"LLVM ERROR: Not supported instr" on avr-unknown-gnu-atmega328

[sobolevn]

I am experiencing a bug when trying to compile my application for Arduino Uno.

Probably, there's a regression somewhere.
Because, it used to work 1 month ago. CI: https://travis-ci.com/github/Rahix/avr-hal/builds/207260821

Original issue: Rahix/avr-hal#124

Output

Step 6/6 : RUN cargo +nightly build --example uno-blink
 ---> Running in fde0189b88d8
    Updating git repository `https://github.com/Rahix/ufmt.git`
    Updating crates.io index
 Downloading crates ...
  Downloaded nb v0.1.3
  Downloaded paste v1.0.4
  Downloaded rustc_version v0.2.3
  Downloaded semver-parser v0.7.0
  Downloaded quote v1.0.8
  Downloaded proc-macro2 v1.0.24
  Downloaded proc-macro-hack v0.5.19
  Downloaded vcell v0.1.3
  Downloaded void v1.0.2
  Downloaded cfg-if v0.1.10
  Downloaded unicode-xid v0.2.1
  Downloaded syn v1.0.58
  Downloaded avr-device-macros v0.2.3
  Downloaded avr-device v0.2.3
  Downloaded semver v0.9.0
  Downloaded panic-halt v0.2.0
  Downloaded nb v1.0.0
  Downloaded embedded-hal v0.2.4
  Downloaded bare-metal v0.2.5
 Downloading crates ...
  Downloaded cc v1.0.60
  Downloaded compiler_builtins v0.1.39
  Downloaded getopts v0.2.21
  Downloaded hashbrown v0.9.0
  Downloaded addr2line v0.14.0
  Downloaded gimli v0.23.0
  Downloaded miniz_oxide v0.4.0
  Downloaded adler v0.2.3
  Downloaded object v0.22.0
  Downloaded unicode-width v0.1.8
  Downloaded rustc-demangle v0.1.18
  Downloaded libc v0.2.79
   Compiling compiler_builtins v0.1.39
   Compiling core v0.0.0 (/usr/local/rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core)
   Compiling proc-macro2 v1.0.24
   Compiling unicode-xid v0.2.1
   Compiling syn v1.0.58
   Compiling semver-parser v0.7.0
   Compiling proc-macro-hack v0.5.19
   Compiling paste v1.0.4
   Compiling semver v0.9.0
   Compiling rustc_version v0.2.3
   Compiling quote v1.0.8
   Compiling bare-metal v0.2.5
   Compiling rustc-std-workspace-core v1.99.0 (/usr/local/rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/rustc-std-workspace-core)
LLVM ERROR: Not supported instr: <MCInst 258 <MCOperand Reg:1> <MCOperand Imm:15> <MCOperand Reg:40>>
error: could not compile `compiler_builtins`

To learn more, run the command again with --verbose.
warning: build failed, waiting for other jobs to finish...
error: build failed
The command '/bin/sh -c cargo +nightly build --example uno-blink' returned a non-zero code: 101

With --release and --verbose:

  Compiling embedded-hal v0.2.4
     Running `rustc --crate-name embedded_hal /Users/sobolev/.cargo/registry/src/github.com-1ecc6299db9ec823/embedded-hal-0.2.4/src/lib.rs --error-format=json --json=diagnostic-rendered-ansi,artifacts --crate-type lib --emit=dep-info,metadata,link -C opt-level=s -C panic=abort -C linker-plugin-lto -C codegen-units=1 -C debuginfo=2 --cfg 'feature="unproven"' -C metadata=503a59343e486e01 -C extra-filename=-503a59343e486e01 --out-dir /Users/sobolev/Desktop/avr-hal/target/avr-atmega328p/release/deps --target /Users/sobolev/Desktop/avr-hal/avr-specs/avr-atmega328p.json -L dependency=/Users/sobolev/Desktop/avr-hal/target/avr-atmega328p/release/deps -L dependency=/Users/sobolev/Desktop/avr-hal/target/release/deps --extern 'noprelude:compiler_builtins=/Users/sobolev/Desktop/avr-hal/target/avr-atmega328p/release/deps/libcompiler_builtins-afa03ed941a63b4f.rmeta' --extern 'noprelude:core=/Users/sobolev/Desktop/avr-hal/target/avr-atmega328p/release/deps/libcore-30308749cc1695e3.rmeta' --extern nb=/Users/sobolev/Desktop/avr-hal/target/avr-atmega328p/release/deps/libnb-e03ff2173c96de6e.rmeta --extern void=/Users/sobolev/Desktop/avr-hal/target/avr-atmega328p/release/deps/libvoid-4cf9d65885018701.rmeta -Z unstable-options --cap-lints allow`
LLVM ERROR: Not supported instr: <MCInst 258 <MCOperand Reg:1> <MCOperand Imm:15> <MCOperand Reg:40>>
error: could not compile `compiler_builtins`

Caused by:
  process didn't exit successfully: `rustc --crate-name compiler_builtins /Users/sobolev/.cargo/registry/src/github.com-1ecc6299db9ec823/compiler_builtins-0.1.39/src/lib.rs --error-format=json --json=diagnostic-rendered-ansi,artifacts --crate-type lib --emit=dep-info,metadata,link -C opt-level=s -C panic=abort -C linker-plugin-lto -C codegen-units=1 -C debuginfo=2 --cfg 'feature="compiler-builtins"' --cfg 'feature="core"' --cfg 'feature="default"' --cfg 'feature="rustc-dep-of-std"' -C metadata=afa03ed941a63b4f -C extra-filename=-afa03ed941a63b4f --out-dir /Users/sobolev/Desktop/avr-hal/target/avr-atmega328p/release/deps --target /Users/sobolev/Desktop/avr-hal/avr-specs/avr-atmega328p.json -Z force-unstable-if-unmarked -L dependency=/Users/sobolev/Desktop/avr-hal/target/avr-atmega328p/release/deps -L dependency=/Users/sobolev/Desktop/avr-hal/target/release/deps --extern core=/Users/sobolev/Desktop/avr-hal/target/avr-atmega328p/release/deps/librustc_std_workspace_core-2709fdbb3f7a5de3.rmeta --cap-lints allow --cfg 'feature="unstable"'` (exit code: 101)
warning: build failed, waiting for other jobs to finish...
error: build failed

Reproduction

1. Clone https://github.com/Rahix/avr-hal
2. Add this Dockefile:

FROM rustlang/rust:nightly-slim

RUN apt-get update \
  && apt-get install --no-install-recommends -y \
    avr-libc \
    binutils-avr \
    gcc-avr \
  && apt-get purge -y --auto-remove -o APT::AutoRemove::RecommendsImportant=false \
  && apt-get clean -y && rm -rf /var/lib/apt/lists/*

COPY . /code

WORKDIR /code/boards/arduino-uno

RUN rustup component add rust-src
RUN cargo +nightly build --example uno-blink

3. Run docker build --tag=ard .

Versions

info: The currently active `rustc` version is `rustc 1.51.0-nightly (c8915eebe 2021-01-07)`

» avr-gcc --version
avr-gcc  9.3.0
Copyright (C) 2019 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

[MabezDev]

Possibly related, but I have started seeing this behavior after updating my xtensa fork from 1.48 -> 1.49. I created an issue on the llvm fork's tracker but perhaps this is actually a Rust issue.

[ysblokje]

I ran into this or closely related issue while trying to get https://github.com/avr-rust/blink to compile. What I have noticed is that it compiles with the nightlies of 2021-01-07 but not after that date. The only thing I noticed between 2021-01-08 is that the version of compiler-builtins got updated from v0.1.36 to v0.1.39.

