[llvm-dev] [RFC] Generate Debug Information for Labels in Function

[Adrian Prantl via llvm-dev]

> On Mar 29, 2018, at 10:55 AM, paul.robinson at sony.com wrote:
> 
> 
> 
>> -----Original Message-----
>> From: llvm-dev [mailto:llvm-dev-bounces at lists.llvm.org] On Behalf Of via
>> llvm-dev
>> Sent: Thursday, March 29, 2018 1:54 PM
>> To: aprantl at apple.com; hsiangkai at gmail.com
>> Cc: llvm-dev at lists.llvm.org
>> Subject: Re: [llvm-dev] [RFC] Generate Debug Information for Labels in
>> Function
>> 
>>> Based on that I think it might be sufficient to have a flag on an IR
>> label
>>> that marks a user-originated label and triggers the backend to create a
>>> DW_TAG_label for it. If we do need source location information for the
>>> DW_TAG_label, we could grab it from the first instruction.
>> 
>> Are there languages where labels are scoped?  If so we'd need explicit
>> metadata to identify the parent scope.  In C/C++ the only scope is the
>> containing function, which I'm guessing we wouldn't need to specify
>> (except for inlined functions? that might need some care to get right).
>> 
>> I feel compelled to point out that the top instructions in a block do not
>> necessarily have a valid source location so we might want to carry that
>> explicitly just for sanity's sake.
> 
> That is, carry the source location explicitly on the label.

Thanks that's a good point. I still wonder what a debugger would do with the source location of a label though? For setting breakpoints it seems redundant with the location of the next instruction. Does GCC emit source location for a label, or just its name? If yes, does GDB do anything with that information?

-- adrian