Re: [lldb-dev] FW: [llvm-dev] Optimised-code debugging experience Round Table
Tom Weaver will answer the councils call! count me in, can't wait to have a good chin wag (talk for our non brit brethren) about debug info and it's many faceted forms. I somewhat agree with Paul's concern about discussing everything, but we can make a judgement call on the day about what we wish to focus on the most. thanks for sorting this out Orlando, looking forward to it. Tom W On Thu, 24 Sep 2020 at 09:00, Cazalet-Hyams, Orlando via lldb-dev < lldb-dev@lists.llvm.org> wrote: > Forwarding to lldb-dev now that I’ve signed up. > > > > *From:* llvm-dev *On Behalf Of > *Cazalet-Hyams, > Orlando via llvm-dev > *Sent:* 24 September 2020 08:54 > *To:* Robinson, Paul ; Eric Christopher < > echri...@gmail.com>; LLDB Dev ; ' > llvm-...@lists.llvm.org' > *Subject:* Re: [llvm-dev] Optimised-code debugging experience Round Table > > > > Hi Paul, Eric, lists, > > > FWIW I agree with Paul here. Given the limited time available for the > discussions I think it makes sense to split up the conversations to keep > them focused. Though, it'd be good to coordinate non-overlapping time > slots. As you say, it is likely that people (including me) would want to > attend more than one of these. > > > Saying that, I've only had 3 people outside of Sony express an interest in > the Round Table that I proposed. At this rate we may not have the requisite > numbers to split. Of course, if that number is indicative of actual turn > out then we won't need to split anyway, but I suspect that there will be > more attendees on the day. > > We must also remember that the Round Table submission deadline is tomorrow > (tonight?). Unless more people express an interest very soon, I think we > might need to fall back onto the single Round Table. > > > Thanks, > > Orlando > > *From:* Robinson, Paul > *Sent:* 23 September 2020 15:21 > *To:* Eric Christopher ; Cazalet-Hyams, Orlando < > orlando.hy...@sony.com>; LLDB Dev ; ' > llvm-...@lists.llvm.org' > *Subject:* RE: [llvm-dev] Optimised-code debugging experience Round Table > > > > Hi Eric & Orlando, > > > > It’s great to see interest in a lot of different aspects of debug info. At > the same time, I’m concerned about a risk to making the topic so broad that > we don’t have time to get through all the things people want to get > through. I’m thinking there’s a different way to slice the topics, > hopefully without much overlap, but that will allow a bit more focus. No > doubt a lot of the same people would be interested in multiple slices, but > by limiting the scope of each conversation I’m hoping we’ll get more > accomplished. I daresay a lot of people interested in debug-info quality > in general might totally tune out a DWARF-nerd discussion > > The slicing could be something like this: > > > >1. Getting LLVM to do a better job of tracking info internally, so >what gets emitted in the end is more representative of the original >program. This should improve the debugging experience by letting the >debugger do a better job of mapping the executing program to the original >source, because the data it works with is more accurate/complete. > 1. This is basically about IR/Metadata handling and representation, > although it might leak into things like the “is_stmt” flag, and doing > better with “prologue_end,” which are currently handled by AsmPrinter. > 2. Better handling of induction variables, entry-values, variables > with multiple locations, etc. >2. Changes to optimization passes/pipelines and codegen, to avoid >borking the source-location and value/variable tracking; again this should >improve the debugging experience by letting the debugger do a better job of >mapping the executing program back to the original source, because that >mapping is simpler. > 1. This is basically about IR/MIR transforms, and is where an Og/O1 > kind of topic would fit. > 2. Also things like extended lifetimes, limiting code > motion/duplication, etc. >3. Changing the DWARF spec itself to improve the completeness and >efficiency of the information it contains. This should improve the >debugging experience by making the DWARF itself a richer information >source, to the extent that it can describe more of what happened to the >original program; also hopefully any efficiency improvements will allow the >debugger to be more responsive. > 1. This is obviously about DWARF itself, although to some extent > how we go about generating it. > 2. Take better advantage of ranges and the .debug_addr table. > dblaikie and clayborg have put up ideas about this. > 3. Figure out a way to allow tracking multiple source locations for > an individual instruction. Right now we mostly give up and set > locations > to line-0 when this happens. > 4. Understand the competing needs of profiling and debugging > consumers, and see what might be doable
