[ipa-branch] Devirtualization - enhanced patch

[Mircea Namolaru <NAMOLARU at il dot ibm dot com>]

Hello,

This patch implements a simple variant of RTA (see "Fast Static Analysis
of C++ Virtual Function Call" by Bacon & Sweeney - OOPSLA'96) for 
devirtualization of C++ function calls. The interprocedural analysis done 
may infer the type of the object  upon which a virtual method is invoked. 
If this happens the virtual call is transformed in a direct call, this 
making possible the inlining  of the method afterward. 

The current patch includes and completes the previous patch:
http://gcc.gnu.org/ml/gcc-patches/2005-09/msg00982.html.
It contains support for transformation of a virtual call in a direct one 
in a more general case. 

This optimization works only for C++ code. To enable it use the option 
-fipa-cha. The option -fdump-ipa-cha generates information in the *.cha 
file.

This optimization assumes that all the application files are available 
to the compiler. The case when only a partial view of the application is
not available is still not supported. In this stage I was more interested
in extending the functionality of this optimization. 

Regression tests successfully passed on Power. 

Mircea

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