`wasm-opt` generates invalid wasm with `-all`

[peter-jerry-ye]

For the given wat file, run

wasm-tools print input.wat | wasm-opt -O1 -S -o - - | wasm-tools validate
wasm-tools print input.wat | wasm-opt -all -O1 -S -o - - | wasm-tools validate

The first one (without -all) works fine, but the second one (with -all) will fail to validate.

Version: 122

Input (shrunk by wasm-tools):

(module
  (type (;0;) (func (result i32)))
  (type (;1;) (func (param i32) (result i32)))
  (export "" (func 3))
  (func (;0;) (type 0) (result i32)
    unreachable
  )
  (func (;1;) (type 0) (result i32)
    unreachable
  )
  (func (;2;) (type 1) (param i32) (result i32)
    (local i32 i32 i32 i32 i32 i32 i32 i32 i32 i32 i32 i32 i32 i32 i32 i32 i32 i32 i32 i32 i32 i32 i32 i32 i32 i32 i32 i32 i32 i32 i32 i32 i32 i32 i32 i32 i32 i32)
    i32.const 0
    loop (type 1) (param i32) (result i32) ;; label = @1
      local.tee 1
      i32.const 15
      i32.add
      local.tee 38
      i32.const -16
      i32.and
      local.set 2
      local.get 2
      if ;; label = @2
        local.get 11
        if ;; label = @3
        else
        end
        local.get 4
        return
      else
      end
      i32.const 0
      if (result i32) ;; label = @2
        i32.const 0
        local.set 22
        local.get 6
        if ;; label = @3
          i32.const 1
          return
        else
        end
        local.get 2
        br 1 (;@1;)
      else
        local.get 6
        if ;; label = @3
        else
          i32.const 0
          return
        end
        i32.const 0
        local.set 29
        i32.const 0
        local.set 30
        call 0
        local.set 26
        local.get 9
        local.set 27
        local.get 26
        local.set 24
        local.get 2
        br 1 (;@1;)
      end
    end
  )
  (func (;3;) (type 1) (param i32) (result i32)
    (local i32 i32 i32 i32 i32 i32 i32 i32 i32 i32 i32 i32 i32 i32 i32 i32 i32 i32 i32 i32 i32 i32 i32 i32 i32 i32 i32 i32 i32 i32 i32 i32 i32 i32 i32 i32 i32 i32 i32)
    local.get 10
    if (result i32) ;; label = @1
      i32.const 1
    else
      call 1
    end
    i32.eqz
    if ;; label = @1
    else
    end
    i32.const 0
    if (result i32) ;; label = @1
      local.get 0
      if ;; label = @2
        local.get 2
        return
      else
      end
      i32.const 0
      if ;; label = @2
        local.get 4
        local.set 23
        i32.const 0
        local.set 24
        i32.const 1
        local.set 25
        local.get 3
        local.set 26
        local.get 3
        local.set 27
        local.get 4
        return
      else
      end
      i32.const 1
      if ;; label = @2
        local.get 5
        if ;; label = @3
          local.get 6
          local.set 32
          i32.const 0
          local.set 33
          i32.const 1
          local.set 34
          local.get 5
          local.set 35
          local.get 6
          return
        else
        end
      else
      end
      i32.const 0
    else
      local.get 0
      local.get 0
      call 2
      i32.ne
      if (result i32) ;; label = @2
        i32.const 0
      else
        i32.const 0
      end
    end
  )
)

[kripken]

I see you emit text here. Binaryen's text format has some nonstandard changes, to reflect Binaryen IR better, see

https://github.com/WebAssembly/binaryen/?tab=readme-ov-file#binaryen-ir

Does the problem go away if you emit a binary? Same question for #7345

[tlively]

What's happening here is that -all causes some additional optimization to be triggered that cause the loop to get type unreachable, which means it is not printed with a (result i32) clause, causing the wast to be invalid. As @kripken mentioned, this is essentially WAI.

[peter-jerry-ye]

@kripken @tlively Thank you for your explanation. The problem does go away when I emit a binary.