const-eval: always do full typed copies #149901

RalfJung · 2025-12-12T07:38:58Z

Perf experiment exploring alternatives to #148967.

This is the maximally naive version that just always does full typed copies. It may be possible to skip some of the validation work if all we care about is resetting padding -- though it's not obvious to me how to do that in a way that actually helps with performance. Also, typed copies at integer type technically do not preserve provenance, which could become relevant in const-eval for the same reason as provenance in padding (see #148470) -- so it's not like we can just skip all types without padding.

RalfJung · 2025-12-12T07:45:32Z

@bors try
@rust-timer queue

const-eval: always do full typed copies

rust-log-analyzer · 2025-12-12T08:10:55Z

The job x86_64-gnu-gcc failed! Check out the build log: (web) (plain enhanced) (plain)

Click to see the possible cause of the failure (guessed by this bot)


---- [mir-opt] tests/mir-opt/pattern_types.rs stdout ----
------rustc stdout------------------------------

------rustc stderr------------------------------
warning: unused variable: `x`
##[warning] --> /checkout/tests/mir-opt/pattern_types.rs:9:9
  |
9 |     let x: pattern_type!(u32 is 1..) = unsafe { std::mem::transmute(2) };
  |         ^ help: if this is intentional, prefix it with an underscore: `_x`
  |
  = note: `#[warn(unused_variables)]` (part of `#[warn(unused)]`) on by default

warning: unused variable: `y`
##[warning]  --> /checkout/tests/mir-opt/pattern_types.rs:11:9
   |
11 |     let y: pattern_type!(u32 is 1..) = unsafe { std::mem::transmute(0) };
   |         ^ help: if this is intentional, prefix it with an underscore: `_y`

warning: function `main` is never used
##[warning] --> /checkout/tests/mir-opt/pattern_types.rs:7:4
  |
7 | fn main() {
  |    ^^^^
  |
  = note: `#[warn(dead_code)]` (part of `#[warn(unused)]`) on by default


