[AMDGPU][NFC] Have helpers to deal with encoding fields. (llvm#82772)

These are hoped to provide more convenient and less error prone
facilities to encode and decode fields than manually defined constants
and functions.

Author: kosarev

llvm/lib/Target/AMDGPU/AMDGPULegalizerInfo.cpp

@@ -4824,9 +4824,8 @@ bool AMDGPULegalizerInfo::legalizeFDIV16(MachineInstr &MI,
   return true;
 }
 
-static const unsigned SPDenormModeBitField =
-    AMDGPU::Hwreg::ID_MODE | (4 << AMDGPU::Hwreg::OFFSET_SHIFT_) |
-    (1 << AMDGPU::Hwreg::WIDTH_M1_SHIFT_);
+static constexpr unsigned SPDenormModeBitField =
+    AMDGPU::Hwreg::HwregEncoding::encode(AMDGPU::Hwreg::ID_MODE, 4, 2);
 
 // Enable or disable FP32 denorm mode. When 'Enable' is true, emit instructions
 // to enable denorm mode. When 'Enable' is false, disable denorm mode.

llvm/lib/Target/AMDGPU/AsmParser/AMDGPUAsmParser.cpp

@@ -7272,11 +7272,11 @@ ParseStatus AMDGPUAsmParser::parseHwreg(OperandVector &Operands) {
 
   if (trySkipId("hwreg", AsmToken::LParen)) {
     OperandInfoTy HwReg(OPR_ID_UNKNOWN);
-    OperandInfoTy Offset(OFFSET_DEFAULT_);
-    OperandInfoTy Width(WIDTH_DEFAULT_);
+    OperandInfoTy Offset(HwregOffset::Default);
+    OperandInfoTy Width(HwregSize::Default);
     if (parseHwregBody(HwReg, Offset, Width) &&
         validateHwreg(HwReg, Offset, Width)) {
-      ImmVal = encodeHwreg(HwReg.Id, Offset.Id, Width.Id);
+      ImmVal = HwregEncoding::encode(HwReg.Id, Offset.Id, Width.Id);
     } else {
       return ParseStatus::Failure;
     }

llvm/lib/Target/AMDGPU/GCNHazardRecognizer.cpp

@@ -177,7 +177,7 @@ static bool isLdsDma(const MachineInstr &MI) {
 static unsigned getHWReg(const SIInstrInfo *TII, const MachineInstr &RegInstr) {
   const MachineOperand *RegOp = TII->getNamedOperand(RegInstr,
                                                      AMDGPU::OpName::simm16);
-  return RegOp->getImm() & AMDGPU::Hwreg::ID_MASK_;
+  return std::get<0>(AMDGPU::Hwreg::HwregEncoding::decode(RegOp->getImm()));
 }
 
 ScheduleHazardRecognizer::HazardType

llvm/lib/Target/AMDGPU/MCTargetDesc/AMDGPUInstPrinter.cpp

@@ -1778,13 +1778,9 @@ void AMDGPUInstPrinter::printSDelayALU(const MCInst *MI, unsigned OpNo,
 
 void AMDGPUInstPrinter::printHwreg(const MCInst *MI, unsigned OpNo,
                                    const MCSubtargetInfo &STI, raw_ostream &O) {
-  unsigned Id;
-  unsigned Offset;
-  unsigned Width;
-
   using namespace llvm::AMDGPU::Hwreg;
   unsigned Val = MI->getOperand(OpNo).getImm();
-  decodeHwreg(Val, Id, Offset, Width);
+  auto [Id, Offset, Width] = HwregEncoding::decode(Val);
   StringRef HwRegName = getHwreg(Id, STI);
 
   O << "hwreg(";
@@ -1793,9 +1789,8 @@ void AMDGPUInstPrinter::printHwreg(const MCInst *MI, unsigned OpNo,
   } else {
     O << Id;
   }
-  if (Width != WIDTH_DEFAULT_ || Offset != OFFSET_DEFAULT_) {
+  if (Width != HwregSize::Default || Offset != HwregOffset::Default)
     O << ", " << Offset << ", " << Width;
-  }
   O << ')';
 }
 

llvm/lib/Target/AMDGPU/SIDefines.h

@@ -549,33 +549,12 @@ enum Id { // HwRegCode, (6) [5:0]
   ID_SQ_PERF_SNAPSHOT_DATA1 = 22,
   ID_SQ_PERF_SNAPSHOT_PC_LO = 23,
   ID_SQ_PERF_SNAPSHOT_PC_HI = 24,
-
-  ID_SHIFT_ = 0,
-  ID_WIDTH_ = 6,
-  ID_MASK_ = (((1 << ID_WIDTH_) - 1) << ID_SHIFT_)
 };
 
 enum Offset : unsigned { // Offset, (5) [10:6]
-  OFFSET_DEFAULT_ = 0,
-  OFFSET_SHIFT_ = 6,
-  OFFSET_WIDTH_ = 5,
-  OFFSET_MASK_ = (((1 << OFFSET_WIDTH_) - 1) << OFFSET_SHIFT_),
-
   OFFSET_MEM_VIOL = 8,
 };
 
-enum WidthMinusOne : unsigned { // WidthMinusOne, (5) [15:11]
-  WIDTH_M1_DEFAULT_ = 31,
-  WIDTH_M1_SHIFT_ = 11,
-  WIDTH_M1_WIDTH_ = 5,
-  WIDTH_M1_MASK_ = (((1 << WIDTH_M1_WIDTH_) - 1) << WIDTH_M1_SHIFT_),
-};
-
-// Some values from WidthMinusOne mapped into Width domain.
-enum Width : unsigned {
-  WIDTH_DEFAULT_ = WIDTH_M1_DEFAULT_ + 1,
-};
-
 enum ModeRegisterMasks : uint32_t {
   FP_ROUND_MASK = 0xf << 0,  // Bits 0..3
   FP_DENORM_MASK = 0xf << 4, // Bits 4..7

llvm/lib/Target/AMDGPU/SIFrameLowering.cpp

@@ -478,14 +478,13 @@ void SIFrameLowering::emitEntryFunctionFlatScratchInit(
         .addImm(0);
       Addc->getOperand(3).setIsDead(); // Mark SCC as dead.
 
