package core:rexcode

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rexcode  ¶

High-performance multi-architecture instruction encoder/decoder/printer library written in Odin. Original author: Brendan Punsky (dotbmp@github).

Architectures  ¶

Every package follows the same API contract (see docs/cross_arch_design.md).

Design  ¶

• Encoder: assembles instructions to machine code with label resolution and per-arch relocation support.
• Decoder: disassembles machine code back to structured instructions.
• Printer: emits assembly text output with optional syntax-highlighting tokens.
• Table-driven: O(1) opcode lookup via precomputed encode/decode tables, serialized to committed binary blobs and #loaded into @(rodata).
• Zero allocations on the hot path: caller provides all buffers.

The isa/ package owns the parts that are the same on every ISA — labels, result/error types, the print framework, token types, and shared formatting helpers. Each architecture package owns its registers, memory model, operand types, mnemonics, encoding tables, and the actual encode_one/decode_one bytes.

Encoding tables  ¶

Each arch's ENCODING_TABLE (the hand-written single source of truth) lives in <arch>/tablegen/, not in the library. A two-stage metaprogram flattens it and emits committed binary blobs that the library #loads into @(rodata) at compile time — no table is built during a normal library build:

odin run isa/<arch>/tablegen            # ENCODING_TABLE -> generated Odin + tables.odin
odin run isa/<arch>/tablegen/generated  # -> isa/<arch>/tables/<arch>.*.bin

Regenerate after editing ENCODING_TABLE. See docs/table_migration.md.

Usage  ¶

import x86 "core:rexcode/isa/x86"

instructions := []x86.Instruction{
	x86.inst_r_r(.MOV, x86.RAX, x86.RDI),
	x86.inst_r_r(.ADD, x86.RAX, x86.RSI),
	x86.inst_none(.RET),
}

code: [4096]u8
relocs: [dynamic]x86.Relocation
errors: [dynamic]x86.Error
result := x86.encode(instructions[:], nil, code[:], &relocs, &errors)

decoded_insts:  [dynamic]x86.Instruction
decoded_info:   [dynamic]x86.Instruction_Info
decoded_labels: [dynamic]x86.Label_Definition
decode_errors:  [dynamic]x86.Error
x86.decode(code[:result.byte_count], nil, &decoded_insts, &decoded_info, &decoded_labels, &decode_errors)

x86.print(decoded_insts[:], decoded_info[:], decoded_labels[:])
disasm := x86.tprint(decoded_insts[:], decoded_info[:], decoded_labels[:])

The same shape works for every other arch — change the import.

Instruction Builders  ¶

x86.inst_none(.RET)
x86.inst_r(.PUSH, x86.RAX)
x86.inst_r_r(.MOV, x86.RAX, x86.RBX)
x86.inst_r_i(.MOV, x86.EAX, 42, 4)
x86.inst_r_r_r(.VADDPS, x86.XMM0, x86.XMM1, x86.XMM2)
x86.inst_m_r(.MOV, x86.mem_base_only(x86.RSP), 8, x86.RAX)
x86.inst_r_m(.MOV, x86.RAX, x86.mem_base_disp(x86.RBP, -8), 8)
x86.inst_rel(.JMP, label_id, 1)

These are hand-written operand-shape constructors (one inst_r_r serves every two-register mnemonic). Each package additionally ships generated, per-mnemonic typed builders in mnemonic_builders.odin — inst_<mnemonic> / emit_<mnemonic> overload sets with the operand types baked in — produced by <arch>/tools/gen_mnemonic_builders.odin and regenerated with luajit build.lua --builders.

Memory Operands  ¶

x86.mem_base_only(x86.RAX)                        // [RAX]
x86.mem_base_disp(x86.RBP, -16)                   // [RBP - 16]
x86.mem_base_index(x86.RAX, x86.RCX, 4)           // [RAX + RCX*4]
x86.mem_base_index_disp(x86.RAX, x86.RCX, 8, 32)  // [RAX + RCX*8 + 32]
x86.mem_rip_disp(0)                               // [RIP + disp]

Labels  ¶

labels: [dynamic]x86.Label_Definition
instructions: [dynamic]x86.Instruction

loop := x86.label(&labels, &instructions)
x86.emit_r(&instructions, .DEC, x86.RDI)
x86.emit_rel(&instructions, .JNZ, loop)

done := x86.label_forward(&labels)
x86.emit_rel(&instructions, .JMP, done)
labels[done] = x86.Label_Definition(len(instructions))

result := x86.encode(instructions[:], labels[:], code[:], &relocs, &errors)

For named labels:

lm: x86.Label_Map
x86.label_map_init(&lm)
defer x86.label_map_destroy(&lm)

loop := x86.label_named(&lm, "loop", &instructions)
done := x86.label_reserve(&lm, "done")
x86.label_set(&lm, "done", &instructions)

result := x86.encode(instructions[:], lm.labels[:], code[:], &relocs, &errors)