thread 'rustc' (30735) panicked at compiler/rustc_const_eval/src/util/check_validity_requirement.rs:192:41:
called `Result::unwrap()` on an `Err` value: InterpErrorInfo(InterpErrorInfoInner { kind: UndefinedBehavior(ValidationError(ValidationErrorInfo { path: None, kind: OutOfRange { value: "0", range: 1..=4294967295, max_value: 4294967295 } })), backtrace: InterpErrorBacktrace { backtrace: None } })
stack backtrace:
   0: __rustc::rust_begin_unwind
   1: core::panicking::panic_fmt
   2: core::result::unwrap_failed
   3: rustc_const_eval::util::check_validity_requirement::validate_scalar_in_layout
   4: <rustc_const_eval::provide::{closure#3} as core::ops::function::FnOnce<(rustc_middle::ty::context::TyCtxt, rustc_middle::ty::consts::int::ScalarInt, rustc_middle::ty::Ty)>>::call_once
   5: <rustc_middle::ty::print::pretty::FmtPrinter as rustc_middle::ty::print::pretty::PrettyPrinter>::pretty_print_const_scalar_int
   6: <rustc_middle::ty::print::pretty::FmtPrinter as rustc_middle::ty::print::pretty::PrettyPrinter>::pretty_print_const_scalar
   7: rustc_middle::mir::pretty::pretty_print_const_value_tcx
   8: <rustc_middle::mir::consts::Const as core::fmt::Display>::fmt
   9: core::fmt::write
  10: <rustc_middle::mir::VarDebugInfoContents as core::fmt::Debug>::fmt
  11: core::fmt::write
  12: <rustc_middle::mir::VarDebugInfo as core::fmt::Debug>::fmt
  13: core::fmt::write
  14: alloc::fmt::format::format_inner
  15: rustc_middle::mir::pretty::write_scope_tree
  16: rustc_middle::mir::pretty::write_scope_tree
  17: rustc_middle::mir::pretty::write_scope_tree
  18: <rustc_middle::mir::pretty::MirWriter>::write_mir_fn
  19: <rustc_middle::mir::pretty::MirDumper>::dump_mir_to_writer
  20: <rustc_middle::mir::pretty::MirDumper>::dump_mir
  21: rustc_mir_transform::pass_manager::run_passes_inner
  22: rustc_mir_transform::run_optimization_passes
  23: rustc_mir_transform::optimized_mir
      [... omitted 2 frames ...]
  24: <rustc_middle::ty::context::TyCtxt>::instance_mir
  25: rustc_data_structures::sync::parallel::par_for_each_in::<&rustc_span::def_id::LocalDefId, &[rustc_span::def_id::LocalDefId], <rustc_middle::ty::context::TyCtxt>::par_hir_body_owners<rustc_interface::passes::analysis::{closure#1}::{closure#0}>::{closure#0}>
  26: <rustc_session::session::Session>::time::<(), rustc_interface::passes::analysis::{closure#1}>
  27: rustc_interface::passes::analysis
      [... omitted 2 frames ...]
  28: <std::thread::local::LocalKey<core::cell::Cell<*const ()>>>::with::<rustc_middle::ty::context::tls::enter_context<<rustc_middle::ty::context::GlobalCtxt>::enter<rustc_interface::passes::create_and_enter_global_ctxt<core::option::Option<rustc_interface::queries::Linker>, rustc_driver_impl::run_compiler::{closure#0}::{closure#2}>::{closure#2}::{closure#0}, core::option::Option<rustc_interface::queries::Linker>>::{closure#1}, core::option::Option<rustc_interface::queries::Linker>>::{closure#0}, core::option::Option<rustc_interface::queries::Linker>>
  29: <rustc_middle::ty::context::TyCtxt>::create_global_ctxt::<core::option::Option<rustc_interface::queries::Linker>, rustc_interface::passes::create_and_enter_global_ctxt<core::option::Option<rustc_interface::queries::Linker>, rustc_driver_impl::run_compiler::{closure#0}::{closure#2}>::{closure#2}::{closure#0}>
  30: <rustc_interface::passes::create_and_enter_global_ctxt<core::option::Option<rustc_interface::queries::Linker>, rustc_driver_impl::run_compiler::{closure#0}::{closure#2}>::{closure#2} as core::ops::function::FnOnce<(&rustc_session::session::Session, rustc_middle::ty::context::CurrentGcx, alloc::sync::Arc<rustc_data_structures::jobserver::Proxy>, &std::sync::once_lock::OnceLock<rustc_middle::ty::context::GlobalCtxt>, &rustc_data_structures::sync::worker_local::WorkerLocal<rustc_middle::arena::Arena>, &rustc_data_structures::sync::worker_local::WorkerLocal<rustc_hir::Arena>, rustc_driver_impl::run_compiler::{closure#0}::{closure#2})>>::call_once::{shim:vtable#0}
  31: rustc_interface::passes::create_and_enter_global_ctxt::<core::option::Option<rustc_interface::queries::Linker>, rustc_driver_impl::run_compiler::{closure#0}::{closure#2}>
  32: rustc_interface::interface::run_compiler::<(), rustc_driver_impl::run_compiler::{closure#0}>::{closure#1}
  33: <scoped_tls::ScopedKey<rustc_span::SessionGlobals>>::set::<rustc_interface::util::run_in_thread_with_globals<rustc_interface::util::run_in_thread_pool_with_globals<rustc_interface::interface::run_compiler<(), rustc_driver_impl::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}::{closure#0}, ()>
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

error: the compiler unexpectedly panicked. this is a bug.

