Cranelift: Specifically formatted valid WASM panics with 'block Insertion point not in the layout'

[bkolobara]

I have been stuck on a WASM module failing to compile under Wasmtime (0.20 and main branch) for some time now.
After a lot of trial and error I have managed to construct a minimal example that fails:

use wasmtime::{Config, Engine, Linker, Module, Store};

fn main() {
    let mut config = Config::new();
    config.wasm_reference_types(true);
    let engine = Engine::new(&config);
    let module = Module::new(
        &engine,
        "
        (module
            (type (;0;) (func (param externref) (result i32)))
            (func $test (type 0) (param externref) (result i32)
                (local i32)
                i32.const 0
                local.tee 1
                i32.const 0
                i32.eq
                if                    
                else
                end
                local.get 1
                local.get 0
                table.set 0
                local.get 1
            )
            (table (;0;) 4 externref)
            (export \"test\" (func $test))
        )",
    )
    .unwrap();

    let store = Store::new(&engine.clone());
    let linker = Linker::new(&store);

    let _instance = linker.instantiate(&module.clone()).unwrap();
}

From my understanding this should be valid WASM, and tools like wasm-validate --enable-all also don't complain about anything, but trying to run this code with RUST_BACKTRACE=1 cargo run results in:

    Finished dev [unoptimized + debuginfo] target(s) in 0.11s
     Running `target/debug/wasmer-bug-report`
thread 'main' panicked at 'block Insertion point not in the layout', /Users/bkolobara/.cargo/registry/src/github.com-1ecc6299db9ec823/cranelift-codegen-0.67.0/src/ir/layout.rs:401:9
stack backtrace:
   0: std::panicking::begin_panic
             at /Users/bkolobara/.rustup/toolchains/nightly-x86_64-apple-darwin/lib/rustlib/src/rust/library/std/src/panicking.rs:505:12
   1: cranelift_codegen::ir::layout::Layout::insert_block_after
             at /Users/bkolobara/.cargo/registry/src/github.com-1ecc6299db9ec823/cranelift-codegen-0.67.0/src/ir/layout.rs:401:9
   2: cranelift_frontend::frontend::FunctionBuilder::insert_block_after
             at /Users/bkolobara/.cargo/registry/src/github.com-1ecc6299db9ec823/cranelift-frontend-0.67.0/src/frontend.rs:233:9
   3: <wasmtime_cranelift::func_environ::FuncEnvironment as cranelift_wasm::environ::spec::FuncEnvironment>::translate_table_set
             at /Users/bkolobara/.cargo/registry/src/github.com-1ecc6299db9ec823/wasmtime-cranelift-0.20.0/src/func_environ.rs:668:17
   4: cranelift_wasm::code_translator::translate_operator
             at /Users/bkolobara/.cargo/registry/src/github.com-1ecc6299db9ec823/cranelift-wasm-0.67.0/src/code_translator.rs:1413:13
   5: cranelift_wasm::func_translator::parse_function_body
             at /Users/bkolobara/.cargo/registry/src/github.com-1ecc6299db9ec823/cranelift-wasm-0.67.0/src/func_translator.rs:235:9
   6: cranelift_wasm::func_translator::FuncTranslator::translate_from_reader
             at /Users/bkolobara/.cargo/registry/src/github.com-1ecc6299db9ec823/cranelift-wasm-0.67.0/src/func_translator.rs:111:9
   7: cranelift_wasm::func_translator::FuncTranslator::translate
             at /Users/bkolobara/.cargo/registry/src/github.com-1ecc6299db9ec823/cranelift-wasm-0.67.0/src/func_translator.rs:64:9
