JIT: Decouple "DoNotEnregister" from liveness - #127932

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jakobbotsch merged 9 commits into
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jakobbotsch:decouple-liveness-dner
May 18, 2026
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JIT: Decouple "DoNotEnregister" from liveness#127932
jakobbotsch merged 9 commits into
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jakobbotsch:decouple-liveness-dner

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@jakobbotschjakobbotsch commented May 7, 2026

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Liveness was marking locals as DNER in various places, including when it found locals to be live into EH handlers.
DNER is sticky and cannot be unset, and we call liveness multiple times, so that made things hard to reason about and led to unnecessary DNER.

This showed up for runtime async functions. Even when we were able to optimize out the try-fault clauses inserted around the body we would often still end up with lvaAsyncContinuationArg unnecessarily DNER'd because we had already marked it as DNER during a previous liveness pass, when it was live into the fault handler.

This PR:

  • Resets lvLiveInOutOfHandler on all locals every time we run liveness
  • Moves all the DNER setting from liveness to LSRA and to lowering
  • Encapsulates lvLiveInOutOfHandler into LclVarDsc::IsLiveInOutOfHandler() and adds an assert(lvTracked) to this function, so it cannot be misused
  • Introduces a few updates to heuristics to use IsLiveInOutOfHandler() in addition to DNER

Diffs aren't all that great, but I think this is a good clean up on its own.

CopilotAI review requested due to automatic review settings May 7, 2026 19:15
@github-actionsgithub-actionsBot added the area-CodeGen-coreclr CLR JIT compiler in src/coreclr/src/jit and related components such as SuperPMI label May 7, 2026
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Comment threadsrc/coreclr/jit/compiler.cpp
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Comment threadsrc/coreclr/jit/lclvars.cpp
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Comment threadsrc/coreclr/jit/regalloc.cpp
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Pull request overview

This PR refactors CoreCLR JIT local liveness/EH handling so that EH “live-in/out-of-handler” state is recomputed each liveness run and lvDoNotEnregister (DNER) is no longer set by liveness, instead being set by regalloc / lowering.

Changes:

  • Recompute and encapsulate EH live-in/out state via LclVarDsc::IsLiveInOutOfHandler() and reset EH/must-init flags each liveness run.
  • Move DNER-setting decisions out of liveness into regalloc (checkForDNER) and lowering (lvSetEHVarsDoNotEnreg), and update heuristics to consult EH-liveness in addition to DNER.
  • Add Compiler::IsEHVarARegCandidate to centralize “EH write-thru candidate” logic and use it in multiple optimizations.

Reviewed changes

Copilot reviewed 20 out of 20 changed files in this pull request and generated 2 comments.

Show a summary per file
FileDescription
src/coreclr/jit/sideeffects.hUse IsLiveInOutOfHandler() for EH-related aliasing decisions.
src/coreclr/jit/regallocwasm.hDeclare checkForDNER for Wasm regalloc.
src/coreclr/jit/regallocwasm.cppCall checkForDNER and use encapsulated EH-live query.
src/coreclr/jit/regalloc.cppAdd checkForDNER and remove DNER-setting from isRegCandidate.
src/coreclr/jit/optimizer.cppSwitch EH-live checks to IsLiveInOutOfHandler().
src/coreclr/jit/morph.cppStop copying EH-live flag during implicit-byref arg retyping.
src/coreclr/jit/lsra.hDeclare checkForDNER for LSRA.
src/coreclr/jit/lsra.cppCall checkForDNER and use IsLiveInOutOfHandler() in LSRA logic.
src/coreclr/jit/lower.cppAdd lvSetEHVarsDoNotEnreg() call to support containment heuristics in lowering.
src/coreclr/jit/liveness.cppReset lvMustInit and EH-live state each liveness run; set EH-live without setting DNER.
src/coreclr/jit/lclvars.cppAdd lvSetEHVarsDoNotEnreg; remove lvaSetVarLiveInOutOfHandler; adjust DNER behavior.
src/coreclr/jit/jiteh.cppTrack when EH clauses are removed post-liveness.
src/coreclr/jit/inductionvariableopts.cppUpdate IV widening heuristics to consider EH-liveness independently of DNER.
src/coreclr/jit/gschecks.cppRemove direct clearing of EH-live flag on shadowing locals.
src/coreclr/jit/gentree.cppAdd Compiler::IsEHVarARegCandidate helper; update EH-live checks.
src/coreclr/jit/earlyprop.cppUpdate EH-live checks to IsLiveInOutOfHandler().
src/coreclr/jit/copyprop.cppAdjust “profitability” gating to compare expected enregistration status incl. EH-liveness.
src/coreclr/jit/compiler.hEncapsulate EH-live flag, add helper APIs, and add optRemovedEHClausesAfterLiveness.
src/coreclr/jit/compiler.cppUpdate enregister stats accounting to include PinningRef unconditionally.
src/coreclr/jit/codegenwasm.cppUpdate EH-live checks to IsLiveInOutOfHandler().
src/coreclr/jit/codegencommon.cppUpdate EH-live checks to IsLiveInOutOfHandler().
Comments suppressed due to low confidence (1)

src/coreclr/jit/compiler.h:5734

  • optRemovedEHClausesAfterLiveness is currently only set/reset (in fgRemoveEHTableEntry and liveness) but not consumed anywhere else. If it’s meant to guard heuristics that rely on IsLiveInOutOfHandler() (e.g., avoid setting DNER based on stale EH liveness after EH removal), consider wiring it into the relevant decision points; otherwise it should be removed to avoid accumulating dead state.
 bool fgBBVarSetsInited = false;
// Track how many artificial ref counts we've added to fgEntryBB (for OSR)

Comment threadsrc/coreclr/jit/lclvars.cpp
Comment threadsrc/coreclr/jit/liveness.cpp Outdated
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Pull request overview

Copilot reviewed 20 out of 20 changed files in this pull request and generated 3 comments.

Comment threadsrc/coreclr/jit/lower.cpp
Comment threadsrc/coreclr/jit/compiler.cpp
Comment threadsrc/coreclr/jit/liveness.cpp Outdated
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Copilot reviewed 20 out of 20 changed files in this pull request and generated 1 comment.

Comment threadsrc/coreclr/jit/gschecks.cpp
This was referenced May 8, 2026
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@dotnet-policy-servicedotnet-policy-serviceBot added the linkable-framework Issues associated with delivering a linker friendly framework label May 12, 2026
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Sorry for the requests, accidentally rebased across a merge here...

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/azp run runtime-coreclr jitstress, runtime-coreclr libraries-jitstress

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cc @dotnet/jit-contrib PTAL @AndyAyersMS

Diffs.

This will be more important for future work once we start optimizing out IR that allows us to remove the EH we inserted for async.

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Pull request overview

Copilot reviewed 20 out of 20 changed files in this pull request and generated 2 comments.

Comment threadsrc/coreclr/jit/lclvars.cpp
Comment threadsrc/coreclr/jit/lower.cpp
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jakobbotsch merged commit b540c36 into dotnet:mainMay 18, 2026
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JIT: Decouple "DoNotEnregister" from liveness - #127932
Merged
jakobbotsch merged 9 commits into
dotnet:mainfrom 
jakobbotsch:decouple-liveness-dner
May 18, 2026
Merged
JIT: Decouple "DoNotEnregister" from liveness#127932
jakobbotsch merged 9 commits into
dotnet:mainfrom 
jakobbotsch:decouple-liveness-dner
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Liveness was marking locals as DNER in various places, including when it found locals to be live into EH handlers.