note: using internal features is not supported and expected to cause internal compiler errors when used incorrectly

note: rustc 1.94.0-nightly (3fc493712 2025-12-12) running on x86_64-unknown-linux-gnu

note: compiler flags: -Z threads=1 -Z simulate-remapped-rust-src-base=/rustc/FAKE_PREFIX -Z translate-remapped-path-to-local-path=no -Z ignore-directory-in-diagnostics-source-blocks=/cargo -Z ignore-directory-in-diagnostics-source-blocks=/checkout/vendor -Z codegen-backend=gcc -C opt-level=1 -Z dump-mir=PreCodegen -Z validate-mir -Z lint-mir -Z dump-mir-exclude-pass-number -Z mir-include-spans=false --crate-type rlib -Z mir-opt-level=4 -Z mir-enable-passes=+ReorderBasicBlocks,+ReorderLocals -Z dump-mir-dir=/checkout/obj/build/x86_64-unknown-linux-gnu/test/mir-opt/pattern_types -C prefer-dynamic -C rpath -C debuginfo=0

query stack during panic:
#0 [optimized_mir] optimizing MIR for `main`
#1 [analysis] running analysis passes on crate `pattern_types`
end of query stack
warning: 3 warnings emitted


------------------------------------------

error: compilation failed!
status: exit status: 101
command: env -u RUSTC_LOG_COLOR RUSTC_ICE="0" RUST_BACKTRACE="short" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/bin/rustc" "/checkout/tests/mir-opt/pattern_types.rs" "-Zthreads=1" "-Zsimulate-remapped-rust-src-base=/rustc/FAKE_PREFIX" "-Ztranslate-remapped-path-to-local-path=no" "-Z" "ignore-directory-in-diagnostics-source-blocks=/cargo" "-Z" "ignore-directory-in-diagnostics-source-blocks=/checkout/vendor" "--sysroot" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2" "-Zcodegen-backend=gcc" "--target=x86_64-unknown-linux-gnu" "--check-cfg" "cfg(test,FALSE)" "-O" "-Copt-level=1" "-Zdump-mir=PreCodegen" "-Zvalidate-mir" "-Zlint-mir" "-Zdump-mir-exclude-pass-number" "-Zmir-include-spans=false" "--crate-type=rlib" "-Zmir-opt-level=4" "-Zmir-enable-passes=+ReorderBasicBlocks,+ReorderLocals" "-Zdump-mir-dir=/checkout/obj/build/x86_64-unknown-linux-gnu/test/mir-opt/pattern_types" "--emit" "mir" "-C" "prefer-dynamic" "--out-dir" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/mir-opt/pattern_types" "-A" "internal_features" "-A" "unused_parens" "-A" "unused_braces" "-Crpath" "-Cdebuginfo=0"
stdout: none
--- stderr -------------------------------
warning: unused variable: `x`
##[warning] --> /checkout/tests/mir-opt/pattern_types.rs:9:9
  |
9 |     let x: pattern_type!(u32 is 1..) = unsafe { std::mem::transmute(2) };
  |         ^ help: if this is intentional, prefix it with an underscore: `_x`
  |
  = note: `#[warn(unused_variables)]` (part of `#[warn(unused)]`) on by default

warning: unused variable: `y`
##[warning]  --> /checkout/tests/mir-opt/pattern_types.rs:11:9
   |
11 |     let y: pattern_type!(u32 is 1..) = unsafe { std::mem::transmute(0) };
   |         ^ help: if this is intentional, prefix it with an underscore: `_y`

warning: function `main` is never used
##[warning] --> /checkout/tests/mir-opt/pattern_types.rs:7:4
  |
7 | fn main() {
  |    ^^^^
  |
  = note: `#[warn(dead_code)]` (part of `#[warn(unused)]`) on by default


