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Rollup merge of #91303 - RalfJung:array-init-align, r=oli-obk

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Miri: fix alignment check in array initialization

https://github.com/rust-lang/rust/pull/85376 introduced a regression in Miri, reported at https://github.com/rust-lang/miri/issues/1919 and https://github.com/rust-lang/miri/issues/1925. This PR fixes that. I will add tests to Miri once this lands.

r? `@oli-obk`
Fixes https://github.com/rust-lang/miri/issues/1919
Fixes https://github.com/rust-lang/miri/issues/1925
This commit is contained in:
Matthias Krüger 2021-11-28 10:42:40 +01:00 • committed by GitHub
commit 7134ae0a8d
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6
compiler/rustc_const_eval/src/interpret/step.rs
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@ -242,11 +242,15 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
let elem_size = first.layout.size; let elem_size = first.layout.size;
let first_ptr = first.ptr; let first_ptr = first.ptr;
let rest_ptr = first_ptr.offset(elem_size, self)?; let rest_ptr = first_ptr.offset(elem_size, self)?;
// For the alignment of `rest_ptr`, we crucially do *not* use `first.align` as
// that place might be more aligned than its type mandates (a `u8` array could
// be 4-aligned if it sits at the right spot in a struct). Instead we use
// `first.layout.align`, i.e., the alignment given by the type.
self.memory.copy_repeatedly( self.memory.copy_repeatedly(
first_ptr, first_ptr,
first.align, first.align,
rest_ptr, rest_ptr,
first.align, first.layout.align.abi,
elem_size, elem_size,
length - 1, length - 1,
/*nonoverlapping:*/ true, /*nonoverlapping:*/ true,