To store a byval parameter the existing code would store as many 8 byte elements
as was required to store the full size of the byval parameter.
For example, a paramter of size 16 would store two element of 8 bytes.
A paramter of size 12 would also store two elements of 8 bytes.
This would sometimes store too many bytes as the size of the paramter is not
always a factor of 8.
This patch fixes that issue and now byval paramters are stored with the correct
number of bytes.
Reviewed By: nemanjai, #powerpc, quinnp, amyk
Differential Revision: https://reviews.llvm.org/D121430
Now we won't copy the byval parameter (bigger than 8 bytes) to
caller's parameter save area. Instead, we will only copy the
byval parameter when it can not be passed entirely in registers
which means we have to use parameter save area according to the
64 bit SVR4 ABI.
Reviewed By: jsji
Differential Revision: https://reviews.llvm.org/D111485