with nightly 2012-01-08

   Compiling bitflags v0.7.0
   Compiling lazy_static v0.2.11
   Compiling compiler_builtins v0.1.36
   Compiling core v0.0.0 (/home/ysblokje/.rustup/toolchains/nightly-2021-01-07-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core)
     Running `rustc --crate-name bitflags /home/ysblokje/.cargo/registry/src/github.com-1ecc6299db9ec823/bitflags-0.7.0/src/lib.rs --error-format=json --json=diagnostic-rendered-ansi,artifacts --crate-type lib --emit=dep-info,metadata,link -C embed-bitcode=no -C debug-assertions=off -C metadata=819c50c018486aec -C extra-filename=-819c50c018486aec --out-dir /home/ysblokje/projecten/rust/blink/target/release/deps -L dependency=/home/ysblokje/projecten/rust/blink/target/release/deps --cap-lints allow`
     Running `rustc --crate-name lazy_static /home/ysblokje/.cargo/registry/src/github.com-1ecc6299db9ec823/lazy_static-0.2.11/src/lib.rs --error-format=json --json=diagnostic-rendered-ansi,artifacts --crate-type lib --emit=dep-info,metadata,link -C embed-bitcode=no -C debug-assertions=off -C metadata=9e197ba8dea1699b -C extra-filename=-9e197ba8dea1699b --out-dir /home/ysblokje/projecten/rust/blink/target/release/deps -L dependency=/home/ysblokje/projecten/rust/blink/target/release/deps --cap-lints allow`
     Running `rustc --crate-name build_script_build /home/ysblokje/.cargo/registry/src/github.com-1ecc6299db9ec823/compiler_builtins-0.1.36/build.rs --error-format=json --json=diagnostic-rendered-ansi --crate-type bin --emit=dep-info,link -C embed-bitcode=no -C debug-assertions=off --cfg 'feature="compiler-builtins"' --cfg 'feature="core"' --cfg 'feature="default"' --cfg 'feature="rustc-dep-of-std"' -C metadata=844e68c26a6a57ce -C extra-filename=-844e68c26a6a57ce --out-dir /home/ysblokje/projecten/rust/blink/target/release/build/compiler_builtins-844e68c26a6a57ce -Z force-unstable-if-unmarked -L dependency=/home/ysblokje/projecten/rust/blink/target/release/deps --cap-lints allow`
     Running `rustc --crate-name core --edition=2018 /home/ysblokje/.rustup/toolchains/nightly-2021-01-07-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/lib.rs --error-format=json --json=diagnostic-rendered-ansi,artifacts --crate-type lib --emit=dep-info,metadata,link -C opt-level=3 -C embed-bitcode=no -C metadata=ffcc0c8e20d5d179 -C extra-filename=-ffcc0c8e20d5d179 --out-dir /home/ysblokje/projecten/rust/blink/target/avr-atmega328p/release/deps --target /home/ysblokje/projecten/rust/blink/avr-atmega328p.json -Z force-unstable-if-unmarked -L dependency=/home/ysblokje/projecten/rust/blink/target/avr-atmega328p/release/deps -L dependency=/home/ysblokje/projecten/rust/blink/target/release/deps --cap-lints allow`
   Compiling xml-rs v0.4.1
     Running `rustc --crate-name xml /home/ysblokje/.cargo/registry/src/github.com-1ecc6299db9ec823/xml-rs-0.4.1/src/lib.rs --error-format=json --json=diagnostic-rendered-ansi,artifacts --crate-type lib --emit=dep-info,metadata,link -C embed-bitcode=no -C debug-assertions=off -C metadata=b4c0432b26e20892 -C extra-filename=-b4c0432b26e20892 --out-dir /home/ysblokje/projecten/rust/blink/target/release/deps -L dependency=/home/ysblokje/projecten/rust/blink/target/release/deps --extern bitflags=/home/ysblokje/projecten/rust/blink/target/release/deps/libbitflags-819c50c018486aec.rmeta --cap-lints allow`
