Use function attribute "stackrealign" to decide whether stack
realignment should be forced.

With this commit, we can now force stack realignment when doing LTO and
do so on a per-function basis. Also, add a new cl::opt option
"stackrealign" to CommandFlags.h which is used to force stack
realignment via llc's command line.

Out-of-tree projects currently using -force-align-stack to force stack
realignment should make changes to attach the attribute to the functions
in the IR.

Differential Revision: http://reviews.llvm.org/D11814


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@247450 91177308-0d34-0410-b5e6-96231b3b80d8
14 files changed