Populate the CurrentBlockAnalysisData's _reachingWrites when creating an OperationTreeAnalysis. #73244
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… an OperationTreeAnalysis. This is similar to what FlowGraphAnalysisData does upon inspecting a new block. Inspection of the lightbulb speedometer test demonstrated that a significant portion of CPU (~8%) in our OOP was spent in AbstractRemoveUnusedParametersAndValuesDiagnosticAnalyzer. Looking at the code a bit indicated that the expensive calls to create/invoke the ControlFlowGraph weren't being short-circuited properly in the trivial cases I tried locally. When a read operation is encountered, the code looks at all writes that are still unread. For each of these, it upates the map to indicate that the write has now been read. However, this wasn't working for parameters as the _reachingWrites collection didn't account for them.
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Going to close this PR without merging. I'm very glad there are good tests in this area, as I've had a pretty difficult time understanding exactly how the CFG and the SymbolUsageAnalysis call to prevent the need to call into work together. I feel like these changes and some more I have locally are generally good, but they end up breaking behaviors that were otherwise masked. Without an extremely good understanding of this area, making performance improvements to this area doesn't seem like a good idea. |
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Populate the CurrentBlockAnalysisData's _reachingWrites when creating an OperationTreeAnalysis.
This is similar to what FlowGraphAnalysisData does upon inspecting a new block.
Inspection of the lightbulb speedometer test demonstrated that a significant portion of CPU (~8%) in our OOP was spent in AbstractRemoveUnusedParametersAndValuesDiagnosticAnalyzer. Looking at the code a bit indicated that the expensive calls to create/invoke the ControlFlowGraph weren't being short-circuited properly in the trivial cases I tried locally.
When a read operation is encountered, the code looks at all writes that are still unread. For each of these, it updates the map to indicate that the write has now been read. However, this wasn't working for parameters as the _reachingWrites collection didn't account for them.
As the image below indicates, of the 8% of CPU over 7% is accountable to the CFG. With that short-circuited more commonly now, we should save quite a bit of CPU during execution of this analyzer.