[PATCH] Don't Promote x86_fp80 byval Pointer Arguments

[Reid Kleckner]

>>! In D5057#14, @tjablin wrote:
> Unless you think that the packing bits between the first and second members of the {i32, i64} structure should be preserved, in which case this is not correct.

If you remove byval and just pass a pointer, you can absolutely access those padding bits in LLVM. I don't think adding byval should change this. If you pass a first-class aggregate instead, then the semantics change, because the semantics of FCAs are the same as passing each element separately.

http://reviews.llvm.org/D5057