MIR validation error at `mir-opt-level>=3`

[cbeuw]

#![feature(custom_mir, core_intrinsics)]
#![allow(unused_parens, unused_assignments, overflowing_literals)]
extern crate core;
use core::intrinsics::mir::*;

#[custom_mir(dialect = "runtime", phase = "initial")]
pub fn fn12(
    mut _6: *mut bool,
    mut _9: *mut bool,
) -> char {
    mir! {
    let _19: i8;
    {
    Goto(bb1)
    }
    bb1 = {
    Call((*_9) = fn13(_6), bb2)
    }
    bb2 = {
    _19 = 115_i8;
    match _19 {
    1 => bb3,
    _ => bb5
    }
    }
    bb3 = {
    Call((*_9) = fn13(_6), bb2)
    }
    bb5 = {
    Return()
    }

    }
}
#[custom_mir(dialect = "runtime", phase = "initial")]
fn fn13(mut _1: *mut bool) -> bool {
    mir! {
    {
    RET = true;
    Return()
    }
    }
}
pub fn main() {}

This compiles fine with rustc -Zmir-opt-level=2 -Copt-level=1 repro.rs, but

% rustc -Zmir-opt-level=3 -Copt-level=1 repro.rs
warning: the feature `custom_mir` is internal to the compiler or standard library
 --> repro.rs:1:12
  |
1 | #![feature(custom_mir, core_intrinsics)]
  |            ^^^^^^^^^^
  |
  = note: using it is strongly discouraged
  = note: `#[warn(internal_features)]` on by default

warning: 1 warning emitted

error: internal compiler error: no errors encountered even though `delay_span_bug` issued

