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JIT: Run full liveness in MinOpts for async - #123500

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JIT: Run full liveness in MinOpts for async#123500
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For MinOpts codegen we used to consider all locals to be live across async suspensions. That results in a lot of extra lifted state. This PR starts to run full liveness to determine this. It turns out that the IR we avoid creating when we do so more than makes up for the cost of running the liveness.

Fix#116370

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Pull request overview

Purpose: This PR optimizes the size of async continuations in MinOpts (unoptimized) code by avoiding the capture of unnecessary JIT-created temporary variables. Previously, all locals (including JIT temps) were considered live across async calls in MinOpts. This change leverages the same invariant used by EnC and OSR: in MinOpts, the JIT only creates a specific set of long-lived state (IL locals and spilled IL stack entries).

Changes:

  • Adds a new lvLiveAcrossAsync bit field to LclVarDsc to mark locals that must be preserved across async suspension points in MinOpts
  • Updates async call setup to aggressively spill IL stack entries to temps and mark them with lvLiveAcrossAsync when compiling in MinOpts
  • Modifies AsyncLiveness::IsLive to check the new field when liveness information is unavailable, returning true only for IL locals or temps marked as live across async

Reviewed changes

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FileDescription
src/coreclr/jit/compiler.hAdds lvLiveAcrossAsync bit field to LclVarDsc and updates impSetupAsyncCall signature to accept numILArgs parameter
src/coreclr/jit/importercalls.cppUpdates impSetupAsyncCall to spill IL stack entries around async calls in MinOpts and marks the resulting temps with lvLiveAcrossAsync; passes numILArgs from call signature to impSetupAsyncCall
src/coreclr/jit/async.cppMarks async ExecutionContext and SynchronizationContext variables with lvLiveAcrossAsync; updates AsyncLiveness::IsLive to check the new field when liveness is unavailable

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@jakobbotschjakobbotsch changed the title JIT: Optimize continuation sizes in MinOptsJIT: Run full liveness in MinOpts for asyncFeb 4, 2026
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cc @dotnet/jit-contrib PTAL @AndyAyersMS

Diffs. Large tier0/minopts improvements.
The tier1 regressions are because we stopped running DCE in the async liveness. Since the regressions are so small it seemed unnecessary to run DCE + rerun liveness in those cases.

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JIT: Compute async liveness for address exposed locals (#124001)
4c4c14a
This should still give correct liveness at async suspension points given
that local addresses cannot be taken across those.
Based on #123500
lewing pushed a commit to lewing/runtime that referenced this pull request Feb 9, 2026
@jakobbotsch@lewing
JIT: Run full liveness in MinOpts for async (dotnet#123500)
7968059
For MinOpts codegen we used to consider all locals to be live across
async suspensions. That results in a lot of extra lifted state. This PR
starts to run full liveness to determine this. It turns out that the IR
we avoid creating when we do so more than makes up for the cost of
running the liveness.
Fixdotnet#116370
@jakobbotschjakobbotsch mentioned this pull request Feb 16, 2026
Closed
iremyux pushed a commit to iremyux/dotnet-runtime that referenced this pull request Mar 2, 2026
@jakobbotsch@iremyux
JIT: Run full liveness in MinOpts for async (dotnet#123500)
b8117b5
For MinOpts codegen we used to consider all locals to be live across
async suspensions. That results in a lot of extra lifted state. This PR
starts to run full liveness to determine this. It turns out that the IR
we avoid creating when we do so more than makes up for the cost of
running the liveness.
Fixdotnet#116370
iremyux pushed a commit to iremyux/dotnet-runtime that referenced this pull request Mar 2, 2026
@jakobbotsch@iremyux
JIT: Compute async liveness for address exposed locals (dotnet#124001)
e4de7a7
This should still give correct liveness at async suspension points given
that local addresses cannot be taken across those.
Based on dotnet#123500
@github-actionsgithub-actionsBot locked and limited conversation to collaborators Mar 9, 2026
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JIT: Run full liveness in MinOpts for async by jakobbotsch · Pull Request #123500 · dotnet/runtime · GitHub
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JIT: Run full liveness in MinOpts for async - #123500
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JIT: Run full liveness in MinOpts for async#123500
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For MinOpts codegen we used to consider all locals to be live across async suspensions. That results in a lot of extra lifted state. This PR starts to run full liveness to determine this. It turns out that the IR we avoid creating when we do so more than makes up for the cost of running the liveness.
Fix#116370
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Pull request overview
Purpose: This PR optimizes the size of async continuations in MinOpts (unoptimized) code by avoiding the capture of unnecessary JIT-created temporary variables. Previously, all locals (including JIT temps) were considered live across async calls in MinOpts. This change leverages the same invariant used by EnC and OSR: in MinOpts, the JIT only creates a specific set of long-lived state (IL locals and spilled IL stack entries).
Changes:
  • Adds a new lvLiveAcrossAsync bit field to LclVarDsc to mark locals that must be preserved across async suspension points in MinOpts
  • Updates async call setup to aggressively spill IL stack entries to temps and mark them with lvLiveAcrossAsync when compiling in MinOpts
  • Modifies AsyncLiveness::IsLive to check the new field when liveness information is unavailable, returning true only for IL locals or temps marked as live across async
Reviewed changes
Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.
FileDescription
src/coreclr/jit/compiler.hAdds lvLiveAcrossAsync bit field to LclVarDsc and updates impSetupAsyncCall signature to accept numILArgs parameter
src/coreclr/jit/importercalls.cppUpdates impSetupAsyncCall to spill IL stack entries around async calls in MinOpts and marks the resulting temps with lvLiveAcrossAsync; passes numILArgs from call signature to impSetupAsyncCall
src/coreclr/jit/async.cppMarks async ExecutionContext and SynchronizationContext variables with lvLiveAcrossAsync; updates AsyncLiveness::IsLive to check the new field when liveness is unavailable
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JIT: Optimize continuation sizes in MinOptsJIT: Run full liveness in MinOpts for asyncFeb 4, 2026
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cc @dotnet/jit-contrib PTAL @AndyAyersMS
Diffs. Large tier0/minopts improvements.

The tier1 regressions are because we stopped running DCE in the async liveness. Since the regressions are so small it seemed unnecessary to run DCE + rerun liveness in those cases.
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JIT: Compute async liveness for address exposed locals (#124001)
4c4c14a
This should still give correct liveness at async suspension points given
that local addresses cannot be taken across those.
Based on #123500
lewing pushed a commit
to lewing/runtime
that referenced
this pull request
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@jakobbotsch@lewing
JIT: Run full liveness in MinOpts for async (dotnet#123500)
7968059
For MinOpts codegen we used to consider all locals to be live across
async suspensions. That results in a lot of extra lifted state. This PR
starts to run full liveness to determine this. It turns out that the IR
we avoid creating when we do so more than makes up for the cost of
running the liveness.
Fixdotnet#116370
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@jakobbotsch@iremyux
JIT: Run full liveness in MinOpts for async (dotnet#123500)
b8117b5
For MinOpts codegen we used to consider all locals to be live across
async suspensions. That results in a lot of extra lifted state. This PR
starts to run full liveness to determine this. It turns out that the IR
we avoid creating when we do so more than makes up for the cost of
running the liveness.
Fixdotnet#116370
iremyux pushed a commit
to iremyux/dotnet-runtime
that referenced
this pull request
Mar 2, 2026
@jakobbotsch@iremyux
JIT: Compute async liveness for address exposed locals (dotnet#124001)
e4de7a7
This should still give correct liveness at async suspension points given
that local addresses cannot be taken across those.
Based on dotnet#123500
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JIT: Run full liveness in MinOpts for async by jakobbotsch · Pull Request #123500 · dotnet/runtime · GitHub
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JIT: Run full liveness in MinOpts for async - #123500
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JIT: Run full liveness in MinOpts for async#123500
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For MinOpts codegen we used to consider all locals to be live across async suspensions. That results in a lot of extra lifted state. This PR starts to run full liveness to determine this. It turns out that the IR we avoid creating when we do so more than makes up for the cost of running the liveness.
Fix#116370
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Pull request overview
Purpose: This PR optimizes the size of async continuations in MinOpts (unoptimized) code by avoiding the capture of unnecessary JIT-created temporary variables. Previously, all locals (including JIT temps) were considered live across async calls in MinOpts. This change leverages the same invariant used by EnC and OSR: in MinOpts, the JIT only creates a specific set of long-lived state (IL locals and spilled IL stack entries).
Changes:
  • Adds a new lvLiveAcrossAsync bit field to LclVarDsc to mark locals that must be preserved across async suspension points in MinOpts
  • Updates async call setup to aggressively spill IL stack entries to temps and mark them with lvLiveAcrossAsync when compiling in MinOpts
  • Modifies AsyncLiveness::IsLive to check the new field when liveness information is unavailable, returning true only for IL locals or temps marked as live across async
Reviewed changes
Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.
FileDescription
src/coreclr/jit/compiler.hAdds lvLiveAcrossAsync bit field to LclVarDsc and updates impSetupAsyncCall signature to accept numILArgs parameter
src/coreclr/jit/importercalls.cppUpdates impSetupAsyncCall to spill IL stack entries around async calls in MinOpts and marks the resulting temps with lvLiveAcrossAsync; passes numILArgs from call signature to impSetupAsyncCall
src/coreclr/jit/async.cppMarks async ExecutionContext and SynchronizationContext variables with lvLiveAcrossAsync; updates AsyncLiveness::IsLive to check the new field when liveness is unavailable
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JIT: Optimize continuation sizes in MinOptsJIT: Run full liveness in MinOpts for asyncFeb 4, 2026
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cc @dotnet/jit-contrib PTAL @AndyAyersMS
Diffs. Large tier0/minopts improvements.

