[tree-ssa] Syntactic structures

[Daniel Berlin]

On Sunday, August 3, 2003, at 12:37 PM, Zdenek Dvorak wrote:

> Hello,
>
>>> 1) are there some optimizations on tree-ssa that benefit from keeping
>>>    all the syntactical structures around.
>>>    , instead of just cfg + chain
>>>
>> The optimizers only see the CFG and a sequence of statements inside 
>> each
>> basic block.  It is true that internally, the statements are organized
>> in a tree-like structure.  That is something that we would eventually
>> want to change, purely for performance reasons.
>>
>> For all intents and purposes, the optimizers are presented a linear
>> sequence of statements contained inside basic blocks.  Have you looked
>> at the statement iterators?
>
> yes.  They are ugly. I would also say they are slow, but this is of
> course just my feeling.

Say what?
How are they "ugly".
It's much nicer than the morass that are RTL iterators.

>
>> This is how you traverse all the statements in the program:
>>
>> FOR_EACH_BB(bb)
>>   for (si = bsi_start (bb); !bsi_end_p (si); bsi_next (&si))
>>      tree stmt = bsi_stmt (si);
>>
>> If you want to traverse in dominator tree order, you simply start a
>> recursive walk at ENTRY_BLOCK_PTR much like tree-ssa.c and
>> tree-ssa-dom.c do.
>>
>> Statement insertion and removal are also supported (both on edges and 
>> in
>> blocks).
>>
>> There are some missing functions in the iterator API, so whatever you
>> find missing, we would like to know.
>
> What I tried is to create (well, actually debug Sebastian's one) a
> split_block function.  It still does not work, although perhaps with a
> day more I could succeed.

We already have one in tree-cfg.c

>
>>> I am mostly decided to postpone the loop optimizer work a bit and
>>> instead clean up this mess.  Would someone mind?
>>>
>> You will have to be more specific.  The word 'mess' is colorful but
>> hardly descriptive.  What is it that you are trying to do?  How is it
>> not working?  What do you think is missing?  Loop optimization will
>> likely expose limitations in the current framework, but we need more
>> specific information to address the problems.
>
> I would like to get rid of the "invisible" part of the tree structures
> (COMPOUND_EXPR, BIND_EXPR, LOOP_EXPR and such).

>
> Zdenek