This is different from the argument passing convention which puts the
first float argument in %f1.
With this patch, all returned floats are treated as if the 'inreg' flag
were set. This means multiple float return values get packed in %f0,
%f1, %f2, ...
Note that when returning a struct in registers, clang will set the
'inreg' flag on the return value, so that behavior is unchanged. This
also happens when returning a float _Complex.
llvm-svn: 199028
3dd52f1fbd