ICE when using `size_of` in `rust-lang/stdarch` tests on `i686-pc-windows-msvc`

[folkertdev]

Code

We hit the following in a stdarch CI job for i686-pc-windows-msvc. Other targets appear to be unaffected.

https://triage.rust-lang.org/gha-logs/rust-lang/stdarch/53655080976?pr=1944

The location is in this definition:

#[target_feature(enable = "sse2")]
unsafe fn load_m128i_word<T>(data: &[T], word_index: usize) -> __m128i {
    let byte_offset = word_index * 16 / size_of::<T>();
    let pointer = data.as_ptr().add(byte_offset) as *const __m128i;
    _mm_loadu_si128(black_box(pointer))
}

I cannot actually reproduce this locally though (I'm on linux, so cannot actually link for this target). Also godbolt still uses a slightly older nightly, the problem does not show up there. Regardless the minimal example should be https://godbolt.org/z/Eanszsdb5.

rust-lang/stdarch#1945 mitigates the issue by using byte_add so the size_of::<T> is no longer needed. We can work around this issue, but it still seems odd.

Meta

rustc --version --verbose:

nightly-x86_64-pc-windows-msvc unchanged - rustc 1.92.0-nightly (2aaa62b89 2025-10-24)

I can't run the command exactly. But the code fails with a recent nightly. The function that errors has not been touched in a while, so this is probably a compiler issue somehow.

Error output

error: internal compiler error: /rustc-dev/2aaa62b89d22b570e560731b03e3d2d6f5c3bbce\compiler\rustc_codegen_ssa\src\mir\intrinsic.rs:123:21: nullary intrinsic size_of must either be in a const block or explicitly opted out because it is inherently a runtime intrinsic
   --> crates\core_arch\src\x86\gfni.rs:886:45
    |
886 |         let byte_offset = word_index * 16 / size_of::<T>();
    |                                             ^^^^^^^^^^^^^^