error: internal compiler error: broken MIR in Item(DefId(0:5 ~ repro[f81f]::fn12)) (after phase change to runtime-optimized) at bb0[1]:
                                use of local _4, which has no storage here
  --> repro.rs:27:18
   |
27 |     Call((*_9) = fn13(_6), bb2)
   |                  ^^^^^^^^
   |
note: delayed at compiler/rustc_const_eval/src/transform/validate.rs:310:22
         0: std::backtrace::Backtrace::create
         1: <rustc_errors::HandlerInner>::emit_diagnostic
         2: <rustc_errors::Handler>::delay_span_bug::<rustc_span::span_encoding::Span, alloc::string::String>
         3: <rustc_const_eval::transform::validate::CfgChecker>::fail::<alloc::string::String>
         4: <rustc_const_eval::transform::validate::CfgChecker as rustc_middle::mir::visit::Visitor>::visit_local
         5: <rustc_const_eval::transform::validate::CfgChecker as rustc_middle::mir::visit::Visitor>::visit_statement
         6: <rustc_const_eval::transform::validate::Validator as rustc_middle::mir::MirPass>::run_pass
         7: rustc_mir_transform::pass_manager::run_passes_inner
         8: rustc_mir_transform::optimized_mir
         9: rustc_query_impl::plumbing::__rust_begin_short_backtrace::<rustc_query_impl::query_impl::optimized_mir::dynamic_query::{closure#2}::{closure#0}, rustc_middle::query::erase::Erased<[u8; 8]>>
        10: <rustc_query_impl::query_impl::optimized_mir::dynamic_query::{closure#2} as core::ops::function::FnOnce<(rustc_middle::ty::context::TyCtxt, rustc_span::def_id::DefId)>>::call_once
        11: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::DynamicConfig<rustc_query_system::query::caches::DefaultCache<rustc_span::def_id::DefId, rustc_middle::query::erase::Erased<[u8; 8]>>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt, false>
        12: rustc_query_impl::query_impl::optimized_mir::get_query_non_incr::__rust_end_short_backtrace
        13: rustc_middle::query::plumbing::query_get_at::<rustc_query_system::query::caches::DefaultCache<rustc_span::def_id::DefId, rustc_middle::query::erase::Erased<[u8; 8]>>>
        14: rustc_mir_transform::cross_crate_inline::cross_crate_inlinable
        15: rustc_query_impl::plumbing::__rust_begin_short_backtrace::<rustc_query_impl::query_impl::cross_crate_inlinable::dynamic_query::{closure#2}::{closure#0}, rustc_middle::query::erase::Erased<[u8; 1]>>
        16: <rustc_query_impl::query_impl::cross_crate_inlinable::dynamic_query::{closure#2} as core::ops::function::FnOnce<(rustc_middle::ty::context::TyCtxt, rustc_span::def_id::DefId)>>::call_once
        17: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::DynamicConfig<rustc_query_system::query::caches::DefaultCache<rustc_span::def_id::DefId, rustc_middle::query::erase::Erased<[u8; 1]>>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt, false>
        18: rustc_query_impl::query_impl::cross_crate_inlinable::get_query_non_incr::__rust_end_short_backtrace
        19: rustc_passes::reachable::item_might_be_inlined
        20: rustc_passes::reachable::reachable_set
        21: rustc_query_impl::plumbing::__rust_begin_short_backtrace::<rustc_query_impl::query_impl::reachable_set::dynamic_query::{closure#2}::{closure#0}, rustc_middle::query::erase::Erased<[u8; 8]>>
        22: <rustc_query_impl::query_impl::reachable_set::dynamic_query::{closure#2} as core::ops::function::FnOnce<(rustc_middle::ty::context::TyCtxt, ())>>::call_once
        23: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::DynamicConfig<rustc_query_system::query::caches::SingleCache<rustc_middle::query::erase::Erased<[u8; 8]>>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt, false>
        24: rustc_query_impl::query_impl::reachable_set::get_query_non_incr::__rust_end_short_backtrace
        25: rustc_codegen_ssa::back::symbol_export::reachable_non_generics_provider
        26: rustc_query_impl::plumbing::__rust_begin_short_backtrace::<rustc_query_impl::query_impl::reachable_non_generics::dynamic_query::{closure#2}::{closure#0}, rustc_middle::query::erase::Erased<[u8; 8]>>
        27: <rustc_query_impl::query_impl::reachable_non_generics::dynamic_query::{closure#2} as core::ops::function::FnOnce<(rustc_middle::ty::context::TyCtxt, rustc_span::def_id::CrateNum)>>::call_once