DNER is sticky and cannot be unset, and we call liveness multiple times, so that made things hard to reason about and led to unnecessary DNER.
This showed up for runtime async functions. Even when we were able to optimize out the try-fault clauses inserted around the body we would often still end up with lvaAsyncContinuationArg unnecessarily DNER'd because we had already marked it as DNER during a previous liveness pass, when it was live into the fault handler.
This PR:
  • Resets lvLiveInOutOfHandler on all locals every time we run liveness
  • Moves all the DNER setting from liveness to LSRA and to lowering
  • Encapsulates lvLiveInOutOfHandler into LclVarDsc::IsLiveInOutOfHandler() and adds an assert(lvTracked) to this function, so it cannot be misused
  • Introduces a few updates to heuristics to use IsLiveInOutOfHandler() in addition to DNER
Diffs aren't all that great, but I think this is a good clean up on its own.
CopilotAI
review requested due to automatic review settings
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Comment threadsrc/coreclr/jit/compiler.cpp
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Comment threadsrc/coreclr/jit/lclvars.cpp
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Comment threadsrc/coreclr/jit/regalloc.cpp
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Pull request overview
This PR refactors CoreCLR JIT local liveness/EH handling so that EH “live-in/out-of-handler” state is recomputed each liveness run and lvDoNotEnregister (DNER) is no longer set by liveness, instead being set by regalloc / lowering.
Changes:
  • Recompute and encapsulate EH live-in/out state via LclVarDsc::IsLiveInOutOfHandler() and reset EH/must-init flags each liveness run.
  • Move DNER-setting decisions out of liveness into regalloc (checkForDNER) and lowering (lvSetEHVarsDoNotEnreg), and update heuristics to consult EH-liveness in addition to DNER.
  • Add Compiler::IsEHVarARegCandidate to centralize “EH write-thru candidate” logic and use it in multiple optimizations.
Reviewed changes
Copilot reviewed 20 out of 20 changed files in this pull request and generated 2 comments.
Show a summary per file
FileDescription
src/coreclr/jit/sideeffects.hUse IsLiveInOutOfHandler() for EH-related aliasing decisions.
src/coreclr/jit/regallocwasm.hDeclare checkForDNER for Wasm regalloc.
src/coreclr/jit/regallocwasm.cppCall checkForDNER and use encapsulated EH-live query.
src/coreclr/jit/regalloc.cppAdd checkForDNER and remove DNER-setting from isRegCandidate.
src/coreclr/jit/optimizer.cppSwitch EH-live checks to IsLiveInOutOfHandler().
src/coreclr/jit/morph.cppStop copying EH-live flag during implicit-byref arg retyping.
src/coreclr/jit/lsra.hDeclare checkForDNER for LSRA.
src/coreclr/jit/lsra.cppCall checkForDNER and use IsLiveInOutOfHandler() in LSRA logic.
src/coreclr/jit/lower.cppAdd lvSetEHVarsDoNotEnreg() call to support containment heuristics in lowering.
src/coreclr/jit/liveness.cppReset lvMustInit and EH-live state each liveness run; set EH-live without setting DNER.
src/coreclr/jit/lclvars.cppAdd lvSetEHVarsDoNotEnreg; remove lvaSetVarLiveInOutOfHandler; adjust DNER behavior.
src/coreclr/jit/jiteh.cppTrack when EH clauses are removed post-liveness.
src/coreclr/jit/inductionvariableopts.cppUpdate IV widening heuristics to consider EH-liveness independently of DNER.
src/coreclr/jit/gschecks.cppRemove direct clearing of EH-live flag on shadowing locals.
src/coreclr/jit/gentree.cppAdd Compiler::IsEHVarARegCandidate helper; update EH-live checks.
src/coreclr/jit/earlyprop.cppUpdate EH-live checks to IsLiveInOutOfHandler().
src/coreclr/jit/copyprop.cppAdjust “profitability” gating to compare expected enregistration status incl. EH-liveness.
src/coreclr/jit/compiler.hEncapsulate EH-live flag, add helper APIs, and add optRemovedEHClausesAfterLiveness.
src/coreclr/jit/compiler.cppUpdate enregister stats accounting to include PinningRef unconditionally.
src/coreclr/jit/codegenwasm.cppUpdate EH-live checks to IsLiveInOutOfHandler().
src/coreclr/jit/codegencommon.cppUpdate EH-live checks to IsLiveInOutOfHandler().
Comments suppressed due to low confidence (1)
src/coreclr/jit/compiler.h:5734
  • optRemovedEHClausesAfterLiveness is currently only set/reset (in fgRemoveEHTableEntry and liveness) but not consumed anywhere else. If it’s meant to guard heuristics that rely on IsLiveInOutOfHandler() (e.g., avoid setting DNER based on stale EH liveness after EH removal), consider wiring it into the relevant decision points; otherwise it should be removed to avoid accumulating dead state.
 bool fgBBVarSetsInited = false;
// Track how many artificial ref counts we've added to fgEntryBB (for OSR)

Comment threadsrc/coreclr/jit/lclvars.cpp
Comment threadsrc/coreclr/jit/liveness.cpp
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Pull request overview
Copilot reviewed 20 out of 20 changed files in this pull request and generated 3 comments.
Comment threadsrc/coreclr/jit/lower.cpp
Comment threadsrc/coreclr/jit/compiler.cpp
Comment threadsrc/coreclr/jit/liveness.cpp
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Copilot reviewed 20 out of 20 changed files in this pull request and generated 1 comment.
Comment threadsrc/coreclr/jit/gschecks.cpp

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Copilot wasn't able to review this pull request because it exceeds the maximum number of files (300). Try reducing the number of changed files and requesting a review from Copilot again.
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Sorry for the requests, accidentally rebased across a merge here...
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/azp run runtime-coreclr jitstress, runtime-coreclr libraries-jitstress
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cc @dotnet/jit-contrib PTAL @AndyAyersMS
Diffs.
This will be more important for future work once we start optimizing out IR that allows us to remove the EH we inserted for async.
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Copilot reviewed 20 out of 20 changed files in this pull request and generated 2 comments.
Comment threadsrc/coreclr/jit/lclvars.cpp
Comment threadsrc/coreclr/jit/lower.cpp
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injectUserscript("// Force GitHub README to respect dark mode\n(function() {\n var style = document.createElement('style');\n style.textContent = '\n .markdown-body {\n color-scheme: dark light;\n }\n .markdown-body pre { background: #161b22 !important; }\n .markdown-body code { background: rgba(110, 118, 129, 0.4) !important; }\n .markdown-body table th, .markdown-body table td { border-color: #30363d !important; }\n .markdown-body img { background: #0d1117; }\n .markdown-body blockquote { border-left-color: #8b949e; }\n .markdown-body hr { border-color: #30363d; }\n ';\n document.head.appendChild(style);\n})();", "GitHub Dark Mode README Fix");
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Skip to content
JIT: Decouple "DoNotEnregister" from liveness - #127932
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dotnet:mainfrom 
jakobbotsch:decouple-liveness-dner
May 18, 2026
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JIT: Decouple "DoNotEnregister" from liveness#127932
jakobbotsch merged 9 commits into
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jakobbotsch:decouple-liveness-dner
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Liveness was marking locals as DNER in various places, including when it found locals to be live into EH handlers.

