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Disable unused variable lint for naked functions

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In most calling conventions, accessing function parameters may require
stack access. However, naked functions have no assembly prelude to set
up stack access.  This is why naked functions may only contain a single
`asm!()` block. All parameter access is done inside the `asm!()` block,
so we cannot validate the liveness of the input parameters. Therefore,
we should disable the lint for naked functions.

rust-lang/rfcs#2774
rust-lang/rfcs#2972
This commit is contained in:
Nathaniel McCallum 2021-08-03 16:45:55 -04:00
parent 7ac0cb0ec1
commit 9c0147c02d
3 changed files with 6 additions and 71 deletions
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5
compiler/rustc_passes/src/liveness.rs
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@ -332,6 +332,11 @@ impl<'tcx> Visitor<'tcx> for IrMaps<'tcx> {
}
}
// Don't run unused pass for #[naked]
if self.tcx.has_attr(def_id, sym::naked) {
return;
}
if let Some(captures) = maps.tcx.typeck(local_def_id).closure_min_captures.get(&def_id) {
for &var_hir_id in captures.keys() {
let var_name = maps.tcx.hir().name(var_hir_id);