diff --git a/compiler/rustc_const_eval/src/interpret/step.rs b/compiler/rustc_const_eval/src/interpret/step.rs index 91341ddacd1..ead172f04a3 100644 --- a/compiler/rustc_const_eval/src/interpret/step.rs +++ b/compiler/rustc_const_eval/src/interpret/step.rs @@ -208,13 +208,13 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> { 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. + // be 4-aligned if it sits at the right spot in a struct). We have to also factor + // in element size. self.mem_copy_repeatedly( first_ptr, - first.align, + dest.align, rest_ptr, - first.layout.align.abi, + dest.align.restrict_for_offset(elem_size), elem_size, length - 1, /*nonoverlapping:*/ true, diff --git a/src/tools/miri/tests/pass/align_repeat_into_packed_field.rs b/src/tools/miri/tests/pass/align_repeat_into_packed_field.rs new file mode 100644 index 00000000000..3affb204205 --- /dev/null +++ b/src/tools/miri/tests/pass/align_repeat_into_packed_field.rs @@ -0,0 +1,22 @@ +#![feature(custom_mir, core_intrinsics)] +use std::intrinsics::mir::*; + +#[repr(packed)] +struct S { field: [u32; 2] } + +#[custom_mir(dialect = "runtime", phase = "optimized")] +fn test() { mir! { + let s: S; + { + // Store a repeat expression directly into a field of a packed struct. + s.field = [0; 2]; + Return() + } +} } + +fn main() { + // Run this a bunch of time to make sure it doesn't pass by chance. + for _ in 0..20 { + test(); + } +} diff --git a/src/tools/miri/tests/pass/issues/issue-miri-1925.rs b/src/tools/miri/tests/pass/align_repeat_into_well_aligned_array.rs similarity index 79% rename from src/tools/miri/tests/pass/issues/issue-miri-1925.rs rename to src/tools/miri/tests/pass/align_repeat_into_well_aligned_array.rs index 86556813491..735251039f7 100644 --- a/src/tools/miri/tests/pass/issues/issue-miri-1925.rs +++ b/src/tools/miri/tests/pass/align_repeat_into_well_aligned_array.rs @@ -4,6 +4,8 @@ use std::mem::size_of; fn main() { let mut a = Params::new(); + // The array itself here happens to be quite well-aligned, but not all its elements have that + // large alignment and we better make sure that is still accepted by Miri. a.key_block = [0; BLOCKBYTES]; }