Your assign_parms changes

[Richard Kenner]

    The patch is trying to prevent GCC from pessimizing code generated for
    argument passing when the word size within the function is larger than
    the word size specified in the ABI for argument passing.  

Right, I understand that, but then why the second change to prohibit this
from being done for CONCAT, which seems a very valuable case?

    I guess we need to update max_parm_reg appropriately when we
    allocate the new reg to operate as a parm within the function.

Most certainly.  And also the parm stack location.