   8: <wasmtime_cranelift::Cranelift as wasmtime_environ::compilation::Compiler>::compile_function
             at /Users/bkolobara/.cargo/registry/src/github.com-1ecc6299db9ec823/wasmtime-cranelift-0.20.0/src/lib.rs:354:22
   9: wasmtime_jit::compiler::Compiler::compile::{{closure}}
             at /Users/bkolobara/.cargo/registry/src/github.com-1ecc6299db9ec823/wasmtime-jit-0.20.0/src/compiler.rs:128:17
  10: core::ops::function::impls::<impl core::ops::function::FnMut<A> for &F>::call_mut
             at /Users/bkolobara/.rustup/toolchains/nightly-x86_64-apple-darwin/lib/rustlib/src/rust/library/core/src/ops/function.rs:247:13
  11: core::iter::adapters::map_try_fold::{{closure}}
             at /Users/bkolobara/.rustup/toolchains/nightly-x86_64-apple-darwin/lib/rustlib/src/rust/library/core/src/iter/adapters/mod.rs:912:28
  12: core::iter::traits::iterator::Iterator::try_fold
             at /Users/bkolobara/.rustup/toolchains/nightly-x86_64-apple-darwin/lib/rustlib/src/rust/library/core/src/iter/traits/iterator.rs:1888:21
  13: <core::iter::adapters::Map<I,F> as core::iter::traits::iterator::Iterator>::try_fold
             at /Users/bkolobara/.rustup/toolchains/nightly-x86_64-apple-darwin/lib/rustlib/src/rust/library/core/src/iter/adapters/mod.rs:938:9
  14: <core::iter::adapters::Map<I,F> as core::iter::traits::iterator::Iterator>::try_fold
             at /Users/bkolobara/.rustup/toolchains/nightly-x86_64-apple-darwin/lib/rustlib/src/rust/library/core/src/iter/adapters/mod.rs:938:9
  15: <core::iter::adapters::TakeWhile<I,P> as core::iter::traits::iterator::Iterator>::try_fold
             at /Users/bkolobara/.rustup/toolchains/nightly-x86_64-apple-darwin/lib/rustlib/src/rust/library/core/src/iter/adapters/mod.rs:2078:13
  16: <core::iter::adapters::Map<I,F> as core::iter::traits::iterator::Iterator>::try_fold
             at /Users/bkolobara/.rustup/toolchains/nightly-x86_64-apple-darwin/lib/rustlib/src/rust/library/core/src/iter/adapters/mod.rs:938:9
  17: <core::iter::adapters::TakeWhile<I,P> as core::iter::traits::iterator::Iterator>::try_fold
             at /Users/bkolobara/.rustup/toolchains/nightly-x86_64-apple-darwin/lib/rustlib/src/rust/library/core/src/iter/adapters/mod.rs:2078:13
  18: <core::iter::adapters::TakeWhile<I,P> as core::iter::traits::iterator::Iterator>::fold
             at /Users/bkolobara/.rustup/toolchains/nightly-x86_64-apple-darwin/lib/rustlib/src/rust/library/core/src/iter/adapters/mod.rs:2093:9
  19: <rayon::iter::fold::FoldFolder<C,ID,F> as rayon::iter::plumbing::Folder<T>>::consume_iter
             at /Users/bkolobara/.cargo/registry/src/github.com-1ecc6299db9ec823/rayon-1.4.1/src/iter/fold.rs:158:20
  20: <rayon::iter::while_some::WhileSomeFolder<C> as rayon::iter::plumbing::Folder<core::option::Option<T>>>::consume_iter
             at /Users/bkolobara/.cargo/registry/src/github.com-1ecc6299db9ec823/rayon-1.4.1/src/iter/while_some.rs:139:21
  21: <rayon::iter::map::MapFolder<C,F> as rayon::iter::plumbing::Folder<T>>::consume_iter
             at /Users/bkolobara/.cargo/registry/src/github.com-1ecc6299db9ec823/rayon-1.4.1/src/iter/map.rs:248:21
  22: <rayon::iter::map::MapFolder<C,F> as rayon::iter::plumbing::Folder<T>>::consume_iter
             at /Users/bkolobara/.cargo/registry/src/github.com-1ecc6299db9ec823/rayon-1.4.1/src/iter/map.rs:248:21
  23: rayon::iter::plumbing::Producer::fold_with
             at /Users/bkolobara/.cargo/registry/src/github.com-1ecc6299db9ec823/rayon-1.4.1/src/iter/plumbing/mod.rs:110:9
  24: rayon::iter::plumbing::bridge_producer_consumer::helper
             at /Users/bkolobara/.cargo/registry/src/github.com-1ecc6299db9ec823/rayon-1.4.1/src/iter/plumbing/mod.rs:438:13
  25: rayon::iter::plumbing::bridge_producer_consumer
             at /Users/bkolobara/.cargo/registry/src/github.com-1ecc6299db9ec823/rayon-1.4.1/src/iter/plumbing/mod.rs:397:12
  26: <rayon::iter::plumbing::bridge::Callback<C> as rayon::iter::plumbing::ProducerCallback<I>>::callback
             at /Users/bkolobara/.cargo/registry/src/github.com-1ecc6299db9ec823/rayon-1.4.1/src/iter/plumbing/mod.rs:373:13
  27: <rayon::vec::Drain<T> as rayon::iter::IndexedParallelIterator>::with_producer
             at /Users/bkolobara/.cargo/registry/src/github.com-1ecc6299db9ec823/rayon-1.4.1/src/vec.rs:130:13
  28: <rayon::vec::IntoIter<T> as rayon::iter::IndexedParallelIterator>::with_producer
             at /Users/bkolobara/.cargo/registry/src/github.com-1ecc6299db9ec823/rayon-1.4.1/src/vec.rs:64:9
  29: rayon::iter::plumbing::bridge
             at /Users/bkolobara/.cargo/registry/src/github.com-1ecc6299db9ec823/rayon-1.4.1/src/iter/plumbing/mod.rs:357:12
  30: <rayon::vec::IntoIter<T> as rayon::iter::ParallelIterator>::drive_unindexed
             at /Users/bkolobara/.cargo/registry/src/github.com-1ecc6299db9ec823/rayon-1.4.1/src/vec.rs:39:9
  31: <rayon::iter::map::Map<I,F> as rayon::iter::ParallelIterator>::drive_unindexed
             at /Users/bkolobara/.cargo/registry/src/github.com-1ecc6299db9ec823/rayon-1.4.1/src/iter/map.rs:49:9
  32: <rayon::iter::map::Map<I,F> as rayon::iter::ParallelIterator>::drive_unindexed
             at /Users/bkolobara/.cargo/registry/src/github.com-1ecc6299db9ec823/rayon-1.4.1/src/iter/map.rs:49:9
  33: <rayon::iter::while_some::WhileSome<I> as rayon::iter::ParallelIterator>::drive_unindexed
             at /Users/bkolobara/.cargo/registry/src/github.com-1ecc6299db9ec823/rayon-1.4.1/src/iter/while_some.rs:44:9
  34: <rayon::iter::fold::Fold<I,ID,F> as rayon::iter::ParallelIterator>::drive_unindexed
             at /Users/bkolobara/.cargo/registry/src/github.com-1ecc6299db9ec823/rayon-1.4.1/src/iter/fold.rs:59:9
  35: <rayon::iter::map::Map<I,F> as rayon::iter::ParallelIterator>::drive_unindexed
             at /Users/bkolobara/.cargo/registry/src/github.com-1ecc6299db9ec823/rayon-1.4.1/src/iter/map.rs:49:9
  36: rayon::iter::reduce::reduce
             at /Users/bkolobara/.cargo/registry/src/github.com-1ecc6299db9ec823/rayon-1.4.1/src/iter/reduce.rs:15:5
  37: rayon::iter::ParallelIterator::reduce
             at /Users/bkolobara/.cargo/registry/src/github.com-1ecc6299db9ec823/rayon-1.4.1/src/iter/mod.rs:981:9
  38: rayon::iter::extend::collect
             at /Users/bkolobara/.cargo/registry/src/github.com-1ecc6299db9ec823/rayon-1.4.1/src/iter/extend.rs:29:5
  39: rayon::iter::collect::<impl rayon::iter::ParallelExtend<T> for alloc::vec::Vec<T>>::par_extend
             at /Users/bkolobara/.cargo/registry/src/github.com-1ecc6299db9ec823/rayon-1.4.1/src/iter/collect/mod.rs:163:28
  40: rayon::iter::from_par_iter::collect_extended
             at /Users/bkolobara/.cargo/registry/src/github.com-1ecc6299db9ec823/rayon-1.4.1/src/iter/from_par_iter.rs:17:5
