Nox

Tools

Compilation backends

Nox compiles the typed program to one of two back ends, which are tested against the same corpus and must produce identical program output.

LLVM (default) QBE
Pipeline typed IR → LLVM IR (.ll) → clang -O2 (or zig cc -O2) → native typed IR → QBE IL (.ssa) → qbe → assembly → cc → native
Code speed faster (roughly 1.5× C on a mixed benchmark suite) good (roughly 1.7× C)
Compile speed fast fast
Scheduler multi-core M:N work-stealing with atomic reference counts single-threaded cooperative
Needs clang or zig on PATH the bundled qbe, and a C compiler for linking
Debug info (-g) no yes (DWARF line tables)
--target cross-compile, --emit-asm, freestanding no yes

How the backend is chosen#

--backend llvm and --backend qbe always win. Otherwise (auto):

  1. freestanding builds, --target, --emit-asm and -g → QBE;
  2. on Windows, LLVM when zig is installed (it links with zig cc -target x86_64-windows-gnu), otherwise QBE with MinGW cc;
  3. on macOS and Linux, LLVM when clang or zig is on PATH; with neither, QBE and a one-line note;
  4. otherwise LLVM.

Asking for LLVM together with -g, --emit-asm or freestanding is an explicit error rather than a silent switch.

The C driver#

The LLVM path needs a C toolchain driver to optimise and link the .ll file. noxc tries clang first, then zig cc (Zig's bundled clang and LLD), so a machine with only Zig installed works. The QBE path links with the system cc (or zig cc for cross targets).

What is the same#

Both back ends implement exactly the language in the reference:

  • integer overflow: plain int wraps, fixed-width integers trap, on both;
  • argument evaluation order, exception semantics, with/defer/finally cleanup order;
  • program output, including float formatting.

What differs (and how code should treat it)#

Difference Guidance
Parallelism: tasks run on a worker pool (LLVM) or interleave on one thread (QBE) write tasks that are correct under both; communicate with channels
spawn/nox.thread.start argument types are wider on LLVM stay within the QBE set for portable code (Concurrency)
-g, --target, --emit-asm, freestanding exist only on QBE choose --backend qbe for those
speed LLVM is faster; neither is a semantic choice

Both back ends are run over the entire golden corpus on every change, and a differential test compares their output.

Intermediate files#

noxc build leaves file.ll (LLVM) or file.ssa and file.s (QBE) next to the executable; they are useful for inspecting the generated code and are safe to delete.

Platforms#

See Platforms for which combinations are tested.

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