[LLVMdev] [RFC] First-class debug info IR: MDLocation (redux)

[Duncan P. N. Exon Smith]

I suspect it would actually be *better* if I got all this in before
the branch, since it'll make cherry-picking testcases easier.

However, these patches themselves (and I suspect a few more prep
commits) don't actually move `MDLocation` into place -- it's not
until then that all the testcase updates have to happen.  I'm not
convinced that (monster) commit will land by tomorrow :(.

> On 2015-Jan-13, at 10:34, Robinson, Paul <Paul_Robinson at playstation.sony.com> wrote:
> 
> Okay, we can deal with it, just seemed like a bit much right around release time.
> --paulr
>  
> From: Eric Christopher [mailto:echristo at gmail.com] 
> Sent: Tuesday, January 13, 2015 10:15 AM
> To: Robinson, Paul; Duncan P. N. Exon Smith; LLVM Developers Mailing List
> Subject: Re: [LLVMdev] [RFC] First-class debug info IR: MDLocation (redux)
>  
> Hi Paul,
>  
> I'm not sure I see any reason to wait until after 3.6. More changes are incoming and it's better to get them over with sooner rather than spread out the pain.
>  
> Thanks!
>  
> -eric
> 
> On Mon Jan 12 2015 at 9:52:48 PM Robinson, Paul <Paul_Robinson at playstation.sony.com> wrote:
> Would you mind terribly waiting a week, until after 3.6 is forked?
> We're barely caught up with the last big metadata syntax change.
> Thanks,
> --paulr
>  
> From: llvmdev-bounces at cs.uiuc.edu [mailto:llvmdev-bounces at cs.uiuc.edu] On Behalf Of Duncan P. N. Exon Smith
> Sent: Monday, January 12, 2015 8:30 PM
> To: LLVM Developers Mailing List
> Subject: [LLVMdev] [RFC] First-class debug info IR: MDLocation (redux)
>  
> After splitting `Metadata` apart from `Value`, I'm finally back to the
> first step [1] of representing debug info more directly in IR [2]:
> `MDLocation`.
> 
> [1]: http://lists.cs.uiuc.edu/pipermail/llvmdev/2014-October/078173.html
>         "First-class debug info IR: MDLocation"
> [2]: http://lists.cs.uiuc.edu/pipermail/llvmdev/2014-October/077715.html
>         "Less memory and greater maintainability for debug info IR"
> 
> I've attached two patches which are both essentially commit-ready (just
> missing LangRef update, AFAIK), although they just add the class and
> assembly/bitcode support.  Once it's in tree, I'll move it into place
> underneath `DebugLoc` and `DILocation` and update the world of
> testcases, publish a script, and so forth.
> 
> Assembly syntax
> ===============
> 
> I've changed the assembly syntax a little since my previous proposal
> [1], but I kept the fundamentals the same:
> 
>   - Fields use key/value pairs and can be specified in any order.
>   - No types (unless you're referencing a `Value`).
>   - Some fields are required (in this case, 'scope:').
>   - Unspecified fields get sane default values.
> 
> Old syntax:
> 
>     !6 = metadata MDLocation(line: 43, column: 7, scope: !4)
> 
> Now it's:
> 
>     !6 = !MDLocation(line: 43, column: 7, scope: !4)
> 
> Here's why:
> 
>   - Dropped 'metadata' since `Metadata` is now typeless \O/.
> 
>   - Added a '!' since it makes the parser simpler (no changes to the
>     lexer, since we can unambiguously reuse the `MetadataVar` token),
>     and follows the rule that "All metadata are identified in syntax by
>     a[n] exclamation point" [3].  (If people are opposed to the extra
>     '!' I can update this sentence instead, but it seems like a handy
>     mnemonic to maintain.)
> 
> [3]: http://llvm.org/docs/LangRef.html#metadata
> 
> Where this is heading
> =====================
> 
> See my previous post [1] ;).
> 
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