The tier1 regressions are because we stopped running DCE in the async liveness. Since the regressions are so small it seemed unnecessary to run DCE + rerun liveness in those cases.
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JIT: Compute async liveness for address exposed locals (#124001)
4c4c14a
This should still give correct liveness at async suspension points given
that local addresses cannot be taken across those.
Based on #123500
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@jakobbotsch@lewing
JIT: Run full liveness in MinOpts for async (dotnet#123500)
7968059
For MinOpts codegen we used to consider all locals to be live across
async suspensions. That results in a lot of extra lifted state. This PR
starts to run full liveness to determine this. It turns out that the IR
we avoid creating when we do so more than makes up for the cost of
running the liveness.
Fixdotnet#116370
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JIT: Run full liveness in MinOpts for async (dotnet#123500)
b8117b5
For MinOpts codegen we used to consider all locals to be live across
async suspensions. That results in a lot of extra lifted state. This PR
starts to run full liveness to determine this. It turns out that the IR
we avoid creating when we do so more than makes up for the cost of
running the liveness.
Fixdotnet#116370
iremyux pushed a commit
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@jakobbotsch@iremyux
JIT: Compute async liveness for address exposed locals (dotnet#124001)
e4de7a7
This should still give correct liveness at async suspension points given
that local addresses cannot be taken across those.
Based on dotnet#123500
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JIT: Run full liveness in MinOpts for async by jakobbotsch · Pull Request #123500 · dotnet/runtime · GitHub
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For MinOpts codegen we used to consider all locals to be live across async suspensions. That results in a lot of extra lifted state. This PR starts to run full liveness to determine this. It turns out that the IR we avoid creating when we do so more than makes up for the cost of running the liveness.
Fix#116370
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Pull request overview
Purpose: This PR optimizes the size of async continuations in MinOpts (unoptimized) code by avoiding the capture of unnecessary JIT-created temporary variables. Previously, all locals (including JIT temps) were considered live across async calls in MinOpts. This change leverages the same invariant used by EnC and OSR: in MinOpts, the JIT only creates a specific set of long-lived state (IL locals and spilled IL stack entries).
Changes:
  • Adds a new lvLiveAcrossAsync bit field to LclVarDsc to mark locals that must be preserved across async suspension points in MinOpts
  • Updates async call setup to aggressively spill IL stack entries to temps and mark them with lvLiveAcrossAsync when compiling in MinOpts
  • Modifies AsyncLiveness::IsLive to check the new field when liveness information is unavailable, returning true only for IL locals or temps marked as live across async
Reviewed changes
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FileDescription
src/coreclr/jit/compiler.hAdds lvLiveAcrossAsync bit field to LclVarDsc and updates impSetupAsyncCall signature to accept numILArgs parameter
src/coreclr/jit/importercalls.cppUpdates impSetupAsyncCall to spill IL stack entries around async calls in MinOpts and marks the resulting temps with lvLiveAcrossAsync; passes numILArgs from call signature to impSetupAsyncCall
src/coreclr/jit/async.cppMarks async ExecutionContext and SynchronizationContext variables with lvLiveAcrossAsync; updates AsyncLiveness::IsLive to check the new field when liveness is unavailable
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JIT: Optimize continuation sizes in MinOptsJIT: Run full liveness in MinOpts for asyncFeb 4, 2026
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cc @dotnet/jit-contrib PTAL @AndyAyersMS
Diffs. Large tier0/minopts improvements.

