Re: type consistency of gimple

[Kenneth Zadeck <zadeck at naturalbridge dot com>]

Richard Guenther wrote:
> On 8/11/06, Kenneth Zadeck <zadeck@naturalbridge.com> wrote:
>> Richard Guenther wrote:
>> > On 8/11/06, Kenneth Zadeck <zadeck@naturalbridge.com> wrote:
>> >> Mark,
>> >>
>> >> I have had some discussions with Honza and Diego about the type
>> >> consistency at the gimple level.  They told me that Andrew was in the
>> >> process of making gimple properly type consistent.
>> >>
>> >> I just wanted to point out how this effects encoding gimple into
>> dwarf.
>> >> If the gimple is type consistent, then it looks like the only place
>> >> where I will need to write type references is at CONVERT_EXPRs and
>> >> NOP_EXPRs.  If it is not type consistent, Diego and Honza do not
>> believe
>> >> that I can properly get away without putting type references at every
>> >> tree node.
>> >>
>> >> This looks like about 20% of the size of writing a function body. 
>> I do
>> >> not know how close Pinskia's project is to completion, but
>> anything that
>> >> you, or any one else, could do to help will pay off for LTO.  It has
>> >> been suggested that I assume that gimple is type consistent as a
>> way to
>> >> force the issue.  I like this idea, but it is not something that I
>> feel
>> >> should be kept a secret either.
>> >
>> > Maybe you can elaborate how you are missing information (assuming
>> > the SSA temporaries still have a type in their "decl" node)? 
>> Especially
>> > fold relies on exact matching types for arithmetic operands, the only
>> > place where type transitions are not explicit in all cases is for
>> > MODIFY_EXPRs which can have an implicit type-conversion from
>> > the type of the RHS to the type of the LHS (see
>> > tree_ssa_useless_type_conversion()).
>> >
>> > Richard.
>> Richard,
>>
>> I actually do not know the details.  From what I was told by Diego and
>> Honza while we were in Russian is that what you say is in fact the gold
>> standard, and unfortunately gcc does not live up to that standard.  The
>> feeling was that Andrew was in fact fixing bugs, not changing the
>> definition of gimple.
>>
>> I am writing this because no one seems to think that Andrew, and the
>> reviewers are really finished with this process and I was just giving a
>> supportive nudge.
>
> Ok, maybe it's about time we put the various patches that are floating
> around to verify this type correctness on the LTO branch?  I know that
> at least at some point we could bootstrap with them.
>
> Richard.
It is quite possible that that may be the correct plan.  We should wait
until some of the gimple elite respond this email.  I know that honza's
patch has rotted because he tried it in russia and it was doa.  I assume
that pinskia has a valid one since he has been beating out the varmints.