 17:04, Roland Westrelin wrote:
>> This code adds a new ideal node, RangeCheckNode that is inserted during parsing when a range check is emitted. The entire change is code refactoring to accommodate the new node. This is preparation work for 8042997 and 8135248.
>> 
>> 8135248 will add a new method to java.util.Arrays:
>> 
>> int checkIndex(int index, int length,
>>               OutOfBoundsToException<T> oobe) throws T, IndexOutOfBoundsException {
>>    if (index < 0 || index >= length)
>>        throw outOfBounds(index, length, length, oobe);
>>    return index;
>> }
>> 
>> 8042997 will intrinsify that method and translate it into a CmpU + RangeCheckNode.
>> 
>> The benefit of the RangeCheckNode is that it will help the compiler locate range checks to optimize even if they don’t strictly follow the pattern of a range check: CmpU + IfNode + LoadRange. The idea of using a node specifically for range checks is from John. 
>> 
>> http://cr.openjdk.java.net/~roland/8137168/webrev.00/
>> 
>> Roland.
>>