upeepz80 - Universal Peephole Optimizer for Z80

A language-agnostic peephole optimization library for Z80 compilers that generate pure Z80 assembly.

upeepz80 provides high-quality optimization passes for compilers targeting the Zilog Z80 processor. Unlike upeep80, this library expects pure Z80 mnemonics in lowercase as input (ld, jp, jr, etc.) and produces optimized Z80 assembly output with lowercase mnemonics.

If your compiler generates 8080 mnemonics (MOV, MVI, LXI, etc.) that need translation to Z80, use upeep80 instead.

• Pattern-based optimization on Z80 assembly
• Redundant load/store elimination
• Jump optimization (jp to jr conversion, jump threading)
• djnz conversion (dec b; jr nz → djnz)
• Stack operation combining (push/pop to ld conversions)
• Dead store elimination
• Tail call optimization (call x; ret → jp x)
• Register copy optimization (push hl; pop de → ld d,h; ld e,l)

• Relative jump optimization (jp → jr where in range)
• djnz loop optimization
• Z80 block instruction awareness
• Direct ld de,(addr) usage (Z80-only instruction)

pip install upeepz80

Or for development:

git clone https://github.com/avwohl/upeepz80.git
cd upeepz80
pip install -e ".[dev]"

from upeepz80 import optimize

# Optimize Z80 assembly code
assembly = """
    ld a,0
    push hl
    pop de
    jp LABEL
LABEL:
    ret
"""

optimized = optimize(assembly)
print(optimized)
# Output:
#     xor a          ; ld a,0 → xor a (smaller)
#     ld d,h         ; push/pop → register moves (faster)
#     ld e,l
#     ret            ; jp to next instruction eliminated

from upeepz80 import PeepholeOptimizer

# Create optimizer
optimizer = PeepholeOptimizer()

# Optimize assembly code
optimized_asm = optimizer.optimize(assembly_text)

# Check statistics
print(f"xor a conversions: {optimizer.stats.get('xor_a', 0)}")
print(f"Jump threading: {optimizer.stats.get('jump_thread', 0)}")
print(f"djnz conversions: {optimizer.stats.get('djnz', 0)}")

The optimizer runs multiple phases:

1. Pattern Matching - Apply peephole patterns (up to 10 passes)
2. Z80-Specific Optimizations - Inline patterns for Z80 instructions
3. Jump Threading - Thread through intermediate jumps
4. Relative Jump Conversion - Convert jp to jr where possible
5. djnz Optimization - Convert dec b; jr nz to djnz
6. Dead Store Elimination - Remove unused stores

upeepz80 is designed to be language-agnostic:

• Works directly on Z80 assembly text
• No knowledge of source language required
• Pattern-based transformation engine
• Zero runtime dependencies

Choose upeepz80 if your compiler already generates Z80 mnemonics. Choose upeep80 if your compiler generates 8080 mnemonics.

• uplm80 - PL/M-80 compiler for Z80 (after migration)
• uada80 - Ada compiler for Z80 (after migration)

pytest

mypy upeepz80

black upeepz80
ruff check upeepz80

Benchmarks on typical compiler workloads:

• Peephole optimization: ~50,000 instructions/second
• Memory usage: Minimal (pattern-based, no large data structures)

Contributions are welcome. Open an issue or a pull request.

This project is licensed under the GNU General Public License v2.0 - see LICENSE for details.

upeepz80 is a sibling project to upeep80, designed for compilers that generate native Z80 assembly. It shares the same optimization algorithms but removes the 8080 translation layer for cleaner, more efficient code when 8080 support isn't needed.

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• ioscpm - Z80/CP/M emulator for iOS and macOS. It emulates the RomWBW HBIOS interface and runs CP/M 2.2 and CP/M 3.
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• scelbal - Floating-point BASIC interpreter for the 8080 processor and CP/M. A translator converts the original 8008 source code to 8080 source code.
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• z80cpmw - Z80/CP/M emulator for Windows. It emulates the RomWBW HBIOS interface and boots CP/M from disk images.

• upeep80 - Optimizer with 8080 input support
• Z80 CPU User Manual