MinGW-w64 runtime library inclusion (Clang-compiled) for proper Win64 support?

[kink]

Of course it is an ABI issue. Since MS doesn't support the x87 
type, it obviously isn't mentioned in the Win64 ABI docs. Clang's 
ABI assumes it is passed by-val on the stack whereas in LDC we 
treat it as a struct > 64 bits and hence pass it by-ref (a 
pointer to a private copy for the callee, allocated by the 
caller; the Win64 way of passing larger structs by-val). Clang 
returns an x87 in the ST(0) x87 register and LDC expects the 
result there - perfect. I guess I'll have to modify Clang/LLVM 
further to pass x87s by-ref, that seems more appropriate to me.
This shouldn't be a problem for Win32 though as x87s should be 
passed ordinarily by-val.