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[AArch64][SME][SDAG] Add basic support for exception handling #159363

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merged 2 commits into from
Sep 29, 2025
Merged

[AArch64][SME][SDAG] Add basic support for exception handling #159363

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2ee4c4b
[AArch64][SME][SDAG] Add basic support for exception handling
MacDue Sep 12, 2025
aeddd0b
Update test
MacDue Sep 17, 2025
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156 changes: 99 additions & 57 deletions llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -8094,13 +8094,76 @@ static SDValue getZT0FrameIndex(MachineFrameInfo &MFI,
DAG.getTargetLoweringInfo().getFrameIndexTy(DAG.getDataLayout()));
}

// Emit a call to __arm_sme_save or __arm_sme_restore.
static SDValue emitSMEStateSaveRestore(const AArch64TargetLowering &TLI,
SelectionDAG &DAG,
AArch64FunctionInfo *Info, SDLoc DL,
SDValue Chain, bool IsSave) {
MachineFunction &MF = DAG.getMachineFunction();
AArch64FunctionInfo *FuncInfo = MF.getInfo<AArch64FunctionInfo>();
FuncInfo->setSMESaveBufferUsed();
TargetLowering::ArgListTy Args;
Args.emplace_back(
DAG.getCopyFromReg(Chain, DL, Info->getSMESaveBufferAddr(), MVT::i64),
PointerType::getUnqual(*DAG.getContext()));

RTLIB::Libcall LC =
IsSave ? RTLIB::SMEABI_SME_SAVE : RTLIB::SMEABI_SME_RESTORE;
SDValue Callee = DAG.getExternalSymbol(TLI.getLibcallName(LC),
TLI.getPointerTy(DAG.getDataLayout()));
auto *RetTy = Type::getVoidTy(*DAG.getContext());
TargetLowering::CallLoweringInfo CLI(DAG);
CLI.setDebugLoc(DL).setChain(Chain).setLibCallee(
TLI.getLibcallCallingConv(LC), RetTy, Callee, std::move(Args));
return TLI.LowerCallTo(CLI).second;
}

static SDValue emitRestoreZALazySave(SDValue Chain, SDLoc DL,
const AArch64TargetLowering &TLI,
const AArch64RegisterInfo &TRI,
AArch64FunctionInfo &FuncInfo,
SelectionDAG &DAG) {
// Conditionally restore the lazy save using a pseudo node.
RTLIB::Libcall LC = RTLIB::SMEABI_TPIDR2_RESTORE;
TPIDR2Object &TPIDR2 = FuncInfo.getTPIDR2Obj();
SDValue RegMask = DAG.getRegisterMask(TRI.getCallPreservedMask(
DAG.getMachineFunction(), TLI.getLibcallCallingConv(LC)));
SDValue RestoreRoutine = DAG.getTargetExternalSymbol(
TLI.getLibcallName(LC), TLI.getPointerTy(DAG.getDataLayout()));
SDValue TPIDR2_EL0 = DAG.getNode(
ISD::INTRINSIC_W_CHAIN, DL, MVT::i64, Chain,
DAG.getConstant(Intrinsic::aarch64_sme_get_tpidr2, DL, MVT::i32));
// Copy the address of the TPIDR2 block into X0 before 'calling' the
// RESTORE_ZA pseudo.
SDValue Glue;
SDValue TPIDR2Block = DAG.getFrameIndex(
TPIDR2.FrameIndex,
DAG.getTargetLoweringInfo().getFrameIndexTy(DAG.getDataLayout()));
Chain = DAG.getCopyToReg(Chain, DL, AArch64::X0, TPIDR2Block, Glue);
Chain =
DAG.getNode(AArch64ISD::RESTORE_ZA, DL, MVT::Other,
{Chain, TPIDR2_EL0, DAG.getRegister(AArch64::X0, MVT::i64),
RestoreRoutine, RegMask, Chain.getValue(1)});
// Finally reset the TPIDR2_EL0 register to 0.
Chain = DAG.getNode(
ISD::INTRINSIC_VOID, DL, MVT::Other, Chain,
DAG.getConstant(Intrinsic::aarch64_sme_set_tpidr2, DL, MVT::i32),
DAG.getConstant(0, DL, MVT::i64));
TPIDR2.Uses++;
return Chain;
}

