Ban projecting into SIMD types [MCP838]

[scottmcm]

Closes rust-lang/compiler-team#838

The actual compiler change here is tiny; there's just a bazillion tests to update.

Since I'm sure I've missed some, for now
r? ghost

[rust-log-analyzer]

The job aarch64-gnu-llvm-19-2 failed! Check out the build log: (web) (plain enhanced) (plain)

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

##[group][AOT] mini_core_hello_world
[AOT] mini_core_hello_world

thread 'rustc' panicked at compiler/rustc_mir_transform/src/validate.rs:80:25:
broken MIR in Item(DefId(0:61 ~ mini_core_hello_world[5866]::main)) (after phase change to runtime-optimized) at bb102[0]:
Projecting into SIMD type main::V is banned by MCP#838
stack backtrace:
   0: __rustc::rust_begin_unwind
             at /rustc/390a0ab5dc4a895235a551e502c3893c3337731d/library/std/src/panicking.rs:697:5
   1: core::panicking::panic_fmt
             at /rustc/390a0ab5dc4a895235a551e502c3893c3337731d/library/core/src/panicking.rs:75:14
   2: <rustc_mir_transform::validate::CfgChecker>::fail::<alloc::string::String>
   3: <rustc_mir_transform::validate::Validator as rustc_mir_transform::pass_manager::MirPass>::run_pass
   4: rustc_mir_transform::pass_manager::run_passes_inner
   5: rustc_mir_transform::run_optimization_passes
   6: rustc_mir_transform::optimized_mir
      [... omitted 3 frames ...]
   7: <rustc_middle::ty::context::TyCtxt>::instance_mir
   8: rustc_monomorphize::mono_checks::check_mono_item
      [... omitted 3 frames ...]
   9: rustc_monomorphize::collector::items_of_instance
      [... omitted 3 frames ...]
  10: rustc_monomorphize::collector::collect_items_rec
  11: rustc_monomorphize::collector::collect_items_root
  12: <rustc_session::session::Session>::time::<(), rustc_monomorphize::collector::collect_crate_mono_items::{closure#1}>
  13: rustc_monomorphize::collector::collect_crate_mono_items
  14: rustc_monomorphize::partitioning::collect_and_partition_mono_items
      [... omitted 3 frames ...]
  15: rustc_codegen_cranelift::driver::aot::run_aot
  16: <rustc_codegen_cranelift::CraneliftCodegenBackend as rustc_codegen_ssa::traits::backend::CodegenBackend>::codegen_crate
  17: <rustc_session::session::Session>::time::<alloc::boxed::Box<dyn core::any::Any>, rustc_interface::passes::start_codegen::{closure#0}>
  18: rustc_interface::passes::start_codegen
  19: <rustc_interface::queries::Linker>::codegen_and_build_linker
  20: <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>>
  21: <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}>
  22: <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}
  23: <alloc::boxed::Box<dyn for<'a> core::ops::function::FnOnce<(&'a rustc_session::session::Session, rustc_middle::ty::context::CurrentGcx, alloc::sync::Arc<rustc_data_structures::jobserver::Proxy>, &'a std::sync::once_lock::OnceLock<rustc_middle::ty::context::GlobalCtxt<'a>>, &'a rustc_data_structures::sync::worker_local::WorkerLocal<rustc_middle::arena::Arena<'a>>, &'a rustc_data_structures::sync::worker_local::WorkerLocal<rustc_hir::Arena<'a>>, rustc_driver_impl::run_compiler::{closure#0}::{closure#2}), Output = core::option::Option<rustc_interface::queries::Linker>>> 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
  24: rustc_interface::passes::create_and_enter_global_ctxt::<core::option::Option<rustc_interface::queries::Linker>, rustc_driver_impl::run_compiler::{closure#0}::{closure#2}>
  25: rustc_span::create_session_globals_then::<(), 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

warning: the ICE couldn't be written to `/checkout/compiler/rustc_codegen_cranelift/rustc-ice-2025-07-12T12_02_49-20618.txt`: Read-only file system (os error 30)

note: rustc 1.90.0-nightly (d4e3dccb0 2025-07-12) running on aarch64-unknown-linux-gnu

note: compiler flags: -C panic=abort -Z panic-abort-tests -Z codegen-backend=cranelift -C symbol-mangling-version=v0 -Z randomize-layout -Z unstable-options -Z macro-backtrace -C split-debuginfo=off -C link-arg=-L/usr/lib/llvm-19/lib -C llvm-args=-import-instr-limit=10 -C link-args=-Wl,-z,origin -C link-args=-Wl,-rpath,$ORIGIN/../lib -C debuginfo=2 -C panic=abort -Z force-unstable-if-unmarked

query stack during panic:
#0 [optimized_mir] optimizing MIR for `main`
#1 [check_mono_item] monomorphization-time checking
#2 [items_of_instance] collecting items used by `main`
#3 [collect_and_partition_mono_items] collect_and_partition_mono_items
end of query stack
"/checkout/obj/build/aarch64-unknown-linux-gnu/stage1-tools/cg_clif/dist/rustc-clif" "-Csymbol-mangling-version=v0" "-Zrandomize-layout" "-Zunstable-options" "--check-cfg=cfg(bootstrap)" "--check-cfg=cfg(llvm_enzyme)" "-Zmacro-backtrace" "-Csplit-debuginfo=off" "-Clink-arg=-L/usr/lib/llvm-19/lib" "-Cllvm-args=-import-instr-limit=10" "-Clink-args=-Wl,-z,origin" "-Clink-args=-Wl,-rpath,$ORIGIN/../lib" "-Alinker-messages" "-L" "crate=/checkout/obj/build/aarch64-unknown-linux-gnu/stage1-tools/cg_clif/build/example" "--out-dir" "/checkout/obj/build/aarch64-unknown-linux-gnu/stage1-tools/cg_clif/build/example" "-Cdebuginfo=2" "--target" "aarch64-unknown-linux-gnu" "-Cpanic=abort" "--check-cfg=cfg(jit)" "example/mini_core_hello_world.rs" exited with status ExitStatus(unix_wait_status(25856))
Command has failed. Rerun with -v to see more details.
Build completed unsuccessfully in 0:11:00
  local time: Sat Jul 12 12:02:49 UTC 2025
  network time: Sat, 12 Jul 2025 12:02:49 GMT
##[error]Process completed with exit code 1.
Post job cleanup.