Refactoring of the GC in preparation for parallel GC
This patch localises the state of the GC into a gc_thread structure,
and reorganises the inner loop of the GC to scavenge one block at a
time from global work lists in each "step". The gc_thread structure
has a "workspace" for each step, in which it collects evacuated
objects until it has a full block to push out to the step's global
list. Details of the algorithm will be on the wiki in due course.
At the moment, THREADED_RTS does not compile, but the single-threaded
GC works (and is 10-20% slower than before).
13 files changed: