Skip to content

Modify MIR building to drop repeat expressions with length zero #95935

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Jump to bottom
Closed
wants to merge 1 commit into from
Closed

Modify MIR building to drop repeat expressions with length zero #95935

wants to merge 1 commit into from

Conversation

JakobDegen
Copy link
Contributor

Closes #74836 .

This version of things was sort of discussed in the issue, but decided against for a reason I don't quite understand. I'm putting this PR up to demonstrate the intended fix, and I've asked on Zulip for clarification over why this is considered problematic.

@rustbot rustbot added the T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. label Apr 11, 2022
@rust-highfive
Copy link
Contributor

r? @oli-obk

(rust-highfive has picked a reviewer for you, use r? to override)

@rust-highfive rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Apr 11, 2022
@JakobDegen
Copy link
Contributor Author

(wow, highfive really likes assigning you to my PRs)

Its important to note that

fn main() {
    let _: &'static [String; 0] = &[String::new(); 0];
}

compiles under this PR, which was not the case before, meaning we could not undo this after it hits stable

@JakobDegen
Copy link
Contributor Author

Hmm, is that check overly restrictive or is there something I'm not understanding here?

@JakobDegen JakobDegen closed this Apr 11, 2022
@oli-obk
Copy link
Contributor

oli-obk commented Apr 11, 2022

Ah.. promotion allows &CONST to get promoted as long as the value doesn't implement Drop or contain UnsafeCell. You basically generated that 😆 . I think you need to generate an Aggregate

@rust-log-analyzer
Copy link
Collaborator

The job x86_64-gnu-llvm-12 failed! Check out the build log: (web) (plain)

Click to see the possible cause of the failure (guessed by this bot) 
   Compiling memchr v2.4.1
   Compiling std v0.0.0 (/checkout/library/std)
   Compiling compiler_builtins v0.1.70
   Compiling unwind v0.0.0 (/checkout/library/unwind)
thread 'rustc' panicked at 'diverge_from called on block with terminator that cannot unwind.', compiler/rustc_mir_build/src/build/scope.rs:1030:9
stack backtrace:
   0:     0x7fcf332527d2 - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::h7a88a4dc96b6b8f8
   1:     0x7fcf332b7468 - core::fmt::write::h42234c3e51154f4c
   2:     0x7fcf33242ce1 - std::io::Write::write_fmt::h5505b6313bdcb0f3
   3:     0x7fcf33255dd6 - std::panicking::default_hook::{{closure}}::hbe1bb29927e8c85b
   4:     0x7fcf332559d5 - std::panicking::default_hook::h30c665989e20cb24
   5:     0x7fcf33d64671 - rustc_driver[2b15ae7948b6e616]::DEFAULT_HOOK::{closure#0}::{closure#0}
   6:     0x7fcf33256741 - std::panicking::rust_panic_with_hook::hab898bc6064aa4ee
   7:     0x7fcf33256549 - std::panicking::begin_panic_handler::{{closure}}::h688434a74a3a0f4f
   8:     0x7fcf33252d74 - std::sys_common::backtrace::__rust_end_short_backtrace::hf938ae7adc39f6fa
   9:     0x7fcf33256279 - rust_begin_unwind
  10:     0x7fcf33208dc3 - core::panicking::panic_fmt::h0eedb34d228802aa
  11:     0x7fcf34c07139 - <rustc_mir_build[1e9d80c4f7d94376]::build::Builder>::as_rvalue
  12:     0x7fcf34c0a7d4 - <rustc_mir_build[1e9d80c4f7d94376]::build::Builder>::expr_into_dest
  13:     0x7fcf34c0a03a - <rustc_mir_build[1e9d80c4f7d94376]::build::Builder>::as_temp_inner
  14:     0x7fcf34c02ecc - <rustc_mir_build[1e9d80c4f7d94376]::build::Builder>::expr_as_place
  15:     0x7fcf34c042f3 - <rustc_mir_build[1e9d80c4f7d94376]::build::Builder>::expr_as_place
  16:     0x7fcf34bfe24b - <rustc_mir_build[1e9d80c4f7d94376]::build::Builder>::ast_block_stmts
  17:     0x7fcf34c20629 - <rustc_mir_build[1e9d80c4f7d94376]::build::Builder>::in_scope::<<rustc_mir_build[1e9d80c4f7d94376]::build::Builder>::ast_block::{closure#2}::{closure#0}, ()>
  18:     0x7fcf34c0c9ca - <rustc_mir_build[1e9d80c4f7d94376]::build::Builder>::expr_into_dest
  19:     0x7fcf34c0a03a - <rustc_mir_build[1e9d80c4f7d94376]::build::Builder>::as_temp_inner
  20:     0x7fcf34c02ecc - <rustc_mir_build[1e9d80c4f7d94376]::build::Builder>::expr_as_place
  21:     0x7fcf34c03804 - <rustc_mir_build[1e9d80c4f7d94376]::build::Builder>::expr_as_place
  22:     0x7fcf34c02d0c - <rustc_mir_build[1e9d80c4f7d94376]::build::Builder>::as_place
  23:     0x7fcf34c0ca04 - <rustc_mir_build[1e9d80c4f7d94376]::build::Builder>::expr_into_dest
  24:     0x7fcf34c21714 - <rustc_mir_build[1e9d80c4f7d94376]::build::Builder>::in_scope::<<rustc_mir_build[1e9d80c4f7d94376]::build::Builder>::expr_into_dest::{closure#0}::{closure#0}, ()>
  25:     0x7fcf34c0baa9 - <rustc_mir_build[1e9d80c4f7d94376]::build::Builder>::expr_into_dest
  26:     0x7fcf34c21714 - <rustc_mir_build[1e9d80c4f7d94376]::build::Builder>::in_scope::<<rustc_mir_build[1e9d80c4f7d94376]::build::Builder>::expr_into_dest::{closure#0}::{closure#0}, ()>
  27:     0x7fcf34c0baa9 - <rustc_mir_build[1e9d80c4f7d94376]::build::Builder>::expr_into_dest
  28:     0x7fcf34bfb04e - rustc_mir_build[1e9d80c4f7d94376]::build::construct_fn::<core[10878fb91fc84a80]::iter::adapters::chain::Chain<alloc[4b492a408420e30b]::vec::into_iter::IntoIter<rustc_mir_build[1e9d80c4f7d94376]::build::ArgInfo>, core[10878fb91fc84a80]::iter::adapters::map::Map<core[10878fb91fc84a80]::iter::adapters::enumerate::Enumerate<core[10878fb91fc84a80]::slice::iter::Iter<rustc_hir[83eb891e04ea7418]::hir::Param>>, rustc_mir_build[1e9d80c4f7d94376]::build::mir_build::{closure#1}::{closure#1}>>>
  29:     0x7fcf34c9faaa - <rustc_infer[e9909202d8948eff]::infer::InferCtxtBuilder>::enter::<rustc_middle[87143a0b6987fc74]::mir::Body, rustc_mir_build[1e9d80c4f7d94376]::build::mir_build::{closure#1}>
  30:     0x7fcf34bf930f - rustc_mir_build[1e9d80c4f7d94376]::build::mir_built
  31:     0x7fcf353b590c - rustc_query_system[6655655853c83e28]::query::plumbing::try_execute_query::<rustc_query_impl[62d43cdc40496630]::plumbing::QueryCtxt, rustc_query_system[6655655853c83e28]::query::caches::DefaultCache<rustc_middle[87143a0b6987fc74]::ty::WithOptConstParam<rustc_span[e033c2886c1ea87]::def_id::LocalDefId>, &rustc_data_structures[e873bb7798a1662c]::steal::Steal<rustc_middle[87143a0b6987fc74]::mir::Body>>>
  32:     0x7fcf354f4b6e - rustc_query_system[6655655853c83e28]::query::plumbing::get_query::<rustc_query_impl[62d43cdc40496630]::queries::mir_built, rustc_query_impl[62d43cdc40496630]::plumbing::QueryCtxt>
  33:     0x7fcf3580fc86 - <rustc_query_impl[62d43cdc40496630]::Queries as rustc_middle[87143a0b6987fc74]::ty::query::QueryEngine>::mir_built
  34:     0x7fcf3442848c - rustc_mir_transform[7b037954339a5e74]::check_unsafety::unsafety_check_result
  35:     0x7fcf34425119 - <rustc_mir_transform[7b037954339a5e74]::check_unsafety::provide::{closure#0} as core[10878fb91fc84a80]::ops::function::FnOnce<(rustc_middle[87143a0b6987fc74]::ty::context::TyCtxt, rustc_span[e033c2886c1ea87]::def_id::LocalDefId)>>::call_once
  36:     0x7fcf353c6bf4 - rustc_query_system[6655655853c83e28]::query::plumbing::try_execute_query::<rustc_query_impl[62d43cdc40496630]::plumbing::QueryCtxt, rustc_query_system[6655655853c83e28]::query::caches::DefaultCache<rustc_span[e033c2886c1ea87]::def_id::LocalDefId, &rustc_middle[87143a0b6987fc74]::mir::query::UnsafetyCheckResult>>
  37:     0x7fcf354b6f40 - rustc_query_system[6655655853c83e28]::query::plumbing::get_query::<rustc_query_impl[62d43cdc40496630]::queries::unsafety_check_result, rustc_query_impl[62d43cdc40496630]::plumbing::QueryCtxt>
  38:     0x7fcf343ef783 - rustc_mir_transform[7b037954339a5e74]::mir_const
  39:     0x7fcf353b590c - rustc_query_system[6655655853c83e28]::query::plumbing::try_execute_query::<rustc_query_impl[62d43cdc40496630]::plumbing::QueryCtxt, rustc_query_system[6655655853c83e28]::query::caches::DefaultCache<rustc_middle[87143a0b6987fc74]::ty::WithOptConstParam<rustc_span[e033c2886c1ea87]::def_id::LocalDefId>, &rustc_data_structures[e873bb7798a1662c]::steal::Steal<rustc_middle[87143a0b6987fc74]::mir::Body>>>
  40:     0x7fcf354f4f2b - rustc_query_system[6655655853c83e28]::query::plumbing::get_query::<rustc_query_impl[62d43cdc40496630]::queries::mir_const, rustc_query_impl[62d43cdc40496630]::plumbing::QueryCtxt>
  41:     0x7fcf3580fcb6 - <rustc_query_impl[62d43cdc40496630]::Queries as rustc_middle[87143a0b6987fc74]::ty::query::QueryEngine>::mir_const
  42:     0x7fcf343f03fc - rustc_mir_transform[7b037954339a5e74]::mir_promoted
  43:     0x7fcf354857fc - rustc_query_system[6655655853c83e28]::query::plumbing::get_query::<rustc_query_impl[62d43cdc40496630]::queries::mir_promoted, rustc_query_impl[62d43cdc40496630]::plumbing::QueryCtxt>
  44:     0x7fcf3580fe06 - <rustc_query_impl[62d43cdc40496630]::Queries as rustc_middle[87143a0b6987fc74]::ty::query::QueryEngine>::mir_promoted
  45:     0x7fcf34f3343a - rustc_borrowck[56119217130bda78]::mir_borrowck
  46:     0x7fcf34f00399 - <rustc_borrowck[56119217130bda78]::provide::{closure#0} as core[10878fb91fc84a80]::ops::function::FnOnce<(rustc_middle[87143a0b6987fc74]::ty::context::TyCtxt, rustc_span[e033c2886c1ea87]::def_id::LocalDefId)>>::call_once
  47:     0x7fcf353c5e84 - rustc_query_system[6655655853c83e28]::query::plumbing::try_execute_query::<rustc_query_impl[62d43cdc40496630]::plumbing::QueryCtxt, rustc_query_system[6655655853c83e28]::query::caches::DefaultCache<rustc_span[e033c2886c1ea87]::def_id::LocalDefId, &rustc_middle[87143a0b6987fc74]::mir::query::BorrowCheckResult>>
  48:     0x7fcf35484a80 - rustc_query_system[6655655853c83e28]::query::plumbing::get_query::<rustc_query_impl[62d43cdc40496630]::queries::mir_borrowck, rustc_query_impl[62d43cdc40496630]::plumbing::QueryCtxt>
  49:     0x7fcf33ecb9dd - <rustc_middle[87143a0b6987fc74]::hir::map::Map>::par_body_owners::<rustc_interface[1e8edbf255833c1]::passes::analysis::{closure#2}::{closure#0}>
  50:     0x7fcf33e6dd20 - <rustc_session[490bd8b11d3080dc]::session::Session>::time::<(), rustc_interface[1e8edbf255833c1]::passes::analysis::{closure#2}>
  51:     0x7fcf33e5e1cb - rustc_interface[1e8edbf255833c1]::passes::analysis
  52:     0x7fcf353ffb2c - rustc_query_system[6655655853c83e28]::query::plumbing::try_execute_query::<rustc_query_impl[62d43cdc40496630]::plumbing::QueryCtxt, rustc_query_system[6655655853c83e28]::query::caches::DefaultCache<(), core[10878fb91fc84a80]::result::Result<(), rustc_errors[3b46f01f9753e7d]::ErrorGuaranteed>>>
  53:     0x7fcf354f1079 - rustc_query_system[6655655853c83e28]::query::plumbing::get_query::<rustc_query_impl[62d43cdc40496630]::queries::analysis, rustc_query_impl[62d43cdc40496630]::plumbing::QueryCtxt>
  54:     0x7fcf33d55f1a - <rustc_interface[1e8edbf255833c1]::passes::QueryContext>::enter::<rustc_driver[2b15ae7948b6e616]::run_compiler::{closure#1}::{closure#2}::{closure#3}, core[10878fb91fc84a80]::result::Result<(), rustc_errors[3b46f01f9753e7d]::ErrorGuaranteed>>
  55:     0x7fcf33cf8e80 - <rustc_interface[1e8edbf255833c1]::interface::Compiler>::enter::<rustc_driver[2b15ae7948b6e616]::run_compiler::{closure#1}::{closure#2}, core[10878fb91fc84a80]::result::Result<core[10878fb91fc84a80]::option::Option<rustc_interface[1e8edbf255833c1]::queries::Linker>, rustc_errors[3b46f01f9753e7d]::ErrorGuaranteed>>
  56:     0x7fcf33cdc486 - rustc_span[e033c2886c1ea87]::with_source_map::<core[10878fb91fc84a80]::result::Result<(), rustc_errors[3b46f01f9753e7d]::ErrorGuaranteed>, rustc_interface[1e8edbf255833c1]::interface::create_compiler_and_run<core[10878fb91fc84a80]::result::Result<(), rustc_errors[3b46f01f9753e7d]::ErrorGuaranteed>, rustc_driver[2b15ae7948b6e616]::run_compiler::{closure#1}>::{closure#1}>
  57:     0x7fcf33d0be57 - rustc_interface[1e8edbf255833c1]::interface::create_compiler_and_run::<core[10878fb91fc84a80]::result::Result<(), rustc_errors[3b46f01f9753e7d]::ErrorGuaranteed>, rustc_driver[2b15ae7948b6e616]::run_compiler::{closure#1}>
  58:     0x7fcf33d1058f - <scoped_tls[5ed4b67c3b198af5]::ScopedKey<rustc_span[e033c2886c1ea87]::SessionGlobals>>::set::<rustc_interface[1e8edbf255833c1]::interface::run_compiler<core[10878fb91fc84a80]::result::Result<(), rustc_errors[3b46f01f9753e7d]::ErrorGuaranteed>, rustc_driver[2b15ae7948b6e616]::run_compiler::{closure#1}>::{closure#0}, core[10878fb91fc84a80]::result::Result<(), rustc_errors[3b46f01f9753e7d]::ErrorGuaranteed>>
  59:     0x7fcf33d57ed9 - std[e4dc215d72d9f73d]::sys_common::backtrace::__rust_begin_short_backtrace::<rustc_interface[1e8edbf255833c1]::util::run_in_thread_pool_with_globals<rustc_interface[1e8edbf255833c1]::interface::run_compiler<core[10878fb91fc84a80]::result::Result<(), rustc_errors[3b46f01f9753e7d]::ErrorGuaranteed>, rustc_driver[2b15ae7948b6e616]::run_compiler::{closure#1}>::{closure#0}, core[10878fb91fc84a80]::result::Result<(), rustc_errors[3b46f01f9753e7d]::ErrorGuaranteed>>::{closure#0}, core[10878fb91fc84a80]::result::Result<(), rustc_errors[3b46f01f9753e7d]::ErrorGuaranteed>>
  60:     0x7fcf33d126c1 - std[e4dc215d72d9f73d]::panicking::try::<core[10878fb91fc84a80]::result::Result<(), rustc_errors[3b46f01f9753e7d]::ErrorGuaranteed>, core[10878fb91fc84a80]::panic::unwind_safe::AssertUnwindSafe<<std[e4dc215d72d9f73d]::thread::Builder>::spawn_unchecked_<rustc_interface[1e8edbf255833c1]::util::run_in_thread_pool_with_globals<rustc_interface[1e8edbf255833c1]::interface::run_compiler<core[10878fb91fc84a80]::result::Result<(), rustc_errors[3b46f01f9753e7d]::ErrorGuaranteed>, rustc_driver[2b15ae7948b6e616]::run_compiler::{closure#1}>::{closure#0}, core[10878fb91fc84a80]::result::Result<(), rustc_errors[3b46f01f9753e7d]::ErrorGuaranteed>>::{closure#0}, core[10878fb91fc84a80]::result::Result<(), rustc_errors[3b46f01f9753e7d]::ErrorGuaranteed>>::{closure#1}::{closure#0}>>
  61:     0x7fcf33d52f52 - <<std[e4dc215d72d9f73d]::thread::Builder>::spawn_unchecked_<rustc_interface[1e8edbf255833c1]::util::run_in_thread_pool_with_globals<rustc_interface[1e8edbf255833c1]::interface::run_compiler<core[10878fb91fc84a80]::result::Result<(), rustc_errors[3b46f01f9753e7d]::ErrorGuaranteed>, rustc_driver[2b15ae7948b6e616]::run_compiler::{closure#1}>::{closure#0}, core[10878fb91fc84a80]::result::Result<(), rustc_errors[3b46f01f9753e7d]::ErrorGuaranteed>>::{closure#0}, core[10878fb91fc84a80]::result::Result<(), rustc_errors[3b46f01f9753e7d]::ErrorGuaranteed>>::{closure#1} as core[10878fb91fc84a80]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  62:     0x7fcf33262df3 - std::sys::unix::thread::Thread::new::thread_start::h2f9ecc8966c8b525
  63:     0x7fcf2d7b3609 - start_thread
  64:     0x7fcf330c6163 - clone
  65:                0x0 - <unknown>
error: internal compiler error: unexpected panic