DNER is sticky and cannot be unset, and we call liveness multiple times, so that made things hard to reason about and led to unnecessary DNER.
This showed up for runtime async functions. Even when we were able to optimize out the try-fault clauses inserted around the body we would often still end up with lvaAsyncContinuationArg unnecessarily DNER'd because we had already marked it as DNER during a previous liveness pass, when it was live into the fault handler.
This PR:
  • Resets lvLiveInOutOfHandler on all locals every time we run liveness
  • Moves all the DNER setting from liveness to LSRA and to lowering
  • Encapsulates lvLiveInOutOfHandler into LclVarDsc::IsLiveInOutOfHandler() and adds an assert(lvTracked) to this function, so it cannot be misused
  • Introduces a few updates to heuristics to use IsLiveInOutOfHandler() in addition to DNER
Diffs aren't all that great, but I think this is a good clean up on its own.
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Comment threadsrc/coreclr/jit/regalloc.cpp
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Pull request overview
This PR refactors CoreCLR JIT local liveness/EH handling so that EH “live-in/out-of-handler” state is recomputed each liveness run and lvDoNotEnregister (DNER) is no longer set by liveness, instead being set by regalloc / lowering.
Changes:
  • Recompute and encapsulate EH live-in/out state via LclVarDsc::IsLiveInOutOfHandler() and reset EH/must-init flags each liveness run.
  • Move DNER-setting decisions out of liveness into regalloc (checkForDNER) and lowering (lvSetEHVarsDoNotEnreg), and update heuristics to consult EH-liveness in addition to DNER.
  • Add Compiler::IsEHVarARegCandidate to centralize “EH write-thru candidate” logic and use it in multiple optimizations.
Reviewed changes
Copilot reviewed 20 out of 20 changed files in this pull request and generated 2 comments.
Show a summary per file
FileDescription
src/coreclr/jit/sideeffects.hUse IsLiveInOutOfHandler() for EH-related aliasing decisions.
src/coreclr/jit/regallocwasm.hDeclare checkForDNER for Wasm regalloc.
src/coreclr/jit/regallocwasm.cppCall checkForDNER and use encapsulated EH-live query.
src/coreclr/jit/regalloc.cppAdd checkForDNER and remove DNER-setting from isRegCandidate.
src/coreclr/jit/optimizer.cppSwitch EH-live checks to IsLiveInOutOfHandler().
src/coreclr/jit/morph.cppStop copying EH-live flag during implicit-byref arg retyping.
src/coreclr/jit/lsra.hDeclare checkForDNER for LSRA.
src/coreclr/jit/lsra.cppCall checkForDNER and use IsLiveInOutOfHandler() in LSRA logic.
src/coreclr/jit/lower.cppAdd lvSetEHVarsDoNotEnreg() call to support containment heuristics in lowering.
src/coreclr/jit/liveness.cppReset lvMustInit and EH-live state each liveness run; set EH-live without setting DNER.
src/coreclr/jit/lclvars.cppAdd lvSetEHVarsDoNotEnreg; remove lvaSetVarLiveInOutOfHandler; adjust DNER behavior.
src/coreclr/jit/jiteh.cppTrack when EH clauses are removed post-liveness.
src/coreclr/jit/inductionvariableopts.cppUpdate IV widening heuristics to consider EH-liveness independently of DNER.
src/coreclr/jit/gschecks.cppRemove direct clearing of EH-live flag on shadowing locals.
src/coreclr/jit/gentree.cppAdd Compiler::IsEHVarARegCandidate helper; update EH-live checks.
src/coreclr/jit/earlyprop.cppUpdate EH-live checks to IsLiveInOutOfHandler().
src/coreclr/jit/copyprop.cppAdjust “profitability” gating to compare expected enregistration status incl. EH-liveness.
src/coreclr/jit/compiler.hEncapsulate EH-live flag, add helper APIs, and add optRemovedEHClausesAfterLiveness.
src/coreclr/jit/compiler.cppUpdate enregister stats accounting to include PinningRef unconditionally.
src/coreclr/jit/codegenwasm.cppUpdate EH-live checks to IsLiveInOutOfHandler().
src/coreclr/jit/codegencommon.cppUpdate EH-live checks to IsLiveInOutOfHandler().
Comments suppressed due to low confidence (1)
src/coreclr/jit/compiler.h:5734
  • optRemovedEHClausesAfterLiveness is currently only set/reset (in fgRemoveEHTableEntry and liveness) but not consumed anywhere else. If it’s meant to guard heuristics that rely on IsLiveInOutOfHandler() (e.g., avoid setting DNER based on stale EH liveness after EH removal), consider wiring it into the relevant decision points; otherwise it should be removed to avoid accumulating dead state.
 bool fgBBVarSetsInited = false;
// Track how many artificial ref counts we've added to fgEntryBB (for OSR)

Comment threadsrc/coreclr/jit/lclvars.cpp
Comment threadsrc/coreclr/jit/liveness.cpp
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Copilot reviewed 20 out of 20 changed files in this pull request and generated 3 comments.
Comment threadsrc/coreclr/jit/lower.cpp
Comment threadsrc/coreclr/jit/compiler.cpp
Comment threadsrc/coreclr/jit/liveness.cpp
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Copilot reviewed 20 out of 20 changed files in this pull request and generated 1 comment.
Comment threadsrc/coreclr/jit/gschecks.cpp

This was referenced May 8, 2026

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Copilot wasn't able to review this pull request because it exceeds the maximum number of files (300). Try reducing the number of changed files and requesting a review from Copilot again.
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Sorry for the requests, accidentally rebased across a merge here...
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/azp run runtime-coreclr jitstress, runtime-coreclr libraries-jitstress
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cc @dotnet/jit-contrib PTAL @AndyAyersMS
Diffs.
This will be more important for future work once we start optimizing out IR that allows us to remove the EH we inserted for async.
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Pull request overview
Copilot reviewed 20 out of 20 changed files in this pull request and generated 2 comments.
Comment threadsrc/coreclr/jit/lclvars.cpp
Comment threadsrc/coreclr/jit/lower.cpp
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, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Highlight search terms from Google/DuckDuckGo/Bing referrer\n(function() {\n var ref = document.referrer;\n var terms = [];\n \n if (ref.includes('google.com') || ref.includes('duckduckgo.com') || ref.includes('bing.com')) {\n var url = new URL(ref);\n var q = url.searchParams.get('q') || url.searchParams.get('p');\n if (q) {\n terms = q.split(/\\s+/).filter(function(t) { return t.length > 2; });\n }\n }\n \n if (terms.length === 0) return;\n \n var style = document.createElement('style');\n style.textContent = '.userscript-highlight { background: #fbbf24; color: #1a1a2e; padding: 1px 3px; border-radius: 2px; }';\n document.head.appendChild(style);\n \n function highlight(node) {\n if (node.nodeType === 3) { // text node\n var text = node.textContent;\n var found = false;\n terms.forEach(function(term) {\n var regex = new RegExp('(' + term.replace(/[.*+?^${}()|[\\]\\\\]/g, '\\\\') + ')', 'gi');\n if (regex.test(text)) {\n found = true;\n var frag = document.createDocumentFragment();\n var parts = text.split(regex);\n parts.forEach(function(part, i) {\n if (i % 2 === 0) {\n frag.appendChild(document.createTextNode(part));\n } else {\n var span = document.createElement('span');\n span.className = 'userscript-highlight';\n span.textContent = part;\n frag.appendChild(span);\n }\n });\n node.parentNode.replaceChild(frag, node);\n }\n });\n } else if (node.nodeType === 1 && node.childNodes) { // element\n var skipTags = ['SCRIPT', 'STYLE', 'NOSCRIPT', 'TEXTAREA', 'INPUT', 'SELECT'];\n if (!skipTags.includes(node.tagName)) {\n Array.from(node.childNodes).forEach(highlight);\n }\n }\n }\n \n highlight(document.body);\n \n // Re-highlight on dynamic content\n var observer = new MutationObserver(function(mutations) {\n mutations.forEach(function(m) {\n m.addedNodes.forEach(function(node) {\n if (node.nodeType === 1 || node.nodeType === 3) highlight(node);\n });\n });\n });\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Highlight Search Terms");
}
} catch(__e) { console.warn('[Userscript:Highlight Search Terms]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

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JIT: Decouple "DoNotEnregister" from liveness - #127932
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jakobbotsch:decouple-liveness-dner
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Merged
JIT: Decouple "DoNotEnregister" from liveness#127932
jakobbotsch merged 9 commits into
dotnet:mainfrom 
jakobbotsch:decouple-liveness-dner
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Liveness was marking locals as DNER in various places, including when it found locals to be live into EH handlers.

