`wasm-opt` fails on 1.87 with "Bulk memory operations require bulk memory"

[printfn]

Code

I made a minimal reproduction here:

https://github.com/printfn/repro/tree/rust-wasm-bulk-memory

I expected to see this happen:
It should build with wasm-pack build

Instead, this happened:
I got an error in wasm-opt: unexpected false: Bulk memory operations require bulk memory [--enable-bulk-memory], on

It looks like this happened because of the LLVM 20 update (#135763).

Full build output

[INFO]: 🎯  Checking for the Wasm target...
[INFO]: 🌀  Compiling to Wasm...
   Compiling proc-macro2 v1.0.95
   Compiling unicode-ident v1.0.18
   Compiling wasm-bindgen-shared v0.2.100
   Compiling log v0.4.27
   Compiling bumpalo v3.17.0
   Compiling rustversion v1.0.20
   Compiling wasm-bindgen v0.2.100
   Compiling cfg-if v1.0.0
   Compiling once_cell v1.21.3
   Compiling quote v1.0.40
   Compiling syn v2.0.101
   Compiling wasm-bindgen-backend v0.2.100
   Compiling wasm-bindgen-macro-support v0.2.100
   Compiling wasm-bindgen-macro v0.2.100
   Compiling repro v0.1.0 (/home/user/Code/repro)
    Finished `release` profile [optimized] target(s) in 2.32s
[INFO]: ⬇️  Installing wasm-bindgen...
[INFO]: Optimizing wasm binaries with `wasm-opt`...
[wasm-validator error in function 2] unexpected false: Bulk memory operations require bulk memory [--enable-bulk-memory], on 
(memory.copy
 (local.get $1)
 (local.get $0)
 (local.get $3)
)
[wasm-validator error in function 2] unexpected false: Bulk memory operations require bulk memory [--enable-bulk-memory], on 
(memory.copy
 (local.get $2)
 (local.get $0)
 (local.get $3)
)
[wasm-validator error in function 10] unexpected false: Bulk memory operations require bulk memory [--enable-bulk-memory], on 
(memory.copy
 (i32.add
  (i32.load offset=4
   (local.get $0)
  )
  (local.get $3)
 )
 (i32.add
  (local.get $2)
  (i32.const 12)
 )
 (local.get $1)
)
[wasm-validator error in function 27] unexpected false: Bulk memory operations require bulk memory [--enable-bulk-memory], on 
(memory.copy
 (i32.add
  (i32.load offset=4
   (local.get $0)
  )
  (local.get $3)
 )
 (local.get $1)
 (local.get $2)
)
Fatal: error validating input
Error: failed to execute `wasm-opt`: exited with exit status: 1
  full command: "/home/user/.cache/.wasm-pack/wasm-opt-1ceaaea8b7b5f7e0/bin/wasm-opt" "/home/user/Code/repro/pkg/repro_bg.wasm" "-o" "/home/user/Code/repro/pkg/repro_bg.wasm-opt.wasm" "-Oz"
To disable `wasm-opt`, add `wasm-opt = false` to your package metadata in your `Cargo.toml`.
Caused by: failed to execute `wasm-opt`: exited with exit status: 1
  full command: "/home/user/.cache/.wasm-pack/wasm-opt-1ceaaea8b7b5f7e0/bin/wasm-opt" "/home/user/Code/repro/pkg/repro_bg.wasm" "-o" "/home/user/Code/repro/pkg/repro_bg.wasm-opt.wasm" "-Oz"
To disable `wasm-opt`, add `wasm-opt = false` to your package metadata in your `Cargo.toml`.

Version it worked on

It most recently worked on: 1.86.0

Version with regression

rustc --version --verbose:

rustc 1.87.0 (17067e9ac 2025-05-09)
binary: rustc
commit-hash: 17067e9ac6d7ecb70e50f92c1944e545188d2359
commit-date: 2025-05-09
host: x86_64-unknown-linux-gnu
release: 1.87.0
LLVM version: 20.1.1

searched nightlies: from nightly-2025-02-15 to nightly-2025-03-29
regressed nightly: nightly-2025-02-18
searched commit range: 5bc6231...ce36a96
regressed commit: ce36a96

bisected with cargo-bisect-rustc v0.6.9

Host triple: x86_64-unknown-linux-gnu
Reproduce with:

cargo bisect-rustc --start=1.86.0 --end=1.87.0 --prompt --target=wasm32-unknown-unknown --script=./script.sh 

[workingjubilee]

We do not own wasm-pack so it is not actually guaranteed to work with our toolchain.

[workingjubilee]

See https://github.com/WebAssembly/tool-conventions/issues if you wish to discuss with the people who decide when LLVM should update its default features, otherwise this is a duplicate.