[trans-mem] Beginning of refactoring

[Torvald Riegel <triegel at redhat dot com>]

Here's the beginning of a refactoring aimed at being able to merge more
TM algorithms later on.

Patch 1: Just a straightfoward rename to make it clear that we're
dispatching on the level of ABI calls, not internals.

Patch 2: _ITM_dropReferences is not sufficiently defined in the ABI. It
seems to target some form of open nesting for txnal wrappers, but the
prose in the ABI specification is unclear. Thus, disable this for now
(aka fatal runtime error), and expect the related tests to fail. Pick it
up again once that the ABI has been improved and the use cases are
clear.

Patch 3: The actual change in how ABI calls are dispatched. Also,
removed method-readonly (broken, will in a similar form reappear in the
family of globallock-based algorithms), and disabled method-wbetl (needs
larger refactoring, will be revived/remerged later).

Ok for branch?


Coarse roadmap of planned future changes:

1) Improve serial-mode performance, which also gives a base for the
implementation of privatization.
2) The globallock family of algorithms (single versioned lock, with undo
or redo logging), and eager or lazy acquisition of the lock on writes.
3) Privatization safety for this globallock (includes user actions and
malloc/free commits).
4) The multilock family of algorithms (variants of LSA).

Other things: More cleanup in the ABI. Documentation.


Torvald

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