[CodeGen] Don't assume that fixed stack objects are aligned in a stack-realigned function.

Summary:
After we make the adjustment, we can assume that for local allocas, but
not for stack parameters, the return address, or any other fixed stack
object (which has a negative offset and therefore lies prior to the
adjusted SP).

Fixes PR26662.

Reviewers: hfinkel, qcolombet, rnk

Subscribers: rnk, llvm-commits

Differential Revision: http://reviews.llvm.org/D18471

llvm-svn: 265886
GitOrigin-RevId: 2f65f35c271f39454b3490238b0eb69e57cb5f65
3 files changed