gcc for MIPS 64 is using a complex method to locate and invoke a function not present in the compilation unit.  What is the name of this code model (and where is it documented)?  I searched but did not find it forthcoming.  It involves $28/$gp and $25/$t9 as some kind of parameter to pass to the called function.

And, is there a bug in this translation (either in code gen or the textual output)?

The following code sequence:

extern int g(int);

int f(int x)
{
    return g(x)   2;
}

generates this output:

        daddiu  $sp,$sp,-16
        sd      $28,0($sp)
        lui     $28,%hi(%neg(%gp_rel(f(int))))
        daddu   $28,$28,$25                             <--- sourcing $25/$t9 
        daddiu  $28,$28,%lo(%neg(%gp_rel(f(int))))
        ld      $25,