diff options
Diffstat (limited to 'compiler')
| -rw-r--r-- | compiler/rustc_codegen_llvm/src/consts.rs | 22 | ||||
| -rw-r--r-- | compiler/rustc_interface/src/tests.rs | 1 | ||||
| -rw-r--r-- | compiler/rustc_session/src/options.rs | 3 |
3 files changed, 17 insertions, 9 deletions
diff --git a/compiler/rustc_codegen_llvm/src/consts.rs b/compiler/rustc_codegen_llvm/src/consts.rs index 901fa9fb047..3ece1659b9e 100644 --- a/compiler/rustc_codegen_llvm/src/consts.rs +++ b/compiler/rustc_codegen_llvm/src/consts.rs @@ -36,11 +36,6 @@ pub fn const_alloc_to_llvm(cx: &CodegenCx<'ll, '_>, alloc: &Allocation) -> &'ll alloc: &'a Allocation, range: Range<usize>, ) { - /// Allocations larger than this will only be codegen'd as entirely initialized or entirely undef. - /// This avoids compile time regressions when an alloc would have many chunks, - /// e.g. for `[(u64, u8); N]`, which has undef padding in each element. - const MAX_PARTIALLY_UNDEF_SIZE: usize = 1024; - let mut chunks = alloc .init_mask() .range_as_init_chunks(Size::from_bytes(range.start), Size::from_bytes(range.end)); @@ -57,21 +52,30 @@ pub fn const_alloc_to_llvm(cx: &CodegenCx<'ll, '_>, alloc: &Allocation) -> &'ll } }; - if range.len() > MAX_PARTIALLY_UNDEF_SIZE { + // Generating partially-uninit consts inhibits optimizations, so it is disabled by default. + // See https://github.com/rust-lang/rust/issues/84565. + let allow_partially_uninit = + match cx.sess().opts.debugging_opts.partially_uninit_const_threshold { + Some(max) => range.len() <= max, + None => false, + }; + + if allow_partially_uninit { + llvals.extend(chunks.map(chunk_to_llval)); + } else { let llval = match (chunks.next(), chunks.next()) { (Some(chunk), None) => { // exactly one chunk, either fully init or fully uninit chunk_to_llval(chunk) } _ => { - // partially uninit + // partially uninit, codegen as if it was initialized + // (using some arbitrary value for uninit bytes) let bytes = alloc.inspect_with_uninit_and_ptr_outside_interpreter(range); cx.const_bytes(bytes) } }; llvals.push(llval); - } else { - llvals.extend(chunks.map(chunk_to_llval)); } } diff --git a/compiler/rustc_interface/src/tests.rs b/compiler/rustc_interface/src/tests.rs index b8961434006..afab919bc3c 100644 --- a/compiler/rustc_interface/src/tests.rs +++ b/compiler/rustc_interface/src/tests.rs @@ -743,6 +743,7 @@ fn test_debugging_options_tracking_hash() { tracked!(no_profiler_runtime, true); tracked!(osx_rpath_install_name, true); tracked!(panic_abort_tests, true); + tracked!(partially_uninit_const_threshold, Some(123)); tracked!(plt, Some(true)); tracked!(polonius, true); tracked!(precise_enum_drop_elaboration, false); diff --git a/compiler/rustc_session/src/options.rs b/compiler/rustc_session/src/options.rs index f36fc29e974..9a1be40558c 100644 --- a/compiler/rustc_session/src/options.rs +++ b/compiler/rustc_session/src/options.rs @@ -1186,6 +1186,9 @@ options! { "support compiling tests with panic=abort (default: no)"), parse_only: bool = (false, parse_bool, [UNTRACKED], "parse only; do not compile, assemble, or link (default: no)"), + partially_uninit_const_threshold: Option<usize> = (None, parse_opt_number, [TRACKED], + "allow generating const initializers with mixed init/uninit bytes, \ + and set the maximum total size of a const allocation for which this is allowed (default: never)"), perf_stats: bool = (false, parse_bool, [UNTRACKED], "print some performance-related statistics (default: no)"), plt: Option<bool> = (None, parse_opt_bool, [TRACKED], |