[PATCH] D21462: [PM] Make the the new pass manageg support fully generic extra arguments to run methods, both for transform passes and analysis passes.

Chandler Carruth via llvm-commits llvm-commits at lists.llvm.org
Fri Jun 17 00:56:02 PDT 2016

chandlerc created this revision.
chandlerc added a subscriber: llvm-commits.
Herald added subscribers: mcrosier, mehdi_amini.

This also allows the analysis manager to use a different set of extra
arguments from the pass manager where useful. Consider passes over
analysis produced units of IR like SCCs of the call graph or loops.
Passes of this nature will often want to refer to the analysis result
that was used to compute their IR units (the call graph or LoopInfo).
And for transformations, they may want to communicate special update
information to the outer pass manager. With this change, it becomes
possible to have a run method for a loop pass that looks more like:

  PreservedAnalyses run(Loop &L, AnalysisManager<Loop, LoopInfo> &AM,
                        LoopInfo &LI, LoopUpdateRecord &UR);

And to query the analysis manager like:

    AM.getResult<MyLoopAnalysis>(L, LI);

This makes accessing the known-available analyses convenient and clear,
and it makes passing customized data structures around easy.

My initial use case is going to be in updating the pass manager layers
when the analysis units of IR change. But there are more use cases here
such as having a layer that lets inner passes signal whether certain
additional passes should be run because of particular simplifications
made. Two desires for this have come up in the past: triggering
additional optimization after successfully unrolling loops, and
triggering additional inlining after collapsing indirect calls to direct

Despite adding this layer of generic extensibility, the *only* change to
existing, simple usage are for places where we forward declare the
AnalysisManager template. We really shouldn't be doing this because of
the fragility exposed here, but currently it makes coping with the
legacy PM code easier.

My next patch will leverage this functionality to extend the CGSCC pass
capabilities to support updating after CG mutations occur.



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