        28: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::DynamicConfig<rustc_query_system::query::caches::VecCache<rustc_span::def_id::CrateNum, rustc_middle::query::erase::Erased<[u8; 8]>>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt, false>
        29: rustc_query_impl::query_impl::reachable_non_generics::get_query_non_incr::__rust_end_short_backtrace
        30: rustc_codegen_ssa::back::symbol_export::is_reachable_non_generic_provider_local
        31: rustc_query_impl::plumbing::__rust_begin_short_backtrace::<rustc_query_impl::query_impl::is_reachable_non_generic::dynamic_query::{closure#2}::{closure#0}, rustc_middle::query::erase::Erased<[u8; 1]>>
        32: <rustc_query_impl::query_impl::is_reachable_non_generic::dynamic_query::{closure#2} as core::ops::function::FnOnce<(rustc_middle::ty::context::TyCtxt, rustc_span::def_id::DefId)>>::call_once
        33: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::DynamicConfig<rustc_query_system::query::caches::DefaultCache<rustc_span::def_id::DefId, rustc_middle::query::erase::Erased<[u8; 1]>>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt, false>
        34: rustc_query_impl::query_impl::is_reachable_non_generic::get_query_non_incr::__rust_end_short_backtrace
        35: <rustc_monomorphize::collector::RootCollector>::push_if_root
        36: rustc_monomorphize::collector::collect_roots
        37: rustc_monomorphize::collector::collect_crate_mono_items
        38: rustc_monomorphize::partitioning::collect_and_partition_mono_items
        39: rustc_query_impl::plumbing::__rust_begin_short_backtrace::<rustc_query_impl::query_impl::collect_and_partition_mono_items::dynamic_query::{closure#2}::{closure#0}, rustc_middle::query::erase::Erased<[u8; 24]>>
        40: <rustc_query_impl::query_impl::collect_and_partition_mono_items::dynamic_query::{closure#2} as core::ops::function::FnOnce<(rustc_middle::ty::context::TyCtxt, ())>>::call_once
        41: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::DynamicConfig<rustc_query_system::query::caches::SingleCache<rustc_middle::query::erase::Erased<[u8; 24]>>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt, false>
        42: rustc_query_impl::query_impl::collect_and_partition_mono_items::get_query_non_incr::__rust_end_short_backtrace
        43: rustc_codegen_ssa::base::codegen_crate::<rustc_codegen_llvm::LlvmCodegenBackend>
        44: <rustc_codegen_llvm::LlvmCodegenBackend as rustc_codegen_ssa::traits::backend::CodegenBackend>::codegen_crate
        45: <rustc_session::session::Session>::time::<alloc::boxed::Box<dyn core::any::Any>, rustc_interface::passes::start_codegen::{closure#0}>
        46: rustc_interface::passes::start_codegen
        47: <rustc_middle::ty::context::GlobalCtxt>::enter::<<rustc_interface::queries::Queries>::ongoing_codegen::{closure#0}, core::result::Result<alloc::boxed::Box<dyn core::any::Any>, rustc_span::ErrorGuaranteed>>
        48: <rustc_interface::queries::Queries>::ongoing_codegen
        49: rustc_span::set_source_map::<core::result::Result<(), rustc_span::ErrorGuaranteed>, rustc_interface::interface::run_compiler<core::result::Result<(), rustc_span::ErrorGuaranteed>, rustc_driver_impl::run_compiler::{closure#1}>::{closure#0}::{closure#0}>
        50: std::sys_common::backtrace::__rust_begin_short_backtrace::<rustc_interface::util::run_in_thread_with_globals<rustc_interface::interface::run_compiler<core::result::Result<(), rustc_span::ErrorGuaranteed>, rustc_driver_impl::run_compiler::{closure#1}>::{closure#0}, core::result::Result<(), rustc_span::ErrorGuaranteed>>::{closure#0}::{closure#0}, core::result::Result<(), rustc_span::ErrorGuaranteed>>
        51: <<std::thread::Builder>::spawn_unchecked_<rustc_interface::util::run_in_thread_with_globals<rustc_interface::interface::run_compiler<core::result::Result<(), rustc_span::ErrorGuaranteed>, rustc_driver_impl::run_compiler::{closure#1}>::{closure#0}, core::result::Result<(), rustc_span::ErrorGuaranteed>>::{closure#0}::{closure#0}, core::result::Result<(), rustc_span::ErrorGuaranteed>>::{closure#1} as core::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
        52: std::sys::unix::thread::Thread::new::thread_start
        53: __pthread_joiner_wake
  --> repro.rs:27:18
   |
27 |     Call((*_9) = fn13(_6), bb2)
   |                  ^^^^^^^^