SDValue AArch64TargetLowering::lowerEHPadEntry(SDValue Chain, SDLoc const &DL,
SelectionDAG &DAG) const {
assert(Chain.getOpcode() == ISD::EntryToken && "Unexpected Chain value");
SDValue Glue = Chain.getValue(1);

MachineFunction &MF = DAG.getMachineFunction();
SMEAttrs SMEFnAttrs = MF.getInfo<AArch64FunctionInfo>()->getSMEFnAttrs();
auto &FuncInfo = *MF.getInfo<AArch64FunctionInfo>();
auto &Subtarget = DAG.getSubtarget<AArch64Subtarget>();
const AArch64RegisterInfo &TRI = *Subtarget.getRegisterInfo();

SMEAttrs SMEFnAttrs = FuncInfo.getSMEFnAttrs();

// The following conditions are true on entry to an exception handler:
// - PSTATE.SM is 0.
Expand All @@ -8115,14 +8178,43 @@ SDValue AArch64TargetLowering::lowerEHPadEntry(SDValue Chain, SDLoc const &DL,
// These mode changes are usually optimized away in catch blocks as they
// occur before the __cxa_begin_catch (which is a non-streaming function),
// but are necessary in some cases (such as for cleanups).
//
// Additionally, if the function has ZA or ZT0 state, we must restore it.

// [COND_]SMSTART SM
if (SMEFnAttrs.hasStreamingInterfaceOrBody())
return changeStreamingMode(DAG, DL, /*Enable=*/true, Chain,
/*Glue*/ Glue, AArch64SME::Always);
Chain = changeStreamingMode(DAG, DL, /*Enable=*/true, Chain,
/*Glue*/ Glue, AArch64SME::Always);
else if (SMEFnAttrs.hasStreamingCompatibleInterface())
Chain = changeStreamingMode(DAG, DL, /*Enable=*/true, Chain, Glue,
AArch64SME::IfCallerIsStreaming);

if (getTM().useNewSMEABILowering())
return Chain;

if (SMEFnAttrs.hasStreamingCompatibleInterface())
return changeStreamingMode(DAG, DL, /*Enable=*/true, Chain, Glue,
AArch64SME::IfCallerIsStreaming);
if (SMEFnAttrs.hasAgnosticZAInterface()) {
// Restore full ZA
Chain = emitSMEStateSaveRestore(*this, DAG, &FuncInfo, DL, Chain,
/*IsSave=*/false);
} else if (SMEFnAttrs.hasZAState() || SMEFnAttrs.hasZT0State()) {
// SMSTART ZA
Chain = DAG.getNode(
AArch64ISD::SMSTART, DL, DAG.getVTList(MVT::Other, MVT::Glue), Chain,
DAG.getTargetConstant(int32_t(AArch64SVCR::SVCRZA), DL, MVT::i32));

// Restore ZT0
if (SMEFnAttrs.hasZT0State()) {
SDValue ZT0FrameIndex =
getZT0FrameIndex(MF.getFrameInfo(), FuncInfo, DAG);
Chain =
DAG.getNode(AArch64ISD::RESTORE_ZT, DL, DAG.getVTList(MVT::Other),
{Chain, DAG.getConstant(0, DL, MVT::i32), ZT0FrameIndex});
}

// Restore ZA
if (SMEFnAttrs.hasZAState())
Chain = emitRestoreZALazySave(Chain, DL, *this, TRI, FuncInfo, DAG);
}

return Chain;
}
Expand Down Expand Up @@ -9240,30 +9332,6 @@ SDValue AArch64TargetLowering::changeStreamingMode(
return GetCheckVL(SMChange.getValue(0), SMChange.getValue(1));
}