DNER is sticky and cannot be unset, and we call liveness multiple times, so that made things hard to reason about and led to unnecessary DNER.
This showed up for runtime async functions. Even when we were able to optimize out the try-fault clauses inserted around the body we would often still end up with lvaAsyncContinuationArg unnecessarily DNER'd because we had already marked it as DNER during a previous liveness pass, when it was live into the fault handler.
This PR:
  • Resets lvLiveInOutOfHandler on all locals every time we run liveness
  • Moves all the DNER setting from liveness to LSRA and to lowering
  • Encapsulates lvLiveInOutOfHandler into LclVarDsc::IsLiveInOutOfHandler() and adds an assert(lvTracked) to this function, so it cannot be misused
  • Introduces a few updates to heuristics to use IsLiveInOutOfHandler() in addition to DNER
Diffs aren't all that great, but I think this is a good clean up on its own.
CopilotAI
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Comment threadsrc/coreclr/jit/compiler.cpp
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Comment threadsrc/coreclr/jit/lclvars.cpp
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Comment threadsrc/coreclr/jit/regalloc.cpp
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Pull request overview
This PR refactors CoreCLR JIT local liveness/EH handling so that EH “live-in/out-of-handler” state is recomputed each liveness run and lvDoNotEnregister (DNER) is no longer set by liveness, instead being set by regalloc / lowering.
Changes:
  • Recompute and encapsulate EH live-in/out state via LclVarDsc::IsLiveInOutOfHandler() and reset EH/must-init flags each liveness run.
  • Move DNER-setting decisions out of liveness into regalloc (checkForDNER) and lowering (lvSetEHVarsDoNotEnreg), and update heuristics to consult EH-liveness in addition to DNER.
  • Add Compiler::IsEHVarARegCandidate to centralize “EH write-thru candidate” logic and use it in multiple optimizations.
Reviewed changes
Copilot reviewed 20 out of 20 changed files in this pull request and generated 2 comments.
Show a summary per file
FileDescription
src/coreclr/jit/sideeffects.hUse IsLiveInOutOfHandler() for EH-related aliasing decisions.
src/coreclr/jit/regallocwasm.hDeclare checkForDNER for Wasm regalloc.
src/coreclr/jit/regallocwasm.cppCall checkForDNER and use encapsulated EH-live query.
src/coreclr/jit/regalloc.cppAdd checkForDNER and remove DNER-setting from isRegCandidate.
src/coreclr/jit/optimizer.cppSwitch EH-live checks to IsLiveInOutOfHandler().
src/coreclr/jit/morph.cppStop copying EH-live flag during implicit-byref arg retyping.
src/coreclr/jit/lsra.hDeclare checkForDNER for LSRA.
src/coreclr/jit/lsra.cppCall checkForDNER and use IsLiveInOutOfHandler() in LSRA logic.
src/coreclr/jit/lower.cppAdd lvSetEHVarsDoNotEnreg() call to support containment heuristics in lowering.
src/coreclr/jit/liveness.cppReset lvMustInit and EH-live state each liveness run; set EH-live without setting DNER.
src/coreclr/jit/lclvars.cppAdd lvSetEHVarsDoNotEnreg; remove lvaSetVarLiveInOutOfHandler; adjust DNER behavior.
src/coreclr/jit/jiteh.cppTrack when EH clauses are removed post-liveness.
src/coreclr/jit/inductionvariableopts.cppUpdate IV widening heuristics to consider EH-liveness independently of DNER.
src/coreclr/jit/gschecks.cppRemove direct clearing of EH-live flag on shadowing locals.
src/coreclr/jit/gentree.cppAdd Compiler::IsEHVarARegCandidate helper; update EH-live checks.
src/coreclr/jit/earlyprop.cppUpdate EH-live checks to IsLiveInOutOfHandler().
src/coreclr/jit/copyprop.cppAdjust “profitability” gating to compare expected enregistration status incl. EH-liveness.
src/coreclr/jit/compiler.hEncapsulate EH-live flag, add helper APIs, and add optRemovedEHClausesAfterLiveness.
src/coreclr/jit/compiler.cppUpdate enregister stats accounting to include PinningRef unconditionally.
src/coreclr/jit/codegenwasm.cppUpdate EH-live checks to IsLiveInOutOfHandler().
src/coreclr/jit/codegencommon.cppUpdate EH-live checks to IsLiveInOutOfHandler().
Comments suppressed due to low confidence (1)
src/coreclr/jit/compiler.h:5734
  • optRemovedEHClausesAfterLiveness is currently only set/reset (in fgRemoveEHTableEntry and liveness) but not consumed anywhere else. If it’s meant to guard heuristics that rely on IsLiveInOutOfHandler() (e.g., avoid setting DNER based on stale EH liveness after EH removal), consider wiring it into the relevant decision points; otherwise it should be removed to avoid accumulating dead state.
 bool fgBBVarSetsInited = false;
// Track how many artificial ref counts we've added to fgEntryBB (for OSR)

Comment threadsrc/coreclr/jit/lclvars.cpp
Comment threadsrc/coreclr/jit/liveness.cpp
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Pull request overview
Copilot reviewed 20 out of 20 changed files in this pull request and generated 3 comments.
Comment threadsrc/coreclr/jit/lower.cpp
Comment threadsrc/coreclr/jit/compiler.cpp
Comment threadsrc/coreclr/jit/liveness.cpp
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Pull request overview
Copilot reviewed 20 out of 20 changed files in this pull request and generated 1 comment.
Comment threadsrc/coreclr/jit/gschecks.cpp

This was referenced May 8, 2026

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Copilot wasn't able to review this pull request because it exceeds the maximum number of files (300). Try reducing the number of changed files and requesting a review from Copilot again.
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Sorry for the requests, accidentally rebased across a merge here...
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/azp run runtime-coreclr jitstress, runtime-coreclr libraries-jitstress
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cc @dotnet/jit-contrib PTAL @AndyAyersMS
Diffs.
This will be more important for future work once we start optimizing out IR that allows us to remove the EH we inserted for async.
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Pull request overview
Copilot reviewed 20 out of 20 changed files in this pull request and generated 2 comments.
Comment threadsrc/coreclr/jit/lclvars.cpp
Comment threadsrc/coreclr/jit/lower.cpp
@jakobbotsch
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, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Strip utm_, fbclid, gclid, etc. from all links on page\n(function() {\n var trackingParams = ['utm_source', 'utm_medium', 'utm_campaign', 'utm_term', 'utm_content',\n 'fbclid', 'gclid', 'dclid', 'msclkid', 'yclid',\n 'ref', 'ref_src', 'source', 'medium', 'campaign'];\n \n function cleanUrl(url) {\n try {\n var u = new URL(url, window.location.origin);\n var changed = false;\n trackingParams.forEach(function(p) {\n if (u.searchParams.has(p)) {\n u.searchParams.delete(p);\n changed = true;\n }\n });\n return changed ? u.toString() : url;\n } catch (e) {\n return url;\n }\n }\n \n function cleanLinks() {\n document.querySelectorAll('a[href]').forEach(function(a) {\n var clean = cleanUrl(a.href);\n if (clean !== a.href) a.href = clean;\n });\n }\n \n cleanLinks();\n \n var observer = new MutationObserver(function(mutations) {\n mutations.forEach(function(m) {\n m.addedNodes.forEach(function(node) {\n if (node.nodeType === 1) {\n if (node.tagName === 'A') cleanLinks();\n node.querySelectorAll('a[href]').forEach(function(a) {\n var clean = cleanUrl(a.href);\n if (clean !== a.href) a.href = clean;\n });\n }\n });\n });\n });\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Remove Tracking Parameters from Links");
}
} catch(__e) { console.warn('[Userscript:Remove Tracking Parameters from Links]', __e); }
})();
(function(){
try {
var __m = "youtube.com";
var __re = new RegExp('^' + "youtube\\.com" + '

Skip to content
JIT: Decouple "DoNotEnregister" from liveness - #127932
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jakobbotsch merged 9 commits into
dotnet:mainfrom 
jakobbotsch:decouple-liveness-dner
May 18, 2026
Merged
JIT: Decouple "DoNotEnregister" from liveness#127932
jakobbotsch merged 9 commits into
dotnet:mainfrom 
jakobbotsch:decouple-liveness-dner
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Liveness was marking locals as DNER in various places, including when it found locals to be live into EH handlers.

