Stream: git-wasmtime

Topic: wasmtime / issue #12317 Cranelift: Pulley ISA exception_p...

Wasmtime GitHub notifications bot (Jan 11 2026 at 22:54):

zzjas opened issue #12317:

.clif Test Case

test compile
target pulley64

function %trigger_bug(i32) -> i32 {
    sig0 = (i32) -> i32 winch
    fn0 = %callee(i32) -> i32 winch

    block0(v0: i32):
        ; try_call triggers the bug by invoking exception handling codegen
        ; Note: We omit exn0 because exception_payload_types is empty
        try_call fn0(v0), sig0, block1(ret0), [ default: block2 ]

    block1(v1: i32):
        return v1

    block2:
        v3 = iconst.i32 -1
        return v3
}

Steps to Reproduce

RUST_BACKTRACE=1 cargo run -p cranelift-tools --bin clif-util -- compile --target pulley64 -p test.clif

Expected Results

No assertion failure

Actual Results

thread 'main' (138509) panicked at cranelift/codegen/src/machinst/abi.rs:2041:13:
assertion `left == right` failed
  left: 0
 right: 2

Versions and Environment

Cranelift version or commit: 67ce1ef23b8a5fb8ab293828cd719402b83d5b5b

Operating system: Ubuntu 22.04.5

Architecture: x86_64

Extra Info

Pulley exception_payload_regs unconditionally returns 2 registers:

https://github.com/bytecodealliance/wasmtime/blob/67ce1ef23b8a5fb8ab293828cd719402b83d5b5b/cranelift/codegen/src/isa/pulley_shared/abi.rs#L563-L569

Other ISAs (x64, aarch64, s390x, riscv64) match on call_conv and return &[] for unsupported conventions like Winch. When try_call is compiled with Winch convention on Pulley, exception_payload_types(Winch) returns 0 elements while exception_payload_regs() returns 2, triggering the assertion at abi.rs:2041.

Thanks for looking into this and please let us know if we missed anything or if you have any feedback!

Wasmtime GitHub notifications bot (Jan 11 2026 at 22:54):

zzjas added the bug label to Issue #12317.

Wasmtime GitHub notifications bot (Jan 11 2026 at 22:54):

zzjas added the cranelift label to Issue #12317.

Wasmtime GitHub notifications bot (Jan 12 2026 at 21:56):

fitzgen commented on issue #12317:

Thanks for the report! Fix in https://github.com/bytecodealliance/wasmtime/pull/12325

Wasmtime GitHub notifications bot (Jan 12 2026 at 22:43):

fitzgen closed issue #12317:

.clif Test Case

test compile
target pulley64

function %trigger_bug(i32) -> i32 {
    sig0 = (i32) -> i32 winch
    fn0 = %callee(i32) -> i32 winch

    block0(v0: i32):
        ; try_call triggers the bug by invoking exception handling codegen
        ; Note: We omit exn0 because exception_payload_types is empty
        try_call fn0(v0), sig0, block1(ret0), [ default: block2 ]

    block1(v1: i32):
        return v1

    block2:
        v3 = iconst.i32 -1
        return v3
}

Steps to Reproduce

RUST_BACKTRACE=1 cargo run -p cranelift-tools --bin clif-util -- compile --target pulley64 -p test.clif

Expected Results

No assertion failure

Actual Results

thread 'main' (138509) panicked at cranelift/codegen/src/machinst/abi.rs:2041:13:
assertion `left == right` failed
  left: 0
 right: 2

Versions and Environment

Cranelift version or commit: 67ce1ef23b8a5fb8ab293828cd719402b83d5b5b

Operating system: Ubuntu 22.04.5

Architecture: x86_64

Extra Info

Pulley exception_payload_regs unconditionally returns 2 registers:

https://github.com/bytecodealliance/wasmtime/blob/67ce1ef23b8a5fb8ab293828cd719402b83d5b5b/cranelift/codegen/src/isa/pulley_shared/abi.rs#L563-L569

Other ISAs (x64, aarch64, s390x, riscv64) match on call_conv and return &[] for unsupported conventions like Winch. When try_call is compiled with Winch convention on Pulley, exception_payload_types(Winch) returns 0 elements while exception_payload_regs() returns 2, triggering the assertion at abi.rs:2041.

Thanks for looking into this and please let us know if we missed anything or if you have any feedback!

Last updated: Jan 29 2026 at 13:25 UTC