error: internal compiler error: broken MIR in Item(DefId(0:5 ~ repro[f81f]::fn12)) (after phase change to runtime-optimized) at bb0[1]:
                                use of local _5, which has no storage here
  --> repro.rs:27:18
   |
27 |     Call((*_9) = fn13(_6), bb2)
   |                  ^^^^^^^^
   |
note: delayed at compiler/rustc_const_eval/src/transform/validate.rs:310:22
         0: std::backtrace::Backtrace::create
         1: <rustc_errors::HandlerInner>::emit_diagnostic
         2: <rustc_errors::Handler>::delay_span_bug::<rustc_span::span_encoding::Span, alloc::string::String>
         3: <rustc_const_eval::transform::validate::CfgChecker>::fail::<alloc::string::String>
         4: <rustc_const_eval::transform::validate::CfgChecker as rustc_middle::mir::visit::Visitor>::visit_local
         5: <rustc_const_eval::transform::validate::CfgChecker as rustc_middle::mir::visit::Visitor>::visit_place
         6: <rustc_const_eval::transform::validate::CfgChecker as rustc_middle::mir::visit::Visitor>::visit_statement
         7: <rustc_const_eval::transform::validate::Validator as rustc_middle::mir::MirPass>::run_pass
         8: rustc_mir_transform::pass_manager::run_passes_inner
         9: rustc_mir_transform::optimized_mir
        10: rustc_query_impl::plumbing::__rust_begin_short_backtrace::<rustc_query_impl::query_impl::optimized_mir::dynamic_query::{closure#2}::{closure#0}, rustc_middle::query::erase::Erased<[u8; 8]>>
        11: <rustc_query_impl::query_impl::optimized_mir::dynamic_query::{closure#2} as core::ops::function::FnOnce<(rustc_middle::ty::context::TyCtxt, rustc_span::def_id::DefId)>>::call_once
        12: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::DynamicConfig<rustc_query_system::query::caches::DefaultCache<rustc_span::def_id::DefId, rustc_middle::query::erase::Erased<[u8; 8]>>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt, false>
        13: rustc_query_impl::query_impl::optimized_mir::get_query_non_incr::__rust_end_short_backtrace
        14: rustc_middle::query::plumbing::query_get_at::<rustc_query_system::query::caches::DefaultCache<rustc_span::def_id::DefId, rustc_middle::query::erase::Erased<[u8; 8]>>>
        15: rustc_mir_transform::cross_crate_inline::cross_crate_inlinable
        16: rustc_query_impl::plumbing::__rust_begin_short_backtrace::<rustc_query_impl::query_impl::cross_crate_inlinable::dynamic_query::{closure#2}::{closure#0}, rustc_middle::query::erase::Erased<[u8; 1]>>
        17: <rustc_query_impl::query_impl::cross_crate_inlinable::dynamic_query::{closure#2} as core::ops::function::FnOnce<(rustc_middle::ty::context::TyCtxt, rustc_span::def_id::DefId)>>::call_once
        18: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::DynamicConfig<rustc_query_system::query::caches::DefaultCache<rustc_span::def_id::DefId, rustc_middle::query::erase::Erased<[u8; 1]>>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt, false>
        19: rustc_query_impl::query_impl::cross_crate_inlinable::get_query_non_incr::__rust_end_short_backtrace
        20: rustc_passes::reachable::item_might_be_inlined
        21: rustc_passes::reachable::reachable_set
        22: rustc_query_impl::plumbing::__rust_begin_short_backtrace::<rustc_query_impl::query_impl::reachable_set::dynamic_query::{closure#2}::{closure#0}, rustc_middle::query::erase::Erased<[u8; 8]>>
        23: <rustc_query_impl::query_impl::reachable_set::dynamic_query::{closure#2} as core::ops::function::FnOnce<(rustc_middle::ty::context::TyCtxt, ())>>::call_once
        24: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::DynamicConfig<rustc_query_system::query::caches::SingleCache<rustc_middle::query::erase::Erased<[u8; 8]>>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt, false>
        25: rustc_query_impl::query_impl::reachable_set::get_query_non_incr::__rust_end_short_backtrace
        26: rustc_codegen_ssa::back::symbol_export::reachable_non_generics_provider
        27: rustc_query_impl::plumbing::__rust_begin_short_backtrace::<rustc_query_impl::query_impl::reachable_non_generics::dynamic_query::{closure#2}::{closure#0}, rustc_middle::query::erase::Erased<[u8; 8]>>
        28: <rustc_query_impl::query_impl::reachable_non_generics::dynamic_query::{closure#2} as core::ops::function::FnOnce<(rustc_middle::ty::context::TyCtxt, rustc_span::def_id::CrateNum)>>::call_once
        29: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::DynamicConfig<rustc_query_system::query::caches::VecCache<rustc_span::def_id::CrateNum, rustc_middle::query::erase::Erased<[u8; 8]>>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt, false>
        30: rustc_query_impl::query_impl::reachable_non_generics::get_query_non_incr::__rust_end_short_backtrace
        31: rustc_codegen_ssa::back::symbol_export::is_reachable_non_generic_provider_local
