;; stack:
;;  0: offset
;; -1: word
(func $MSTORE8
  (local $sp i32)

  (local $offset i32)

  (local $offset0 i64)
  (local $offset1 i64)
  (local $offset2 i64)
  (local $offset3 i64)

  ;; load args from the stack
  (local.set $offset0 (i64.load          (global.get $sp)))
  (local.set $offset1 (i64.load (i32.add (global.get $sp) (i32.const 8))))
  (local.set $offset2 (i64.load (i32.add (global.get $sp) (i32.const 16))))
  (local.set $offset3 (i64.load (i32.add (global.get $sp) (i32.const 24))))

  (local.set $offset 
             (call $check_overflow (local.get $offset0)
                                   (local.get $offset1)
                                   (local.get $offset2)
                                   (local.get $offset3)))

  (call $memusegas (local.get $offset) (i32.const 1))

  ;; pop stack
  (local.set $sp (i32.sub (global.get $sp) (i32.const 32)))
  (local.set $offset (i32.add (local.get $offset) (global.get $memstart)))
  (i32.store8 (i32.add (local.get $offset) (i32.const 0)) (i32.load (local.get $sp)))
)