local-cse introduces side effects via local.tee, blocking DCE in O3

Given the following code:

(module
  (type $0 (func))
  (type $1 (func (param i32 i32) (result i32)))
  (import "External" "external_function" (func $external_function (type $0)))
  (func $_start (type $1) (param $0 i32) (param $1 i32) (result i32)
    (local $2 i32) (local $4 i32) (local $7 i32) (local $8 i32) (local $11 i32) (local $13 i32)
    global.get $__stack_pointer
    local.set $2
    local.get $2
    i64.const 0
    i64.store offset=1752
    i32.const 4058
    local.set $4
    local.get $2
    local.get $4
    i32.add
    i32.const 1
    i32.add
    local.set $7
    i32.const 4058
    local.set $8
    local.get $2
    local.get $8
    i32.add
    i32.const 1
    i32.add
    local.set $11
    local.get $7
    local.get $11
    i32.ne
    local.set $13
    block  ;; label = @1
      local.get $13
      i32.eqz
      br_if 0 (;@1;)
      call $external_function
    end
    unreachable)
  (memory $0 259 259)
  (global $__stack_pointer (mut i32) (i32.const 0))
  (export "_start" (func $_start)))

wasm-opt (862aeb9) eliminates the dead br_if body by -all -O2 but can not do that by -all -O3.

After analysis, O3 performs one more local-cse than O2, thus introducing local.tee (e.g., combining local.set + local.get). However, it also introduces side effect, which blocks constant propagation and then finally blocks DCE

Specifically, through local-cse, wasm-opt transforms the condition (always false) of br_if statements from

(i32.ne
 (i32.add
  (i32.add
   (local.get $0)
   (i32.const 4058)
  )
  (i32.const 1)
 )
 (i32.add
  (i32.add
   (local.get $0)
   (i32.const 4058)
  )
  (i32.const 1)
 )
)

to

(i32.ne
 (local.tee $2
  (i32.add
   (i32.add
    (local.get $0)
    (i32.const 4058)
   )
   (i32.const 1)
  )
 )
 (local.get $2)
)

thus blocking the constant propagation, leading to DCE missed optimization.

Overall, I think it is a missed optimization.

Start by reproducing the wasm-opt behavior from the issue with the supplied WebAssembly, comparing -all -O2 and -all -O3. Trace the extra local-cse pass and its local.tee transformation, then verify that the always-false br_if body is removed after the optimization pipeline.