low addresses

               +-------------------------+
     %sp  -->  | 16 words for storing    |
               | LOCAL and IN registers  |
               +-------------------------+
               |  one:-word pointer to   |
               | aggregate return value  |
               +-------------------------+
               |   6 words for callee    |
               |   to store register     |
               |     arguments           |
               +-------------------------+
               |  outgoing parameters    |
               |  past the 6th, if any   |
               +-------------------------+
               |  space, if needed, for  |
               |  compiler temporaries   |
               |   and saved floating-   |
               |    point registers      |
               +-------------------------+

               +-------------------------+
               |    space dynamically    |
               |    allocated via the    |
               |  alloca() library call  |
               +-------------------------+
               |  space, if needed, for  |
               |    automatic arrays,    |
               |    aggregates, and      |
               |   addressable scalar    |
               |       automatics        |
               +-------------------------+
    %fp  -->
                     high addresses