[lldb-dev] FW: [llvm-dev] Optimised-code debugging experience Round Table
Forwarding to lldb-dev now that I’ve signed up. From: llvm-dev On Behalf Of Cazalet-Hyams, Orlando via llvm-dev Sent: 24 September 2020 08:54 To: Robinson, Paul ; Eric Christopher ; LLDB Dev ; 'llvm-...@lists.llvm.org' Subject: Re: [llvm-dev] Optimised-code debugging experience Round Table Hi Paul, Eric, lists, FWIW I agree with Paul here. Given the limited time available for the discussions I think it makes sense to split up the conversations to keep them focused. Though, it'd be good to coordinate non-overlapping time slots. As you say, it is likely that people (including me) would want to attend more than one of these. Saying that, I've only had 3 people outside of Sony express an interest in the Round Table that I proposed. At this rate we may not have the requisite numbers to split. Of course, if that number is indicative of actual turn out then we won't need to split anyway, but I suspect that there will be more attendees on the day. We must also remember that the Round Table submission deadline is tomorrow (tonight?). Unless more people express an interest very soon, I think we might need to fall back onto the single Round Table. Thanks, Orlando From: Robinson, Paul mailto:paul.robin...@sony.com>> Sent: 23 September 2020 15:21 To: Eric Christopher mailto:echri...@gmail.com>>; Cazalet-Hyams, Orlando mailto:orlando.hy...@sony.com>>; LLDB Dev mailto:lldb-dev@lists.llvm.org>>; 'llvm-...@lists.llvm.org' mailto:llvm-...@lists.llvm.org>> Subject: RE: [llvm-dev] Optimised-code debugging experience Round Table Hi Eric & Orlando, It’s great to see interest in a lot of different aspects of debug info. At the same time, I’m concerned about a risk to making the topic so broad that we don’t have time to get through all the things people want to get through. I’m thinking there’s a different way to slice the topics, hopefully without much overlap, but that will allow a bit more focus. No doubt a lot of the same people would be interested in multiple slices, but by limiting the scope of each conversation I’m hoping we’ll get more accomplished. I daresay a lot of people interested in debug-info quality in general might totally tune out a DWARF-nerd discussion The slicing could be something like this: 1. Getting LLVM to do a better job of tracking info internally, so what gets emitted in the end is more representative of the original program. This should improve the debugging experience by letting the debugger do a better job of mapping the executing program to the original source, because the data it works with is more accurate/complete. * This is basically about IR/Metadata handling and representation, although it might leak into things like the “is_stmt” flag, and doing better with “prologue_end,” which are currently handled by AsmPrinter. * Better handling of induction variables, entry-values, variables with multiple locations, etc. 2. Changes to optimization passes/pipelines and codegen, to avoid borking the source-location and value/variable tracking; again this should improve the debugging experience by letting the debugger do a better job of mapping the executing program back to the original source, because that mapping is simpler. * This is basically about IR/MIR transforms, and is where an Og/O1 kind of topic would fit. * Also things like extended lifetimes, limiting code motion/duplication, etc. 3. Changing the DWARF spec itself to improve the completeness and efficiency of the information it contains. This should improve the debugging experience by making the DWARF itself a richer information source, to the extent that it can describe more of what happened to the original program; also hopefully any efficiency improvements will allow the debugger to be more responsive. * This is obviously about DWARF itself, although to some extent how we go about generating it. * Take better advantage of ranges and the .debug_addr table. dblaikie and clayborg have put up ideas about this. * Figure out a way to allow tracking multiple source locations for an individual instruction. Right now we mostly give up and set locations to line-0 when this happens. * Understand the competing needs of profiling and debugging consumers, and see what might be doable there. (Although this might be tough enough to be its own topic.) 4. Debug-info testing/validation. How do we decide what is “correct”? * What are the tools we have, what are they good/bad at, what’s missing? I hear that round-tables can be proposed for either ~half hour or ~full hour, so with more focused topics we might rather have shorter sessions? Thanks, --paulr From: llvm-dev mailto:llvm-dev-boun...@lists.llvm.org>> On Behalf Of Eric Christopher via llvm-dev Sent: Tuesday, September 22, 2020 2:42 PM To: Cazalet-Hyams, Orlando mailto:orlando.hy...@sony.com>>; LLDB Dev mailto:lldb-dev@lists.llvm.org>> Cc:
