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Auto merge of #94527 - oli-obk:undef_scalars, r=nagisa,erikdesjardin

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Let CTFE to handle partially uninitialized unions without marking the entire value as uninitialized.

follow up to #94411

To fix https://github.com/rust-lang/rust/issues/69488 and by extension fix https://github.com/rust-lang/rust/issues/94371, we should stop treating types like `MaybeUninit<usize>` as something that the `Scalar` type in the interpreter engine can represent. So we add a new field to `abi::Primitive` that records whether the primitive is nested in a union

cc `@RalfJung`

r? `@ghost`
This commit is contained in:
bors 2022-04-05 16:46:13 +00:00
commit f262ca12aa
42 changed files with 466 additions and 333 deletions
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7
compiler/rustc_const_eval/src/interpret/terminator.rs
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@ -189,12 +189,15 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
// that will take care to make it UB to leave the range, just
// like for transmute).
(abi::Abi::Scalar(caller), abi::Abi::Scalar(callee)) => {
caller.value == callee.value
caller.primitive() == callee.primitive()
}
(
abi::Abi::ScalarPair(caller1, caller2),
abi::Abi::ScalarPair(callee1, callee2),
) => caller1.value == callee1.value && caller2.value == callee2.value,
) => {
caller1.primitive() == callee1.primitive()
&& caller2.primitive() == callee2.primitive()
}
// Be conservative
_ => false,
}