thread 'rustc' (30735) panicked at compiler/rustc_const_eval/src/util/check_validity_requirement.rs:192:41:
called `Result::unwrap()` on an `Err` value: InterpErrorInfo(InterpErrorInfoInner { kind: UndefinedBehavior(ValidationError(ValidationErrorInfo { path: None, kind: OutOfRange { value: "0", range: 1..=4294967295, max_value: 4294967295 } })), backtrace: InterpErrorBacktrace { backtrace: None } })
stack backtrace:
   0: __rustc::rust_begin_unwind
   1: core::panicking::panic_fmt
   2: core::result::unwrap_failed
   3: rustc_const_eval::util::check_validity_requirement::validate_scalar_in_layout
   4: <rustc_const_eval::provide::{closure#3} as core::ops::function::FnOnce<(rustc_middle::ty::context::TyCtxt, rustc_middle::ty::consts::int::ScalarInt, rustc_middle::ty::Ty)>>::call_once
   5: <rustc_middle::ty::print::pretty::FmtPrinter as rustc_middle::ty::print::pretty::PrettyPrinter>::pretty_print_const_scalar_int
   6: <rustc_middle::ty::print::pretty::FmtPrinter as rustc_middle::ty::print::pretty::PrettyPrinter>::pretty_print_const_scalar
   7: rustc_middle::mir::pretty::pretty_print_const_value_tcx
   8: <rustc_middle::mir::consts::Const as core::fmt::Display>::fmt
   9: core::fmt::write
  10: <rustc_middle::mir::VarDebugInfoContents as core::fmt::Debug>::fmt
  11: core::fmt::write
  12: <rustc_middle::mir::VarDebugInfo as core::fmt::Debug>::fmt
  13: core::fmt::write
  14: alloc::fmt::format::format_inner
  15: rustc_middle::mir::pretty::write_scope_tree
  16: rustc_middle::mir::pretty::write_scope_tree
  17: rustc_middle::mir::pretty::write_scope_tree
  18: <rustc_middle::mir::pretty::MirWriter>::write_mir_fn
  19: <rustc_middle::mir::pretty::MirDumper>::dump_mir_to_writer
  20: <rustc_middle::mir::pretty::MirDumper>::dump_mir
  21: rustc_mir_transform::pass_manager::run_passes_inner
  22: rustc_mir_transform::run_optimization_passes
  23: rustc_mir_transform::optimized_mir
      [... omitted 2 frames ...]
  24: <rustc_middle::ty::context::TyCtxt>::instance_mir
  25: rustc_data_structures::sync::parallel::par_for_each_in::<&rustc_span::def_id::LocalDefId, &[rustc_span::def_id::LocalDefId], <rustc_middle::ty::context::TyCtxt>::par_hir_body_owners<rustc_interface::passes::analysis::{closure#1}::{closure#0}>::{closure#0}>
  26: <rustc_session::session::Session>::time::<(), rustc_interface::passes::analysis::{closure#1}>
  27: rustc_interface::passes::analysis
      [... omitted 2 frames ...]
  28: <std::thread::local::LocalKey<core::cell::Cell<*const ()>>>::with::<rustc_middle::ty::context::tls::enter_context<<rustc_middle::ty::context::GlobalCtxt>::enter<rustc_interface::passes::create_and_enter_global_ctxt<core::option::Option<rustc_interface::queries::Linker>, rustc_driver_impl::run_compiler::{closure#0}::{closure#2}>::{closure#2}::{closure#0}, core::option::Option<rustc_interface::queries::Linker>>::{closure#1}, core::option::Option<rustc_interface::queries::Linker>>::{closure#0}, core::option::Option<rustc_interface::queries::Linker>>
  29: <rustc_middle::ty::context::TyCtxt>::create_global_ctxt::<core::option::Option<rustc_interface::queries::Linker>, rustc_interface::passes::create_and_enter_global_ctxt<core::option::Option<rustc_interface::queries::Linker>, rustc_driver_impl::run_compiler::{closure#0}::{closure#2}>::{closure#2}::{closure#0}>
  30: <rustc_interface::passes::create_and_enter_global_ctxt<core::option::Option<rustc_interface::queries::Linker>, rustc_driver_impl::run_compiler::{closure#0}::{closure#2}>::{closure#2} as core::ops::function::FnOnce<(&rustc_session::session::Session, rustc_middle::ty::context::CurrentGcx, alloc::sync::Arc<rustc_data_structures::jobserver::Proxy>, &std::sync::once_lock::OnceLock<rustc_middle::ty::context::GlobalCtxt>, &rustc_data_structures::sync::worker_local::WorkerLocal<rustc_middle::arena::Arena>, &rustc_data_structures::sync::worker_local::WorkerLocal<rustc_hir::Arena>, rustc_driver_impl::run_compiler::{closure#0}::{closure#2})>>::call_once::{shim:vtable#0}
  31: rustc_interface::passes::create_and_enter_global_ctxt::<core::option::Option<rustc_interface::queries::Linker>, rustc_driver_impl::run_compiler::{closure#0}::{closure#2}>
  32: rustc_interface::interface::run_compiler::<(), rustc_driver_impl::run_compiler::{closure#0}>::{closure#1}
  33: <scoped_tls::ScopedKey<rustc_span::SessionGlobals>>::set::<rustc_interface::util::run_in_thread_with_globals<rustc_interface::util::run_in_thread_pool_with_globals<rustc_interface::interface::run_compiler<(), rustc_driver_impl::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}::{closure#0}, ()>
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

