ICE: assertion failed: `(left == right)` in type_of.rs

[fenhl]

I just ran into this ICE:

thread 'rustc' panicked at 'assertion failed: `(left == right)`
  left: `Size { raw: 404 }`,
 right: `Size { raw: 400 }`', src/librustc_codegen_llvm/type_of.rs:148:9
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/blob/master/CONTRIBUTING.md#bug-reports

note: rustc 1.38.0-nightly (71f9384e3 2019-07-12) running on armv7-unknown-linux-gnueabihf

note: compiler flags: -C opt-level=3 --crate-type lib

note: some of the compiler flags provided by cargo are hidden

https://github.com/rust-lang/rust/blob/master/src/librustc_codegen_llvm/type_of.rs#L148

I can't share the code but here are some observations:

• The ICE occurs in debug mode as well.
• It does not occur when running cargo check.
• It does not occur on my MacBook (same nightly, different architecture).

[hellow554]

Can you try to isolate the code, e.g. produce some code (not longer than 50 lines) that reproduces this issue?

[fenhl]

I have no idea where to even start. Maybe a cargo-bisect-rustc run will help.

[hellow554]

How big is the code? You could start by removing 'mod xxx' in your main.rs. Remove types that are not needed. Then if you only have a few files left, merge them into one and remove more things (e.g. not needed functions, structs, enums), try to replace macros with their actual content.

[fenhl]

Using cargo-bisect-rustc I have determined that the ICE started to appear with 853f300 (#62407). I'll try to isolate the code now.

[jbg]

i'm hitting this too, will see if i can make a small repro.

building for armv7-unknown-linux-gnueabihf target from a linux x86_64 host.

[jbg]

My project doesn't build for ARM even with rustc 1.37.0-nightly (088b98730 2019-07-03), which casts doubt on the above rollup merge containing the cause, I think. (Also possible that there are two similar bugs introduced at different times.) I'll try to bisect.

thread 'rustc' panicked at 'assertion failed: `(left == right)`
  left: `Size { raw: 604 }`,
 right: `Size { raw: 600 }`', src/librustc_codegen_llvm/type_of.rs:148:9

[jbg]

My bisect indicates the regression was introduced in 848e0a2. Armed with this clue I'm trying to figure out which part of my (giant) project is triggering it in order to make a repro.