     Running `/home/ysblokje/projecten/rust/blink/target/release/build/compiler_builtins-844e68c26a6a57ce/build-script-build`
   Compiling xmltree v0.4.0
     Running `rustc --crate-name xmltree /home/ysblokje/.cargo/registry/src/github.com-1ecc6299db9ec823/xmltree-0.4.0/src/lib.rs --error-format=json --json=diagnostic-rendered-ansi,artifacts --crate-type lib --emit=dep-info,metadata,link -C embed-bitcode=no -C debug-assertions=off -C metadata=8db81bdf93bace3e -C extra-filename=-8db81bdf93bace3e --out-dir /home/ysblokje/projecten/rust/blink/target/release/deps -L dependency=/home/ysblokje/projecten/rust/blink/target/release/deps --extern xml=/home/ysblokje/projecten/rust/blink/target/release/deps/libxml-b4c0432b26e20892.rmeta --cap-lints allow`
   Compiling avr-mcu v0.2.6
     Running `rustc --crate-name avr_mcu /home/ysblokje/.cargo/registry/src/github.com-1ecc6299db9ec823/avr-mcu-0.2.6/src/lib.rs --error-format=json --json=diagnostic-rendered-ansi --crate-type lib --emit=dep-info,metadata,link -C embed-bitcode=no -C debug-assertions=off -C metadata=b852a77c84ba31c9 -C extra-filename=-b852a77c84ba31c9 --out-dir /home/ysblokje/projecten/rust/blink/target/release/deps -L dependency=/home/ysblokje/projecten/rust/blink/target/release/deps --extern lazy_static=/home/ysblokje/projecten/rust/blink/target/release/deps/liblazy_static-9e197ba8dea1699b.rmeta --extern xmltree=/home/ysblokje/projecten/rust/blink/target/release/deps/libxmltree-8db81bdf93bace3e.rmeta --cap-lints allow`
   Compiling ruduino v0.2.0
     Running `rustc --crate-name build_script_build --edition=2018 /home/ysblokje/.cargo/registry/src/github.com-1ecc6299db9ec823/ruduino-0.2.0/core_generator/build.rs --error-format=json --json=diagnostic-rendered-ansi --crate-type bin --emit=dep-info,link -C embed-bitcode=no -C debug-assertions=off -C metadata=4760d8c36b441576 -C extra-filename=-4760d8c36b441576 --out-dir /home/ysblokje/projecten/rust/blink/target/release/build/ruduino-4760d8c36b441576 -L dependency=/home/ysblokje/projecten/rust/blink/target/release/deps --extern avr_mcu=/home/ysblokje/projecten/rust/blink/target/release/deps/libavr_mcu-b852a77c84ba31c9.rlib --cap-lints allow`
     Running `/home/ysblokje/projecten/rust/blink/target/release/build/ruduino-4760d8c36b441576/build-script-build`
   Compiling rustc-std-workspace-core v1.99.0 (/home/ysblokje/.rustup/toolchains/nightly-2021-01-07-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/rustc-std-workspace-core)
     Running `rustc --crate-name rustc_std_workspace_core --edition=2018 /home/ysblokje/.rustup/toolchains/nightly-2021-01-07-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/rustc-std-workspace-core/lib.rs --error-format=json --json=diagnostic-rendered-ansi,artifacts --crate-type lib --emit=dep-info,metadata,link -C opt-level=3 -C embed-bitcode=no -C metadata=720e5134eae211e9 -C extra-filename=-720e5134eae211e9 --out-dir /home/ysblokje/projecten/rust/blink/target/avr-atmega328p/release/deps --target /home/ysblokje/projecten/rust/blink/avr-atmega328p.json -Z force-unstable-if-unmarked -L dependency=/home/ysblokje/projecten/rust/blink/target/avr-atmega328p/release/deps -L dependency=/home/ysblokje/projecten/rust/blink/target/release/deps --extern core=/home/ysblokje/projecten/rust/blink/target/avr-atmega328p/release/deps/libcore-ffcc0c8e20d5d179.rmeta --cap-lints allow`
