[all-commits] [llvm/llvm-project] a60050: [mlir][dataflow] Allow re-run all analyses in Data...

[Hongren Zheng via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: a60050cf1966eb8d46253c8da13df52ac8b9ec33
      https://github.com/llvm/llvm-project/commit/a60050cf1966eb8d46253c8da13df52ac8b9ec33
  Author: Hongren Zheng <i at zenithal.me>
  Date:   2024-12-23 (Mon, 23 Dec 2024)

  Changed paths:
    M mlir/include/mlir/Analysis/DataFlowFramework.h

  Log Message:
  -----------
  [mlir][dataflow] Allow re-run all analyses in DataFlowSolver (#120881)

In downstream (check https://github.com/google/heir/pull/1228,
especially [this
commit](https://github.com/ZenithalHourlyRate/heir/commit/fbf0b2733f1f60e852c757602afac65a4364e30c);
also check https://github.com/google/heir/pull/1154) we often need to
re-run the analysis during the transformation pass as IR get changed
based on the analysis result and analysis continuously get invalidated.

There are solutions to it like `getOrCreateState` for newly created
`Value` (`AnchorT`), but warning is that the new state does not
propagate! This is quite unexpected as user of analysis would expect it
to propagate. We downstream used to use `solver->propagateIfChanged` but
that turned out to be not working, see detailed writeup in
https://github.com/google/heir/issues/1153.

Just call `initializeAndRun` repeatedly also does not solve the problem
as `analysisStates` is not cleared and the monotonicity of
`AnalysisState` will make the analysis invalid as `join` will not work
as expected (the first join is no longer `join(uninitialized, init
value)`, instead it becomes `join(higher value, init value)`.

To correctly re-run the analysis, either a new `DataFlowSolver` is
created, or we can just clear the `analysisState`.



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