DNER is sticky and cannot be unset, and we call liveness multiple times, so that made things hard to reason about and led to unnecessary DNER.
This showed up for runtime async functions. Even when we were able to optimize out the try-fault clauses inserted around the body we would often still end up with lvaAsyncContinuationArg unnecessarily DNER'd because we had already marked it as DNER during a previous liveness pass, when it was live into the fault handler.
This PR:
  • Resets lvLiveInOutOfHandler on all locals every time we run liveness
  • Moves all the DNER setting from liveness to LSRA and to lowering
  • Encapsulates lvLiveInOutOfHandler into LclVarDsc::IsLiveInOutOfHandler() and adds an assert(lvTracked) to this function, so it cannot be misused
  • Introduces a few updates to heuristics to use IsLiveInOutOfHandler() in addition to DNER
Diffs aren't all that great, but I think this is a good clean up on its own.
CopilotAI
review requested due to automatic review settings
May 7, 2026 19:15
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View reviewed changes
Comment threadsrc/coreclr/jit/compiler.cpp
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Comment threadsrc/coreclr/jit/lclvars.cpp
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Comment threadsrc/coreclr/jit/regalloc.cpp
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Pull request overview
This PR refactors CoreCLR JIT local liveness/EH handling so that EH “live-in/out-of-handler” state is recomputed each liveness run and lvDoNotEnregister (DNER) is no longer set by liveness, instead being set by regalloc / lowering.
Changes:
  • Recompute and encapsulate EH live-in/out state via LclVarDsc::IsLiveInOutOfHandler() and reset EH/must-init flags each liveness run.
  • Move DNER-setting decisions out of liveness into regalloc (checkForDNER) and lowering (lvSetEHVarsDoNotEnreg), and update heuristics to consult EH-liveness in addition to DNER.
  • Add Compiler::IsEHVarARegCandidate to centralize “EH write-thru candidate” logic and use it in multiple optimizations.
Reviewed changes
Copilot reviewed 20 out of 20 changed files in this pull request and generated 2 comments.
Show a summary per file
FileDescription
src/coreclr/jit/sideeffects.hUse IsLiveInOutOfHandler() for EH-related aliasing decisions.
src/coreclr/jit/regallocwasm.hDeclare checkForDNER for Wasm regalloc.
src/coreclr/jit/regallocwasm.cppCall checkForDNER and use encapsulated EH-live query.
src/coreclr/jit/regalloc.cppAdd checkForDNER and remove DNER-setting from isRegCandidate.
src/coreclr/jit/optimizer.cppSwitch EH-live checks to IsLiveInOutOfHandler().
src/coreclr/jit/morph.cppStop copying EH-live flag during implicit-byref arg retyping.
src/coreclr/jit/lsra.hDeclare checkForDNER for LSRA.
src/coreclr/jit/lsra.cppCall checkForDNER and use IsLiveInOutOfHandler() in LSRA logic.
src/coreclr/jit/lower.cppAdd lvSetEHVarsDoNotEnreg() call to support containment heuristics in lowering.
src/coreclr/jit/liveness.cppReset lvMustInit and EH-live state each liveness run; set EH-live without setting DNER.
src/coreclr/jit/lclvars.cppAdd lvSetEHVarsDoNotEnreg; remove lvaSetVarLiveInOutOfHandler; adjust DNER behavior.
src/coreclr/jit/jiteh.cppTrack when EH clauses are removed post-liveness.
src/coreclr/jit/inductionvariableopts.cppUpdate IV widening heuristics to consider EH-liveness independently of DNER.
src/coreclr/jit/gschecks.cppRemove direct clearing of EH-live flag on shadowing locals.
src/coreclr/jit/gentree.cppAdd Compiler::IsEHVarARegCandidate helper; update EH-live checks.
src/coreclr/jit/earlyprop.cppUpdate EH-live checks to IsLiveInOutOfHandler().
src/coreclr/jit/copyprop.cppAdjust “profitability” gating to compare expected enregistration status incl. EH-liveness.
src/coreclr/jit/compiler.hEncapsulate EH-live flag, add helper APIs, and add optRemovedEHClausesAfterLiveness.
src/coreclr/jit/compiler.cppUpdate enregister stats accounting to include PinningRef unconditionally.
src/coreclr/jit/codegenwasm.cppUpdate EH-live checks to IsLiveInOutOfHandler().
src/coreclr/jit/codegencommon.cppUpdate EH-live checks to IsLiveInOutOfHandler().
Comments suppressed due to low confidence (1)
src/coreclr/jit/compiler.h:5734
  • optRemovedEHClausesAfterLiveness is currently only set/reset (in fgRemoveEHTableEntry and liveness) but not consumed anywhere else. If it’s meant to guard heuristics that rely on IsLiveInOutOfHandler() (e.g., avoid setting DNER based on stale EH liveness after EH removal), consider wiring it into the relevant decision points; otherwise it should be removed to avoid accumulating dead state.
 bool fgBBVarSetsInited = false;
// Track how many artificial ref counts we've added to fgEntryBB (for OSR)

Comment threadsrc/coreclr/jit/lclvars.cpp
Comment threadsrc/coreclr/jit/liveness.cpp
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Copilot reviewed 20 out of 20 changed files in this pull request and generated 3 comments.
Comment threadsrc/coreclr/jit/lower.cpp
Comment threadsrc/coreclr/jit/compiler.cpp
Comment threadsrc/coreclr/jit/liveness.cpp
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Copilot reviewed 20 out of 20 changed files in this pull request and generated 1 comment.
Comment threadsrc/coreclr/jit/gschecks.cpp

This was referenced May 8, 2026

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Copilot wasn't able to review this pull request because it exceeds the maximum number of files (300). Try reducing the number of changed files and requesting a review from Copilot again.
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Sorry for the requests, accidentally rebased across a merge here...
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/azp run runtime-coreclr jitstress, runtime-coreclr libraries-jitstress
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cc @dotnet/jit-contrib PTAL @AndyAyersMS
Diffs.
This will be more important for future work once we start optimizing out IR that allows us to remove the EH we inserted for async.
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Copilot reviewed 20 out of 20 changed files in this pull request and generated 2 comments.
Comment threadsrc/coreclr/jit/lclvars.cpp
Comment threadsrc/coreclr/jit/lower.cpp
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, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Auto-enable theater mode on YouTube\n(function() {\n function tryTheater() {\n var btn = document.querySelector('button[aria-label=\"Theater mode\"], ytd-player #player button[title=\"Theater mode\"]');\n if (btn && !btn.classList.contains('activated')) {\n btn.click();\n }\n }\n \n // Try immediately\n tryTheater();\n \n // Try after navigation (SPA)\n var lastUrl = location.href;\n setInterval(function() {\n if (location.href !== lastUrl) {\n lastUrl = location.href;\n setTimeout(tryTheater, 500);\n }\n }, 1000);\n \n // Also try on player load\n var observer = new MutationObserver(tryTheater);\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "YouTube Theater Mode Default");
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JIT: Decouple "DoNotEnregister" from liveness - #127932
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jakobbotsch:decouple-liveness-dner
May 18, 2026
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JIT: Decouple "DoNotEnregister" from liveness#127932
jakobbotsch merged 9 commits into
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jakobbotsch:decouple-liveness-dner
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Liveness was marking locals as DNER in various places, including when it found locals to be live into EH handlers.