error: the compiler unexpectedly panicked. this is a bug.

note: using internal features is not supported and expected to cause internal compiler errors when used incorrectly

note: rustc 1.94.0-nightly (3fc493712 2025-12-12) running on x86_64-unknown-linux-gnu

note: compiler flags: -Z threads=1 -Z simulate-remapped-rust-src-base=/rustc/FAKE_PREFIX -Z translate-remapped-path-to-local-path=no -Z ignore-directory-in-diagnostics-source-blocks=/cargo -Z ignore-directory-in-diagnostics-source-blocks=/checkout/vendor -Z codegen-backend=gcc -C opt-level=1 -Z dump-mir=PreCodegen -Z validate-mir -Z lint-mir -Z dump-mir-exclude-pass-number -Z mir-include-spans=false --crate-type rlib -Z mir-opt-level=4 -Z mir-enable-passes=+ReorderBasicBlocks,+ReorderLocals -Z dump-mir-dir=/checkout/obj/build/x86_64-unknown-linux-gnu/test/mir-opt/pattern_types -C prefer-dynamic -C rpath -C debuginfo=0

query stack during panic:
#0 [optimized_mir] optimizing MIR for `main`
#1 [analysis] running analysis passes on crate `pattern_types`
end of query stack

For more information how to resolve CI failures of this job, visit this link.

rust-bors · 2025-12-12T10:12:30Z

☀️ Try build successful (CI)
Build commit: db4e1d2 (db4e1d23234d93b5e96ecc768b35d9090c32cddf, parent: 5b150d238fbd4fe7bc2cd3140d8e6fb4406099fa)

rust-timer · 2025-12-12T11:48:15Z

Finished benchmarking commit (db4e1d2): comparison URL.

Overall result: ❌✅ regressions and improvements - please read the text below

Benchmarking this pull request means it may be perf-sensitive – we'll automatically label it not fit for rolling up. You can override this, but we strongly advise not to, due to possible changes in compiler perf.

Next Steps: If you can justify the regressions found in this try perf run, please do so in sufficient writing along with @rustbot label: +perf-regression-triaged. If not, please fix the regressions and do another perf run. If its results are neutral or positive, the label will be automatically removed.

@bors rollup=never
@rustbot label: -S-waiting-on-perf +perf-regression

Instruction count

Our most reliable metric. Used to determine the overall result above. However, even this metric can be noisy.

	mean	range	count
Regressions ❌ (primary)	1.5%	[0.1%, 13.4%]	58
Regressions ❌ (secondary)	34.5%	[0.2%, 320.6%]	82
Improvements ✅ (primary)	-0.4%	[-0.6%, -0.2%]	9
Improvements ✅ (secondary)	-0.5%	[-1.2%, -0.0%]	30
All ❌✅ (primary)	1.2%	[-0.6%, 13.4%]	67

Max RSS (memory usage)

Results (primary -2.9%, secondary -1.4%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	2.9%	[1.8%, 6.4%]	5
Improvements ✅ (primary)	-2.9%	[-4.1%, -1.7%]	2
Improvements ✅ (secondary)	-4.5%	[-6.4%, -2.9%]	7
All ❌✅ (primary)	-2.9%	[-4.1%, -1.7%]	2

Cycles

Results (primary 4.4%, secondary 261.5%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	4.4%	[2.3%, 8.2%]	9
Regressions ❌ (secondary)	268.7%	[1.8%, 1393.3%]	37
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-3.3%	[-3.3%, -3.3%]	1
All ❌✅ (primary)	4.4%	[2.3%, 8.2%]	9

Binary size

This benchmark run did not return any relevant results for this metric.

