ICE: broken mir with -Zunsound-mir-opts: simplify arm identity #78628

matthiaskrgr · 2020-11-01T13:57:00Z

Code

from ./src/test/ui/mir/issue-77359-simplify-arm-identity.rs

// run-pass

#![allow(dead_code)]

#[derive(Debug)]
enum MyEnum {
    Variant2,
    Variant3,
}

fn f(arg3: bool) -> MyStruct {
	match if arg3 { Some(MyEnum::Variant3) } else { None } {
		Some(t) => {
			let ah = t;
			return MyStruct(Some(ah));
		}
		_ => MyStruct(None)
	}
}

#[derive(Debug)]
struct MyStruct(Option<MyEnum>);

fn main() {
    f(true);
}

Error output

error: internal compiler error: broken MIR in Item(WithOptConstParam { did: DefId(0:3 ~ issue_77359_simplify_arm_identity[317d]::f), const_param_did: None }) (end of phase Optimization) at bb5[0]:
use of local _5, which has no storage here
  --> ./src/test/ui/mir/issue-77359-simplify-arm-identity.rs:15:20
   |
15 |             return MyStruct(Some(ah));
   |                             ^^^^^^^^
   |
   = note: delayed at compiler/rustc_mir/src/transform/validate.rs:171:36

thread 'rustc' panicked at 'no errors encountered even though `delay_span_bug` issued', compiler/rustc_errors/src/lib.rs:958:13
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

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 1.49.0-nightly (1d5b7c3c9 2020-11-01) running on x86_64-unknown-linux-gnu

note: compiler flags: -Z unsound-mir-opts

query stack during panic:
end of query stack

Backtrace

error: internal compiler error: broken MIR in Item(WithOptConstParam { did: DefId(0:3 ~ issue_77359_simplify_arm_identity[317d]::f), const_param_did: None }) (end of phase Optimization) at bb5[0]:
use of local _5, which has no storage here
  --> ./src/test/ui/mir/issue-77359-simplify-arm-identity.rs:15:20
   |
15 |             return MyStruct(Some(ah));
   |                             ^^^^^^^^
   |
   = note: delayed at compiler/rustc_mir/src/transform/validate.rs:171:36

thread 'rustc' panicked at 'no errors encountered even though `delay_span_bug` issued', compiler/rustc_errors/src/lib.rs:958:13
stack backtrace:
   0:     0x7ffaf14ba5f0 - std::backtrace_rs::backtrace::libunwind::trace::h448c56741b6011d3
                               at /rustc/1d5b7c3c96a86c96f1fbf1441475028df94d165a/library/std/src/../../backtrace/src/backtrace/libunwind.rs:100:5
   1:     0x7ffaf14ba5f0 - std::backtrace_rs::backtrace::trace_unsynchronized::h2d26397c5720fdbb
                               at /rustc/1d5b7c3c96a86c96f1fbf1441475028df94d165a/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
   2:     0x7ffaf14ba5f0 - std::sys_common::backtrace::_print_fmt::h720a2f61f75b9f58
                               at /rustc/1d5b7c3c96a86c96f1fbf1441475028df94d165a/library/std/src/sys_common/backtrace.rs:67:5
   3:     0x7ffaf14ba5f0 - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::h8d62bbfda6d5c836
                               at /rustc/1d5b7c3c96a86c96f1fbf1441475028df94d165a/library/std/src/sys_common/backtrace.rs:46:22
   4:     0x7ffaf152a52c - core::fmt::write::h1857a60b204f1b6a
                               at /rustc/1d5b7c3c96a86c96f1fbf1441475028df94d165a/library/core/src/fmt/mod.rs:1078:17
   5:     0x7ffaf14ac252 - std::io::Write::write_fmt::h16a9fe7680ac245c
                               at /rustc/1d5b7c3c96a86c96f1fbf1441475028df94d165a/library/std/src/io/mod.rs:1518:15
   6:     0x7ffaf14bf5a5 - std::sys_common::backtrace::_print::h9ba51a6db618de7d
                               at /rustc/1d5b7c3c96a86c96f1fbf1441475028df94d165a/library/std/src/sys_common/backtrace.rs:49:5
   7:     0x7ffaf14bf5a5 - std::sys_common::backtrace::print::h5f20e41c85e91716
                               at /rustc/1d5b7c3c96a86c96f1fbf1441475028df94d165a/library/std/src/sys_common/backtrace.rs:36:9
   8:     0x7ffaf14bf5a5 - std::panicking::default_hook::{{closure}}::h5b7294ca19e8edab
                               at /rustc/1d5b7c3c96a86c96f1fbf1441475028df94d165a/library/std/src/panicking.rs:208:50
   9:     0x7ffaf14bf248 - std::panicking::default_hook::hb3948d1f74b6ff4c
                               at /rustc/1d5b7c3c96a86c96f1fbf1441475028df94d165a/library/std/src/panicking.rs:227:9
  10:     0x7ffaf1d8e158 - rustc_driver::report_ice::h1ddbc5609a6e1f37
  11:     0x7ffaf14bfea6 - std::panicking::rust_panic_with_hook::h55d23fef0ad751bc
                               at /rustc/1d5b7c3c96a86c96f1fbf1441475028df94d165a/library/std/src/panicking.rs:597:17
  12:     0x7ffaf14bf9c7 - std::panicking::begin_panic_handler::{{closure}}::h56ae74c6dea6e141
                               at /rustc/1d5b7c3c96a86c96f1fbf1441475028df94d165a/library/std/src/panicking.rs:499:13
  13:     0x7ffaf14baa8c - std::sys_common::backtrace::__rust_end_short_backtrace::h3c4721f56689fae4
                               at /rustc/1d5b7c3c96a86c96f1fbf1441475028df94d165a/library/std/src/sys_common/backtrace.rs:141:18
  14:     0x7ffaf14bf929 - rust_begin_unwind
                               at /rustc/1d5b7c3c96a86c96f1fbf1441475028df94d165a/library/std/src/panicking.rs:495:5
  15:     0x7ffaf14bf8db - std::panicking::begin_panic_fmt::h447a9fe10c3ac155
                               at /rustc/1d5b7c3c96a86c96f1fbf1441475028df94d165a/library/std/src/panicking.rs:437:5
  16:     0x7ffaf4dff1c1 - rustc_errors::HandlerInner::flush_delayed::hcdae04493e012a6e
  17:     0x7ffaf4dfbb91 - <rustc_errors::HandlerInner as core::ops::drop::Drop>::drop::h27a485c12bfd5a8a
  18:     0x7ffaf1d9b606 - core::ptr::drop_in_place::hac2c86d61f6a657d
  19:     0x7ffaf1da0796 - <alloc::rc::Rc<T> as core::ops::drop::Drop>::drop::h60c965ef9381f1d3
  20:     0x7ffaf1d46b2d - core::ptr::drop_in_place::h11c56312c481deac
  21:     0x7ffaf1d36a2c - rustc_span::with_source_map::h4e49cbd9a39d01b4
  22:     0x7ffaf1da70c1 - scoped_tls::ScopedKey<T>::set::hca96dcfe1d32eebf
  23:     0x7ffaf1daed75 - std::sys_common::backtrace::__rust_begin_short_backtrace::h21cfd4855c5058aa
  24:     0x7ffaf1d17188 - core::ops::function::FnOnce::call_once{{vtable.shim}}::h2df6ccf8e166462a
  25:     0x7ffaf14ceeaa - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::h9e7afb7a0a438236
                               at /rustc/1d5b7c3c96a86c96f1fbf1441475028df94d165a/library/alloc/src/boxed.rs:1307:9
  26:     0x7ffaf14ceeaa - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::h70c646c4271337a1
                               at /rustc/1d5b7c3c96a86c96f1fbf1441475028df94d165a/library/alloc/src/boxed.rs:1307:9
  27:     0x7ffaf14ceeaa - std::sys::unix::thread::Thread::new::thread_start::h35d2b8d36f210d02
                               at /rustc/1d5b7c3c96a86c96f1fbf1441475028df94d165a/library/std/src/sys/unix/thread.rs:89:17
  28:     0x7ffaf13ca3e9 - start_thread
  29:     0x7ffaf12e7293 - __GI___clone
  30:                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 1.49.0-nightly (1d5b7c3c9 2020-11-01) running on x86_64-unknown-linux-gnu

note: compiler flags: -Z unsound-mir-opts

query stack during panic:
end of query stack

The text was updated successfully, but these errors were encountered:

jonas-schievink · 2020-11-01T14:07:02Z

This is probably #77359

matthiaskrgr · 2020-11-01T14:12:52Z

Hm, the issue is already a couple of weeks old while I was not able to reproduce this one a few days ago.

matthiaskrgr · 2020-11-01T14:19:28Z

This happens since a6403b0 🤔

tmiasko · 2020-11-21T12:22:13Z

Yes, this is a duplicate of #77359. The changes from #78147 fixed the validator, so the bug is now correctly identified when incorrect transform is enabled with -Zunsound-mir-opts.

