release_33 branch: proposing r183984

[Dimitry Andric]

Hi,

For the 3.3 release branch, I would like to propose merging r183984:

r183984 from llvm trunk (by Derek Schuff):

  Make PrologEpilogInserter save/restore all callee saved registers in
  functions which call __builtin_unwind_init()

  __builtin_unwind_init() is an undocumented gcc intrinsic which has
  this effect, and is used in libgcc_eh.

  Goes part of the way toward fixing PR8541.

It obsoletes the ugly hack we had to do in FreeBSD to libgcc's unwind code to work around very tricky crash problems (see http://svnweb.freebsd.org/changeset/base/245272 ), and should also work for arches other than x86_64.

This commit should apply to the release_33 branch without modification.

-Dimitry