DNER is sticky and cannot be unset, and we call liveness multiple times, so that made things hard to reason about and led to unnecessary DNER.
This showed up for runtime async functions. Even when we were able to optimize out the try-fault clauses inserted around the body we would often still end up with lvaAsyncContinuationArg unnecessarily DNER'd because we had already marked it as DNER during a previous liveness pass, when it was live into the fault handler.
This PR:
  • Resets lvLiveInOutOfHandler on all locals every time we run liveness
  • Moves all the DNER setting from liveness to LSRA and to lowering
  • Encapsulates lvLiveInOutOfHandler into LclVarDsc::IsLiveInOutOfHandler() and adds an assert(lvTracked) to this function, so it cannot be misused
  • Introduces a few updates to heuristics to use IsLiveInOutOfHandler() in addition to DNER
Diffs aren't all that great, but I think this is a good clean up on its own.
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Comment threadsrc/coreclr/jit/compiler.cpp
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Comment threadsrc/coreclr/jit/lclvars.cpp
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Comment threadsrc/coreclr/jit/regalloc.cpp
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Pull request overview
This PR refactors CoreCLR JIT local liveness/EH handling so that EH “live-in/out-of-handler” state is recomputed each liveness run and lvDoNotEnregister (DNER) is no longer set by liveness, instead being set by regalloc / lowering.
Changes:
  • Recompute and encapsulate EH live-in/out state via LclVarDsc::IsLiveInOutOfHandler() and reset EH/must-init flags each liveness run.
  • Move DNER-setting decisions out of liveness into regalloc (checkForDNER) and lowering (lvSetEHVarsDoNotEnreg), and update heuristics to consult EH-liveness in addition to DNER.
  • Add Compiler::IsEHVarARegCandidate to centralize “EH write-thru candidate” logic and use it in multiple optimizations.
Reviewed changes
Copilot reviewed 20 out of 20 changed files in this pull request and generated 2 comments.
Show a summary per file
FileDescription
src/coreclr/jit/sideeffects.hUse IsLiveInOutOfHandler() for EH-related aliasing decisions.
src/coreclr/jit/regallocwasm.hDeclare checkForDNER for Wasm regalloc.
src/coreclr/jit/regallocwasm.cppCall checkForDNER and use encapsulated EH-live query.
src/coreclr/jit/regalloc.cppAdd checkForDNER and remove DNER-setting from isRegCandidate.
src/coreclr/jit/optimizer.cppSwitch EH-live checks to IsLiveInOutOfHandler().
src/coreclr/jit/morph.cppStop copying EH-live flag during implicit-byref arg retyping.
src/coreclr/jit/lsra.hDeclare checkForDNER for LSRA.
src/coreclr/jit/lsra.cppCall checkForDNER and use IsLiveInOutOfHandler() in LSRA logic.
src/coreclr/jit/lower.cppAdd lvSetEHVarsDoNotEnreg() call to support containment heuristics in lowering.
src/coreclr/jit/liveness.cppReset lvMustInit and EH-live state each liveness run; set EH-live without setting DNER.
src/coreclr/jit/lclvars.cppAdd lvSetEHVarsDoNotEnreg; remove lvaSetVarLiveInOutOfHandler; adjust DNER behavior.
src/coreclr/jit/jiteh.cppTrack when EH clauses are removed post-liveness.
src/coreclr/jit/inductionvariableopts.cppUpdate IV widening heuristics to consider EH-liveness independently of DNER.
src/coreclr/jit/gschecks.cppRemove direct clearing of EH-live flag on shadowing locals.
src/coreclr/jit/gentree.cppAdd Compiler::IsEHVarARegCandidate helper; update EH-live checks.
src/coreclr/jit/earlyprop.cppUpdate EH-live checks to IsLiveInOutOfHandler().
src/coreclr/jit/copyprop.cppAdjust “profitability” gating to compare expected enregistration status incl. EH-liveness.
src/coreclr/jit/compiler.hEncapsulate EH-live flag, add helper APIs, and add optRemovedEHClausesAfterLiveness.
src/coreclr/jit/compiler.cppUpdate enregister stats accounting to include PinningRef unconditionally.
src/coreclr/jit/codegenwasm.cppUpdate EH-live checks to IsLiveInOutOfHandler().
src/coreclr/jit/codegencommon.cppUpdate EH-live checks to IsLiveInOutOfHandler().
Comments suppressed due to low confidence (1)
src/coreclr/jit/compiler.h:5734
  • optRemovedEHClausesAfterLiveness is currently only set/reset (in fgRemoveEHTableEntry and liveness) but not consumed anywhere else. If it’s meant to guard heuristics that rely on IsLiveInOutOfHandler() (e.g., avoid setting DNER based on stale EH liveness after EH removal), consider wiring it into the relevant decision points; otherwise it should be removed to avoid accumulating dead state.
 bool fgBBVarSetsInited = false;
// Track how many artificial ref counts we've added to fgEntryBB (for OSR)

Comment threadsrc/coreclr/jit/lclvars.cpp
Comment threadsrc/coreclr/jit/liveness.cpp
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Pull request overview
Copilot reviewed 20 out of 20 changed files in this pull request and generated 3 comments.
Comment threadsrc/coreclr/jit/lower.cpp
Comment threadsrc/coreclr/jit/compiler.cpp
Comment threadsrc/coreclr/jit/liveness.cpp
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Pull request overview
Copilot reviewed 20 out of 20 changed files in this pull request and generated 1 comment.
Comment threadsrc/coreclr/jit/gschecks.cpp

This was referenced May 8, 2026

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Copilot wasn't able to review this pull request because it exceeds the maximum number of files (300). Try reducing the number of changed files and requesting a review from Copilot again.
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Sorry for the requests, accidentally rebased across a merge here...
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/azp run runtime-coreclr jitstress, runtime-coreclr libraries-jitstress
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cc @dotnet/jit-contrib PTAL @AndyAyersMS
Diffs.
This will be more important for future work once we start optimizing out IR that allows us to remove the EH we inserted for async.
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Pull request overview
Copilot reviewed 20 out of 20 changed files in this pull request and generated 2 comments.
Comment threadsrc/coreclr/jit/lclvars.cpp
Comment threadsrc/coreclr/jit/lower.cpp
@jakobbotsch
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, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Remove or un-stick sticky/fixed headers that block content\n(function() {\n function unstick() {\n document.querySelectorAll('header, nav, [role=\"banner\"], .header, .navbar, .sticky, .fixed-top, [style*=\"position: fixed\"], [style*=\"position:sticky\"]').forEach(function(el) {\n if (el.style.position === 'fixed' || el.style.position === 'sticky' || \n getComputedStyle(el).position === 'fixed' || getComputedStyle(el).position === 'sticky') {\n el.style.position = 'static';\n el.style.top = 'auto';\n el.style.zIndex = 'auto';\n }\n });\n }\n \n unstick();\n \n var observer = new MutationObserver(unstick);\n observer.observe(document.body, { childList: true, subtree: true, attributes: true, attributeFilter: ['style', 'class'] });\n})();", "Kill Sticky Headers");
}
} catch(__e) { console.warn('[Userscript:Kill Sticky Headers]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

Skip to content
JIT: Decouple "DoNotEnregister" from liveness - #127932
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jakobbotsch merged 9 commits into
dotnet:mainfrom 
jakobbotsch:decouple-liveness-dner
May 18, 2026
Merged
JIT: Decouple "DoNotEnregister" from liveness#127932
jakobbotsch merged 9 commits into
dotnet:mainfrom 
jakobbotsch:decouple-liveness-dner
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Liveness was marking locals as DNER in various places, including when it found locals to be live into EH handlers.

