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[AArch64] Stop reserved registers from being saved in prolog/epilog #138448

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[AArch64] Stop reserved registers from being saved in prolog/epilog #138448

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6 changes: 6 additions & 0 deletions llvm/lib/Target/AArch64/AArch64FrameLowering.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -3619,6 +3619,12 @@ void AArch64FrameLowering::determineCalleeSaves(MachineFunction &MF,
if (Reg == BasePointerReg)
SavedRegs.set(Reg);

// Don't save manually reserved registers set through -ffixed-reg.
if (RegInfo->isUserReservedReg(MF, Reg)) {
SavedRegs.reset(Reg);
continue;
}

bool RegUsed = SavedRegs.test(Reg);
unsigned PairedReg = AArch64::NoRegister;
const bool RegIsGPR64 = AArch64::GPR64RegClass.contains(Reg);
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17 changes: 17 additions & 0 deletions llvm/lib/Target/AArch64/AArch64RegisterInfo.cpp
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Expand Up @@ -518,6 +518,18 @@ AArch64RegisterInfo::getStrictlyReservedRegs(const MachineFunction &MF) const {
return Reserved;
}

BitVector
AArch64RegisterInfo::getUserReservedRegs(const MachineFunction &MF) const {
BitVector Reserved(getNumRegs());
for (size_t i = 0; i < AArch64::GPR32commonRegClass.getNumRegs(); ++i) {
// ReserveXRegister is set for registers manually reserved
// through -ffixed-reg.
if (MF.getSubtarget<AArch64Subtarget>().isXRegisterReserved(i))
markSuperRegs(Reserved, AArch64::GPR32commonRegClass.getRegister(i));
}
return Reserved;
}

BitVector
AArch64RegisterInfo::getReservedRegs(const MachineFunction &MF) const {
BitVector Reserved(getNumRegs());
Expand Down Expand Up @@ -551,6 +563,11 @@ bool AArch64RegisterInfo::isReservedReg(const MachineFunction &MF,
return getReservedRegs(MF)[Reg];
}

bool AArch64RegisterInfo::isUserReservedReg(const MachineFunction &MF,
MCRegister Reg) const {
return getUserReservedRegs(MF)[Reg];
}

bool AArch64RegisterInfo::isStrictlyReservedReg(const MachineFunction &MF,
MCRegister Reg) const {
return getStrictlyReservedRegs(MF)[Reg];
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2 changes: 2 additions & 0 deletions llvm/lib/Target/AArch64/AArch64RegisterInfo.h
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Expand Up @@ -35,6 +35,7 @@ class AArch64RegisterInfo final : public AArch64GenRegisterInfo {
}

bool isReservedReg(const MachineFunction &MF, MCRegister Reg) const;
bool isUserReservedReg(const MachineFunction &MF, MCRegister Reg) const;
bool isStrictlyReservedReg(const MachineFunction &MF, MCRegister Reg) const;
bool isAnyArgRegReserved(const MachineFunction &MF) const;
void emitReservedArgRegCallError(const MachineFunction &MF) const;
Expand Down Expand Up @@ -93,6 +94,7 @@ class AArch64RegisterInfo final : public AArch64GenRegisterInfo {
const uint32_t *getWindowsStackProbePreservedMask() const;

BitVector getStrictlyReservedRegs(const MachineFunction &MF) const;
BitVector getUserReservedRegs(const MachineFunction &MF) const;
BitVector getReservedRegs(const MachineFunction &MF) const override;
std::optional<std::string>
explainReservedReg(const MachineFunction &MF,
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