The tier1 regressions are because we stopped running DCE in the async liveness. Since the regressions are so small it seemed unnecessary to run DCE + rerun liveness in those cases.
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JIT: Compute async liveness for address exposed locals (#124001)
4c4c14a
This should still give correct liveness at async suspension points given
that local addresses cannot be taken across those.
Based on #123500
lewing pushed a commit
to lewing/runtime
that referenced
this pull request
Feb 9, 2026
@jakobbotsch@lewing
JIT: Run full liveness in MinOpts for async (dotnet#123500)
7968059
For MinOpts codegen we used to consider all locals to be live across
async suspensions. That results in a lot of extra lifted state. This PR
starts to run full liveness to determine this. It turns out that the IR
we avoid creating when we do so more than makes up for the cost of
running the liveness.
Fixdotnet#116370
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@jakobbotsch@iremyux
JIT: Run full liveness in MinOpts for async (dotnet#123500)
b8117b5
For MinOpts codegen we used to consider all locals to be live across
async suspensions. That results in a lot of extra lifted state. This PR
starts to run full liveness to determine this. It turns out that the IR
we avoid creating when we do so more than makes up for the cost of
running the liveness.
Fixdotnet#116370
iremyux pushed a commit
to iremyux/dotnet-runtime
that referenced
this pull request
Mar 2, 2026
@jakobbotsch@iremyux
JIT: Compute async liveness for address exposed locals (dotnet#124001)
e4de7a7
This should still give correct liveness at async suspension points given
that local addresses cannot be taken across those.
Based on dotnet#123500
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JIT: Run full liveness in MinOpts for async by jakobbotsch · Pull Request #123500 · dotnet/runtime · GitHub
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JIT: Run full liveness in MinOpts for async - #123500
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JIT: Run full liveness in MinOpts for async#123500
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For MinOpts codegen we used to consider all locals to be live across async suspensions. That results in a lot of extra lifted state. This PR starts to run full liveness to determine this. It turns out that the IR we avoid creating when we do so more than makes up for the cost of running the liveness.
Fix#116370
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Pull request overview
Purpose: This PR optimizes the size of async continuations in MinOpts (unoptimized) code by avoiding the capture of unnecessary JIT-created temporary variables. Previously, all locals (including JIT temps) were considered live across async calls in MinOpts. This change leverages the same invariant used by EnC and OSR: in MinOpts, the JIT only creates a specific set of long-lived state (IL locals and spilled IL stack entries).
Changes:
  • Adds a new lvLiveAcrossAsync bit field to LclVarDsc to mark locals that must be preserved across async suspension points in MinOpts
  • Updates async call setup to aggressively spill IL stack entries to temps and mark them with lvLiveAcrossAsync when compiling in MinOpts
  • Modifies AsyncLiveness::IsLive to check the new field when liveness information is unavailable, returning true only for IL locals or temps marked as live across async
Reviewed changes
Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.
FileDescription
src/coreclr/jit/compiler.hAdds lvLiveAcrossAsync bit field to LclVarDsc and updates impSetupAsyncCall signature to accept numILArgs parameter
src/coreclr/jit/importercalls.cppUpdates impSetupAsyncCall to spill IL stack entries around async calls in MinOpts and marks the resulting temps with lvLiveAcrossAsync; passes numILArgs from call signature to impSetupAsyncCall
src/coreclr/jit/async.cppMarks async ExecutionContext and SynchronizationContext variables with lvLiveAcrossAsync; updates AsyncLiveness::IsLive to check the new field when liveness is unavailable
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cc @dotnet/jit-contrib PTAL @AndyAyersMS
Diffs. Large tier0/minopts improvements.

