uplm80 0.2.20

Highly optimizing PL/M-80 compiler targeting 8080/Z80

uplm80 - PL/M-80 Compiler

A modern PL/M-80 compiler targeting Intel 8080 and Zilog Z80 assembly language.

PL/M-80 was the primary systems programming language for CP/M and other 8080/Z80 operating systems. This compiler can rebuild original CP/M utilities from their PL/M source code.

Repository: https://github.com/avwohl/uplm80

Features

• Full PL/M-80 language support
• Targets both 8080 and Z80 instruction sets
• Multi-file compilation with cross-module optimization
• Multiple optimization passes (peephole, post-assembly tail merging)
• Generates relocatable object files compatible with standard CP/M linkers
• Produces code competitive with the original Digital Research compiler

Code Quality

Compiled output is comparable to the original Digital Research PL/M-80 compiler:

Program	DR PL/M-80	uplm80	Difference
PIP.COM	7424 bytes	7127 bytes	-4.0%

Installation

Quick install from PyPI:

pip install uplm80 um80 upeepz80

Platform-specific guides:

• Raspberry Pi: See README_RASPBERRY_PI.md
• General/Development: See INSTALL.md

Or install from source:

git clone https://github.com/avwohl/uplm80.git
cd uplm80
pip install -e .

Usage

Compile PL/M-80 to Assembly

uplm80 input.plm -o output.mac

Or run as a module:

python -m uplm80.compiler input.plm -o output.mac

Options:

• -t 8080 or -t z80 - Target CPU (default: Z80)
• -m cpm or -m bare - Runtime mode (default: cpm)
  • cpm: For new PL/M programs, maximum stack under BDOS
  • bare: Original Digital Research compatible (jump to start-3)
• -o output.mac - Output file name
• -O 0|1|2|3 - Optimization level (default: 2)
• -D SYMBOL - Define conditional compilation symbol (can be repeated)

Multi-File Compilation

Compile multiple source files together for optimal cross-module optimization:

uplm80 main.plm helper.plm library.plm -o output.mac

When multiple files are provided:

• All files are parsed together before code generation
• A unified call graph is built across all modules
• Local variable storage (??AUTO) is optimally allocated based on which procedures can be active simultaneously across module boundaries
• A single combined output file is generated

This produces better code than compiling files separately, as the compiler can share local variable storage between procedures in different modules that never call each other.

Assemble and Link

Use your preferred 8080/Z80 assembler and linker. Example with um80/ul80:

um80 output.mac                              # Assemble to .rel
ul80 -o program.com output.rel runtime.rel   # Link to CP/M .com

Language Reference

PL/M-80 is a typed systems programming language with:

• Data types: BYTE (8-bit), ADDRESS (16-bit)
• Variables: Scalars, arrays, structures, BASED variables (pointers)
• Control flow: DO/END, DO WHILE, DO CASE, IF/THEN/ELSE
• Procedures: With parameters, local variables, recursion
• Built-in functions: HIGH, LOW, DOUBLE, SHL, SHR, ROL, ROR, etc.
• I/O: INPUT, OUTPUT for port access

Example:

hello: DO;
    DECLARE message DATA ('Hello, World!$');
    DECLARE i BYTE;

    print: PROCEDURE(addr) PUBLIC;
        DECLARE addr ADDRESS;
        /* CP/M BDOS print string */
        CALL mon1(9, addr);
    END print;

    CALL print(.message);
END hello;

See examples/hello_cpm.plm for a complete working example.

For more on CP/M BDOS usage, see docs/BDOS_REFERENCE.md.

Conditional Compilation

Later versions of PL/M-80 added conditional compilation directives embedded in comments. This allows the same source to be compiled for different configurations (e.g., CP/M 2.2 vs CP/M 3, single-user vs MP/M).

Directives

Directive	Description
/** $set (NAME) **/	Define a symbol
/** $reset (NAME) **/	Undefine a symbol
/** $cond **/	Enable conditional compilation
/** $if NAME **/	Include following code if NAME is defined
/** $else **/	Else branch
/** $endif **/	End conditional block

Example

/** $set (CPM3) **/
/** $cond **/

DECLARE
/** $if CPM3 **/
    VERSION LITERALLY '30H',
/** $else **/
    VERSION LITERALLY '22H',
/** $endif **/
    MAXFILES BYTE;

Command Line

Symbols can also be defined from the command line:

uplm80 pip.plm -D CPM3 -D MPM -o pip.mac

Runtime Library

The compiler generates calls to these runtime routines (provide in a separate .rel file):

Routine	Description
??MUL	16-bit unsigned multiply
??DIV	16-bit unsigned divide
??MOD	16-bit unsigned modulo
??SHL	16-bit shift left
??SHR	16-bit logical shift right
??SHRS	16-bit arithmetic shift right
??MOVE	Block memory move

Runtime Modes

CP/M Mode (default: -m cpm)

For new PL/M programs. Provides maximum stack space by using the area under BDOS:

• Program starts with ORG 100H (CP/M TPA)
• Stack is set from BDOS address at location 0006H: LD HL,(6) / LD SP,HL
• Maximum available stack (all memory between program end and BDOS)
• Entry code calls main procedure with CALL MAIN
• Returns to CP/M with JP 0 (warm boot) when main returns
• Requires CP/M stubs: MON1, MON2, MON3, BOOT
• System variables: BDISK, MAXB, FCB, BUFF, IOBYTE

Bare Metal Mode (-m bare)

For original Digital Research PL/M-80 compatibility. Programs begin with a jump to start-3:

• Entry begins with JP ??START to jump over local stack buffer
• Uses locally-defined stack (64 bytes in program image)
• Entry code at ??START sets SP to ??STACK label, then calls MAIN
• Compatible with original Digital Research programs (ED.PLM, PIP.PLM, etc.)
• Program can define custom entry point via DATA declarations
• No automatic OS return (program controls its own exit behavior)

Project Structure

uplm80/
├── compiler.py    # Main compiler driver
├── lexer.py       # Tokenizer
├── parser.py      # PL/M-80 parser
├── ast_nodes.py   # AST definitions
├── codegen.py     # Code generator
├── peephole.py    # Peephole optimizer
└── symbols.py     # Symbol table

License

This project is licensed under the GNU General Public License v3.0 or later - see the LICENSE file for details.

Contributing

Contributions are welcome! Please feel free to submit issues and pull requests.

Acknowledgments

• Intel for creating PL/M-80
• Digital Research for creating CP/M
• The CP/M source code preservation efforts that made the original PL/M sources available