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[Clang] Fix unnecessary extra return block emmited during function epilog after musttail call #134282

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[Clang] Fix unnecessary extra return block emmited during function epilog after musttail call #134282

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[Clang] Fix unnecessary extra return block emmited during function ep…
kiran-isaac Mar 31, 2025
3f59a59
format fix
kiran-isaac Apr 3, 2025
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8 changes: 7 additions & 1 deletion clang/lib/CodeGen/CGCall.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -3897,6 +3897,13 @@ void CodeGenFunction::EmitFunctionEpilog(const CGFunctionInfo &FI,
return;
}

// If there is no valid insert point, we won't emit a return.
// The insert point could be null if we have already emitted a return
// (e.g. if musttail)
if (!HaveInsertPoint()) {
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@efriedma-quic efriedma-quic Apr 3, 2025

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The placement of this check doesn't seem right; probably it should be before we start constructing instructions?
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@rnk rnk Apr 3, 2025

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This patch could use tests in general, and I wanted to add, you should be able to cover this case with a musttail call in a void-returning function, which should exercise one of the paths above.
return;
}

llvm::DebugLoc RetDbgLoc;
llvm::Value *RV = nullptr;
QualType RetTy = FI.getReturnType();
Expand Down Expand Up @@ -5990,7 +5997,6 @@ RValue CodeGenFunction::EmitCall(const CGFunctionInfo &CallInfo,
else
Builder.CreateRet(CI);
Builder.ClearInsertionPoint();
EnsureInsertPoint();
return GetUndefRValue(RetTy);
}

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5 changes: 4 additions & 1 deletion clang/lib/CodeGen/CGExprComplex.cpp
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Expand Up @@ -1491,7 +1491,10 @@ void CodeGenFunction::EmitComplexExprIntoLValue(const Expr *E, LValue dest,
"Invalid complex expression to emit");
ComplexExprEmitter Emitter(*this);
ComplexPairTy Val = Emitter.Visit(const_cast<Expr*>(E));
Emitter.EmitStoreOfComplex(Val, dest, isInit);
// The insert point may be empty if we have just emmited a
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@efriedma-quic efriedma-quic Apr 3, 2025

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Suggested change
// The insert point may be empty if we have just emmited a
// The insert point may be empty if we have just emitted a
// musttail call.
if (HaveInsertPoint())
Emitter.EmitStoreOfComplex(Val, dest, isInit);
}

/// EmitStoreOfComplex - Store a complex number into the specified l-value.
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