Define the freestanding memory-operation runtime contract

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Evaluación

Dificultad
5/5
Tiempo estimado
Más de una semana
Aptitud para principiantes
25/100
Tipo de issue
Nueva funcionalidad
Claridad
Bien especificado
Estado de actividad
Activo
Stack tecnológico
rust
Área
compilers

Línea de trabajo

Start with llvm/src/codegen/ir.rs at the linked starting point, then reproduce the O0/O2 object builds and inspect undefined symbols with llvm-nm. Discuss the design with @LunaStev before implementation. Done means the runtime ownership contract is documented, applied consistently to optimized loops and aggregate operations, and checked for overlapping memmove, zero-length operations, and unintended hosted linkage.

Escrito por el modelo de indexación a partir del texto del issue.

Descripción

discussion enhancement

Motivation

A raw byte-zeroing loop has no undefined symbol at O0, but O2 creates llvm.memset and the object has an undefined memset symbol. --freestanding disables default libc/libm links but does not prevent this lowering. This behavior is also common in C freestanding compilers; the gap is an explicit Wave ownership/provider contract.

Starting points: llvm/src/codegen/ir.rs.

fun clear(p: ptr<u8>, n: i64) { var i: i64 = 0; while (i < n) { deref p[i] = 0; i += 1; } }

Reproduced at 73aff59e on Linux amd64/LLVM 21.1.8: build with --freestanding --target=x86_64-unknown-none-elf --emit=obj at O0/O2, then inspect with llvm-nm --undefined-only. Only O2 has U memset in the sampled loop.

Scope

Decide compiler-owned memory helpers versus an explicit caller-supplied kernel runtime contract. Cover memcpy/memmove/memset and optimized loops/aggregates, including preservation of memory semantics.

Completion criteria

  • Agree on and document whether memory primitives are compiler-owned or explicitly provided by the freestanding environment.
  • Implement the approved contract consistently for optimized loops and aggregate copies/initialization.
  • Inspect O0/O2 undefined symbols and test overlapping memmove and zero-length operations without accidental hosted linkage.

Design required. Please mention @LunaStev to discuss the design before starting implementation.

Lenguaje dominante
Rust
Estrellas
56
Forks
21
Merge medio
23 h 20 min
PR fusionados (30 d)
45

Preparar el entorno

Primeros pasos

  1. Lee el issue completo y luego la guía de contribución del proyecto.
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  3. Haz un fork del repositorio y trabaja en una rama.
  4. Abre un pull request que haga referencia al número del issue.

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