     Running `rustc --crate-name compiler_builtins /home/ysblokje/.cargo/registry/src/github.com-1ecc6299db9ec823/compiler_builtins-0.1.36/src/lib.rs --error-format=json --json=diagnostic-rendered-ansi,artifacts --crate-type lib --emit=dep-info,metadata,link -C opt-level=3 -C embed-bitcode=no --cfg 'feature="compiler-builtins"' --cfg 'feature="core"' --cfg 'feature="default"' --cfg 'feature="rustc-dep-of-std"' -C metadata=75f365d68b064d0e -C extra-filename=-75f365d68b064d0e --out-dir /home/ysblokje/projecten/rust/blink/target/avr-atmega328p/release/deps --target /home/ysblokje/projecten/rust/blink/avr-atmega328p.json -Z force-unstable-if-unmarked -L dependency=/home/ysblokje/projecten/rust/blink/target/avr-atmega328p/release/deps -L dependency=/home/ysblokje/projecten/rust/blink/target/release/deps --extern core=/home/ysblokje/projecten/rust/blink/target/avr-atmega328p/release/deps/librustc_std_workspace_core-720e5134eae211e9.rmeta --cap-lints allow --cfg 'feature="unstable"'`
     Running `rustc --crate-name ruduino --edition=2018 /home/ysblokje/.cargo/registry/src/github.com-1ecc6299db9ec823/ruduino-0.2.0/src/lib.rs --error-format=json --json=diagnostic-rendered-ansi --crate-type lib --emit=dep-info,metadata,link -C opt-level=3 -C embed-bitcode=no -C metadata=333d03c3c0aad4c4 -C extra-filename=-333d03c3c0aad4c4 --out-dir /home/ysblokje/projecten/rust/blink/target/avr-atmega328p/release/deps --target /home/ysblokje/projecten/rust/blink/avr-atmega328p.json -L dependency=/home/ysblokje/projecten/rust/blink/target/avr-atmega328p/release/deps -L dependency=/home/ysblokje/projecten/rust/blink/target/release/deps --extern 'noprelude:compiler_builtins=/home/ysblokje/projecten/rust/blink/target/avr-atmega328p/release/deps/libcompiler_builtins-75f365d68b064d0e.rmeta' --extern 'noprelude:core=/home/ysblokje/projecten/rust/blink/target/avr-atmega328p/release/deps/libcore-ffcc0c8e20d5d179.rmeta' -Z unstable-options --cap-lints allow`
   Compiling blink v0.1.0 (/home/ysblokje/projecten/rust/blink)
     Running `rustc --crate-name blink --edition=2018 src/main.rs --error-format=json --json=diagnostic-rendered-ansi --crate-type bin --emit=dep-info,link -C opt-level=3 -C embed-bitcode=no -C metadata=1f47a526ca0061c6 -C extra-filename=-1f47a526ca0061c6 --out-dir /home/ysblokje/projecten/rust/blink/target/avr-atmega328p/release/deps --target /home/ysblokje/projecten/rust/blink/avr-atmega328p.json -L dependency=/home/ysblokje/projecten/rust/blink/target/avr-atmega328p/release/deps -L dependency=/home/ysblokje/projecten/rust/blink/target/release/deps --extern 'noprelude:compiler_builtins=/home/ysblokje/projecten/rust/blink/target/avr-atmega328p/release/deps/libcompiler_builtins-75f365d68b064d0e.rlib' --extern 'noprelude:core=/home/ysblokje/projecten/rust/blink/target/avr-atmega328p/release/deps/libcore-ffcc0c8e20d5d179.rlib' --extern ruduino=/home/ysblokje/projecten/rust/blink/target/avr-atmega328p/release/deps/libruduino-333d03c3c0aad4c4.rlib -Z unstable-options`
    Finished release [optimized] target(s) in 8.88s