Backtrace

stack backtrace:
   0:     0x7ffcb6953a22 - std::backtrace_rs::backtrace::win64::trace
                               at /rustc/2aaa62b89d22b570e560731b03e3d2d6f5c3bbce/library\std\src\..\..\backtrace\src\backtrace\win64.rs:85
   1:     0x7ffcb6953a22 - std::backtrace_rs::backtrace::trace_unsynchronized
                               at /rustc/2aaa62b89d22b570e560731b03e3d2d6f5c3bbce/library\std\src\..\..\backtrace\src\backtrace\mod.rs:66
   2:     0x7ffcb6953a22 - std::sys::backtrace::_print_fmt
                               at /rustc/2aaa62b89d22b570e560731b03e3d2d6f5c3bbce/library\std\src\sys\backtrace.rs:66
   3:     0x7ffcb6953a22 - std::sys::backtrace::impl$0::print::impl$0::fmt
                               at /rustc/2aaa62b89d22b570e560731b03e3d2d6f5c3bbce/library\std\src\sys\backtrace.rs:39
   4:     0x7ffcb696912a - core::fmt::rt::Argument::fmt
                               at /rustc/2aaa62b89d22b570e560731b03e3d2d6f5c3bbce/library\core\src\fmt\rt.rs:173
   5:     0x7ffcb696912a - core::fmt::write
                               at /rustc/2aaa62b89d22b570e560731b03e3d2d6f5c3bbce/library\core\src\fmt\mod.rs:1469
   6:     0x7ffcb691ad47 - std::io::default_write_fmt
                               at /rustc/2aaa62b89d22b570e560731b03e3d2d6f5c3bbce/library\std\src\io\mod.rs:639
   7:     0x7ffcb691ad47 - std::io::Write::write_fmt<std::sys::stdio::windows::Stderr>
                               at /rustc/2aaa62b89d22b570e560731b03e3d2d6f5c3bbce/library\std\src\io\mod.rs:1954
   8:     0x7ffcb69336c5 - std::sys::backtrace::BacktraceLock::print
                               at /rustc/2aaa62b89d22b570e560731b03e3d2d6f5c3bbce/library\std\src\sys\backtrace.rs:42
   9:     0x7ffcb693b079 - std::panicking::default_hook::closure$0
                               at /rustc/2aaa62b89d22b570e560731b03e3d2d6f5c3bbce/library\std\src\panicking.rs:301
  10:     0x7ffcb693ae68 - std::panicking::default_hook
                               at /rustc/2aaa62b89d22b570e560731b03e3d2d6f5c3bbce/library\std\src\panicking.rs:328
  11:     0x7ffcb813e074 - core[b98089486264e17e]::slice::sort::unstable::heapsort::heapsort::<((rustc_lint_defs[e3689d7f24339034]::Level, &str), usize), <((rustc_lint_defs[e3689d7f24339034]::Level, &str), usize) as core[b98089486264e17e]::cmp::PartialOrd>::lt>
  12:     0x7ffcb693b93a - std::panicking::panic_with_hook
                               at /rustc/2aaa62b89d22b570e560731b03e3d2d6f5c3bbce/library\std\src\panicking.rs:842
  13:     0x7ffcba7ffea3 - RINvNtNtNtNtCsfVqf9Geh42o_4core5slice4sort6stable9quicksort9quicksortTjRNtNtCsdbijmOdzUpw_12rustc_errors7snippet10AnnotationENCINvMNtCscy1wuF44rYE_5alloc5sliceSB15_11sort_by_keyTINtNtBa_3cmp7ReversejEbENCNCNvMs4_NtB1c_7emitterNtB3o_12HumanEmitter18render_s
  14:     0x7ffcba7f3d59 - std[fdcb0a6535607765]::sys::backtrace::__rust_end_short_backtrace::<std[fdcb0a6535607765]::panicking::begin_panic<rustc_errors[998a81b21785ad88]::ExplicitBug>::{closure#0}, !>
  15:     0x7ffcba7f3a18 - std[fdcb0a6535607765]::panicking::begin_panic::<rustc_errors[998a81b21785ad88]::ExplicitBug>
  16:     0x7ffcba80dd25 - <rustc_errors[998a81b21785ad88]::diagnostic::BugAbort as rustc_errors[998a81b21785ad88]::diagnostic::EmissionGuarantee>::emit_producing_guarantee
  17:     0x7ffcba69cfbf - RINvMs6_NtCskhOX23LNGmh_9hashbrown3rawINtB6_8RawTablejE14reserve_rehashNCINvNtNtCskn0Ger2eFdV_8indexmap3map4core8get_hashTNtNtCsajN8g4cgE90_9rustc_hir3def9NamespaceNtNtCsgtMjEw7bnrM_10rustc_span6symbol6SymbolEINtNtCsfVqf9Geh42o_4core6option6OptionNtNtB2G_6
  18:     0x7ffcba6c5ba6 - <rustc_data_structures[e923fc13fbe84b36]::profiling::SelfProfilerRef>::exec::cold_call::<<rustc_data_structures[e923fc13fbe84b36]::profiling::SelfProfilerRef>::incr_result_hashing::{closure#0}>
