Performance and Evaluation of Lisp Systems - Dreamsongs

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2.5.4 Systemic Quantities Vector
To speed up various operations, a vector of commonly referred to constants
and procedures is pointed to by a register dedicated to the purpose. This vector
contains the quantities T, (), the locks mentioned above, constants defining the
sizes of some objects, the addresses of the CONSers, and addresses of routines
that allocate, de-allocate, and search special lookup blocks on the stack. Calling
these routines is inexpensive compared to the cost of a normal procedure call.
2.5.5 Function Calls
All arguments are passed on the stack. Temporary storage for each function
is also on the stack. Six stack slots are allocated for the basic function call: a slot
for one returned value (multiple values are handled separately), a spare PC slot,
the return PC, an old temporaries pointer slot, an old closure pointer slot, and
an old frame pointer slot. The arguments, pointer temporaries, and nonpointer
temporaries are above these slots.
Self-recursive calls go to a distinguished label at the front of the compiled
code. This saves an indirect memory reference through the function cell. The
pipeline hardware can value-predict the new PC; this allows the pipeline to proceed
more smoothly than it does in the indirect memory-reference case. However,
tracing such calls is not possible.
2.5.6 Remarks
MacLisp.
The S-1 supports PDL-allocated numbers in much the same fashion as