with nightly 2012-01-08

       Fresh bitflags v0.7.0
       Fresh lazy_static v0.2.11
       Fresh core v0.0.0 (/home/ysblokje/.rustup/toolchains/nightly-2021-01-07-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core)
       Fresh xml-rs v0.4.1
       Fresh xmltree v0.4.0
       Fresh rustc-std-workspace-core v1.99.0 (/home/ysblokje/.rustup/toolchains/nightly-2021-01-07-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/rustc-std-workspace-core)
       Fresh avr-mcu v0.2.6
       Fresh compiler_builtins v0.1.36
   Compiling compiler_builtins v0.1.39
       Fresh ruduino v0.2.0
     Running `rustc --crate-name compiler_builtins /home/ysblokje/.cargo/registry/src/github.com-1ecc6299db9ec823/compiler_builtins-0.1.39/src/lib.rs --error-format=json --json=diagnostic-rendered-ansi --crate-type lib --emit=dep-info,metadata,link -C opt-level=3 -C embed-bitcode=no --cfg 'feature="compiler-builtins"' --cfg 'feature="default"' -C metadata=58d3ac8f36249c98 -C extra-filename=-58d3ac8f36249c98 --out-dir /home/ysblokje/projecten/rust/blink/target/avr-atmega328p/release/deps --target /home/ysblokje/projecten/rust/blink/avr-atmega328p.json -L dependency=/home/ysblokje/projecten/rust/blink/target/avr-atmega328p/release/deps -L dependency=/home/ysblokje/projecten/rust/blink/target/release/deps --extern 'noprelude:compiler_builtins=/home/ysblokje/projecten/rust/blink/target/avr-atmega328p/release/deps/libcompiler_builtins-75f365d68b064d0e.rmeta' --extern 'noprelude:core=/home/ysblokje/projecten/rust/blink/target/avr-atmega328p/release/deps/libcore-ffcc0c8e20d5d179.rmeta' -Z unstable-options --cap-lints allow --cfg 'feature="unstable"'`
LLVM ERROR: Not supported instr: <MCInst 258 <MCOperand Reg:1> <MCOperand Imm:15> <MCOperand Reg:45>>
error: could not compile `compiler_builtins`

Caused by:
  process didn't exit successfully: `rustc --crate-name compiler_builtins /home/ysblokje/.cargo/registry/src/github.com-1ecc6299db9ec823/compiler_builtins-0.1.39/src/lib.rs --error-format=json --json=diagnostic-rendered-ansi --crate-type lib --emit=dep-info,metadata,link -C opt-level=3 -C embed-bitcode=no --cfg 'feature="compiler-builtins"' --cfg 'feature="default"' -C metadata=58d3ac8f36249c98 -C extra-filename=-58d3ac8f36249c98 --out-dir /home/ysblokje/projecten/rust/blink/target/avr-atmega328p/release/deps --target /home/ysblokje/projecten/rust/blink/avr-atmega328p.json -L dependency=/home/ysblokje/projecten/rust/blink/target/avr-atmega328p/release/deps -L dependency=/home/ysblokje/projecten/rust/blink/target/release/deps --extern 'noprelude:compiler_builtins=/home/ysblokje/projecten/rust/blink/target/avr-atmega328p/release/deps/libcompiler_builtins-75f365d68b064d0e.rmeta' --extern 'noprelude:core=/home/ysblokje/projecten/rust/blink/target/avr-atmega328p/release/deps/libcore-ffcc0c8e20d5d179.rmeta' -Z unstable-options --cap-lints allow --cfg 'feature="unstable"'` (exit code: 101)

I hope this helps.

[Rahix]

If someone has the patience, I think it would help to bisect the exact commit of compiler-builtins which leads to this regression.

I would assume this is a multi-layer problem: A change in compiler-builtins makes rustc emit instructions which the LLVM AVR backend cannot (yet?) lower correctly.

[stappersg]

I feel challenged to do git bisect.

However I have yet no clue how to tell cargo it should use the compiler-builtins that is being git bisected. So pointers to a rough direction are very welcome. (The direction I start going is tweaking cargo.toml.)

IJsblokje: Dank je wel voor de versie 0.1.36 werkt, v0.1.39 niet meer

[bjorn3]

I think running cargo build --release --target <TARGET_TRIPLE> in a checkout of this repo will reproduce the bug. If this is the case you can simply use git bisect and run that build command at every step.

[stappersg]

What I found with tab completion:

$ cargo build --release --target 
thumbv6m-none-eabi        x86_64-unknown-linux-gnu

That lacks the target_triple avr-unknown-gnu-atmega328 this issue is about.

What should I do make cargo aware of an AVR microcontroller target?

