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Rollup merge of #124504 - gurry:123710-union-ICE, r=oli-obk

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Mark unions non-const-propagatable in `KnownPanicsLint` without calling layout

Fixes #123710

The ICE occurs during the layout calculation of the union `InvalidTag` in #123710 because the following assert fails:5fe8b697e7/compiler/rustc_abi/src/layout.rs (L289-L292)

The layout calculation is invoked by `KnownPanicsLint` when it is trying to figure out which locals it can const prop. Since `KnownPanicsLint` is never actually going to const props unions thanks to PR https://github.com/rust-lang/rust/pull/121628 there's no point calling layout to check if it can. So in this fix I skip the call to layout and just mark the local non-const propagatable if it is a union.
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许杰友 Jieyou Xu (Joe) 2024-04-29 18:03:24 +01:00 • committed by GitHub
commit 43265f5721
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4 changed files with 64 additions and 24 deletions
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20
compiler/rustc_mir_transform/src/known_panics_lint.rs
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@ -896,13 +896,19 @@ impl CanConstProp {
};
for (local, val) in cpv.can_const_prop.iter_enumerated_mut() {
let ty = body.local_decls[local].ty;
match tcx.layout_of(param_env.and(ty)) {
Ok(layout) if layout.size < Size::from_bytes(MAX_ALLOC_LIMIT) => {}
// Either the layout fails to compute, then we can't use this local anyway
// or the local is too large, then we don't want to.
_ => {
*val = ConstPropMode::NoPropagation;
continue;
if ty.is_union() {
// Do not const prop unions as they can
// ICE during layout calc
*val = ConstPropMode::NoPropagation;
} else {
match tcx.layout_of(param_env.and(ty)) {
Ok(layout) if layout.size < Size::from_bytes(MAX_ALLOC_LIMIT) => {}
// Either the layout fails to compute, then we can't use this local anyway
// or the local is too large, then we don't want to.
_ => {
*val = ConstPropMode::NoPropagation;
continue;
}
}
}
}