  41: rayon::iter::from_par_iter::<impl rayon::iter::FromParallelIterator<T> for alloc::vec::Vec<T>>::from_par_iter
             at /Users/bkolobara/.cargo/registry/src/github.com-1ecc6299db9ec823/rayon-1.4.1/src/iter/from_par_iter.rs:30:9
  42: rayon::iter::ParallelIterator::collect
             at /Users/bkolobara/.cargo/registry/src/github.com-1ecc6299db9ec823/rayon-1.4.1/src/iter/mod.rs:1973:9
  43: rayon::result::<impl rayon::iter::FromParallelIterator<core::result::Result<T,E>> for core::result::Result<C,E>>::from_par_iter
             at /Users/bkolobara/.cargo/registry/src/github.com-1ecc6299db9ec823/rayon-1.4.1/src/result.rs:121:26
  44: rayon::iter::ParallelIterator::collect
             at /Users/bkolobara/.cargo/registry/src/github.com-1ecc6299db9ec823/rayon-1.4.1/src/iter/mod.rs:1973:9
  45: wasmtime_jit::compiler::Compiler::compile
             at /Users/bkolobara/.cargo/registry/src/github.com-1ecc6299db9ec823/wasmtime-jit-0.20.0/src/compiler.rs:126:21
  46: wasmtime_jit::instantiate::CompilationArtifacts::build
             at /Users/bkolobara/.cargo/registry/src/github.com-1ecc6299db9ec823/wasmtime-jit-0.20.0/src/instantiate.rs:95:13
  47: wasmtime::module::Module::compile::{{closure}}
             at /Users/bkolobara/.cargo/registry/src/github.com-1ecc6299db9ec823/wasmtime-0.20.0/src/module.rs:308:17
  48: core::ops::function::FnOnce::call_once
             at /Users/bkolobara/.rustup/toolchains/nightly-x86_64-apple-darwin/lib/rustlib/src/rust/library/core/src/ops/function.rs:227:5
  49: wasmtime_cache::ModuleCacheEntry::get_data
             at /Users/bkolobara/.cargo/registry/src/github.com-1ecc6299db9ec823/wasmtime-cache-0.20.0/src/lib.rs:59:28
  50: wasmtime::module::Module::compile
             at /Users/bkolobara/.cargo/registry/src/github.com-1ecc6299db9ec823/wasmtime-0.20.0/src/module.rs:306:25
  51: wasmtime::module::Module::from_binary_unchecked
             at /Users/bkolobara/.cargo/registry/src/github.com-1ecc6299db9ec823/wasmtime-0.20.0/src/module.rs:276:9
  52: wasmtime::module::Module::from_binary
             at /Users/bkolobara/.cargo/registry/src/github.com-1ecc6299db9ec823/wasmtime-0.20.0/src/module.rs:245:18
  53: wasmtime::module::Module::new
             at /Users/bkolobara/.cargo/registry/src/github.com-1ecc6299db9ec823/wasmtime-0.20.0/src/module.rs:156:9
  54: wasmer_bug_report::main
             at ./src/main.rs:7:18
  55: core::ops::function::FnOnce::call_once
             at /Users/bkolobara/.rustup/toolchains/nightly-x86_64-apple-darwin/lib/rustlib/src/rust/library/core/src/ops/function.rs:227:5
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

Note that if the empty if-else-end block is removed it compiles fine. Or if the externref table.set is removed it also works fine. But this exact instruction sequence fails.

It could also be that I'm miss-understanding the WASM specification and that this is not valid WASM.

[tschneidereit]

Thank you for reporting this, @bkolobara!

@alexcrichton or @fitzgen, can you take a look?

[alexcrichton]

Thanks for the report! I've minimized this a bit more as

(module
  (func $test (param i32) (result externref)
        i32.const 0
        if
        else
        end
        local.get 0
        table.get 0
  )
  (table 4 externref)
  (export "test" (func $test))
)

and it can reproduce with the CLI by just feeding in the test-case. I've got a fix at #2350 for this I believe.