Bootstrap: 473.727s -> 474.872s (0.24%)
Artifact size: 389.29 MiB -> 386.79 MiB (-0.64%)

traviscross · 2025-12-12T16:29:54Z

While we're here...

@craterbot check

craterbot · 2025-12-12T16:30:09Z

👌 Experiment pr-149901 created and queued.
🤖 Automatically detected try build db4e1d2
🔍 You can check out the queue and this experiment's details.

ℹ️ Crater is a tool to run experiments across parts of the Rust ecosystem. Learn more

craterbot · 2025-12-23T21:31:46Z

🚧 Experiment pr-149901 is now running

ℹ️ Crater is a tool to run experiments across parts of the Rust ecosystem. Learn more

craterbot · 2025-12-25T13:08:34Z

🎉 Experiment pr-149901 is completed!
📊 18 regressed and 1 fixed (758298 total)
📊 2128 spurious results on the retry-regressed-list.txt, consider a retry¹ if this is a significant amount.
📰 Open the summary report.

⚠️ If you notice any spurious failure please add them to the denylist!
ℹ️ Crater is a tool to run experiments across parts of the Rust ecosystem. Learn more

re-run the experiment with crates=https://crater-reports.s3.amazonaws.com/pr-149901/retry-regressed-list.txt ↩

theemathas · 2025-12-25T15:09:10Z

The regressions.... look genuine?

traviscross · 2025-12-25T22:03:24Z

@craterbot check p=1 crates=https://crater-reports.s3.amazonaws.com/pr-149901/retry-regressed-list.txt

craterbot · 2025-12-25T22:03:30Z

👌 Experiment pr-149901-1 created and queued.
🤖 Automatically detected try build db4e1d2
🔍 You can check out the queue and this experiment's details.

ℹ️ Crater is a tool to run experiments across parts of the Rust ecosystem. Learn more

RalfJung · 2025-12-26T18:07:04Z

Yeah it's not too surprising that some const code out there has UB. I am honestly surprised the number is so small, that's a good sign IMO. :)

craterbot · 2025-12-27T01:11:50Z

🚧 Experiment pr-149901-1 is now running

ℹ️ Crater is a tool to run experiments across parts of the Rust ecosystem. Learn more

craterbot · 2025-12-27T07:37:43Z

🎉 Experiment pr-149901-1 is completed!
📊 16 regressed and 0 fixed (1989 total)
📊 141 spurious results on the retry-regressed-list.txt, consider a retry¹ if this is a significant amount.
📰 Open the summary report.

⚠️ If you notice any spurious failure please add them to the denylist!
ℹ️ Crater is a tool to run experiments across parts of the Rust ecosystem. Learn more

re-run the experiment with crates=https://crater-reports.s3.amazonaws.com/pr-149901-1/retry-regressed-list.txt ↩

theemathas · 2025-12-27T10:00:01Z

I looked at all the regressions. The service-install crate has a "compile error -> ICE" regression which is a nondeterministic ICE, and this exact same crate has had this nondeterministic ICE before. See #147966 (comment)

Other than that, all regressions involved code doing UB in const that was previously undetected.

