Nicolai Hähnle via llvm-dev
2020-Jul-16 07:25 UTC
[llvm-dev] [RFC] Introducing classes for the codegen driven by new pass manager
On Wed, Jul 15, 2020 at 6:39 PM Chen, Yuanfang via llvm-dev <llvm-dev at lists.llvm.org> wrote:> Indeed, but there is a distinction about their position in the pipeline. We run opt & codegen pipeline separately,Why, though? Is there a reason why this inherently makes sense, or is it just a historical accident? At least to me it seems that it would make more sense to run all passes within a single pipeline. Cheers, Nicolai> > Do you run “codegen” IR passes with regular IR passes? If so, do you mind sharing the use cases? I might have missed this use case. > > ________________________________________ > From: Matt Arsenault <whatmannerofburgeristhis at gmail.com> on behalf of Matt Arsenault <arsenm2 at gmail.com> > Sent: Wednesday, July 15, 2020 9:31 AM > To: Chen, Yuanfang > Cc: Robinson, Paul; llvm-dev at lists.llvm.org > Subject: Re: [llvm-dev] [RFC] Introducing classes for the codegen driven by new pass manager > > > > > On Jul 15, 2020, at 12:28, Chen, Yuanfang <Yuanfang.Chen at sony.com> wrote: > > > > In codegen with NPM, I've made all codegen passes (IR or MIR pass) to be only driven by `llc`. Both due to the way NPM registering pass (on-demand&dynamic instead of static initialization in Legacy PM), and reduce the confusion about which tool (`llc` or `opt`) to test codegen IR passes. > > > > > I think there’s no real distinction between “codegen” IR passes and noncodegen IR passes. I routinely run “codegen only” passes with opt in conjunction with other passes when experimenting. I think losing the ability to run any IR pass with opt would be a functionality regression. > > -Matt > _______________________________________________ > LLVM Developers mailing list > llvm-dev at lists.llvm.org > https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev-- Lerne, wie die Welt wirklich ist, aber vergiss niemals, wie sie sein sollte.
Chen, Yuanfang via llvm-dev
2020-Jul-17 00:00 UTC
[llvm-dev] [RFC] Introducing classes for the codegen driven by new pass manager
TBH, I don't know the history of this choice. Although it makes sense from the debugging/testing point of view. We have IR / MIR difference so it makes sense to have their own pipeline (yeah, MIR pipeline is prefixed with an IR pipeline to prepare the module, but that is just implementation detail). And then we have opt/llc to test the pipeline separately. Combining them in a single pipeline is possible, but AFAIK it does not have many benefits in practice. ________________________________________ From: Nicolai Hähnle <nhaehnle at gmail.com> Sent: Thursday, July 16, 2020 12:25 AM To: Chen, Yuanfang Cc: Matt Arsenault; llvm-dev at lists.llvm.org Subject: Re: [llvm-dev] [RFC] Introducing classes for the codegen driven by new pass manager On Wed, Jul 15, 2020 at 6:39 PM Chen, Yuanfang via llvm-dev <llvm-dev at lists.llvm.org> wrote:> Indeed, but there is a distinction about their position in the pipeline. We run opt & codegen pipeline separately,Why, though? Is there a reason why this inherently makes sense, or is it just a historical accident? At least to me it seems that it would make more sense to run all passes within a single pipeline. Cheers, Nicolai> > Do you run “codegen” IR passes with regular IR passes? If so, do you mind sharing the use cases? I might have missed this use case. > > ________________________________________ > From: Matt Arsenault <whatmannerofburgeristhis at gmail.com> on behalf of Matt Arsenault <arsenm2 at gmail.com> > Sent: Wednesday, July 15, 2020 9:31 AM > To: Chen, Yuanfang > Cc: Robinson, Paul; llvm-dev at lists.llvm.org > Subject: Re: [llvm-dev] [RFC] Introducing classes for the codegen driven by new pass manager > > > > > On Jul 15, 2020, at 12:28, Chen, Yuanfang <Yuanfang.Chen at sony.com> wrote: > > > > In codegen with NPM, I've made all codegen passes (IR or MIR pass) to be only driven by `llc`. Both due to the way NPM registering pass (on-demand&dynamic instead of static initialization in Legacy PM), and reduce the confusion about which tool (`llc` or `opt`) to test codegen IR passes. > > > > > I think there’s no real distinction between “codegen” IR passes and noncodegen IR passes. I routinely run “codegen only” passes with opt in conjunction with other passes when experimenting. I think losing the ability to run any IR pass with opt would be a functionality regression. > > -Matt > _______________________________________________ > LLVM Developers mailing list > llvm-dev at lists.llvm.org > https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev-- Lerne, wie die Welt wirklich ist, aber vergiss niemals, wie sie sein sollte.
Craig Topper via llvm-dev
2020-Jul-21 18:53 UTC
[llvm-dev] [RFC] Introducing classes for the codegen driven by new pass manager
One thing I want to mention. I believe in the current legacy pass manager implementation only one MachineFunction ever exists at a time. It is deleted before the next MachineFunction is created. This is very important for memory usage. I think the MachineOutliner being in the pipeline may create an exception to this. I think the initial version of retpoline used a ModulePass and that had to be changed to avoid excessive memory usage. ~Craig On Thu, Jul 16, 2020 at 5:01 PM Chen, Yuanfang via llvm-dev < llvm-dev at lists.llvm.org> wrote:> TBH, I don't know the history of this choice. Although it makes sense from > the debugging/testing point of view. We have IR / MIR difference so it > makes sense to have their own pipeline (yeah, MIR pipeline is prefixed with > an IR pipeline to prepare the module, but that is just implementation > detail). And then we have opt/llc to test the pipeline separately. > Combining them in a single pipeline is possible, but AFAIK it does not have > many benefits in practice. > > ________________________________________ > From: Nicolai Hähnle <nhaehnle at gmail.com> > Sent: Thursday, July 16, 2020 12:25 AM > To: Chen, Yuanfang > Cc: Matt Arsenault; llvm-dev at lists.llvm.org > Subject: Re: [llvm-dev] [RFC] Introducing classes for the codegen driven > by new pass manager > > On Wed, Jul 15, 2020 at 6:39 PM Chen, Yuanfang via llvm-dev > <llvm-dev at lists.llvm.org> wrote: > > Indeed, but there is a distinction about their position in the pipeline. > We run opt & codegen pipeline separately, > > Why, though? Is there a reason why this inherently makes sense, or is > it just a historical accident? At least to me it seems that it would > make more sense to run all passes within a single pipeline. > > Cheers, > Nicolai > > > > > > > Do you run “codegen” IR passes with regular IR passes? If so, do you > mind sharing the use cases? I might have missed this use case. > > > > ________________________________________ > > From: Matt Arsenault <whatmannerofburgeristhis at gmail.com> on behalf of > Matt Arsenault <arsenm2 at gmail.com> > > Sent: Wednesday, July 15, 2020 9:31 AM > > To: Chen, Yuanfang > > Cc: Robinson, Paul; llvm-dev at lists.llvm.org > > Subject: Re: [llvm-dev] [RFC] Introducing classes for the codegen driven > by new pass manager > > > > > > > > > On Jul 15, 2020, at 12:28, Chen, Yuanfang <Yuanfang.Chen at sony.com> > wrote: > > > > > > In codegen with NPM, I've made all codegen passes (IR or MIR pass) to > be only driven by `llc`. Both due to the way NPM registering pass > (on-demand&dynamic instead of static initialization in Legacy PM), and > reduce the confusion about which tool (`llc` or `opt`) to test codegen IR > passes. > > > > > > > > > I think there’s no real distinction between “codegen” IR passes and > noncodegen IR passes. I routinely run “codegen only” passes with opt in > conjunction with other passes when experimenting. I think losing the > ability to run any IR pass with opt would be a functionality regression. > > > > -Matt > > _______________________________________________ > > LLVM Developers mailing list > > llvm-dev at lists.llvm.org > > https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev > > > > -- > Lerne, wie die Welt wirklich ist, > aber vergiss niemals, wie sie sein sollte. > _______________________________________________ > LLVM Developers mailing list > llvm-dev at lists.llvm.org > https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev >-------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20200721/562ee4f6/attachment.html>