Performance and Evaluation of Lisp Systems - Dreamsongs

§ 2.10 Portable Standard Lisp 67
The PSL compiler has a number of passes, some of which were introduced to
aid in the portability:
1. Lisp macros expanded, and the Lisp source decorated with
type information.
2. Compilation of Lisp to an ‘abstract’ register machine whose
instructions are called ‘cmacros.’ Redundant loads and
stores are avoided by tracking register contents.
3. Essentially machine-independent optimization of the
‘cmacro’ form (jump optimizations, peephole, etc).
4. Expanding ‘cmacros’ into LAP for the target machine by
using pattern-driven tables.
5. Some peephole optimization of the target machine LAP.
6. Output of LAP in a number of different forms: a) in-core
assembly for direct execution, b) output as a FASL file for
later fast loading, or c) output as symbolic assembly code
for target machine assembler for bootstrapping.
A PSL implementation for a new machine consists of the following:
1. Choosing memory layout and tagging
2. Writing code generators and linkage routines to the sys-
tems language
3. Writing some IO primitives in assembly code or some other
systems language (C, PASCAL, and FORTRAN have been
used)
4. Testing primitives and code generators
5. Selecting an appropriate garbage collector
6. Cross-compiling a kernel (‘mini-Lisp’) to assembly code,
assembling, and linking on the target machine