        32: rustc_query_impl::plumbing::__rust_begin_short_backtrace::<rustc_query_impl::query_impl::is_reachable_non_generic::dynamic_query::{closure#2}::{closure#0}, rustc_middle::query::erase::Erased<[u8; 1]>>
        33: <rustc_query_impl::query_impl::is_reachable_non_generic::dynamic_query::{closure#2} as core::ops::function::FnOnce<(rustc_middle::ty::context::TyCtxt, rustc_span::def_id::DefId)>>::call_once
        34: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::DynamicConfig<rustc_query_system::query::caches::DefaultCache<rustc_span::def_id::DefId, rustc_middle::query::erase::Erased<[u8; 1]>>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt, false>
        35: rustc_query_impl::query_impl::is_reachable_non_generic::get_query_non_incr::__rust_end_short_backtrace
        36: <rustc_monomorphize::collector::RootCollector>::push_if_root
        37: rustc_monomorphize::collector::collect_roots
        38: rustc_monomorphize::collector::collect_crate_mono_items
        39: rustc_monomorphize::partitioning::collect_and_partition_mono_items
        40: rustc_query_impl::plumbing::__rust_begin_short_backtrace::<rustc_query_impl::query_impl::collect_and_partition_mono_items::dynamic_query::{closure#2}::{closure#0}, rustc_middle::query::erase::Erased<[u8; 24]>>
        41: <rustc_query_impl::query_impl::collect_and_partition_mono_items::dynamic_query::{closure#2} as core::ops::function::FnOnce<(rustc_middle::ty::context::TyCtxt, ())>>::call_once
        42: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::DynamicConfig<rustc_query_system::query::caches::SingleCache<rustc_middle::query::erase::Erased<[u8; 24]>>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt, false>
        43: rustc_query_impl::query_impl::collect_and_partition_mono_items::get_query_non_incr::__rust_end_short_backtrace
        44: rustc_codegen_ssa::base::codegen_crate::<rustc_codegen_llvm::LlvmCodegenBackend>
        45: <rustc_codegen_llvm::LlvmCodegenBackend as rustc_codegen_ssa::traits::backend::CodegenBackend>::codegen_crate
        46: <rustc_session::session::Session>::time::<alloc::boxed::Box<dyn core::any::Any>, rustc_interface::passes::start_codegen::{closure#0}>
        47: rustc_interface::passes::start_codegen
        48: <rustc_middle::ty::context::GlobalCtxt>::enter::<<rustc_interface::queries::Queries>::ongoing_codegen::{closure#0}, core::result::Result<alloc::boxed::Box<dyn core::any::Any>, rustc_span::ErrorGuaranteed>>
        49: <rustc_interface::queries::Queries>::ongoing_codegen
        50: rustc_span::set_source_map::<core::result::Result<(), rustc_span::ErrorGuaranteed>, rustc_interface::interface::run_compiler<core::result::Result<(), rustc_span::ErrorGuaranteed>, rustc_driver_impl::run_compiler::{closure#1}>::{closure#0}::{closure#0}>
        51: std::sys_common::backtrace::__rust_begin_short_backtrace::<rustc_interface::util::run_in_thread_with_globals<rustc_interface::interface::run_compiler<core::result::Result<(), rustc_span::ErrorGuaranteed>, rustc_driver_impl::run_compiler::{closure#1}>::{closure#0}, core::result::Result<(), rustc_span::ErrorGuaranteed>>::{closure#0}::{closure#0}, core::result::Result<(), rustc_span::ErrorGuaranteed>>
        52: <<std::thread::Builder>::spawn_unchecked_<rustc_interface::util::run_in_thread_with_globals<rustc_interface::interface::run_compiler<core::result::Result<(), rustc_span::ErrorGuaranteed>, rustc_driver_impl::run_compiler::{closure#1}>::{closure#0}, core::result::Result<(), rustc_span::ErrorGuaranteed>>::{closure#0}::{closure#0}, core::result::Result<(), rustc_span::ErrorGuaranteed>>::{closure#1} as core::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
        53: std::sys::unix::thread::Thread::new::thread_start
        54: __pthread_joiner_wake
  --> repro.rs:27:18
   |
27 |     Call((*_9) = fn13(_6), bb2)
   |                  ^^^^^^^^

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

note: please attach the file at `/Users/andy/Code/rustlantis/rustc-ice-2023-10-29T11_56_45-53492.txt` to your bug report

note: compiler flags: -Z mir-opt-level=3 -C opt-level=1

query stack during panic:
end of query stack

% rustc -v --version
rustc 1.75.0-nightly (e5cfc5547 2023-10-28)
binary: rustc
commit-hash: e5cfc55477eceed1317a02189fdf77a4a98f2124
commit-date: 2023-10-28
host: aarch64-apple-darwin
release: 1.75.0-nightly
LLVM version: 17.0.3

[saethlin]

The minimal set of flags to trip this is:

-Copt-level=1 -Zmir-enable-passes=+ConstProp -Zinline-mir

I think you need -Copt-level=1 because if I add -Ztreat-err-as-bug we can see this is hit from cross_crate_inlinable:

#0 [optimized_mir] optimizing MIR for `fn12`
#1 [cross_crate_inlinable] whether the item should be made inlinable across crates
#2 [reachable_set] reachability
#3 [reachable_non_generics] looking up the exported symbols of a crate
#4 [is_reachable_non_generic] checking whether `fn12` is an exported symbol
#5 [collect_and_partition_mono_items] collect_and_partition_mono_items