Regressed dependencies

baby_shark 0.3.3: Used MaybeUninit::assume_init to create uninitialized data https://docs.rs/crate/baby_shark/0.3.3/source/src/voxel/meshing/lookup_table.rs#3037
I don't understand why this wasn't detected as a root regression on its own.

cglue 0.2.14: Creates dangling reference which was never dereferenced. Also does shenanigans with layout of RawWaker. Seems to be fixed in a newer version of cglue.

igneous-labs/inf-1.5 and igneous-labs/solido-legacy-sdk: Depends on const_crypto, which was also found to be broken in this crater run

Regressed root results

Lohann/merkle-patricia-trie-demo: Created a dangling reference before coercing to a raw pointer https://github.com/Lohann/merkle-patricia-trie-demo/blob/e5202c18669ac4cba1de29ec7f24d3720217901f/rust/merkle-patricia-trie-js/src/storage.rs#L15-L16

TadaHrd/AES-rust: Code copied from aes_rust, which was also found to be broken in this crater run

wyhhh/snake: Transmuted a None::<usize> into a byte array https://github.com/wyhhh/snake/blob/11f56dd02d38f264bbd71b77bbac42345b6b3f3e/src/main.rs#L58-L62 https://github.com/wyhhh/vec_list/blob/54cdf5eb83ed18b3919f6d45b10b10e4c9e0acf1/src/lib.rs#L26-L32 https://github.com/wyhhh/wutil/blob/cc203a0f14359f0502d79ff3db99d6e1c0f2f65a/src/convert.rs#L37

aes_rust: Used MaybeUninit::assume_init to create uninitialized data https://docs.rs/crate/aes_rust/latest/source/src/indexed_str.rs#18

const_crypto: Used slice::from_raw_parts to create unaligned slice reference https://docs.rs/crate/const-crypto/latest/source/src/bs58.rs#122-128

const_lookup_map: Used MaybeUninit::assume_init to create uninitialized data https://docs.rs/crate/const_lookup_map/latest/source/src/lib.rs#152-155

igneous-labs/solido-legacy-sdk: Already mentioned as regressed dependency

lunka: Used MaybeUninit::assume_init to create uninitialized data https://docs.rs/crate/lunka/latest/source/src/reg.rs#40 https://docs.rs/crate/lunka/latest/source/src/cdef/auxlib.rs#47

mesh_to_vox: Used MaybeUninit::assume_innit to create uninitialized data https://docs.rs/crate/mesh_to_vox/latest/source/src/octree.rs#193

vptr: Used a union to create a null reference https://docs.rs/vptr-macros/0.2.2/src/vptr_macros/macros.rs.html#126

const-eval: always do full typed copies

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rustbot added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Dec 12, 2025

RalfJung mentioned this pull request Dec 12, 2025

const-eval: always do mem-to-mem copies if there might be padding involved #148967

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rust-bors bot added a commit that referenced this pull request Dec 12, 2025

Auto merge of #149901 - RalfJung:const-eval-typed, r=<try>

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const-eval: always do full typed copies

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rustbot added the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Dec 12, 2025

traviscross added the I-lang-radar Items that are on lang's radar and will need eventual work or consideration. label Dec 12, 2025

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rustbot added perf-regression Performance regression. and removed S-waiting-on-perf Status: Waiting on a perf run to be completed. labels Dec 12, 2025

craterbot added S-waiting-on-crater Status: Waiting on a crater run to be completed. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Dec 12, 2025

craterbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-crater Status: Waiting on a crater run to be completed. labels Dec 25, 2025

craterbot added S-waiting-on-crater Status: Waiting on a crater run to be completed. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Dec 25, 2025

craterbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-crater Status: Waiting on a crater run to be completed. labels Dec 27, 2025

RalfJung closed this Jan 6, 2026

rustbot removed the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Jan 6, 2026

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const-eval: always do full typed copies #149901

const-eval: always do full typed copies #149901

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RalfJung commented Dec 12, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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rust-timer commented Dec 12, 2025

Overall result: ❌✅ regressions and improvements - please read the text below

Instruction count

Max RSS (memory usage)

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traviscross commented Dec 12, 2025

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theemathas commented Dec 25, 2025

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RalfJung commented Dec 26, 2025

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theemathas commented Dec 27, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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Regressed dependencies

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RalfJung commented Dec 12, 2025 •

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theemathas commented Dec 27, 2025 •

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