[Jikesrvm-core] [ jikesrvm-Patches-1396338 ] Exploit commutativity in CSE - RFE 1147152

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Patches item #1396338, was opened at 2006-01-03 22:43
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Category: None
Group: None
Status: Open
Resolution: None
Priority: 5
Submitted By: Bernardo Pastorelli (bpastore)
Assigned to: Nobody/Anonymous (nobody)
Summary: Exploit commutativity in CSE - RFE 1147152

Initial Comment:
I added a new attribute to every operator: commutative.
If an operator is marked as commutative, the equals
method of class AvailableExpression checks both:
- l.op1 similar r.op1 && l.op2 similar r.op2
- l.op1 similar r.op2 && l.op2 similar r.op1
to define if two available expressions are equivalent.

The patch is based on Jikes RVM 2.4.2.
I tested the code on Linux Intel.

A different approach could have been to define a total
ordering on the operands. Using this ordering, in case
the operand was commutative, the constructor of
AvailableExpression could have been assigned to op1 the
smallest operand and to op2 the greatest one. This way
only one check had been required in equals. But define
that ordering seemd to be quite complex, so I decided
for the current implementation. Let me know if you
prefer the one based on defining the ordering and
changing the constructor; I can try to implement it.


        STATEMENT OF ORIGIN FOR A SINGLE CONTRIBUTOR

I, __Bernardo Pastorelli____: 

(a) represent that either:

  (i) I am the only author and owner of the contributed
software 
      (described as/entitled
____________________________), 
      which was neither derived nor copied from any
other software,
  or 

 (ii) that any exception to (i) is software which was
obtained under the 
      CPL (Common Public License), 

and   

(b)  hereby agree to license this contributed software
under the CPL.


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