JIT: Further liveness cleanups#123999
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jakobbotsch merged 5 commits intodotnet:mainfrom Feb 5, 2026
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Tagging subscribers to this area: @JulieLeeMSFT, @jakobbotsch |
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Pull request overview
This PR refactors the JIT liveness analysis code to improve code organization and maintainability. The main goal is to separate different liveness phases into distinct functions and consolidate related functionality.
Changes:
- Replaced runtime check
fgIsDoingEarlyLivenesswith compile-time template parameterIsEarly - Moved
fgLocalVarLivenessChangedinto theLivenessclass asm_livenessChanged - Renamed private member fields in
Livenessclass fromfgCur*prefix tom_cur*prefix for consistency - Removed the
LiveVarAnalysisclass and merged its functionality into theLivenessclass - Removed unnecessary optimization level checks (
opts.MinOpts()) since liveness only runs when optimizations are enabled - Split the generic
fgLocalVarLiveness()into separate specialized functions:fgSsaLiveness(),fgAsyncLiveness(),fgPostLowerLiveness()
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Copilot reviewed 6 out of 6 changed files in this pull request and generated no comments.
Show a summary per file
| File | Description |
|---|---|
| src/coreclr/jit/liveness.cpp | Main refactoring: field renames, template parameter addition, class consolidation, optimization check removal, new specialized liveness functions |
| src/coreclr/jit/compiler.h | Updated function declarations, removed obsolete fields fgLocalVarLivenessChanged and fgIsDoingEarlyLiveness |
| src/coreclr/jit/ssabuilder.cpp | Updated call from fgLocalVarLiveness() to fgSsaLiveness() |
| src/coreclr/jit/lower.cpp | Updated calls from fgLocalVarLiveness() to fgPostLowerLiveness() |
| src/coreclr/jit/compiler.cpp | Updated call from fgLocalVarLiveness() to fgSsaLiveness() |
| src/coreclr/jit/async.cpp | Updated call from fgLocalVarLiveness() to fgAsyncLiveness() |
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cc @dotnet/jit-contrib PTAL @AndyAyersMS No asm diffs, some throughput diffs (mostly improvements). |
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Feb 4, 2026
This was referenced Feb 4, 2026
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- Give each liveness phase its own separate function - Remove `Compiler::fgIsDoingEarlyLiveness` in favor of a new config option in `Liveness` - Move `fgLocalVarLivenessChanged` into `Liveness` - Rename some fields in `Liveness` - Remove optimization level checks in liveness since we only run liveness when optimizing and have done so for a while - Remove the `LiveVarAnalysis` class and merge it into the `Liveness` class No diffs expected. The last change here (removing `LiveVarAnalysis`) has some TP regressions on MSVC, once again related to inlining decisions.
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Compiler::fgIsDoingEarlyLivenessin favor of a new config option inLivenessfgLocalVarLivenessChangedintoLivenessLivenessLiveVarAnalysisclass and merge it into theLivenessclassNo diffs expected. The last change here (removing
LiveVarAnalysis) has some TP regressions on MSVC, once again related to inlining decisions.