  19:     0x7ffcba6c5ded - <rustc_data_structures[e923fc13fbe84b36]::profiling::SelfProfilerRef>::exec::cold_call::<<rustc_data_structures[e923fc13fbe84b36]::profiling::SelfProfilerRef>::incr_result_hashing::{closure#0}>
  20:     0x7ffcba6b58c6 - core[b98089486264e17e]::slice::sort::unstable::ipnsort::<(<rustc_middle[f6dd1b8378577f3a]::mir::mono::CodegenUnit>::items_in_deterministic_order::ItemSortKey, usize), <(<rustc_middle[f6dd1b8378577f3a]::mir::mono::CodegenUnit>::items_in_deterministic_order::ItemSortKey, usize) as core[b98089486264e17e]::cmp::PartialOrd>::lt>
  21:     0x7ffcba6b3f19 - rustc_middle[f6dd1b8378577f3a]::util::bug::span_bug_fmt::<rustc_span[bff4d55158526bb0]::span_encoding::Span>
  22:     0x7ffcb3f772ff - RINvNtNtNtNtCsfVqf9Geh42o_4core5slice4sort6stable9quicksort9quicksortTNtNtCscy1wuF44rYE_5alloc6string6StringB16_ENCINvMNtB1a_5sliceSB15_7sort_byNCINvXs1g_NtNtNtB1a_11collections5btree3mapINtB2s_8BTreeMapB16_B16_EINtNtNtNtBa_4iter6traits7collect12FromIterat
  23:     0x7ffcb6a38794 - <alloc[9229d7763bf6039e]::raw_vec::RawVec<rustc_middle[f6dd1b8378577f3a]::ty::generic_args::GenericArg>>::grow_one
  24:     0x7ffcb69e4ce8 - <hashbrown[8b98e98ecbed7280]::raw::RawTable<((&rustc_codegen_llvm[357ea2b0bcfec854]::llvm::ffi::Metadata, usize), &rustc_codegen_llvm[357ea2b0bcfec854]::llvm::ffi::Metadata)>>::reserve_rehash::<hashbrown[8b98e98ecbed7280]::map::make_hasher<(&rustc_codegen_llvm[357ea2b0bcfec854]::llvm::ffi::Metadata, usize), &rustc_codegen_llvm[357ea2b0bcfec854]::llvm::ffi::Metadata, rustc_hash[686f3a0f6317ec19]::FxBuildHasher>::{closure#0}>
  25:     0x7ffcb6a6f8f6 - <alloc[9229d7763bf6039e]::raw_vec::RawVec<rustc_middle[f6dd1b8378577f3a]::ty::generic_args::GenericArg>>::grow_one
  26:     0x7ffcb3fb3b62 - <rustc_codegen_llvm[357ea2b0bcfec854]::LlvmCodegenBackend as rustc_codegen_ssa[2dd9de867fa07561]::traits::backend::ExtraBackendMethods>::compile_codegen_unit
  27:     0x7ffcb3f537b8 - rustc_interface[cfc686cb91dae03b]::interface::parse_cfg
  28:     0x7ffcb3fbada3 - <rustc_codegen_llvm[357ea2b0bcfec854]::LlvmCodegenBackend as rustc_codegen_ssa[2dd9de867fa07561]::traits::backend::CodegenBackend>::codegen_crate
  29:     0x7ffcb3f20c38 - <rustc_interface[cfc686cb91dae03b]::queries::Linker>::codegen_and_build_linker
  30:     0x7ffcb3ec9c5f - std[fdcb0a6535607765]::sys::backtrace::__rust_begin_short_backtrace::<<std[fdcb0a6535607765]::thread::Builder>::spawn_unchecked_<ctrlc[60f1abb1ac11c8e9]::set_handler_inner<rustc_driver_impl[fdad9a0dfcd1ba21]::install_ctrlc_handler::{closure#0}>::{closure#0}, ()>::{closure#1}::{closure#0}::{closure#0}, ()>
  31:     0x7ffcb3ec27df - RINvNtNtCslMVXBJ6PtkL_3std3sys9backtrace28___rust_begin_short_backtraceNCNCINvNtCshPZ0O03mfVL_15rustc_interface4util26run_in_thread_with_globalsNCINvB1e_31run_in_thread_pool_with_globalsNCINvNtB1g_9interface12run_compileruNCNvCslMk0CRZ32z5_17rustc_driver_i
  32:     0x7ffcb3ed087d - std[fdcb0a6535607765]::sys::backtrace::__rust_begin_short_backtrace::<<std[fdcb0a6535607765]::thread::Builder>::spawn_unchecked_<ctrlc[60f1abb1ac11c8e9]::set_handler_inner<rustc_driver_impl[fdad9a0dfcd1ba21]::install_ctrlc_handler::{closure#0}>::{closure#0}, ()>::{closure#1}::{closure#0}::{closure#0}, ()>
  33:     0x7ffcb692bbbd - alloc::boxed::impl$29::call_once
                               at /rustc/2aaa62b89d22b570e560731b03e3d2d6f5c3bbce/library\alloc\src\boxed.rs:2005
  34:     0x7ffcb692bbbd - alloc::boxed::impl$29::call_once
                               at /rustc/2aaa62b89d22b570e560731b03e3d2d6f5c3bbce/library\alloc\src\boxed.rs:2005
  35:     0x7ffcb692bbbd - std::sys::thread::windows::impl$0::new::thread_start
                               at /rustc/2aaa62b89d22b570e560731b03e3d2d6f5c3bbce/library\std\src\sys\thread\windows.rs:60
  36:     0x7ffd023ce8d7 - BaseThreadInitThunk
  37:     0x7ffd0464c53c - RtlUserThreadStart