The tier1 regressions are because we stopped running DCE in the async liveness. Since the regressions are so small it seemed unnecessary to run DCE + rerun liveness in those cases.
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JIT: Compute async liveness for address exposed locals (#124001)
4c4c14a
This should still give correct liveness at async suspension points given
that local addresses cannot be taken across those.
Based on #123500
lewing pushed a commit
to lewing/runtime
that referenced
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Feb 9, 2026
@jakobbotsch@lewing
JIT: Run full liveness in MinOpts for async (dotnet#123500)
7968059
For MinOpts codegen we used to consider all locals to be live across
async suspensions. That results in a lot of extra lifted state. This PR
starts to run full liveness to determine this. It turns out that the IR
we avoid creating when we do so more than makes up for the cost of
running the liveness.
Fixdotnet#116370
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JIT: Run full liveness in MinOpts for async (dotnet#123500)
b8117b5
For MinOpts codegen we used to consider all locals to be live across
async suspensions. That results in a lot of extra lifted state. This PR
starts to run full liveness to determine this. It turns out that the IR
we avoid creating when we do so more than makes up for the cost of
running the liveness.
Fixdotnet#116370
iremyux pushed a commit
to iremyux/dotnet-runtime
that referenced
this pull request
Mar 2, 2026
@jakobbotsch@iremyux
JIT: Compute async liveness for address exposed locals (dotnet#124001)
e4de7a7
This should still give correct liveness at async suspension points given
that local addresses cannot be taken across those.
Based on dotnet#123500
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JIT: Run full liveness in MinOpts for async by jakobbotsch · Pull Request #123500 · dotnet/runtime · GitHub
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JIT: Run full liveness in MinOpts for async - #123500
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jakobbotsch merged 21 commits into
dotnet:mainfrom 
jakobbotsch:minopts-async-live-set
Feb 6, 2026
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JIT: Run full liveness in MinOpts for async#123500
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For MinOpts codegen we used to consider all locals to be live across async suspensions. That results in a lot of extra lifted state. This PR starts to run full liveness to determine this. It turns out that the IR we avoid creating when we do so more than makes up for the cost of running the liveness.
Fix#116370
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Pull request overview
Purpose: This PR optimizes the size of async continuations in MinOpts (unoptimized) code by avoiding the capture of unnecessary JIT-created temporary variables. Previously, all locals (including JIT temps) were considered live across async calls in MinOpts. This change leverages the same invariant used by EnC and OSR: in MinOpts, the JIT only creates a specific set of long-lived state (IL locals and spilled IL stack entries).
Changes:
  • Adds a new lvLiveAcrossAsync bit field to LclVarDsc to mark locals that must be preserved across async suspension points in MinOpts
  • Updates async call setup to aggressively spill IL stack entries to temps and mark them with lvLiveAcrossAsync when compiling in MinOpts
  • Modifies AsyncLiveness::IsLive to check the new field when liveness information is unavailable, returning true only for IL locals or temps marked as live across async
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FileDescription
src/coreclr/jit/compiler.hAdds lvLiveAcrossAsync bit field to LclVarDsc and updates impSetupAsyncCall signature to accept numILArgs parameter
src/coreclr/jit/importercalls.cppUpdates impSetupAsyncCall to spill IL stack entries around async calls in MinOpts and marks the resulting temps with lvLiveAcrossAsync; passes numILArgs from call signature to impSetupAsyncCall
src/coreclr/jit/async.cppMarks async ExecutionContext and SynchronizationContext variables with lvLiveAcrossAsync; updates AsyncLiveness::IsLive to check the new field when liveness is unavailable
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Diffs. Large tier0/minopts improvements.