[catcatmu]

After running a git bisect, it looks like the commit which causes the issue is: 1d15e4e5043edcde12b8a2412f084c387f07ecc6 - Construct signed division functions differently

And the last good commit is:
e9688c68a5dd3ebe98f27386c6459afaf87c0468 - Remove unneeded code from asymmetric.rs

Bisect was run using:
cargo +nightly-2021-01-07 build -Z build-std=core --release --target boards/avr-atmega328p.json

The target config was from here: https://github.com/Rahix/avr-hal/blob/master/avr-specs/avr-atmega328p.json

[Rahix]

Nice work @catcatmu! I can't do it myself right now unfortunately, but maybe someone can generate the LLVM IR from before and after this commit? E.g. using

cargo +nightly-2021-01-07 rustc -Z build-std=core --target boards/avr-atmega328p.json -- --emit=llvm-ir -o /path/to/output-directory

Otherwise I will try taking a look later this weekend.

[catcatmu]

Tar of different llvm-ir output (minus the build libs)
rust-avr-400.tar.gz

Folders:

1. bad-debug: The broken commit in debug mode: Works
2. bad-release: The broken commit in release mode: Fails LLVM ERROR: Not supported instr: <MCInst 25...
3. good-debug: The good commit in debug mode: Works
4. good-release: The good commit in release mode: Works

Notes:

1. Works in debug mode, fails in release mode.

[stappersg]

Thanks

(I'm having a look at it

gs0604@trancilo:~/src/rust/RustAVR
$ tar tf rust-avr-400.tar.gz 
bad-debug/
bad-debug/ir-97326bb640629c90.d
bad-debug/ir-97326bb640629c90.ll
bad-release/
bad-release/ir-abab196ba785c327.d
bad-release/ir-abab196ba785c327.compiler_builtins.a06dgpxu-cgu.0.rcgu.ll
bad-release/error
good-debug/
good-debug/ir-97326bb640629c90.d
good-debug/ir-97326bb640629c90.ll
good-release/
good-release/ir-abab196ba785c327.d
good-release/ir-abab196ba785c327.ll
gs0604@trancilo:~/src/rust/RustAVR
$ mkdir issue400
gs0604@trancilo:~/src/rust/RustAVR
$ cd issue400/
gs0604@trancilo:~/src/rust/RustAVR/issue400
$ tar xf ../rust-avr-400.tar.gz 
gs0604@trancilo:~/src/rust/RustAVR/issue400
$ 

to express more apprication then a simple thanks 😄

[stappersg]

And I admit that I lack knowledge about what I'm looking at.

[Rahix]

Okay, I got closer ... A minimal reproducer (llc -filetype=obj broken.ll):

source_filename = "compiler_builtins.27zd1rau-cgu.0"
target datalayout = "e-P1-p:16:8-i8:8-i16:8-i32:8-i64:8-f32:8-f64:8-n8-a:8"
target triple = "avr-unknown-unknown"

declare dso_local fastcc { i128, i128 } @specialized_div_rem_u128(i128, i128) unnamed_addr addrspace(1) #0

define hidden i128 @__divmodti4(i128 %a, i128 %b, i128* %rem) unnamed_addr addrspace(1) #0 {
start:
  %b_neg = icmp slt i128 %b, 0
  %b2.0 = select i1 %b_neg, i128 0, i128 %b
  %0 = tail call fastcc addrspace(1) { i128, i128 } @specialized_div_rem_u128(i128 undef, i128 %b2.0) #4
  unreachable
}

attributes #0 = { "target-cpu"="atmega328" }
attributes #1 = { nounwind readnone speculatable willreturn }
attributes #2 = { cold noreturn nounwind }
attributes #3 = { nounwind willreturn }
attributes #4 = { nounwind }

!llvm.module.flags = !{!0}

!0 = !{i32 7, !"PIC Level", i32 2}

This produces invalid assembly containing the stdwstk/AVR::STDWSPQRr pseudo-instruction (that's the MCInst 258 from the error message) which for some reason is not lowered into real instructions.

This definitely needs to be fixed on LLVM side but I wonder if we could, in the meantime, disable [iu]128 intrinsics for AVR in compiler-builtins? I doubt anyone is using them right now and as it is broken either way, this will at least make other programs compile again...

[stappersg]

make other programs compile again...

Yes, that would be great