Ths patch builds upon commit rGc21866476e14, which added support for by-value arguments in a single register. With this patch the by-value argument support on AIX is extended to by-value arguments that will fit within available GPRs.
I've moved the 5-8 byte tests, which were aix64 specific into aix-cc-byval.ll because they now work as multi GPR tests in 32-bit. I've added a 64-byte by-value argument as an aix64 only test. When the caller by-value support is complete, the aix-cc-byval-limitation tests will be deleted and the aix64-cc-byval.ll tests should be folded into aix-cc-byval.ll.
Remaining caller by-value argument work:
-by-val args, which require alignment greater than PtrByteSize.
-by-val args, which pass either partially or completely in stack memory.
If all we need PeekVA for is its ValNo lets do unsigned ValNo = ArgLocs[I].getValNo()