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JIT: Don't clone or unroll cold loops #115744

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Merged
merged 1 commit into from
May 21, 2025
Merged

JIT: Don't clone or unroll cold loops #115744

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6 changes: 6 additions & 0 deletions src/coreclr/jit/loopcloning.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1885,6 +1885,12 @@ bool Compiler::optShouldCloneLoop(FlowGraphNaturalLoop* loop, LoopCloneContext*
//
bool Compiler::optIsLoopClonable(FlowGraphNaturalLoop* loop, LoopCloneContext* context)
{
if (loop->GetHeader()->isRunRarely())
{
JITDUMP("Loop cloning: rejecting loop " FMT_LP ". Loop is cold.\n", loop->GetIndex());
return false;
}

const bool requireIterable = !doesMethodHaveGuardedDevirtualization();
NaturalLoopIterInfo* iterInfo = context->GetLoopIterInfo(loop->GetIndex());

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6 changes: 6 additions & 0 deletions src/coreclr/jit/optimizer.cpp
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Expand Up @@ -1390,6 +1390,12 @@ bool Compiler::optTryUnrollLoop(FlowGraphNaturalLoop* loop, bool* changedIR)
assert(UNROLL_LIMIT_SZ[SMALL_CODE] == 0);
assert(UNROLL_LIMIT_SZ[COUNT_OPT_CODE] == 0);

if (loop->GetHeader()->isRunRarely())
{
JITDUMP("Failed to unroll loop " FMT_LP ": Loop is cold.\n", loop->GetIndex());
return false;
}

NaturalLoopIterInfo iterInfo;
if (!loop->AnalyzeIteration(&iterInfo))
{
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