Fix the incorrect merge logic for back edges for GlobalFlowStateAnalysis #6029
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Fixes dotnet#6015 `GlobalFlowStateAnalysisValueSet.Unset` is used to represent unanalyzed flow state, `GlobalFlowStateAnalysisValueSet.Empty` is used to represent analyzed flow state with no analysis values. We initialize the flow states for the entry basic block of the CFG with `Unset` value, but never replace the `Unset` with `Empty` for subsequent passes. This in turn leads to incorrect merge when a `Known` value flows from the back edge to the loop start and ends up overriding the `Unset` value instead of being overridden by the `Empty` value. Now we correctly perform this merge logic. I verified that prior to this fix, the added unit test hang due to this issue. I also verified that building the github repo cited in the feedback ticket with platform compat analyzer also leads to a hang before this fix. Both these repros are fixed after this PR.
Evangelink
reviewed
Jun 23, 2022
| { | ||
| return value1; | ||
| return GlobalFlowStateAnalysisValueSet.Empty; |
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It's not entirely clear to me why you always set Empty in the case of merge.
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@Evangelink This matches the intended merge logic also documented in
. I goofed up in the merge implementationThere was a problem hiding this comment.
Didn't read the doc... sorry :)
Evangelink
approved these changes
Jun 23, 2022
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@mavasani JFYI: the build failures with NuGet errors: NU1504, NU1505 I can also see locally |
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@jmarolf is this a known issue? |
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@mavasani @buyaa-n Functionality for that on NuGet-side was implemented in NuGet/NuGet.Client#4484. I'm fixing the error in #6032 |
let me take a look |
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/azp run |
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Azure Pipelines successfully started running 3 pipeline(s). |
Codecov Report
@@ Coverage Diff @@
## main #6029 +/- ##
==========================================
- Coverage 96.03% 96.03% -0.01%
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Files 1338 1338
Lines 307164 307197 +33
Branches 9787 9788 +1
==========================================
+ Hits 294978 295007 +29
- Misses 9809 9812 +3
- Partials 2377 2378 +1 |
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Fixes #6015
GlobalFlowStateAnalysisValueSet.Unsetis used to represent unanalyzed flow state,GlobalFlowStateAnalysisValueSet.Emptyis used to represent analyzed flow state with no analysis values. We initialize the flow states for the entry basic block of the CFG withUnsetvalue, but never replace theUnsetwithEmptyfor subsequent passes. This in turn leads to incorrect merge when aKnownvalue flows from the back edge to the loop start and ends up overriding theUnsetvalue instead of being overridden by theEmptyvalue. Now we correctly perform this merge logic.I verified that prior to this fix, the added unit test hang due to this issue. I also verified that building the github repo cited in the feedback ticket with platform compat analyzer also leads to a hang before this fix. Both these repros are fixed after this PR.