🚀 go-pugleaf

Looking at some of the assembly generated by gcc (on a SPARC) I noticed 
that unions and structs are passed from function to function by reference
and not thru registers. However when compiling with -freg-struct-return 
small unions and structs *are* returned in a register, but still not passed 
in registers. 

Try something like this to see what happens:
-------------------------------8<-----------------------------
#include <stdio.h>
typedef union value
       {
         long n;
         char *s;
         union value *v;
       } Value; 

Value AddNumbers(Value O1,Value O2)
{
  return O1.n+O2.n;
}

int main(int argc,char *argv[])
{
  Value L1,L2,L3;
  L1.n = 1;
  L2.n = 2;
  L3 = AddNumbers(L1,L2);
  printf("%ld %ld %ld\n",L1.n,L2.n,L3.n);
}
--------------------------------8<----------------------------
The above example is the way I would like to do things in a compiler that 
generates ANSI C code. On a SPARC with gcc 2.4.5 you'll see that the result
of AddNumbers goes to a register (%o0) but the parameters O1 and O2 are 
both pointers. Therefore passing small unions and structs introduces a 
rather large overhead. Is there any reason why small unions and structs 
can't be passed directly (in registers). 

                                                         Paul.