[PATCH] Skip base pointer usage if SP isn't touched by asm

[Reid Kleckner]

  Thanks!

  What I anticipate is that someone somewhere will hit the fatal error path with:
  - a stack realignment
  - inline asm
  - a dynamic alloca
  ... and complain.  But that's OK, because it's better than a miscompile.  :)

http://llvm-reviews.chandlerc.com/D1317

BRANCH
  ms-asm-esi

ARCANIST PROJECT
  llvm