The tier1 regressions are because we stopped running DCE in the async liveness. Since the regressions are so small it seemed unnecessary to run DCE + rerun liveness in those cases.
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JIT: Compute async liveness for address exposed locals (#124001)
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JIT: Run full liveness in MinOpts for async (dotnet#123500)
7968059
For MinOpts codegen we used to consider all locals to be live across
async suspensions. That results in a lot of extra lifted state. This PR
starts to run full liveness to determine this. It turns out that the IR
we avoid creating when we do so more than makes up for the cost of
running the liveness.
Fixdotnet#116370
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JIT: Run full liveness in MinOpts for async (dotnet#123500)
b8117b5
For MinOpts codegen we used to consider all locals to be live across
async suspensions. That results in a lot of extra lifted state. This PR
starts to run full liveness to determine this. It turns out that the IR
we avoid creating when we do so more than makes up for the cost of
running the liveness.
Fixdotnet#116370
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JIT: Compute async liveness for address exposed locals (dotnet#124001)
e4de7a7
This should still give correct liveness at async suspension points given
that local addresses cannot be taken across those.
Based on dotnet#123500
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JIT: Run full liveness in MinOpts for async by jakobbotsch · Pull Request #123500 · dotnet/runtime · GitHub
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JIT: Run full liveness in MinOpts for async - #123500
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For MinOpts codegen we used to consider all locals to be live across async suspensions. That results in a lot of extra lifted state. This PR starts to run full liveness to determine this. It turns out that the IR we avoid creating when we do so more than makes up for the cost of running the liveness.
Fix#116370
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Pull request overview
Purpose: This PR optimizes the size of async continuations in MinOpts (unoptimized) code by avoiding the capture of unnecessary JIT-created temporary variables. Previously, all locals (including JIT temps) were considered live across async calls in MinOpts. This change leverages the same invariant used by EnC and OSR: in MinOpts, the JIT only creates a specific set of long-lived state (IL locals and spilled IL stack entries).
Changes:
  • Adds a new lvLiveAcrossAsync bit field to LclVarDsc to mark locals that must be preserved across async suspension points in MinOpts
  • Updates async call setup to aggressively spill IL stack entries to temps and mark them with lvLiveAcrossAsync when compiling in MinOpts
  • Modifies AsyncLiveness::IsLive to check the new field when liveness information is unavailable, returning true only for IL locals or temps marked as live across async
Reviewed changes
Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.
FileDescription
src/coreclr/jit/compiler.hAdds lvLiveAcrossAsync bit field to LclVarDsc and updates impSetupAsyncCall signature to accept numILArgs parameter
src/coreclr/jit/importercalls.cppUpdates impSetupAsyncCall to spill IL stack entries around async calls in MinOpts and marks the resulting temps with lvLiveAcrossAsync; passes numILArgs from call signature to impSetupAsyncCall
src/coreclr/jit/async.cppMarks async ExecutionContext and SynchronizationContext variables with lvLiveAcrossAsync; updates AsyncLiveness::IsLive to check the new field when liveness is unavailable
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cc @dotnet/jit-contrib PTAL @AndyAyersMS
Diffs. Large tier0/minopts improvements.

