Thoughts about semantics of BB_VISITED

[Daniel Berlin]

On Fri, 7 Jan 2005, Zdenek Dvorak wrote:

> Hello,
>
>>>>> because get_loop_body is often used on places where (lots of) new blocks
>>>>> get created (like unroller).  Resizing the sbitmap would be quite
>>>>> annoying.
>>>>
>>>> Also, it's quite annoying to have to keep resetting these flags.  I don't
>>>> think a simple read-only helper should be altering the basic block flags.
>>>> All i did was ask for the loop body.
>>>
>>> it does not change them -- they must be clear on the entry, and they are
>>> clear on the exit.
>>
>> It will clear them if they aren't cleared, at least on some blocks.  This
>> is obvious from the definition of dfs_enumerate_from.
>
> no, it is obvious that dfs_enumerate_from does not work unless the marks
> are clear.

It clears at least one of them anyway, as you'll note it's result always 
at least consists of the first block it sees, and it always clears the 
visited flags of the result.