[LLVMdev] [RFC] First-class debug info IR: MDLocation (redux)
Eric Christopher
echristo at gmail.com
Tue Jan 13 10:13:58 PST 2015
This LGTM. I like the new syntax. Feel free to commit as soon as you have
the LangRef changes handy.
-eric
On Mon Jan 12 2015 at 8:34:18 PM Duncan P. N. Exon Smith <
dexonsmith at apple.com> wrote:
> 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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