Ben Gamari authored Oct 30, 2015 and Ben Gamari committed Oct 30, 2015

Previously this was introduced in D524 as a compile-time constant.
Sadly, this isn't flexible enough to allow for environments where
ulimits restrict the maximum address space size (see, for instance,

Consequently, we are forced to make this dynamic. In principle this
shouldn't be so terrible as we can place both the beginning and end
addresses within the same cache line, likely incurring only one or so
additional instruction in HEAP_ALLOCED.

Test Plan: validate

Reviewers: austin, simonmar

Reviewed By: simonmar

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D1353

GHC Trac Issues: #10877