df6ba0c4ac
rustc_codegen_llvm: don't assume offsets are always aligned. Fixes #53728 by taking into account not just overall type alignment and the field's alignment when determining whether a field is aligned or not ("packed"), but also the field's offset within the type. Previously, rustc assumed that the offset was always at least as aligned as `min(struct.align, field.align)`. However, there's no real reason to have that assumption, and it obviously can't always be true after we implement `#[repr(align(N), pack(K))]`. There's also a case today where that assumption is not true, involving niche discriminants in enums: Suppose that we have the code in #53728: ```Rust #[repr(u16)] enum DeviceKind { Nil = 0, } #[repr(packed)] struct DeviceInfo { endianness: u8, device_kind: DeviceKind, } struct Wrapper { device_info: DeviceInfo, data: u32 } ``` Observe the layout of `Option<Wrapper>`. It has an alignment of 4 because of the `u32`. `device_info.device_kind` is a good niche field to use, which means the enum ends up with this layout: ``` size = 8 align = 4 fields = [ { offset=1, type=u16 } // discriminant, .<Some>.device_info.device_kind ] ``` And here we have an discriminant with alignment 2 (`u16`) but offset 1. |
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| .. | ||
| bootstrap | ||
| build_helper | ||
| ci | ||
| dlmalloc@c99638dc2e | ||
| doc | ||
| etc | ||
| grammar | ||
| jemalloc@1f5a28755e | ||
| liballoc | ||
| liballoc_jemalloc | ||
| liballoc_system | ||
| libarena | ||
| libbacktrace@f4d02bbdbf | ||
| libcompiler_builtins@0703bfa725 | ||
| libcore | ||
| libfmt_macros | ||
| libgraphviz | ||
| liblibc@1844a772b6 | ||
| libpanic_abort | ||
| libpanic_unwind | ||
| libproc_macro | ||
| libprofiler_builtins | ||
| librustc | ||
| librustc_allocator | ||
| librustc_apfloat | ||
| librustc_asan | ||
| librustc_borrowck | ||
| librustc_codegen_llvm | ||
| librustc_codegen_utils | ||
| librustc_cratesio_shim | ||
| librustc_data_structures | ||
| librustc_driver | ||
| librustc_errors | ||
| librustc_fs_util | ||
| librustc_incremental | ||
| librustc_lint | ||
| librustc_llvm | ||
| librustc_lsan | ||
| librustc_metadata | ||
| librustc_metadata_utils | ||
| librustc_mir | ||
| librustc_msan | ||
| librustc_passes | ||
| librustc_platform_intrinsics | ||
| librustc_plugin | ||
| librustc_privacy | ||
| librustc_resolve | ||
| librustc_save_analysis | ||
| librustc_target | ||
| librustc_traits | ||
| librustc_tsan | ||
| librustc_typeck | ||
| librustdoc | ||
| libserialize | ||
| libstd | ||
| libsyntax | ||
| libsyntax_ext | ||
| libsyntax_pos | ||
| libterm | ||
| libtest | ||
| libunwind | ||
| llvm@2a1cdeadd3 | ||
| llvm-emscripten@2717444753 | ||
| rtstartup | ||
| rustc | ||
| rustllvm | ||
| stdsimd@05c2f61c38 | ||
| test | ||
| tools | ||
| .gitignore | ||
| Cargo.lock | ||
| Cargo.toml | ||
| README.md | ||
| stage0.txt | ||
This directory contains the source code of the rust project, including:
rustcand its testslibstd- Various submodules for tools, like rustdoc, rls, etc.
For more information on how various parts of the compiler work, see the rustc guide.
Their is also useful content in the following READMEs, which are gradually being moved over to the guide:
- https://github.com/rust-lang/rust/tree/master/src/librustc/ty/query
- https://github.com/rust-lang/rust/tree/master/src/librustc/dep_graph
- https://github.com/rust-lang/rust/blob/master/src/librustc/infer/region_constraints
- https://github.com/rust-lang/rust/tree/master/src/librustc/infer/higher_ranked
- https://github.com/rust-lang/rust/tree/master/src/librustc/infer/lexical_region_resolve