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JIT: Disable recursive tailcall to loop opt in OSR methods #113625

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Mar 18, 2025
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JIT: Disable recursive tailcall to loop opt in OSR methods #113625

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30 changes: 12 additions & 18 deletions src/coreclr/jit/morph.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -4686,8 +4686,13 @@ GenTree* Compiler::fgMorphPotentialTailCall(GenTreeCall* call)
// fgMorphRecursiveFastTailCallIntoLoop() is not handling update of generic context while transforming
// a recursive call into a loop. Another option is to modify gtIsRecursiveCall() to check that the
// generic type parameters of both caller and callee generic method are the same.
if (opts.compTailCallLoopOpt && canFastTailCall && gtIsRecursiveCall(call) && !lvaReportParamTypeArg() &&
!lvaKeepAliveAndReportThis() && !call->IsVirtual() && !hasStructParam && !varTypeIsStruct(call->TypeGet()))
//
// For OSR, we prefer to tailcall for call counting + potential transition
// into the actual tier1 version.
//
if (opts.compTailCallLoopOpt && canFastTailCall && !opts.IsOSR() && gtIsRecursiveCall(call) &&
!lvaReportParamTypeArg() && !lvaKeepAliveAndReportThis() && !call->IsVirtual() && !hasStructParam &&
!varTypeIsStruct(call->TypeGet()))
{
fastTailCallToLoop = true;
}
Expand Down Expand Up @@ -6161,23 +6166,12 @@ void Compiler::fgMorphRecursiveFastTailCallIntoLoop(BasicBlock* block, GenTreeCa
// Remove the call
fgRemoveStmt(block, lastStmt);

assert(!opts.IsOSR());
// Set the loop edge.
BasicBlock* entryBB;
if (opts.IsOSR())
{
// Todo: this may not look like a viable loop header.
// Might need the moral equivalent of an init BB.
entryBB = fgEntryBB;
}
else
{
assert(doesMethodHaveRecursiveTailcall());

// TODO-Cleanup: We should really be expanding tailcalls into loops
// much earlier than this, at a place where we do not need to have
// hacky workarounds to figure out what the actual IL entry block is.
entryBB = fgGetFirstILBlock();
}
// TODO-Cleanup: We should really be expanding tailcalls into loops much
// earlier than this, at a place where we can just use the init BB here.
BasicBlock* entryBB = fgGetFirstILBlock();
assert(doesMethodHaveRecursiveTailcall());

FlowEdge* const newEdge = fgAddRefPred(entryBB, block);
block->SetKindAndTargetEdge(BBJ_ALWAYS, newEdge);
Expand Down
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