Add support for disjoint helper id address space

[Alan-Jowett]

Add support for disjoint helper id address space

Signed-off-by: Alan Jowett alan.jowett@microsoft.com

[coveralls]

Coverage decreased (-0.4%) to 95.182% when pulling 4410943 on Alan-Jowett:issue66 into c7c019c on iovisor:master.

[jpsamaroo]

Why not have the helper resolver just return an index into the ext_funcs array? Do you have a need for arbitrary functions to be returned (since you could really return whatever you want)? It feels like we're adding a whole extra layer of independent complexity, when we could just reuse what already exists.

[Alan-Jowett]

@jpsamaroo That is an excellent point. Technically, the helper ids that were originally in the program don't have to be the same as the ones passed to the jitter.

To solve this for my scenario I can do the following:

1. Build a table of the original helper IDs
2. Resolve original helper IDs to literal addresses
3. Register table index -> literal address with jitter
4. Replace original helper ID -> table index in the byte code

The jitter will then do the right thing of replacing IMM value (which is a table index at this point) with literal address.

No need to modify the jitter.

I think I will go ahead and close this PR.

[Alan-Jowett]

Changed the caller to re-map helper ids from our disjointed address space to the supported [0,63] address space.