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Rollup merge of #103729 - RalfJung:align-of-val-packed, r=oli-obk

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interpret: fix align_of_val on packed types

Fixes https://github.com/rust-lang/miri/issues/2632

r? `@oli-obk`
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Dylan DPC 2022-11-01 14:12:26 +05:30 • committed by GitHub
commit 20528baac4
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3 changed files with 30 additions and 1 deletions
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9
compiler/rustc_const_eval/src/interpret/eval_context.rs
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@ -598,7 +598,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
// the last field). Can't have foreign types here, how would we
// adjust alignment and size for them?
let field = layout.field(self, layout.fields.count() - 1);
let Some((unsized_size, unsized_align)) = self.size_and_align_of(metadata, &field)? else {
let Some((unsized_size, mut unsized_align)) = self.size_and_align_of(metadata, &field)? else {
// A field with an extern type. We don't know the actual dynamic size
// or the alignment.
return Ok(None);
@ -614,6 +614,13 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
// Return the sum of sizes and max of aligns.
let size = sized_size + unsized_size; // `Size` addition
// Packed types ignore the alignment of their fields.
if let ty::Adt(def, _) = layout.ty.kind() {
if def.repr().packed() {
unsized_align = sized_align;
}
}
// Choose max of two known alignments (combined value must
// be aligned according to more restrictive of the two).
let align = sized_align.max(unsized_align);