[llvm-dev] [GlobalISel][RFC] Thoughts on MachineModulePass

[Eric Christopher via llvm-dev]

Hi Marcello,

Can you elaborate here a bit more? Mostly what it sounds like is just a
direct port of Module pass to run over MFs, similar to what AsmPrinter does
today, but also being able to have some analysis passes as well?

I realize my question seems a bit vague, but I'm trying to get a better
idea of what the use case is here as it sounds like something that we could
have the "MF pipeline" have and use and be (possibly) a better place to
stick the AsmPrinter (we'd need to figure out things like globals, but that
might be it).

Thanks!

-eric

On Fri, Jan 22, 2016 at 10:44 PM Marcello Maggioni via llvm-dev <
llvm-dev at lists.llvm.org> wrote:

> The pass, the perspective of our use case, would need to be able some kind
> of synchronization point in the pipeline between MF passes (such that all
> the MF passes before have run on all the MachineFunctions in the Module
> before running the MachineModule pass)
> Currently the MachineFunctions are processed from the beginning to the end
> making it difficult to be able to do Machine level analysis without awful
> tricks (where we get information from multiple functions and merge them
> together in some way).
> Immutable passes would also need to be accessible.
>
> An important design decision would be to understand what can and cannot a
> MachineModulePass do to a hypotetical MachineModule (can it add
> MachineFunctions that are not connected to IR machine functions like a
> MachineFunction pass can add MachineBasicBlocks not connected to IR
> BasicBlocks?)
>
> Marcello
>
> > On 22 Jan 2016, at 15:16, Quentin Colombet <qcolombet at apple.com> wrote:
> >
> > Hi,
> >
> > In the initial thread of the proposal for GlobalISel, I have mentioned
> that it may be interesting to have a kind of MachineModulePass.
> > Marcello mentioned this would be useful for their current pipeline.
> >
> > I am interested in knowing:
> > 1. If anyone else is interested for such concept?
> > 2. What kind of information should we make accessible in an hypothetical
> MachineModule? I.e., how do you plan to use the MachineModulePass so that
> we make the right design decisions for the MachineModule feeding those
> passes?
> > 3. Who would be willing to work on that?
> >
> > Thanks,
> > -Quentin
>
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