[Fulgen301]

Bisection points to 4b3ba58.

[folkertdev]

Neat, yeah #147793 would make sense for this to have regressed.

Are there other things you can learn about that regression? E.g. does it also fail for the other msvc targets, or for i686-pc-windows-gnu. Because I am confused by why this would only show up for this particular target (and hence what would be a good test case). Did you use the godbolt code to reproduce this, or something else?

[Fulgen301]

I ran cargo test --profile=dev within stdarch\crates\core_arch. It also fails for x86_64-pc-windows-msvc as well as x86_64-pc-windows-gnu.
I'll see if I can find a reproducer, at least copy pasting the intrinsic definition and the test case to a new cargo project doesn't cause it to error.

[saethlin]

The way you are struggling to reproduce this makes me think that somehow GVN or some other MIR opt is on the scene, trying to evaluate MIR in an odd context.

I thought I'd be able to get my bearings on what part of the compiler is related here by looking at the backtrace, but I'm pretty sure the backtrace you shared is just completely fried. I don't think we are passing through RawVec::grow_one and then into HashMap internals, then passing through sort internals twice inside of launching a panic.

[Noratrieb]

The stdarch code calls the intrinsic directly (https://github.com/folkertdev/stdarch/blob/5c1c436524c0bbc8db83577f42f8bea9006a7b75/crates/core_arch/src/x86/gfni.rs#L748), which is not how size_of is now implemented: https://github.com/rust-lang/rust/pull/147793/files#diff-02049689ae3bb7ac98af3418ad8fdca219bfa1227cb6cad31afc72bdbae30e27L336

If I understand this correctly, the intrinsic should be removed?

[Noratrieb]

Ah no it is still called in the const definition of the trait: https://github.com/rust-lang/rust/pull/147793/files#diff-02049689ae3bb7ac98af3418ad8fdca219bfa1227cb6cad31afc72bdbae30e27R1242

[Noratrieb]

Yeah this is super trivial to reproduce on x86-64 Linux, so I assume all platforms

#![feature(core_intrinsics)]
pub fn meow() -> usize {
  core::intrinsics::size_of::<u8>()
}

error: internal compiler error: /rustc-dev/2aaa62b89d22b570e560731b03e3d2d6f5c3bbce/compiler/rustc_codegen_ssa/src/mir/intrinsic.rs:123:21: nullary intrinsic size_of must either be in a const block or explicitly opted out because it is inherently a runtime intrinsic
 --> a.rs:3:3
  |
3 |   core::intrinsics::size_of::<u8>()
  |   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^