DNER is sticky and cannot be unset, and we call liveness multiple times, so that made things hard to reason about and led to unnecessary DNER.
This showed up for runtime async functions. Even when we were able to optimize out the try-fault clauses inserted around the body we would often still end up with lvaAsyncContinuationArg unnecessarily DNER'd because we had already marked it as DNER during a previous liveness pass, when it was live into the fault handler.
This PR:
  • Resets lvLiveInOutOfHandler on all locals every time we run liveness
  • Moves all the DNER setting from liveness to LSRA and to lowering
  • Encapsulates lvLiveInOutOfHandler into LclVarDsc::IsLiveInOutOfHandler() and adds an assert(lvTracked) to this function, so it cannot be misused
  • Introduces a few updates to heuristics to use IsLiveInOutOfHandler() in addition to DNER
Diffs aren't all that great, but I think this is a good clean up on its own.
CopilotAI
review requested due to automatic review settings
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Comment threadsrc/coreclr/jit/lclvars.cpp
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Comment threadsrc/coreclr/jit/regalloc.cpp
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Pull request overview
This PR refactors CoreCLR JIT local liveness/EH handling so that EH “live-in/out-of-handler” state is recomputed each liveness run and lvDoNotEnregister (DNER) is no longer set by liveness, instead being set by regalloc / lowering.
Changes:
  • Recompute and encapsulate EH live-in/out state via LclVarDsc::IsLiveInOutOfHandler() and reset EH/must-init flags each liveness run.
  • Move DNER-setting decisions out of liveness into regalloc (checkForDNER) and lowering (lvSetEHVarsDoNotEnreg), and update heuristics to consult EH-liveness in addition to DNER.
  • Add Compiler::IsEHVarARegCandidate to centralize “EH write-thru candidate” logic and use it in multiple optimizations.
Reviewed changes
Copilot reviewed 20 out of 20 changed files in this pull request and generated 2 comments.
Show a summary per file
FileDescription
src/coreclr/jit/sideeffects.hUse IsLiveInOutOfHandler() for EH-related aliasing decisions.
src/coreclr/jit/regallocwasm.hDeclare checkForDNER for Wasm regalloc.
src/coreclr/jit/regallocwasm.cppCall checkForDNER and use encapsulated EH-live query.
src/coreclr/jit/regalloc.cppAdd checkForDNER and remove DNER-setting from isRegCandidate.
src/coreclr/jit/optimizer.cppSwitch EH-live checks to IsLiveInOutOfHandler().
src/coreclr/jit/morph.cppStop copying EH-live flag during implicit-byref arg retyping.
src/coreclr/jit/lsra.hDeclare checkForDNER for LSRA.
src/coreclr/jit/lsra.cppCall checkForDNER and use IsLiveInOutOfHandler() in LSRA logic.
src/coreclr/jit/lower.cppAdd lvSetEHVarsDoNotEnreg() call to support containment heuristics in lowering.
src/coreclr/jit/liveness.cppReset lvMustInit and EH-live state each liveness run; set EH-live without setting DNER.
src/coreclr/jit/lclvars.cppAdd lvSetEHVarsDoNotEnreg; remove lvaSetVarLiveInOutOfHandler; adjust DNER behavior.
src/coreclr/jit/jiteh.cppTrack when EH clauses are removed post-liveness.
src/coreclr/jit/inductionvariableopts.cppUpdate IV widening heuristics to consider EH-liveness independently of DNER.
src/coreclr/jit/gschecks.cppRemove direct clearing of EH-live flag on shadowing locals.
src/coreclr/jit/gentree.cppAdd Compiler::IsEHVarARegCandidate helper; update EH-live checks.
src/coreclr/jit/earlyprop.cppUpdate EH-live checks to IsLiveInOutOfHandler().
src/coreclr/jit/copyprop.cppAdjust “profitability” gating to compare expected enregistration status incl. EH-liveness.
src/coreclr/jit/compiler.hEncapsulate EH-live flag, add helper APIs, and add optRemovedEHClausesAfterLiveness.
src/coreclr/jit/compiler.cppUpdate enregister stats accounting to include PinningRef unconditionally.
src/coreclr/jit/codegenwasm.cppUpdate EH-live checks to IsLiveInOutOfHandler().
src/coreclr/jit/codegencommon.cppUpdate EH-live checks to IsLiveInOutOfHandler().
Comments suppressed due to low confidence (1)
src/coreclr/jit/compiler.h:5734
  • optRemovedEHClausesAfterLiveness is currently only set/reset (in fgRemoveEHTableEntry and liveness) but not consumed anywhere else. If it’s meant to guard heuristics that rely on IsLiveInOutOfHandler() (e.g., avoid setting DNER based on stale EH liveness after EH removal), consider wiring it into the relevant decision points; otherwise it should be removed to avoid accumulating dead state.
 bool fgBBVarSetsInited = false;
// Track how many artificial ref counts we've added to fgEntryBB (for OSR)

Comment threadsrc/coreclr/jit/lclvars.cpp
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Comment threadsrc/coreclr/jit/gschecks.cpp

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Sorry for the requests, accidentally rebased across a merge here...
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/azp run runtime-coreclr jitstress, runtime-coreclr libraries-jitstress
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cc @dotnet/jit-contrib PTAL @AndyAyersMS
Diffs.
This will be more important for future work once we start optimizing out IR that allows us to remove the EH we inserted for async.
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Pull request overview
Copilot reviewed 20 out of 20 changed files in this pull request and generated 2 comments.
Comment threadsrc/coreclr/jit/lclvars.cpp
Comment threadsrc/coreclr/jit/lower.cpp
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, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Universal Dark Mode - works on any site\n(function() {\n var enabled = true;\n \n function applyDarkMode() {\n if (!enabled) return;\n \n // Create style element if it doesn't exist\n var style = document.getElementById('universal-dark-mode-style');\n if (!style) {\n style = document.createElement('style');\n style.id = 'universal-dark-mode-style';\n document.head.appendChild(style);\n }\n \n // Dark mode CSS - inverts colors but preserves images/video\n style.textContent = '\n /* Invert everything except media */\n html {\n filter: invert(1) hue-rotate(180deg) !important;\n background: #1a1a2e !important;\n }\n \n /* Restore images, videos, iframes, canvas */\n img, video, iframe, canvas, svg, picture, [style*=\"background-image\"] {\n filter: invert(1) hue-rotate(180deg) !important;\n }\n \n /* Preserve specific elements that should not be inverted */\n .no-dark-mode, .no-dark-mode *,\n [data-theme=\"light\"], [data-theme=\"light\"],\n .ace_editor, .ace_editor *,\n .CodeMirror, .CodeMirror *,\n .monaco-editor, .monaco-editor *,\n .markdown-body pre, .markdown-body pre *,\n .highlight, .highlight *,\n pre code, pre code * {\n filter: none !important;\n }\n \n /* Fix common UI elements */\n .modal, .popup, .dropdown-menu, .tooltip, .popover {\n filter: invert(1) hue-rotate(180deg) !important;\n background: #2d2d44 !important;\n border-color: #444 !important;\n }\n \n /* Scrollbars */\n ::-webkit-scrollbar { background: #1a1a2e !important; }\n ::-webkit-scrollbar-thumb { background: #444 !important; }\n ::-webkit-scrollbar-thumb:hover { background: #555 !important; }\n \n /* Selection */\n ::selection { background: #4ecdc4 !important; color: #1a1a2e !important; }\n ::-moz-selection { background: #4ecdc4 !important; color: #1a1a2e !important; }\n ';\n }\n \n function removeDarkMode() {\n var style = document.getElementById('universal-dark-mode-style');\n if (style) style.remove();\n }\n \n // Toggle with Alt+Shift+D\n document.addEventListener('keydown', function(e) {\n if (e.altKey && e.shiftKey && e.key === 'D') {\n e.preventDefault();\n enabled = !enabled;\n if (enabled) {\n applyDarkMode();\n console.log('[Universal Dark Mode] Enabled');\n } else {\n removeDarkMode();\n console.log('[Universal Dark Mode] Disabled');\n }\n }\n });\n \n // Apply on load\n applyDarkMode();\n \n // Re-apply on dynamic content\n var observer = new MutationObserver(function(mutations) {\n if (enabled && !document.getElementById('universal-dark-mode-style')) {\n applyDarkMode();\n }\n });\n observer.observe(document.head, { childList: true });\n \n console.log('[Universal Dark Mode] Loaded - Press Alt+Shift+D to toggle');\n})();", "Universal Dark Mode");
}
} catch(__e) { console.warn('[Userscript:Universal Dark Mode]', __e); }
})();
})();

