Handle field and array-element outputs accepted in statement assembly

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Valutazione

Difficoltà
4/5
Tempo stimato
3-5 giorni
Idoneità per principianti
53/100
Tipo di issue
Bug
Chiarezza
Specificata chiaramente
Stato di attività
Attiva
Stack tecnologico
rust
Ambito
compilers

Direzione di ricerca

Start at llvm/src/statement/asm.rs, especially the statement asm output-place lowering near line 259, and trace how semantic checking accepts field and index lvalues. Compare the struct-field and array-element repros with the plain variable control, then inspect existing asm tests for output storage and evaluation order. Done means supported outputs reach IR and store to the selected place with single, source-ordered address evaluation, or unsupported forms receive a source diagnostic.

Scritto dal modello di indicizzazione a partire dal testo della issue.

Descrizione

bug help wanted

Problem

Statement-form assembly accepts assignable struct fields and array elements as outputs during semantic checking, but LLVM lowering only handles a variable or a dereferenced variable. Validated programs reach E9001 instead of supported output lowering or a source diagnostic.

Starting point: statement asm output-place lowering.

Reproduction

Audited canonical master e1f8effd195b6339c3979b1e091e63c25f1da983 on Linux amd64 with checkout-built Wave 0.0.1-alpha-dev, matching std, Rust 1.89.0, Cargo jobs=2 and LLVM 21.1.8. The master SHA was rechecked before registration.

Save either example as repro.wave:

struct S { x: i64; }
fun main() {
    var s: S = S { x: 0 };
    asm {
        "mov rax, 7"
        out("rax") s.x
        clobber("nostack")
    };
}

Array variant:

fun main() {
    var a: array<i64, 1> = [0];
    asm {
        "mov rax, 7"
        out("rax") a[0]
        clobber("nostack")
    };
}

target/debug/wavec --std-root "$PWD/std" check repro.wave
target/debug/wavec --std-root "$PWD/std" --error-format=json build repro.wave --emit=ir --out-dir .tmp/asm-output-repro

Semantic checking accepts the output. IR generation exits 1 with E9001 and:

out(...) target must be variable or deref var for now: IndexAccess { ... }
compiler panic location: llvm/src/statement/asm.rs:303:18

The field variant reaches the same restricted output-place path. A plain variable output is the control case. This report establishes semantic-check/IR behavior; it does not claim execution on another architecture.

Scope

Lower the typed addresses of supported field/index output lvalues with correct storage width, source order and single evaluation. Reject any deliberately unsupported output form during semantic checking with a source diagnostic rather than an internal error. Preserve constant/mutability checks, constraints and clobbers.

Related: #512 concerns typed asm input expressions, #397 malformed asm syntax and #409 the general backend diagnostic channel. This issue is specifically the accepted output-address shape.

Completion criteria

  • Both examples build through IR/object generation without E9001, or receive an intentional source diagnostic if a documented output restriction applies.
  • Supported cases store the output in the selected field/element at execution.
  • Side-effecting index/address computations run once in source order.
  • Plain variables, supported pointer outputs, mutability checks and architecture feature gating retain coverage.
Lingua principale
Rust
Stelle
56
Fork
21
Merge medio
22h 57m
PR unite (30g)
46

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