Stream: git-wasmtime

Topic: wasmtime / issue #6725 Cranelift: Unable to lower `iconst...

view this post on Zulip Wasmtime GitHub notifications bot (Jul 13 2023 at 22:32):

afonso360 opened issue #6725:

:wave: Hey,

I ran fuzzgen on AArch64 today and it found an issue.

.clif Test Case

test compile
set opt_level=speed_and_size
target aarch64

function %a() -> i32x4 {
    const7 = 0x00000000000000000000000000000000

block0:
    v52 = vconst.i32x4 const7
    v53 = icmp eq v52, v52
    v63 = icmp ne v52, v52
    v64 = bor v53, v63
    return v64
}

This is what the function looks after egraphs:

function %a() -> i32x4 fast {
block0:
    v65 = iconst.i32x4 1
    return v65  ; v65 = 1
}

Steps to Reproduce

Expected Results

The function to compile

Actual Results

     Running `/home/afonso/git/wasmtime/target/debug/clif-util compile --target aarch64 --set opt_level=speed_and_size ./lmao.clif`
thread 'main' panicked at 'internal error: entered unreachable code: no rule matched for term imm at src/isa/aarch64/inst.isle line 2883; should it be partial?', /home/afonso/git/wasmtime/target/debug/build/cranelift-codegen-7af9571f8465fadc/out/isle_aarch64.rs:5554:5
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

Versions and Environment

Cranelift version or commit: main (04b8edd2f538286d91c167d231628874c5bc29b7)

Operating system: Linux

Architecture: AArch64

Extra Info

Bisect points to dcf0ea9ff367034a43e65552e2a30d0ba8cbd95e which is so long ago that I'm really surprised we haven't caught this earlier.

view this post on Zulip Wasmtime GitHub notifications bot (Jul 13 2023 at 22:32):

afonso360 added the bug label to Issue #6725.

view this post on Zulip Wasmtime GitHub notifications bot (Jul 13 2023 at 22:32):

afonso360 added the cranelift:area:aarch64 label to Issue #6725.

view this post on Zulip Wasmtime GitHub notifications bot (Jul 13 2023 at 22:32):

afonso360 added the cranelift label to Issue #6725.

view this post on Zulip Wasmtime GitHub notifications bot (Jul 13 2023 at 22:46):

jameysharp commented on issue #6725:

Huh. I believe this is because we're missing the ty_int/fits_in_64 constraints for these two rules:

(rule (compose_icmp ty 0 _ _ _) (subsume (iconst ty (imm64 0))))
(rule (compose_icmp ty 7 _ _ _) (subsume (iconst ty (imm64 1))))

However the surrounding rules are not written to handle compose_icmp failing to match, so fixing this isn't super trivial.

In all the other compose_icmp cases, it still generates an icmp instruction and so the rules should be valid even for vector types.

I guess the easiest fix is to refuse to apply any of these optimizations on vectors.

We could also solve this as part of fixing #6038.

view this post on Zulip Wasmtime GitHub notifications bot (Jul 14 2023 at 17:09):

alexcrichton commented on issue #6725:

I'll note that this is reachable from wasm:

(module
  (func (param v128) (result v128)
    (i8x16.eq (local.get 0) (local.get 0))
    (i8x16.ne (local.get 0) (local.get 0))
    v128.or)
)

and it fails not only for AArch64:

$ wasmtime compile foo.wat --emit-clif clif --target x86_64
thread '<unnamed>' panicked at 'should be implemented in ISLE: inst = `v7 = iconst.i8x16 1`, type = `Some(types::I8X16)`', /Users/alex/.cargo/registry/src/index.crates.io-6f17d22bba15001f/cranelift-codegen-0.97.1/src/machinst/lower.rs:749:21
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
$ wasmtime compile foo.wat --emit-clif clif --target aarch64
thread '<unnamed>' panicked at 'internal error: entered unreachable code: no rule matched for term imm at src/isa/aarch64/inst.isle line 2883; should it be partial?', /var/folders/70/cx6_8hz93jz7kj_km0_5c9_40000gn/T/cargo-install26VIDu/release/build/cranelift-codegen-e94e1c35edbd285d/out/isle_aarch64.rs:5536:5
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

view this post on Zulip Wasmtime GitHub notifications bot (Jul 14 2023 at 17:09):

alexcrichton edited a comment on issue #6725:

I'll note that this is reachable from wasm:

(module
  (func (param v128) (result v128)
    (i8x16.eq (local.get 0) (local.get 0))
    (i8x16.ne (local.get 0) (local.get 0))
    v128.or)
)

and it fails not only for AArch64:

$ wasmtime compile foo.wat --target x86_64
thread '<unnamed>' panicked at 'should be implemented in ISLE: inst = `v7 = iconst.i8x16 1`, type = `Some(types::I8X16)`', /Users/alex/.cargo/registry/src/index.crates.io-6f17d22bba15001f/cranelift-codegen-0.97.1/src/machinst/lower.rs:749:21
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
$ wasmtime compile foo.wat --target aarch64
thread '<unnamed>' panicked at 'internal error: entered unreachable code: no rule matched for term imm at src/isa/aarch64/inst.isle line 2883; should it be partial?', /var/folders/70/cx6_8hz93jz7kj_km0_5c9_40000gn/T/cargo-install26VIDu/release/build/cranelift-codegen-e94e1c35edbd285d/out/isle_aarch64.rs:5536:5
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

view this post on Zulip Wasmtime GitHub notifications bot (Jul 14 2023 at 19:20):

alexcrichton commented on issue #6725:

Fixed in https://github.com/bytecodealliance/wasmtime/pull/6728#event-9824618437

view this post on Zulip Wasmtime GitHub notifications bot (Jul 14 2023 at 19:20):

alexcrichton closed issue #6725:

:wave: Hey,

I ran fuzzgen on AArch64 today and it found an issue.

.clif Test Case

test compile
set opt_level=speed_and_size
target aarch64

function %a() -> i32x4 {
    const7 = 0x00000000000000000000000000000000

block0:
    v52 = vconst.i32x4 const7
    v53 = icmp eq v52, v52
    v63 = icmp ne v52, v52
    v64 = bor v53, v63
    return v64
}

This is what the function looks after egraphs:

function %a() -> i32x4 fast {
block0:
    v65 = iconst.i32x4 1
    return v65  ; v65 = 1
}

Steps to Reproduce

Expected Results

The function to compile

Actual Results

     Running `/home/afonso/git/wasmtime/target/debug/clif-util compile --target aarch64 --set opt_level=speed_and_size ./lmao.clif`
thread 'main' panicked at 'internal error: entered unreachable code: no rule matched for term imm at src/isa/aarch64/inst.isle line 2883; should it be partial?', /home/afonso/git/wasmtime/target/debug/build/cranelift-codegen-7af9571f8465fadc/out/isle_aarch64.rs:5554:5
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

Versions and Environment

Cranelift version or commit: main (04b8edd2f538286d91c167d231628874c5bc29b7)

Operating system: Linux

Architecture: AArch64

Extra Info

Bisect points to dcf0ea9ff367034a43e65552e2a30d0ba8cbd95e which is so long ago that I'm really surprised we haven't caught this earlier.

Last updated: Oct 23 2024 at 20:03 UTC