thread 'rustc' (286495) panicked at /rustc-dev/2aaa62b89d22b570e560731b03e3d2d6f5c3bbce/compiler/rustc_codegen_ssa/src/mir/intrinsic.rs:123:21:
Box<dyn Any>
stack backtrace:
   0:     0x7f083e04fa13 - <std::sys::backtrace::BacktraceLock::print::DisplayBacktrace as core::fmt::Display>::fmt::h8f9d3be17a281b2f
   1:     0x7f083e801b98 - core::fmt::write::he40896efaf9d9055
   2:     0x7f083e003da3 - std::io::Write::write_fmt::h34b46ca48d1c5c92
   3:     0x7f083e015592 - std::sys::backtrace::BacktraceLock::print::h0e2fdddf9038fd34
   4:     0x7f083e01b669 - std::panicking::default_hook::{{closure}}::h86ae99680d19974c
   5:     0x7f083e01b193 - std::panicking::default_hook::h90f5fbe062a4b783
   6:     0x7f083d01cf51 - std[4523e878f5ee40d0]::panicking::update_hook::<alloc[91b21b2f42ef06bc]::boxed::Box<rustc_driver_impl[4f6c29d38b392073]::install_ice_hook::{closure#1}>>::{closure#0}
   7:     0x7f083e01ba8f - std::panicking::panic_with_hook::hd8308519547a2d36
   8:     0x7f083d056de1 - std[4523e878f5ee40d0]::panicking::begin_panic::<rustc_errors[1419c6ff33230f5d]::ExplicitBug>::{closure#0}
   9:     0x7f083d04afd6 - std[4523e878f5ee40d0]::sys::backtrace::__rust_end_short_backtrace::<std[4523e878f5ee40d0]::panicking::begin_panic<rustc_errors[1419c6ff33230f5d]::ExplicitBug>::{closure#0}, !>
  10:     0x7f083d04ac67 - std[4523e878f5ee40d0]::panicking::begin_panic::<rustc_errors[1419c6ff33230f5d]::ExplicitBug>
  11:     0x7f083d0628a1 - <rustc_errors[1419c6ff33230f5d]::diagnostic::BugAbort as rustc_errors[1419c6ff33230f5d]::diagnostic::EmissionGuarantee>::emit_producing_guarantee
  12:     0x7f083d5d77ec - <rustc_errors[1419c6ff33230f5d]::DiagCtxtHandle>::span_bug::<rustc_span[d7563905e8197364]::span_encoding::Span, alloc[91b21b2f42ef06bc]::string::String>
  13:     0x7f083d5fad87 - rustc_middle[4fc2546b21c56f41]::util::bug::opt_span_bug_fmt::<rustc_span[d7563905e8197364]::span_encoding::Span>::{closure#0}
  14:     0x7f083d5fb08a - rustc_middle[4fc2546b21c56f41]::ty::context::tls::with_opt::<rustc_middle[4fc2546b21c56f41]::util::bug::opt_span_bug_fmt<rustc_span[d7563905e8197364]::span_encoding::Span>::{closure#0}, !>::{closure#0}
  15:     0x7f083d5ebdfb - rustc_middle[4fc2546b21c56f41]::ty::context::tls::with_context_opt::<rustc_middle[4fc2546b21c56f41]::ty::context::tls::with_opt<rustc_middle[4fc2546b21c56f41]::util::bug::opt_span_bug_fmt<rustc_span[d7563905e8197364]::span_encoding::Span>::{closure#0}, !>::{closure#0}, !>
  16:     0x7f083ba0ce57 - rustc_middle[4fc2546b21c56f41]::util::bug::span_bug_fmt::<rustc_span[d7563905e8197364]::span_encoding::Span>
  17:     0x7f083f6d0166 - <rustc_codegen_ssa[3e9ea480912b8b47]::mir::FunctionCx<rustc_codegen_llvm[e5b9b35d4d788c4a]::builder::GenericBuilder<rustc_codegen_llvm[e5b9b35d4d788c4a]::context::FullCx>>>::codegen_intrinsic_call
  18:     0x7f083fbd19d0 - rustc_codegen_ssa[3e9ea480912b8b47]::mir::codegen_mir::<rustc_codegen_llvm[e5b9b35d4d788c4a]::builder::GenericBuilder<rustc_codegen_llvm[e5b9b35d4d788c4a]::context::FullCx>>
  19:     0x7f083eaf89c6 - rustc_codegen_llvm[e5b9b35d4d788c4a]::base::compile_codegen_unit::module_codegen
  20:     0x7f083fb6f51f - <rustc_codegen_llvm[e5b9b35d4d788c4a]::LlvmCodegenBackend as rustc_codegen_ssa[3e9ea480912b8b47]::traits::backend::ExtraBackendMethods>::compile_codegen_unit
  21:     0x7f083fb6d541 - <rustc_codegen_llvm[e5b9b35d4d788c4a]::LlvmCodegenBackend as rustc_codegen_ssa[3e9ea480912b8b47]::traits::backend::CodegenBackend>::codegen_crate
  22:     0x7f083fab8c70 - <rustc_interface[abe2772c3d8b98bd]::queries::Linker>::codegen_and_build_linker
  23:     0x7f083fab59d4 - <rustc_interface[abe2772c3d8b98bd]::passes::create_and_enter_global_ctxt<core[308d27a00c808a37]::option::Option<rustc_interface[abe2772c3d8b98bd]::queries::Linker>, rustc_driver_impl[4f6c29d38b392073]::run_compiler::{closure#0}::{closure#2}>::{closure#2} as core[308d27a00c808a37]::ops::function::FnOnce<(&rustc_session[688b8ac127adfd68]::session::Session, rustc_middle[4fc2546b21c56f41]::ty::context::CurrentGcx, alloc[91b21b2f42ef06bc]::sync::Arc<rustc_data_structures[3293cc7e350cbc36]::jobserver::Proxy>, &std[4523e878f5ee40d0]::sync::once_lock::OnceLock<rustc_middle[4fc2546b21c56f41]::ty::context::GlobalCtxt>, &rustc_data_structures[3293cc7e350cbc36]::sync::worker_local::WorkerLocal<rustc_middle[4fc2546b21c56f41]::arena::Arena>, &rustc_data_structures[3293cc7e350cbc36]::sync::worker_local::WorkerLocal<rustc_hir[9ad7a1acb80adbb3]::Arena>, rustc_driver_impl[4f6c29d38b392073]::run_compiler::{closure#0}::{closure#2})>>::call_once::{shim:vtable#0}
  24:     0x7f083f99b922 - rustc_interface[abe2772c3d8b98bd]::interface::run_compiler::<(), rustc_driver_impl[4f6c29d38b392073]::run_compiler::{closure#0}>::{closure#1}
  25:     0x7f083f54c280 - std[4523e878f5ee40d0]::sys::backtrace::__rust_begin_short_backtrace::<rustc_interface[abe2772c3d8b98bd]::util::run_in_thread_with_globals<rustc_interface[abe2772c3d8b98bd]::util::run_in_thread_pool_with_globals<rustc_interface[abe2772c3d8b98bd]::interface::run_compiler<(), rustc_driver_impl[4f6c29d38b392073]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>
  26:     0x7f083f54bf64 - <<std[4523e878f5ee40d0]::thread::Builder>::spawn_unchecked_<rustc_interface[abe2772c3d8b98bd]::util::run_in_thread_with_globals<rustc_interface[abe2772c3d8b98bd]::util::run_in_thread_pool_with_globals<rustc_interface[abe2772c3d8b98bd]::interface::run_compiler<(), rustc_driver_impl[4f6c29d38b392073]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>::{closure#1} as core[308d27a00c808a37]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  27:     0x7f083f54a8ef - std::sys::thread::unix::Thread::new::thread_start::ha29b37a9d3bc8cc1
  28:     0x7f083909a97a - start_thread
  29:     0x7f0839122d2c - __GI___clone3
  30:                0x0 - <unknown>

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

note: please attach the file at `/tmp/scratchZvL9eATQK/rustc-ice-2025-10-25T21_45_58-286461.txt` to your bug report

note: compiler flags: --crate-type lib

query stack during panic:
end of query stack
error: aborting due to 1 previous error; 1 warning emitted

I even have a working backtrace that's not doing heapsort inside grow_one 🎉