Graph colouring and local register allocation

Hello all,


Register allocation based on graph colouring is a global register
allocation technique. Most of the modern compliers will have both
global register allocation and local register allocation.


Graph colouring based allocator primarily depends on interference
graph for allocating registers. In the interference graph after its
build will have both the local and global virtual registers(with
respect to a block) as the nodes. These are the nodes that will be
considered later stages of the allocator, as in select and simplify of
chatins/briggs register allocator. If this is the case, what is the
purpose of a separate local register allocator?


As I Am Implementing A Register Allocator Based On Briggs Optimistic
Register Allocator Which Works On The Pseudo Assembly Instructions, I
Would Want To Know The Need Of A Local Register Allocator.


Any help would be appreciated.


Regards,
Shafi.

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