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


note: we would appreciate a bug report: https://github.com/rust-lang/rust/issues/new?labels=C-bug%2C+I-ICE%2C+T-compiler&template=ice.md

note: rustc 1.62.0-nightly (3a6d5285c 2022-04-11) running on x86_64-unknown-linux-gnu

note: compiler flags: --crate-type lib -C opt-level=3 -C embed-bitcode=no -C codegen-units=1 -C debuginfo=0 -C debug-assertions=on -C symbol-mangling-version=legacy -Z unstable-options -Z unstable-options -Z macro-backtrace -C link-args=-Wl,-z,origin -C link-args=-Wl,-rpath,$ORIGIN/../lib -C prefer-dynamic -C llvm-args=-import-instr-limit=10 -C embed-bitcode=yes -Z crate-attr=doc(html_root_url="https://doc.rust-lang.org/nightly/") -Z binary-dep-depinfo -Z force-unstable-if-unmarked
note: some of the compiler flags provided by cargo are hidden

query stack during panic:
query stack during panic:
#0 [mir_built] building MIR for `sync::atomic::<impl at library/core/src/sync/atomic.rs:941:1: 1410:2>::from_mut`
#1 [unsafety_check_result] unsafety-checking `sync::atomic::<impl at library/core/src/sync/atomic.rs:941:1: 1410:2>::from_mut`
#2 [mir_const] processing MIR for `sync::atomic::<impl at library/core/src/sync/atomic.rs:941:1: 1410:2>::from_mut`
#3 [mir_promoted] processing `sync::atomic::<impl at library/core/src/sync/atomic.rs:941:1: 1410:2>::from_mut`
#4 [mir_borrowck] borrow-checking `sync::atomic::<impl at library/core/src/sync/atomic.rs:941:1: 1410:2>::from_mut`
#5 [analysis] running analysis passes on this crate
error: could not compile `core`
Build completed unsuccessfully in 0:04:11

Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
Reviewers
No reviews
Assignees

@oli-obk oli-obk

Labels
S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue.
Projects
None yet
Milestone
No milestone
Development

Successfully merging this pull request may close these issues.

Initializing a zero-length array leaks the initializer
5 participants
@JakobDegen @rust-highfive @oli-obk @rust-log-analyzer @rustbot