[llvm-dev] RFC: Exposing TargetTransformInfo factories from TargetMachine

[mbraun via llvm-dev]

I think that would make a lot of sense and avoid a lot of the complicated code. Though I think I’d rather see a function in TargetMachine taking a const Function argument, rather than a SubtargetInfo function[1] (you can still implement the TargetMachine function via a sub target function behind the scenes of course).

- Matthias

[1] At least seeing that the SubtargetInfo has a number of lib/CodeGen specific interfaces in it so it had to be moved to include/llvm/CodeGen I’d rather not see it is used in code outside lib/CodeGen or lib/Target.

> On Dec 18, 2017, at 6:26 PM, Eric Christopher via llvm-dev <llvm-dev at lists.llvm.org> wrote:
> 
> Instead, is there any reason why TTI for a given Subtarget shouldn't live on the Subtarget? Just construct it the same way we do TargetLowering, etc?
> 
> -eric
> 
> On Fri, Dec 15, 2017 at 10:13 AM Sanjoy Das via llvm-dev <llvm-dev at lists.llvm.org <mailto:llvm-dev at lists.llvm.org>> wrote:
> On Fri, Dec 15, 2017 at 5:30 AM, Hal Finkel <hfinkel at anl.gov <mailto:hfinkel at anl.gov>> wrote:
> > Are there reasons why we might not want to do this? Other options we should
> > consider?
> 
> It does make the TargetMachine -> TargetIRAnalysis path less abstract,
> but given that all targets have the same pattern of instantiating a
> TargetIRAnalysis with a Function->TargetTransformInfo hook, the
> abstraction does not seem particularly useful.
> 
> I might do even a simpler form of the patch though -- instead of
> returning a function pointer from TargetMachine, just add a virtual
> function to TargetMachine that creates the TargetTransformInfo
> directly from a Function.
> 
> -- Sanjoy
> 
> >
> >  -Hal
> >
> >>
> >> [0]:  XLA is a machine learning focussed linear algebra compiler
> >> https://www.tensorflow.org/performance/xla/ <https://www.tensorflow.org/performance/xla/> that uses LLVM for its CPU
> >> and GPU backends.
> >>
> >> -- Sanjoy
> >> _______________________________________________
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> >
> >
> > --
> > Hal Finkel
> > Lead, Compiler Technology and Programming Languages
> > Leadership Computing Facility
> > Argonne National Laboratory
> >
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