Dead-store-elimintation removes visible stores from divergent paths

[alexcrichton]

This input:

(module
  (memory (export "mem") 1)
  (func (export "f") (param $p i32) (param $q i32)
    (i32.store (i32.const 0) (i32.const 111))
    (if (local.get $p)
      (then (i32.store (i32.const 0) (i32.const 222)))
      (else
        (i32.store (local.get $q) (i32.const 7))
        (loop (br 0))))
  )
  (func (export "get") (result i32) (i32.load (i32.const 0)))
)

(assert_trap (invoke "f" (i32.const 0) (i32.const 65536)) "out of bounds memory access")
(assert_return (invoke "get") (i32.const 111))

yields:

$ cargo run wast -O opt-level=0 repro.wast
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.11s
     Running `/home/alex/code/wasmtime2/target/debug/wasmtime wast -O opt-level=0 repro.wast`
$ cargo run wast repro.wast
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.11s
     Running `/home/alex/code/wasmtime2/target/debug/wasmtime wast repro.wast`
Error: failed to run script file 'repro.wast'

Caused by:
    0: failed directive on repro.wast:16
    1: result 0 didn't match
    2: expected                111 / 0x000000000000006f
actual                    0 / 0x0000000000000000

An LLM report, if useful, is here

[alexcrichton]

cc @fitzgen