[PATCH] D32821: Add DWARF verifiers to verify address ranges are correct and scoped correctly.

[Greg Clayton via llvm-commits]

> On May 8, 2017, at 4:03 PM, David Blaikie <dblaikie at gmail.com> wrote:
> 
> 
> 
> On Wed, May 3, 2017 at 1:57 PM Greg Clayton <clayborg at gmail.com <mailto:clayborg at gmail.com>> wrote:
>> On May 3, 2017, at 1:45 PM, David Blaikie <dblaikie at gmail.com <mailto:dblaikie at gmail.com>> wrote:
>> 
>> 
>> 
>> On Wed, May 3, 2017 at 1:32 PM Greg Clayton via Phabricator <reviews at reviews.llvm.org <mailto:reviews at reviews.llvm.org>> wrote:
>> clayborg added a comment.
>> 
>> In https://reviews.llvm.org/D32821#745213 <https://reviews.llvm.org/D32821#745213>, @dblaikie wrote:
>> 
>> > I haven't followed some of the design direction Adrian's been pointing this work in - so all of this is subject to discussion, etc:
>> >
>> > 1. I'd expect not to build an entire representation of all ranges up-front, then verify them (uses more memory, etc) - but rather verify during a traversal of the DIEs instead
>> 
>> 
>> The whole reason we need this is to look for overlapping functions between all CUs. This helps us to identify exactly which DIEs overlap.
>> 
>> If it's true that no DIEs should overlap, and all DIEs should be a subset of their parent - then there's no need to compare two DIEs that aren't siblings* because they can't overlap. The only comparisons that should be needed would be between immediate siblings, and siblings and parents - not all possible pairs of nodes. Right?
> 
> That is how this is coded. Only top DW_TAG_subprogram DIEs get added to the AllFunctionRangeInfos. So when checking for overlap, we just check between adjacent DW_TAG_subprogram. Since these are in a std::set, they are ordered already. So we just check:
> 
> for I in AllFunctionRangeInfos.size():
>   AllFunctionRangeInfos[I].Contains(AllFunctionRangeInfos[I+1])
> 
> Ah, that makes loads of sense - nice!
> 
> So why aren't the lexical blocks scopes handled the same way?

They are now. The new NonOverlappingRanges class does this by storing things a std::set. We now check everything on the fly.
> 
> 
> (& indeed, this is what I'm getting at about the duplicate code across this - I'm not understanding why there are two different ways of testing intersects or subset - and two different codepaths for the error messages too)
> 
> What I'm picturing is a single device, much like what I wrote in the patch I provided last week, I think. That device/class represents a scope (in the general sense, not the lexical_scope sense), with an optional parent node + range and a list of children node+ranges. There would be an explicit instance for the file level (with no parent) that is used by every compile_unit's ranges. Another (hopefully local/non-member version, passed down - but it could be a member) created when visiting a top level compile unit - for its subprograms. And any number more created on the stack for the lexical scopes.

That is essentially what we have now, we just have a const class and one in/out class.
> 
> This object would handle error message printing for both sibling overlap and not-contained-in-parent errors, in one place with one message/handling/etc.

I guess we could switch over to using NonOverlappingRanges in the DieRangeInfo as well. I didn't want to put the error handling inside these classes because they need to access the error count. This is pretty close to what is there now, I just don't use NonOverlappingRanges in the DieRangeInfo currently... I will switch that over and see what simplifies out.

Greg

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