RS/6000 Function Result Conventions (32-bit)

A function procedure returns its result value to the calling procedure in one of three ways, depending upon the data type:

1. In register GPR3
2. In register FPR1
3. In a temporary storage area provided by the caller

If the result is returned in a temporary storage area, the calling procedure provides the temporary area and passes its address as the first (hidden) parameter in the call.