[ipa-branch] Devirtualization

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

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 may be transformed in a direct call, this 

making possible the inlining  of the method afterward. 

The current patch contains the analysis part. For transforming a virtual 
call in a direct call it uses already existent GCC code that works only 
in limited cases. This means that currently, even if we infer the type of 
the object for a virtual call, not always this virtual call is transformed 

in a direct one. This will be fixed by a further patch with support for 
transformation of a virtual call in a direct one in the general case. 

This optimization works only for C++ code. To enable it use the option 
-fipa-cha. It is assumes that all the application files are compiled 
together. The option -fdump-ipa-cha generates information in the *.cha 
file.

Bootstrapping done, regression test successfully on Power. 



Mircea

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