The tier1 regressions are because we stopped running DCE in the async liveness. Since the regressions are so small it seemed unnecessary to run DCE + rerun liveness in those cases.
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JIT: Compute async liveness for address exposed locals (#124001)
4c4c14a
This should still give correct liveness at async suspension points given
that local addresses cannot be taken across those.
Based on #123500
lewing pushed a commit
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that referenced
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@jakobbotsch@lewing
JIT: Run full liveness in MinOpts for async (dotnet#123500)
7968059
For MinOpts codegen we used to consider all locals to be live across
async suspensions. That results in a lot of extra lifted state. This PR
starts to run full liveness to determine this. It turns out that the IR
we avoid creating when we do so more than makes up for the cost of
running the liveness.
Fixdotnet#116370
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JIT: Run full liveness in MinOpts for async (dotnet#123500)
b8117b5
For MinOpts codegen we used to consider all locals to be live across
async suspensions. That results in a lot of extra lifted state. This PR
starts to run full liveness to determine this. It turns out that the IR
we avoid creating when we do so more than makes up for the cost of
running the liveness.
Fixdotnet#116370
iremyux pushed a commit
to iremyux/dotnet-runtime
that referenced
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Mar 2, 2026
@jakobbotsch@iremyux
JIT: Compute async liveness for address exposed locals (dotnet#124001)
e4de7a7
This should still give correct liveness at async suspension points given
that local addresses cannot be taken across those.
Based on dotnet#123500
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JIT: Run full liveness in MinOpts for async by jakobbotsch · Pull Request #123500 · dotnet/runtime · GitHub
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JIT: Run full liveness in MinOpts for async - #123500
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For MinOpts codegen we used to consider all locals to be live across async suspensions. That results in a lot of extra lifted state. This PR starts to run full liveness to determine this. It turns out that the IR we avoid creating when we do so more than makes up for the cost of running the liveness.
Fix#116370
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Pull request overview
Purpose: This PR optimizes the size of async continuations in MinOpts (unoptimized) code by avoiding the capture of unnecessary JIT-created temporary variables. Previously, all locals (including JIT temps) were considered live across async calls in MinOpts. This change leverages the same invariant used by EnC and OSR: in MinOpts, the JIT only creates a specific set of long-lived state (IL locals and spilled IL stack entries).
Changes:
  • Adds a new lvLiveAcrossAsync bit field to LclVarDsc to mark locals that must be preserved across async suspension points in MinOpts
  • Updates async call setup to aggressively spill IL stack entries to temps and mark them with lvLiveAcrossAsync when compiling in MinOpts
  • Modifies AsyncLiveness::IsLive to check the new field when liveness information is unavailable, returning true only for IL locals or temps marked as live across async
Reviewed changes
Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.
FileDescription
src/coreclr/jit/compiler.hAdds lvLiveAcrossAsync bit field to LclVarDsc and updates impSetupAsyncCall signature to accept numILArgs parameter
src/coreclr/jit/importercalls.cppUpdates impSetupAsyncCall to spill IL stack entries around async calls in MinOpts and marks the resulting temps with lvLiveAcrossAsync; passes numILArgs from call signature to impSetupAsyncCall
src/coreclr/jit/async.cppMarks async ExecutionContext and SynchronizationContext variables with lvLiveAcrossAsync; updates AsyncLiveness::IsLive to check the new field when liveness is unavailable
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cc @dotnet/jit-contrib PTAL @AndyAyersMS
Diffs. Large tier0/minopts improvements.

The tier1 regressions are because we stopped running DCE in the async liveness. Since the regressions are so small it seemed unnecessary to run DCE + rerun liveness in those cases.
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/azp run Fuzzlyn
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JIT: Compute async liveness for address exposed locals (#124001)
4c4c14a
This should still give correct liveness at async suspension points given
that local addresses cannot be taken across those.
Based on #123500
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JIT: Run full liveness in MinOpts for async (dotnet#123500)
7968059
For MinOpts codegen we used to consider all locals to be live across
async suspensions. That results in a lot of extra lifted state. This PR
starts to run full liveness to determine this. It turns out that the IR
we avoid creating when we do so more than makes up for the cost of
running the liveness.
Fixdotnet#116370
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@jakobbotsch@iremyux
JIT: Run full liveness in MinOpts for async (dotnet#123500)
b8117b5
For MinOpts codegen we used to consider all locals to be live across
async suspensions. That results in a lot of extra lifted state. This PR
starts to run full liveness to determine this. It turns out that the IR
we avoid creating when we do so more than makes up for the cost of
running the liveness.
Fixdotnet#116370
iremyux pushed a commit
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that referenced
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Mar 2, 2026
@jakobbotsch@iremyux
JIT: Compute async liveness for address exposed locals (dotnet#124001)
e4de7a7
This should still give correct liveness at async suspension points given
that local addresses cannot be taken across those.
Based on dotnet#123500
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JIT: Avoid capturing all jit temps in debug for runtime async


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