// Emit a call to __arm_sme_save or __arm_sme_restore.
static SDValue emitSMEStateSaveRestore(const AArch64TargetLowering &TLI,
SelectionDAG &DAG,
AArch64FunctionInfo *Info, SDLoc DL,
SDValue Chain, bool IsSave) {
MachineFunction &MF = DAG.getMachineFunction();
AArch64FunctionInfo *FuncInfo = MF.getInfo<AArch64FunctionInfo>();
FuncInfo->setSMESaveBufferUsed();
TargetLowering::ArgListTy Args;
Args.emplace_back(
DAG.getCopyFromReg(Chain, DL, Info->getSMESaveBufferAddr(), MVT::i64),
PointerType::getUnqual(*DAG.getContext()));

RTLIB::Libcall LC =
IsSave ? RTLIB::SMEABI_SME_SAVE : RTLIB::SMEABI_SME_RESTORE;
SDValue Callee = DAG.getExternalSymbol(TLI.getLibcallName(LC),
TLI.getPointerTy(DAG.getDataLayout()));
auto *RetTy = Type::getVoidTy(*DAG.getContext());
TargetLowering::CallLoweringInfo CLI(DAG);
CLI.setDebugLoc(DL).setChain(Chain).setLibCallee(
TLI.getLibcallCallingConv(LC), RetTy, Callee, std::move(Args));
return TLI.LowerCallTo(CLI).second;
}

static AArch64SME::ToggleCondition
getSMToggleCondition(const SMECallAttrs &CallAttrs) {
if (!CallAttrs.caller().hasStreamingCompatibleInterface() ||
Expand Down Expand Up @@ -10023,33 +10091,7 @@ AArch64TargetLowering::LowerCall(CallLoweringInfo &CLI,
{Result, DAG.getConstant(0, DL, MVT::i32), ZTFrameIdx});

if (RequiresLazySave) {
// Conditionally restore the lazy save using a pseudo node.
RTLIB::Libcall LC = RTLIB::SMEABI_TPIDR2_RESTORE;
TPIDR2Object &TPIDR2 = FuncInfo->getTPIDR2Obj();
SDValue RegMask = DAG.getRegisterMask(
TRI->getCallPreservedMask(MF, getLibcallCallingConv(LC)));
SDValue RestoreRoutine = DAG.getTargetExternalSymbol(
getLibcallName(LC), getPointerTy(DAG.getDataLayout()));
SDValue TPIDR2_EL0 = DAG.getNode(
ISD::INTRINSIC_W_CHAIN, DL, MVT::i64, Result,
DAG.getConstant(Intrinsic::aarch64_sme_get_tpidr2, DL, MVT::i32));
// Copy the address of the TPIDR2 block into X0 before 'calling' the
// RESTORE_ZA pseudo.
SDValue Glue;
SDValue TPIDR2Block = DAG.getFrameIndex(
TPIDR2.FrameIndex,
DAG.getTargetLoweringInfo().getFrameIndexTy(DAG.getDataLayout()));
Result = DAG.getCopyToReg(Result, DL, AArch64::X0, TPIDR2Block, Glue);
Result =
DAG.getNode(AArch64ISD::RESTORE_ZA, DL, MVT::Other,
{Result, TPIDR2_EL0, DAG.getRegister(AArch64::X0, MVT::i64),
RestoreRoutine, RegMask, Result.getValue(1)});
// Finally reset the TPIDR2_EL0 register to 0.
Result = DAG.getNode(
ISD::INTRINSIC_VOID, DL, MVT::Other, Result,
DAG.getConstant(Intrinsic::aarch64_sme_set_tpidr2, DL, MVT::i32),
DAG.getConstant(0, DL, MVT::i64));
TPIDR2.Uses++;
Result = emitRestoreZALazySave(Result, DL, *this, *TRI, *FuncInfo, DAG);
} else if (RequiresSaveAllZA) {
Result = emitSMEStateSaveRestore(*this, DAG, FuncInfo, DL, Result,
/*IsSave=*/false);
Expand Down
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