Alexendoo · 2021-03-02T12:34:38Z

~~No longer ICEs on latest nightly, bisect shows since #78360~~

bjorn3 · 2021-03-02T13:37:23Z

Does it still ICE if you enable optimizations?

Alexendoo · 2021-03-02T15:04:14Z

It does, looks like it's still an ICE

Alexendoo · 2022-04-12T20:59:37Z

This (and #77359) no longer ICE since #95125, seems to be the case for any opt level

cc @JakobDegen is that intentional or is #94177 still pending?

JakobDegen · 2022-04-12T21:09:55Z

This is only the case because the changes to MIR make that opt completely broken and just never fire under any circumstances. #94177 needs to be revised because of that change, but the plan is still for it to fix these bugs for real

Delete `SimplifyArmIdentity` and `SimplifyBranchSame` mir opts I had attempted to fix the first of these opts in rust-lang#94177 . However, despite that PR already being a full re-write, it still did not fix some of the core soundness issues. The optimizations that are attempted here are likely to be desirable, but I do not expect any of the currently written code to survive into a sound implementation. Deleting the code keeps us from having to maintain the passes in the meantime. Closes rust-lang#77359 , closes rust-lang#72800 , closes rust-lang#78628 r? `@cjgillot`

Delete `SimplifyArmIdentity` and `SimplifyBranchSame` mir opts I had attempted to fix the first of these opts in rust-lang#94177 . However, despite that PR already being a full re-write, it still did not fix some of the core soundness issues. The optimizations that are attempted here are likely to be desirable, but I do not expect any of the currently written code to survive into a sound implementation. Deleting the code keeps us from having to maintain the passes in the meantime. Closes rust-lang#77359 , closes rust-lang#72800 , closes rust-lang#78628 r? ``@cjgillot``

matthiaskrgr added C-bug Category: This is a bug. I-ICE Issue: The compiler panicked, giving an Internal Compilation Error (ICE) ❄️ T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Nov 1, 2020

jonas-schievink added the A-mir-opt Area: MIR optimizations label Nov 1, 2020

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rustbot added the requires-nightly This issue requires a nightly compiler in some way. label Nov 1, 2020

rust-lang-glacier-bot added the glacier ICE tracked in rust-lang/glacier. label Dec 12, 2020

github-actions bot mentioned this issue Mar 2, 2021

ices/78628.sh: fixed with no errors rust-lang/glacier#675

Merged

Alexendoo added the E-needs-test Call for participation: An issue has been fixed and does not reproduce, but no test has been added. label Mar 2, 2021

Alexendoo removed the E-needs-test Call for participation: An issue has been fixed and does not reproduce, but no test has been added. label Mar 2, 2021

This was referenced May 10, 2021

LLVM/MIR optimizations to simplify the new RFC3058 ? desugaring #85133

Closed

Implement the new desugaring from try_trait_v2 #84767

Merged

JakobDegen mentioned this issue Feb 20, 2022

Fix SimplifyArmIdentity MIR opt #94177

Closed

github-actions bot mentioned this issue Apr 12, 2022

ices/78628.sh: fixed with no errors rust-lang/glacier#1213

Merged

JakobDegen mentioned this issue Jan 24, 2023

Delete SimplifyArmIdentity and SimplifyBranchSame mir opts #107256

Merged

bors closed this as completed in c2f46df Jan 26, 2023

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ICE: broken mir with -Zunsound-mir-opts: simplify arm identity #78628

ICE: broken mir with -Zunsound-mir-opts: simplify arm identity #78628

matthiaskrgr commented Nov 1, 2020

jonas-schievink commented Nov 1, 2020

matthiaskrgr commented Nov 1, 2020

matthiaskrgr commented Nov 1, 2020

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tmiasko commented Nov 21, 2020

Alexendoo commented Mar 2, 2021 •

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bjorn3 commented Mar 2, 2021

Alexendoo commented Mar 2, 2021

Alexendoo commented Apr 12, 2022

JakobDegen commented Apr 12, 2022

ICE: broken mir with -Zunsound-mir-opts: simplify arm identity #78628

ICE: broken mir with -Zunsound-mir-opts: simplify arm identity #78628

Comments

matthiaskrgr commented Nov 1, 2020

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jonas-schievink commented Nov 1, 2020

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tmiasko commented Nov 21, 2020

Alexendoo commented Mar 2, 2021 • edited Loading

bjorn3 commented Mar 2, 2021

Alexendoo commented Mar 2, 2021

Alexendoo commented Apr 12, 2022

JakobDegen commented Apr 12, 2022

Alexendoo commented Mar 2, 2021 •

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