values types for Java

[Andrew Haley]

Patrik Reali writes:
 > Andrew Haley writes:
 > > Patrik Reali writes:
 > >  >
 > >  >  [proposal http://gcc.gnu.org/ml/java/2003-10/msg00169.html]
 > >
 > > I don't see the point of this.
 > >
 > > If we can show at compile time that an object does not escape the
 > > context (either a method or a thread) where it was created, we can
 > > automagically stack assign that object.  Escape analysis for Java is
 > > quite well understood;
 > >
 > > J.-D. Choi, M. Gupta, M. Serrano, V. C. Sreedhar, and S. Midki.
 > > Escape analysis for Java.  In Object-Oriented Programming, Systems,
 > > Languages, and Applications (OOPSLA), 1999. Languages (POPL), 2002.
 > > http://www.research.ibm.com/jalapeno/publication.html#oopsla99_escape
 > 
 > This is true, but works only for static compilers.

Well, this is the gcj mailing list, and gcj is a static compiler.

 > As soon as classes jitted or dynamically loaded, this gets more
 > difficult to achieve. The paper doesn't mention the cost of the
 > algorithm, but often escape analysis is expensive and thus not
 > appropriate for jitters.

The paper describes the algorithm that the IBM jit uses.

Andrew.