The old code assumed that if an argument doesn't fit into the available
registers, none of the subsequent arguments do, either. But that's
wrong: passing 7 doubles, then a two-double struct, then another double
should generate code that passes the 9th argument in the 8th register
and the two-double struct on the stack. We now do so.
However, this patch does not yet fix the function calling code to do the
right thing in the same case.
2d3458363e