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JIT: Decouple "DoNotEnregister" from liveness - #127932
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jakobbotsch:decouple-liveness-dner
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JIT: Decouple "DoNotEnregister" from liveness#127932
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jakobbotsch:decouple-liveness-dner
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Liveness was marking locals as DNER in various places, including when it found locals to be live into EH handlers.

DNER is sticky and cannot be unset, and we call liveness multiple times, so that made things hard to reason about and led to unnecessary DNER.
This showed up for runtime async functions. Even when we were able to optimize out the try-fault clauses inserted around the body we would often still end up with lvaAsyncContinuationArg unnecessarily DNER'd because we had already marked it as DNER during a previous liveness pass, when it was live into the fault handler.
This PR:
  • Resets lvLiveInOutOfHandler on all locals every time we run liveness
  • Moves all the DNER setting from liveness to LSRA and to lowering
  • Encapsulates lvLiveInOutOfHandler into LclVarDsc::IsLiveInOutOfHandler() and adds an assert(lvTracked) to this function, so it cannot be misused
  • Introduces a few updates to heuristics to use IsLiveInOutOfHandler() in addition to DNER
Diffs aren't all that great, but I think this is a good clean up on its own.
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Comment threadsrc/coreclr/jit/lclvars.cpp
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Comment threadsrc/coreclr/jit/regalloc.cpp
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Pull request overview
This PR refactors CoreCLR JIT local liveness/EH handling so that EH “live-in/out-of-handler” state is recomputed each liveness run and lvDoNotEnregister (DNER) is no longer set by liveness, instead being set by regalloc / lowering.
Changes:
  • Recompute and encapsulate EH live-in/out state via LclVarDsc::IsLiveInOutOfHandler() and reset EH/must-init flags each liveness run.
  • Move DNER-setting decisions out of liveness into regalloc (checkForDNER) and lowering (lvSetEHVarsDoNotEnreg), and update heuristics to consult EH-liveness in addition to DNER.
  • Add Compiler::IsEHVarARegCandidate to centralize “EH write-thru candidate” logic and use it in multiple optimizations.
Reviewed changes
Copilot reviewed 20 out of 20 changed files in this pull request and generated 2 comments.
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FileDescription
src/coreclr/jit/sideeffects.hUse IsLiveInOutOfHandler() for EH-related aliasing decisions.
src/coreclr/jit/regallocwasm.hDeclare checkForDNER for Wasm regalloc.
src/coreclr/jit/regallocwasm.cppCall checkForDNER and use encapsulated EH-live query.
src/coreclr/jit/regalloc.cppAdd checkForDNER and remove DNER-setting from isRegCandidate.
src/coreclr/jit/optimizer.cppSwitch EH-live checks to IsLiveInOutOfHandler().
src/coreclr/jit/morph.cppStop copying EH-live flag during implicit-byref arg retyping.
src/coreclr/jit/lsra.hDeclare checkForDNER for LSRA.
src/coreclr/jit/lsra.cppCall checkForDNER and use IsLiveInOutOfHandler() in LSRA logic.
src/coreclr/jit/lower.cppAdd lvSetEHVarsDoNotEnreg() call to support containment heuristics in lowering.
src/coreclr/jit/liveness.cppReset lvMustInit and EH-live state each liveness run; set EH-live without setting DNER.
src/coreclr/jit/lclvars.cppAdd lvSetEHVarsDoNotEnreg; remove lvaSetVarLiveInOutOfHandler; adjust DNER behavior.
src/coreclr/jit/jiteh.cppTrack when EH clauses are removed post-liveness.
src/coreclr/jit/inductionvariableopts.cppUpdate IV widening heuristics to consider EH-liveness independently of DNER.
src/coreclr/jit/gschecks.cppRemove direct clearing of EH-live flag on shadowing locals.
src/coreclr/jit/gentree.cppAdd Compiler::IsEHVarARegCandidate helper; update EH-live checks.
src/coreclr/jit/earlyprop.cppUpdate EH-live checks to IsLiveInOutOfHandler().
src/coreclr/jit/copyprop.cppAdjust “profitability” gating to compare expected enregistration status incl. EH-liveness.
src/coreclr/jit/compiler.hEncapsulate EH-live flag, add helper APIs, and add optRemovedEHClausesAfterLiveness.
src/coreclr/jit/compiler.cppUpdate enregister stats accounting to include PinningRef unconditionally.
src/coreclr/jit/codegenwasm.cppUpdate EH-live checks to IsLiveInOutOfHandler().
src/coreclr/jit/codegencommon.cppUpdate EH-live checks to IsLiveInOutOfHandler().
Comments suppressed due to low confidence (1)
src/coreclr/jit/compiler.h:5734
  • optRemovedEHClausesAfterLiveness is currently only set/reset (in fgRemoveEHTableEntry and liveness) but not consumed anywhere else. If it’s meant to guard heuristics that rely on IsLiveInOutOfHandler() (e.g., avoid setting DNER based on stale EH liveness after EH removal), consider wiring it into the relevant decision points; otherwise it should be removed to avoid accumulating dead state.
 bool fgBBVarSetsInited = false;
// Track how many artificial ref counts we've added to fgEntryBB (for OSR)

Comment threadsrc/coreclr/jit/lclvars.cpp
Comment threadsrc/coreclr/jit/liveness.cpp
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Pull request overview
Copilot reviewed 20 out of 20 changed files in this pull request and generated 3 comments.
Comment threadsrc/coreclr/jit/lower.cpp
Comment threadsrc/coreclr/jit/compiler.cpp
Comment threadsrc/coreclr/jit/liveness.cpp
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Pull request overview
Copilot reviewed 20 out of 20 changed files in this pull request and generated 1 comment.
Comment threadsrc/coreclr/jit/gschecks.cpp

This was referenced May 8, 2026

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Copilot wasn't able to review this pull request because it exceeds the maximum number of files (300). Try reducing the number of changed files and requesting a review from Copilot again.
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Sorry for the requests, accidentally rebased across a merge here...
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/azp run runtime-coreclr jitstress, runtime-coreclr libraries-jitstress
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cc @dotnet/jit-contrib PTAL @AndyAyersMS
Diffs.
This will be more important for future work once we start optimizing out IR that allows us to remove the EH we inserted for async.
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Pull request overview
Copilot reviewed 20 out of 20 changed files in this pull request and generated 2 comments.
Comment threadsrc/coreclr/jit/lclvars.cpp
Comment threadsrc/coreclr/jit/lower.cpp
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