<16 x float> is 64-byte aligned (for some reason),
which gets us into the stack realignment code. The
computation changing FP-relative offsets to SP-relative
was broken, assiging a spill temp to a location
also used for parameter passing. This
fixes it by rounding up the stack frame to a multiple
of the largest alignment (I concluded it wasn't fixable
without doing this, but I'm not very sure.)
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@52750 91177308-0d34-0410-b5e6-96231b3b80d8
b5dae00325