Don't promote byval pointer arguments when when their size in bits is
not equal to their alloc size in bits. This can happen for x86_fp80,
where the size in bits is 80 but the alloca size in bits in 128.
Promoting these types can break passing unions of x86_fp80s and other
types.
Patch by Thomas Jablin!
Reviewed By: rnk
Differential Revision: http://reviews.llvm.org/D5057
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@216693 91177308-0d34-0410-b5e6-96231b3b80d8
8f58e02646