llvm dev - Dec 2017 - Passes to add/validate synthetic debug info

Hi,

I've prototyped a pair of passes which 1) add synthetic debug info to a
Module and 2) determine how much of that info is lost. The idea is to make it
easier to write targeted test cases for debug info preservation. For example,
here is a quick way to test that Mem2Reg doesn't drop debug info from one
test input:
> ; RUN: opt < %s -debugify -mem2reg -check-debugify -S 2>&1 |
FileCheck %s
> ; CHECK: CheckDebugify: PASS
So far, I've used this utility to identify problems in LSR and instcombine
(haven't gotten around to filing bugs yet). There's some more discussion
about this utility on the thread "RFC: [GlobalISel] Towards a generic MI
combiner framework", where Amara and Daniel suggested trying something
similar at the MI level.

I've put the passes up for review here https://reviews.llvm.org/D40512
<https://reviews.llvm.org/D40512>. I just wanted to ping llvm-dev to raise
awareness about the proposed passes, and to see if anyone in the community has
concerns/feedback.

thanks,
vedant
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On Mon, Dec 4, 2017 at 1:44 PM, Vedant Kumar <vsk at apple.com>
wrote:
> Hi,
>
> I've prototyped a pair of passes which 1) add synthetic debug info to a
> Module and 2) determine how much of that info is lost. The idea is to make
> it easier to write targeted test cases for debug info preservation. For
> example, here is a quick way to test that Mem2Reg doesn't drop debug
info
> from one test input:
>
> ; RUN: opt < %s -debugify -mem2reg -check-debugify -S 2>&1 |
FileCheck %s
> ; CHECK: CheckDebugify: PASS
>
>
> So far, I've used this utility to identify problems in LSR and
instcombine
> (haven't gotten around to filing bugs yet). There's some more
discussion
> about this utility on the thread "RFC: [GlobalISel] Towards a generic
MI
> combiner framework", where Amara and Daniel suggested trying something
> similar at the MI level.
>
> I've put the passes up for review here https://reviews.llvm.org/D40512.
I
> just wanted to ping llvm-dev to raise awareness about the proposed passes,
> and to see if anyone in the community has concerns/feedback.
>
> thanks,
> vedant
After you addressed all my comments, this is pretty close to me. I'll
take another look today or tomorrow but I'm confident we can iterate
in tree.
In other words, +1 from me (you may want to wait a week or so before
committing so that people have a chance to take a look).


-- 
Davide

"There are no solved problems; there are only problems that are more
or less solved" -- Henri Poincare

Thanks everybody for your feedback on the patch! I think I've addressed all
of it now. I'll commit this tomorrow barring any further comments.

best,
vedant
> On Dec 4, 2017, at 2:18 PM, Davide Italiano <davide at freebsd.org>
wrote:
> 
> On Mon, Dec 4, 2017 at 1:44 PM, Vedant Kumar <vsk at apple.com>
wrote:
>> Hi,
>> 
>> I've prototyped a pair of passes which 1) add synthetic debug info
to a
>> Module and 2) determine how much of that info is lost. The idea is to
make
>> it easier to write targeted test cases for debug info preservation. For
>> example, here is a quick way to test that Mem2Reg doesn't drop
debug info
>> from one test input:
>> 
>> ; RUN: opt < %s -debugify -mem2reg -check-debugify -S 2>&1 |
FileCheck %s
>> ; CHECK: CheckDebugify: PASS
>> 
>> 
>> So far, I've used this utility to identify problems in LSR and
instcombine
>> (haven't gotten around to filing bugs yet). There's some more
discussion
>> about this utility on the thread "RFC: [GlobalISel] Towards a
generic MI
>> combiner framework", where Amara and Daniel suggested trying
something
>> similar at the MI level.
>> 
>> I've put the passes up for review here
https://reviews.llvm.org/D40512. I
>> just wanted to ping llvm-dev to raise awareness about the proposed
passes,
>> and to see if anyone in the community has concerns/feedback.
>> 
>> thanks,
>> vedant
> 
> After you addressed all my comments, this is pretty close to me. I'll
> take another look today or tomorrow but I'm confident we can iterate
> in tree.
> In other words, +1 from me (you may want to wait a week or so before
> committing so that people have a chance to take a look).
> 
> 
> -- 
> Davide
> 
> "There are no solved problems; there are only problems that are more
> or less solved" -- Henri Poincare
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