5e2e2eb5da
Return to the usual whitespace-skipping istreams. No need to go beyond word-based parsing. This exercise reinforces the amount of duplication between load_program() and transform_immediate(). |
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|---|---|---|
| .. | ||
| teensy | ||
| 000organization.cc | ||
| 001help.cc | ||
| 002test.cc | ||
| 003trace.cc | ||
| 003trace.test.cc | ||
| 010core.cc | ||
| 011direct_addressing.cc | ||
| 012indirect_addressing.cc | ||
| 013immediate_addressing.cc | ||
| 014index_addressing.cc | ||
| 015jump_relative.cc | ||
| 016jump_relative.cc | ||
| 017functions.cc | ||
| 019syscalls.cc | ||
| 020elf.cc | ||
| 021translate.cc | ||
| 022transform_immediate.cc | ||
| Readme.md | ||
| build | ||
| build_and_test_until | ||
| cheatsheet.pdf | ||
| clean | ||
| edit | ||
| ex1 | ||
| ex1.1.subx | ||
| ex1.2.subx | ||
| ex2 | ||
| ex2.subx | ||
| ex3 | ||
| ex3.subx | ||
| ex4 | ||
| ex4.subx | ||
| g | ||
| gen | ||
| gg | ||
| nrun | ||
| opcodes | ||
| run | ||
| subx | ||
| subx.vim | ||
| test_layers | ||
| vimrc.vim | ||
Readme.md
The SubX VM
Bytecode interpreter for a subset of the 32-bit x86 ISA.
- Only instructions that operate on the 32-bit E*X registers. (No floating-point yet.)
- Only instructions that assume a flat address space; no instructions that use segment registers.
- No instructions that check the carry or parity flags; arithmetic operations always operate on signed integers (while bitwise operations always operate on unsigned integers)
- Only relative jump instructions (with 8-bit or 16-bit offsets).
These rules yield a clean instruction set. We don't care about running arbitrary binaries, just those generated by our forthcoming Mu compiler.
Targeting a VM enables more comprehensive tests for the compiler, without requiring access to processor/memory state without getting bogged down in details of the ELF format, ABI, STABS debugging format, etc., etc.
Having the VM implement a real (and ubiquitous) instruction set makes it easy to generate native binaries outside of tests.
Just unit tests so far:
./subx test
x86 instruction set resources used in building this: