[AArch64][GlobalISel] Select llvm.aarch64.neon.st2 intrinsics

[paquette]

Summary

Add manual selection code similar to the code in AArch64ISelDAGToDAG, and add createTuple helpers similar to the code there as well.

This accounted for around 111 fallbacks while building clang for AArch64 with GlobalISel.

This also should make it easy to add selection code for other store intrinsics.

As a minor cleanup, this uses createQTuple in the other place where we use REG_SEQUENCE.

https://godbolt.org/z/5cn4MMGo3

[jroelofs]

llvm/test/CodeGen/AArch64/GlobalISel/select-st2.mir

245

It's so weird to me that the st2 intrinsic generates an st1 instruction, but SDAG does it so... 🤷‍♂️

[craig.topper]

llvm/lib/Target/AArch64/GISel/AArch64InstructionSelector.cpp

5082

I suspect you meant || here. I'm getting a warning from gcc "warning: suggest parentheses around comparison in operand of ‘|’ [-Wparentheses]"

[paquette]

llvm/lib/Target/AArch64/GISel/AArch64InstructionSelector.cpp

5082

Oh, yes, you're right. Will fix shortly.

llvm/lib/Target/AArch64/GISel/AArch64InstructionSelector.cpp

case AArch64::GPRRegBankID:
     return 32;
   case AArch64::FPRRegBankID:
     return 8;
   default:
     llvm_unreachable("Tried to get minimum size for unknown register bank.");
   }
 }
 
+/// Create a REG_SEQUENCE instruction using the registers in \p Regs.
+/// Helper function for functions like createDTuple and createQTuple.
+///
+/// \p RegClassIDs - The list of register class IDs available for some tuple of
+/// a scalar class. E.g. QQRegClassID, QQQRegClassID, QQQQRegClassID. This is
+/// expected to contain between 2 and 4 tuple classes.
+///
+/// \p SubRegs - The list of subregister classes associated with each register
+/// class ID in \p RegClassIDs. E.g., QQRegClassID should use the qsub0
+/// subregister class. The index of each subregister class is expected to
+/// correspond with the index of each register class.
+///
+/// \returns Either the destination register of REG_SEQUENCE instruction that
+/// was created, or the 0th element of \p Regs if \p Regs contains a single
+/// element.
+static Register createTuple(ArrayRef<Register> Regs,
+                            const unsigned RegClassIDs[],
+                            const unsigned SubRegs[], MachineIRBuilder &MIB) {
+  unsigned NumRegs = Regs.size();
+  if (NumRegs == 1)
+    return Regs[0];
+  assert(NumRegs >= 2 && NumRegs <= 4 &&
+         "Only support between two and 4 registers in a tuple!");
+  const TargetRegisterInfo *TRI = MIB.getMF().getSubtarget().getRegisterInfo();
+  auto *DesiredClass = TRI->getRegClass(RegClassIDs[NumRegs - 2]);
+  auto RegSequence =
+      MIB.buildInstr(TargetOpcode::REG_SEQUENCE, {DesiredClass}, {});
+  for (unsigned I = 0, E = Regs.size(); I < E; ++I) {
+    RegSequence.addUse(Regs[I]);
+    RegSequence.addImm(SubRegs[I]);
+  }
+  return RegSequence.getReg(0);
+}
+
+/// Create a tuple of D-registers using the registers in \p Regs.
+static Register createDTuple(ArrayRef<Register> Regs, MachineIRBuilder &MIB) {
+  static const unsigned RegClassIDs[] = {
+      AArch64::DDRegClassID, AArch64::DDDRegClassID, AArch64::DDDDRegClassID};
+  static const unsigned SubRegs[] = {AArch64::dsub0, AArch64::dsub1,
+                                     AArch64::dsub2, AArch64::dsub3};
+  return createTuple(Regs, RegClassIDs, SubRegs, MIB);
+}
+
+/// Create a tuple of Q-registers using the registers in \p Regs.
+static Register createQTuple(ArrayRef<Register> Regs, MachineIRBuilder &MIB) {
+  static const unsigned RegClassIDs[] = {
+      AArch64::QQRegClassID, AArch64::QQQRegClassID, AArch64::QQQQRegClassID};
+  static const unsigned SubRegs[] = {AArch64::qsub0, AArch64::qsub1,
+                                     AArch64::qsub2, AArch64::qsub3};
+  return createTuple(Regs, RegClassIDs, SubRegs, MIB);
+}
+
 static Optional<uint64_t> getImmedFromMO(const MachineOperand &Root) {
   auto &MI = *Root.getParent();
   auto &MBB = *MI.getParent();
   auto &MF = *MBB.getParent();
   auto &MRI = MF.getRegInfo();
   uint64_t Immed;
   if (Root.isImm())
     Immed = Root.getImm();
auto Copy =
             .addReg(TBL1.getReg(0), 0, AArch64::dsub);
     RBI.constrainGenericRegister(Copy.getReg(0), AArch64::FPR64RegClass, MRI);
     I.eraseFromParent();
     return true;
   }
 
   // For TBL2 we need to emit a REG_SEQUENCE to tie together two consecutive
   // Q registers for regalloc.
-  auto RegSeq = MIB.buildInstr(TargetOpcode::REG_SEQUENCE,
-                               {&AArch64::QQRegClass}, {Src1Reg})
-                    .addImm(AArch64::qsub0)
-                    .addUse(Src2Reg)
-                    .addImm(AArch64::qsub1);
-
+  SmallVector<Register, 2> Regs = {Src1Reg, Src2Reg};
+  auto RegSeq = createQTuple(Regs, MIB);
   auto TBL2 = MIB.buildInstr(AArch64::TBLv16i8Two, {I.getOperand(0)},
                              {RegSeq, IndexLoad->getOperand(0)});
-  constrainSelectedInstRegOperands(*RegSeq, TII, TRI, RBI);
   constrainSelectedInstRegOperands(*TBL2, TII, TRI, RBI);
   I.eraseFromParent();
   return true;
 }
 
 MachineInstr *AArch64InstructionSelector::emitLaneInsert(
     Optional<Register> DstReg, Register SrcReg, Register EltReg,
     unsigned LaneIdx, const RegisterBank &RB,
case Intrinsic::trap:
     break;
   case Intrinsic::debugtrap:
     MIB.buildInstr(AArch64::BRK, {}, {}).addImm(0xF000);
     break;
   case Intrinsic::ubsantrap:
     MIB.buildInstr(AArch64::BRK, {}, {})
         .addImm(I.getOperand(1).getImm() | ('U' << 8));
     break;
+  case Intrinsic::aarch64_neon_st2: {
+    Register Src1 = I.getOperand(1).getReg();
+    Register Src2 = I.getOperand(2).getReg();
+    Register Ptr = I.getOperand(3).getReg();
+    LLT Ty = MRI.getType(Src1);
+    const LLT S8 = LLT::scalar(8);
+    const LLT S16 = LLT::scalar(16);
+    const LLT S32 = LLT::scalar(32);
+    const LLT S64 = LLT::scalar(64);
+    const LLT P0 = LLT::pointer(0, 64);
+    unsigned Opc;
+    if (Ty == LLT::fixed_vector(8, S8))
+      Opc = AArch64::ST2Twov8b;
+    else if (Ty == LLT::fixed_vector(16, S8))
+      Opc = AArch64::ST2Twov16b;
+    else if (Ty == LLT::fixed_vector(4, S16))
+      Opc = AArch64::ST2Twov4h;
+    else if (Ty == LLT::fixed_vector(8, S16))
+      Opc = AArch64::ST2Twov8h;
+    else if (Ty == LLT::fixed_vector(2, S32))
+      Opc = AArch64::ST2Twov2s;
+    else if (Ty == LLT::fixed_vector(4, S32))
+      Opc = AArch64::ST2Twov4s;
+    else if (Ty == LLT::fixed_vector(2, S64) || Ty == LLT::fixed_vector(2, P0))
+      Opc = AArch64::ST2Twov2d;
+    else if (Ty == S64 | Ty == P0)
+      Opc = AArch64::ST1Twov1d;
+    else
+      llvm_unreachable("Unexpected type for st2!");
+    SmallVector<Register, 2> Regs = {Src1, Src2};
+    Register Tuple = Ty.getSizeInBits() == 128 ? createQTuple(Regs, MIB)
+                                               : createDTuple(Regs, MIB);
+    auto Store = MIB.buildInstr(Opc, {}, {Tuple, Ptr});
+    Store.cloneMemRefs(I);
+    constrainSelectedInstRegOperands(*Store, TII, TRI, RBI);
+    break;
+  }
   }
 
   I.eraseFromParent();
   return true;
 }
 
 bool AArch64InstructionSelector::selectIntrinsic(MachineInstr &I,
                                                  MachineRegisterInfo &MRI) {

llvm/test/CodeGen/AArch64/GlobalISel/select-st2.mir

+# NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py
+# RUN: llc -mtriple=aarch64 -run-pass=instruction-select -verify-machineinstrs %s -o - | FileCheck %s
+
+...
+---
+name:            v8i8_ST2Twov8b
+legalized:       true
+regBankSelected: true
+tracksRegLiveness: true
+body:             |
+  bb.0:
+    liveins: $d0, $d1, $x0
+
+    ; CHECK-LABEL: name: v8i8_ST2Twov8b
+    ; CHECK: liveins: $d0, $d1, $x0
+    ; CHECK: %ptr:gpr64sp = COPY $x0
+    ; CHECK: %src1:fpr64 = COPY $d0
+    ; CHECK: %src2:fpr64 = COPY $d1
+    ; CHECK: [[REG_SEQUENCE:%[0-9]+]]:dd = REG_SEQUENCE %src1, %subreg.dsub0, %src2, %subreg.dsub1
+    ; CHECK: ST2Twov8b [[REG_SEQUENCE]], %ptr :: (store (<2 x s64>))
+    ; CHECK: RET_ReallyLR
+    %ptr:gpr(p0) = COPY $x0
+    %src1:fpr(<8 x s8>) = COPY $d0
+    %src2:fpr(<8 x s8>) = COPY $d1
+    G_INTRINSIC_W_SIDE_EFFECTS intrinsic(@llvm.aarch64.neon.st2), %src1(<8 x s8>), %src2(<8 x s8>), %ptr(p0) :: (store (<2 x s64>))
+    RET_ReallyLR
+
+...
+---
+name:            v16i8_ST2Twov16b
+
+legalized:       true
+regBankSelected: true
+tracksRegLiveness: true
+body:             |
+  bb.0:
+    liveins: $q0, $q1, $x0
+
+    ; CHECK-LABEL: name: v16i8_ST2Twov16b
+    ; CHECK: liveins: $q0, $q1, $x0
+    ; CHECK: %ptr:gpr64sp = COPY $x0
+    ; CHECK: %src1:fpr128 = COPY $q0
+    ; CHECK: %src2:fpr128 = COPY $q1
+    ; CHECK: [[REG_SEQUENCE:%[0-9]+]]:qq = REG_SEQUENCE %src1, %subreg.qsub0, %src2, %subreg.qsub1
+    ; CHECK: ST2Twov16b [[REG_SEQUENCE]], %ptr :: (store (<4 x s64>))
+    ; CHECK: RET_ReallyLR
+    %ptr:gpr(p0) = COPY $x0
+    %src1:fpr(<16 x s8>) = COPY $q0
+    %src2:fpr(<16 x s8>) = COPY $q1
+    G_INTRINSIC_W_SIDE_EFFECTS intrinsic(@llvm.aarch64.neon.st2), %src1(<16 x s8>), %src2(<16 x s8>), %ptr(p0) :: (store (<4 x s64>))
+    RET_ReallyLR
+
+...
+---
+name:            v4i16_ST2Twov4h
+
+legalized:       true
+regBankSelected: true
+tracksRegLiveness: true
+body:             |
+  bb.0:
+    liveins: $d0, $d1, $x0
+
+    ; CHECK-LABEL: name: v4i16_ST2Twov4h
+    ; CHECK: liveins: $d0, $d1, $x0
+    ; CHECK: %ptr:gpr64sp = COPY $x0
+    ; CHECK: %src1:fpr64 = COPY $d0
+    ; CHECK: %src2:fpr64 = COPY $d1
+    ; CHECK: [[REG_SEQUENCE:%[0-9]+]]:dd = REG_SEQUENCE %src1, %subreg.dsub0, %src2, %subreg.dsub1
+    ; CHECK: ST2Twov4h [[REG_SEQUENCE]], %ptr :: (store (<2 x s64>))
+    ; CHECK: RET_ReallyLR
+    %ptr:gpr(p0) = COPY $x0
+    %src1:fpr(<4 x s16>) = COPY $d0
+    %src2:fpr(<4 x s16>) = COPY $d1
+    G_INTRINSIC_W_SIDE_EFFECTS intrinsic(@llvm.aarch64.neon.st2), %src1(<4 x s16>), %src2(<4 x s16>), %ptr(p0) :: (store (<2 x s64>))
+    RET_ReallyLR
+
+...
+---
+name:            v8i16_ST2Twov8h
+
+legalized:       true
+regBankSelected: true
+tracksRegLiveness: true
+body:             |
+  bb.0:
+    liveins: $q0, $q1, $x0
+
+    ; CHECK-LABEL: name: v8i16_ST2Twov8h
+    ; CHECK: liveins: $q0, $q1, $x0
+    ; CHECK: %ptr:gpr64sp = COPY $x0
+    ; CHECK: %src1:fpr128 = COPY $q0
+    ; CHECK: %src2:fpr128 = COPY $q1
+    ; CHECK: [[REG_SEQUENCE:%[0-9]+]]:qq = REG_SEQUENCE %src1, %subreg.qsub0, %src2, %subreg.qsub1
+    ; CHECK: ST2Twov8h [[REG_SEQUENCE]], %ptr :: (store (<4 x s64>))
+    ; CHECK: RET_ReallyLR
+    %ptr:gpr(p0) = COPY $x0
+    %src1:fpr(<8 x s16>) = COPY $q0
+    %src2:fpr(<8 x s16>) = COPY $q1
+    G_INTRINSIC_W_SIDE_EFFECTS intrinsic(@llvm.aarch64.neon.st2), %src1(<8 x s16>), %src2(<8 x s16>), %ptr(p0) :: (store (<4 x s64>))
+    RET_ReallyLR
+
+...
+---
+name:            v2i32_ST2Twov2s
+legalized:       true
+regBankSelected: true
+tracksRegLiveness: true
+body:             |
+  bb.0:
+    liveins: $d0, $d1, $x0
+
+    ; CHECK-LABEL: name: v2i32_ST2Twov2s
+    ; CHECK: liveins: $d0, $d1, $x0
+    ; CHECK: %ptr:gpr64sp = COPY $x0
+    ; CHECK: %src1:fpr64 = COPY $d0
+    ; CHECK: %src2:fpr64 = COPY $d1
+    ; CHECK: [[REG_SEQUENCE:%[0-9]+]]:dd = REG_SEQUENCE %src1, %subreg.dsub0, %src2, %subreg.dsub1
+    ; CHECK: ST2Twov2s [[REG_SEQUENCE]], %ptr :: (store (<2 x s64>))
+    ; CHECK: RET_ReallyLR
+    %ptr:gpr(p0) = COPY $x0
+    %src1:fpr(<2 x s32>) = COPY $d0
+    %src2:fpr(<2 x s32>) = COPY $d1
+    G_INTRINSIC_W_SIDE_EFFECTS intrinsic(@llvm.aarch64.neon.st2), %src1(<2 x s32>), %src2(<2 x s32>), %ptr(p0) :: (store (<2 x s64>))
+    RET_ReallyLR
+
+...
+---
+name:            v4i32_ST2Twov4s
+legalized:       true
+regBankSelected: true
+tracksRegLiveness: true
+body:             |
+  bb.0:
+    liveins: $q0, $q1, $x0
+
+    ; CHECK-LABEL: name: v4i32_ST2Twov4s
+    ; CHECK: liveins: $q0, $q1, $x0
+    ; CHECK: %ptr:gpr64sp = COPY $x0
+    ; CHECK: %src1:fpr128 = COPY $q0
+    ; CHECK: %src2:fpr128 = COPY $q1
+    ; CHECK: [[REG_SEQUENCE:%[0-9]+]]:qq = REG_SEQUENCE %src1, %subreg.qsub0, %src2, %subreg.qsub1
+    ; CHECK: ST2Twov4s [[REG_SEQUENCE]], %ptr :: (store (<4 x s64>))
+    ; CHECK: RET_ReallyLR
+    %ptr:gpr(p0) = COPY $x0
+    %src1:fpr(<4 x s32>) = COPY $q0
+    %src2:fpr(<4 x s32>) = COPY $q1
+    G_INTRINSIC_W_SIDE_EFFECTS intrinsic(@llvm.aarch64.neon.st2), %src1(<4 x s32>), %src2(<4 x s32>), %ptr(p0) :: (store (<4 x s64>))
+    RET_ReallyLR
+
+...
+---
+name:            v2i64_ST2Twov2d_s64_elts
+legalized:       true
+regBankSelected: true
+tracksRegLiveness: true
+body:             |
+  bb.0:
+    liveins: $q0, $q1, $x0
+
+    ; CHECK-LABEL: name: v2i64_ST2Twov2d_s64_elts
+    ; CHECK: liveins: $q0, $q1, $x0
+    ; CHECK: %ptr:gpr64sp = COPY $x0
+    ; CHECK: %src1:fpr128 = COPY $q0
+    ; CHECK: %src2:fpr128 = COPY $q1
+    ; CHECK: [[REG_SEQUENCE:%[0-9]+]]:qq = REG_SEQUENCE %src1, %subreg.qsub0, %src2, %subreg.qsub1
+    ; CHECK: ST2Twov2d [[REG_SEQUENCE]], %ptr :: (store (<4 x s64>))
+    ; CHECK: RET_ReallyLR
+    %ptr:gpr(p0) = COPY $x0
+    %src1:fpr(<2 x s64>) = COPY $q0
+    %src2:fpr(<2 x s64>) = COPY $q1
+    G_INTRINSIC_W_SIDE_EFFECTS intrinsic(@llvm.aarch64.neon.st2), %src1(<2 x s64>), %src2(<2 x s64>), %ptr(p0) :: (store (<4 x s64>))
+    RET_ReallyLR
+
+...
+---
+name:            v2i64_ST2Twov2d_s64_p0_elts
+legalized:       true
+regBankSelected: true
+tracksRegLiveness: true
+body:             |
+  bb.0:
+    liveins: $q0, $q1, $x0
+
+    ; CHECK-LABEL: name: v2i64_ST2Twov2d_s64_p0_elts
+    ; CHECK: liveins: $q0, $q1, $x0
+    ; CHECK: %ptr:gpr64sp = COPY $x0
+    ; CHECK: %src1:fpr128 = COPY $q0
+    ; CHECK: %src2:fpr128 = COPY $q1
+    ; CHECK: [[REG_SEQUENCE:%[0-9]+]]:qq = REG_SEQUENCE %src1, %subreg.qsub0, %src2, %subreg.qsub1
+    ; CHECK: ST2Twov2d [[REG_SEQUENCE]], %ptr :: (store (<4 x s64>))
+    ; CHECK: RET_ReallyLR
+    %ptr:gpr(p0) = COPY $x0
+    %src1:fpr(<2 x p0>) = COPY $q0
+    %src2:fpr(<2 x p0>) = COPY $q1
+    G_INTRINSIC_W_SIDE_EFFECTS intrinsic(@llvm.aarch64.neon.st2), %src1(<2 x p0>), %src2(<2 x p0>), %ptr(p0) :: (store (<4 x s64>))
+    RET_ReallyLR
+
+...
+---
+name:            v1i64_ST1Twov1d_s64
+legalized:       true
+regBankSelected: true
+tracksRegLiveness: true
+body:             |
+  bb.0:
+    liveins: $x0, $x1, $x2
+
+    ; CHECK-LABEL: name: v1i64_ST1Twov1d_s64
+    ; CHECK: liveins: $x0, $x1, $x2
+    ; CHECK: %ptr:gpr64sp = COPY $x0
+    ; CHECK: %src1:gpr64all = COPY $x0
+    ; CHECK: %src2:gpr64all = COPY $x1
+    ; CHECK: [[REG_SEQUENCE:%[0-9]+]]:dd = REG_SEQUENCE %src1, %subreg.dsub0, %src2, %subreg.dsub1
+    ; CHECK: ST1Twov1d [[REG_SEQUENCE]], %ptr :: (store (<2 x s64>))
+    ; CHECK: RET_ReallyLR
+    %ptr:gpr(p0) = COPY $x0
+    %src1:gpr(s64) = COPY $x0
+    %src2:gpr(s64) = COPY $x1
+    G_INTRINSIC_W_SIDE_EFFECTS intrinsic(@llvm.aarch64.neon.st2), %src1(s64), %src2(s64), %ptr(p0) :: (store (<2 x s64>))
+    RET_ReallyLR
+
+...
+---
+name:            v1i64_ST1Twov1d_p0
+legalized:       true
+regBankSelected: true
+tracksRegLiveness: true
+body:             |
+  bb.0:
+    liveins: $x0, $x1, $x2
+
+    ; CHECK-LABEL: name: v1i64_ST1Twov1d_p0
+    ; CHECK: liveins: $x0, $x1, $x2
+    ; CHECK: %ptr:gpr64sp = COPY $x0
+    ; CHECK: %src1:gpr64all = COPY $x0
+    ; CHECK: %src2:gpr64all = COPY $x1
+    ; CHECK: [[REG_SEQUENCE:%[0-9]+]]:dd = REG_SEQUENCE %src1, %subreg.dsub0, %src2, %subreg.dsub1
+    ; CHECK: ST1Twov1d [[REG_SEQUENCE]], %ptr :: (store (<2 x s64>))
+    ; CHECK: RET_ReallyLR
+    %ptr:gpr(p0) = COPY $x0
+    %src1:gpr(p0) = COPY $x0
+    %src2:gpr(p0) = COPY $x1
+    G_INTRINSIC_W_SIDE_EFFECTS intrinsic(@llvm.aarch64.neon.st2), %src1(p0), %src2(p0), %ptr(p0) :: (store (<2 x s64>))
+    RET_ReallyLR
+
+...