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[Xtensa] Remove unnecessary MOVSP in epilogue. (LLVM-83) #44

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[Xtensa] Remove unnecessary MOVSP in epilogue. (LLVM-83) #44

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9 changes: 7 additions & 2 deletions llvm/lib/Target/Xtensa/XtensaFrameLowering.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -245,8 +245,13 @@ void XtensaFrameLowering::emitEpilogue(MachineFunction &MF,
for (unsigned i = 0; i < MFI.getCalleeSavedInfo().size(); ++i)
--I;
if (STI.isWinABI()) {
// Insert instruction "movsp $sp, $fp" at this location.
BuildMI(MBB, I, dl, TII.get(Xtensa::MOVSP), SP).addReg(FP);
// In most architectures, we need to explicitly restore the stack pointer
// before returning.
//
// For Xtensa Windowed Register option, it is not needed to explicitly
// restore the stack pointer. Reason being is that on function return,
// the window of the caller (including the old stack pointer) gets
// restored anyways.
} else {
BuildMI(MBB, I, dl, TII.get(Xtensa::OR), SP).addReg(FP).addReg(FP);
}
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