Ben Gamari authored Oct 30, 2015 and Ben Gamari committed Nov 01, 2015

Here we add a `same_value $sp` instruction to our default unwinding
rules to ensure that the implicit `$sp = CFA` rule (which `libdw`
appears to exhibit on x86_64) doesn't overwrite it (necessary since we
don't use $sp to track our call stack).

See Phab Diff D1189 for details on how we arrived at this resolution.

Reviewers: scpmw, austin, simonmar

Reviewed By: austin, simonmar

Subscribers: thomie, simonmar

Differential Revision: https://phabricator.haskell.org/D1224