insertBlock :: CmmBlock -> BlockEnv CmmBlock -> BlockEnv CmmBlock
insertBlock block map =
  ASSERT(isNothing $ mapLookup id map)
  mapInsert id block map
  where id = entryLabel block
insertBlock :: CmmBlock -> BlockEnv CmmBlock -> BlockEnv CmmBlock
insertBlock block map =
  ASSERT(isNothing $ mapLookup id map)
  mapInsert id block map
  where id = entryLabel block
insertBlock block map =
  ASSERT(isNothing $ mapLookup id map)
  mapInsert id block map
  where id = entryLabel block