// Printer wants id→name; Label_Map stores name→id, so invert once.
names := make(x86.Label_Names, len(lm.names), context.temp_allocator)   // BYTE OFFSET -> name
for name, id in lm.names { names[x86.Label_Offset(u32(lm.labels[id]))] = name }
x86.print(decoded_insts[:], decoded_info[:], lm.labels[:], label_names = &names)

Driver script (build.lua)  ¶

build.lua (LuaJIT) drives the pre-build metaprograms, validations, and tests across every ISA, with cross-platform gating (Linux / macOS / Windows) and a clear report. With no flags it prints help, including what's available on the current platform.

luajit build.lua                 # help + platform availability
luajit build.lua all             # everything: generate -> builders -> validate -> test
luajit build.lua --gen --isa x86 # only regenerate one ISA's tables
luajit build.lua --builders      # regenerate the typed mnemonic builders (all ISAs)
luajit build.lua --check --test  # validate + test the committed tables
luajit build.lua --verify        # external-tool round-trip where the tool is installed
luajit build.lua --list          # ISA x task availability matrix for this platform

Tasks: --gen (table metaprograms), --builders (regenerate each ISA's mnemonic_builders.odin), --check (compile + structural invariants), --test (run the suites), --verify (round-trip vs llvm-mc/da65/ca65/ armips/…), --idempotent (re-gen and confirm byte-stable). Scope with --isa <list>. It uses the in-repo ./odin — build that first.

Gating: x86's --test JIT-executes x86-64 code, so it runs only on an x86-64 host; --verify needs the matching tool in PATH (retro ISAs use shell scripts, skipped on Windows). Anything unavailable is skipped with a note, never fatal.

Running Tests  ¶

Each package has its own test suite:

odin run isa/x86/tests
odin run isa/arm32/tests
odin run isa/arm64/tests
odin run isa/mips/tests
odin run isa/mos6502/tests
odin run isa/mos65816/tests
odin run isa/ppc/tests
odin run isa/ppc_vle/tests
odin run isa/riscv/tests
odin run isa/rsp/tests

Verification harnesses  ¶

Each arch has a verification harness under isa/<arch>/tools/:

• dump_verify_input.odin — emits the per-entry hex/asm manifest.
• verify_against_<tool>.* — runs the canonical external assembler/ disassembler and compares. LLVM-mc for the seven modern archs, plus da65/ca65/armips/powerpc-eabivle-as for retro/embedded ISAs.

Project Structure  ¶

rexcode/
	isa/                # shared ISA core: labels, status, print framework, label-inference
		x86/            # x86-64 / i386
		arm32/          # AArch32
		arm64/          # AArch64
		mips/           # MIPS (R1..R6 + ASEs + coprocessors)
		mos6502/        # NMOS 6502 family
		mos65816/       # W65C816S
		ppc/            # PowerPC (Power ISA 3.1)
		ppc_vle/        # Freescale VLE (sibling of ppc)
		riscv/          # RISC-V
		rsp/            # N64 RSP
	ir/                 # shared IR core (parallels isa/; see docs/ir_design.md)
	wasm/               # WebAssembly (an IR; destined for ir/wasm once the IR layer settles)
	docs/               # cross-arch design + IR design + per-arch design docs

Each ISA is imported as core:rexcode/isa/<arch> (e.g. core:rexcode/isa/x86); the shared core is core:rexcode/isa. Per-package layout (canonical, enforced by the cross-arch contract):

isa/<arch>/
	encoder.odin         # encode() — two-pass, label/reloc-aware
	decoder.odin         # decode()
	printer.odin         # sb/sbln/print/println/aprint/aprintln/tprint/tprintln/bprint/bprintln/fprint/fprintln/wprint/wprintln
	registers.odin       # Register, REG_* classes, typed enums
	operands.odin        # Operand, Memory, Operand_Kind, op_* constructors
	instructions.odin    # Instruction, inst_* operand-shape builders
	mnemonic_builders.odin # generated: inst_<mnem>/emit_<mnem> typed builders
	encoding_types.odin  # Encoding, Encoding_Flags, isa re-exports
	tables.odin          # generated: #load()s the binary tables into @(rodata) + accessors
	tables/              # committed binary blobs (<arch>.*.bin) the library #loads
	mnemonics.odin       # Mnemonic enum (u16, INVALID=0)
	reloc.odin           # Relocation_Type + Relocation
	tablegen/            # ENCODING_TABLE (source of truth) + gen.odin metaprogram
	tests/               # smoke, pipeline_smoke, sweep
	tools/               # dump_verify_input, verify_against_*, gen_mnemonic_builders

Cross-architecture API design  ¶

See docs/cross_arch_design.md for the naming contract every arch package follows.