-      BuildMI(MBB, I, DL, TII->get(AMDGPU::S_SETREG_B32)).
-        addReg(FlatScrInitLo).
-        addImm(int16_t(AMDGPU::Hwreg::ID_FLAT_SCR_LO |
-                       (31 << AMDGPU::Hwreg::WIDTH_M1_SHIFT_)));
-      BuildMI(MBB, I, DL, TII->get(AMDGPU::S_SETREG_B32)).
-        addReg(FlatScrInitHi).
-        addImm(int16_t(AMDGPU::Hwreg::ID_FLAT_SCR_HI |
-                       (31 << AMDGPU::Hwreg::WIDTH_M1_SHIFT_)));
+      using namespace AMDGPU::Hwreg;
+      BuildMI(MBB, I, DL, TII->get(AMDGPU::S_SETREG_B32))
+          .addReg(FlatScrInitLo)
+          .addImm(int16_t(HwregEncoding::encode(ID_FLAT_SCR_LO, 0, 32)));
+      BuildMI(MBB, I, DL, TII->get(AMDGPU::S_SETREG_B32))
+          .addReg(FlatScrInitHi)
+          .addImm(int16_t(HwregEncoding::encode(ID_FLAT_SCR_HI, 0, 32)));
       return;
     }
 

llvm/lib/Target/AMDGPU/SIISelLowering.cpp

@@ -3960,7 +3960,7 @@ SDValue SITargetLowering::lowerGET_ROUNDING(SDValue Op,
   assert(Op.getValueType() == MVT::i32);
 
   uint32_t BothRoundHwReg =
-      AMDGPU::Hwreg::encodeHwreg(AMDGPU::Hwreg::ID_MODE, 0, 4);
+      AMDGPU::Hwreg::HwregEncoding::encode(AMDGPU::Hwreg::ID_MODE, 0, 4);
   SDValue GetRoundBothImm = DAG.getTargetConstant(BothRoundHwReg, SL, MVT::i32);
 
   SDValue IntrinID =
@@ -4195,8 +4195,8 @@ SITargetLowering::emitGWSMemViolTestLoop(MachineInstr &MI,
 
   MachineBasicBlock::iterator I = LoopBB->end();
 
-  const unsigned EncodedReg = AMDGPU::Hwreg::encodeHwreg(
-    AMDGPU::Hwreg::ID_TRAPSTS, AMDGPU::Hwreg::OFFSET_MEM_VIOL, 1);
+  const unsigned EncodedReg = AMDGPU::Hwreg::HwregEncoding::encode(
+      AMDGPU::Hwreg::ID_TRAPSTS, AMDGPU::Hwreg::OFFSET_MEM_VIOL, 1);
 
   // Clear TRAP_STS.MEM_VIOL
   BuildMI(*LoopBB, LoopBB->begin(), DL, TII->get(AMDGPU::S_SETREG_IMM32_B32))
@@ -4999,18 +4999,16 @@ MachineBasicBlock *SITargetLowering::EmitInstrWithCustomInserter(
     // Otherwise there was overflow and the result is hi2:0. In both cases the
     // result should represent the actual time at some point during the sequence
     // of three getregs.
+    using namespace AMDGPU::Hwreg;
     Register RegHi1 = MRI.createVirtualRegister(&AMDGPU::SReg_32RegClass);
     BuildMI(*BB, MI, DL, TII->get(AMDGPU::S_GETREG_B32), RegHi1)
-        .addImm(AMDGPU::Hwreg::encodeHwreg(AMDGPU::Hwreg::ID_SHADER_CYCLES_HI,
-                                           0, 32));
+        .addImm(HwregEncoding::encode(ID_SHADER_CYCLES_HI, 0, 32));
     Register RegLo1 = MRI.createVirtualRegister(&AMDGPU::SReg_32RegClass);
     BuildMI(*BB, MI, DL, TII->get(AMDGPU::S_GETREG_B32), RegLo1)
-        .addImm(
-            AMDGPU::Hwreg::encodeHwreg(AMDGPU::Hwreg::ID_SHADER_CYCLES, 0, 32));
+        .addImm(HwregEncoding::encode(ID_SHADER_CYCLES, 0, 32));
     Register RegHi2 = MRI.createVirtualRegister(&AMDGPU::SReg_32RegClass);
     BuildMI(*BB, MI, DL, TII->get(AMDGPU::S_GETREG_B32), RegHi2)
-        .addImm(AMDGPU::Hwreg::encodeHwreg(AMDGPU::Hwreg::ID_SHADER_CYCLES_HI,
-                                           0, 32));
+        .addImm(HwregEncoding::encode(ID_SHADER_CYCLES_HI, 0, 32));
     BuildMI(*BB, MI, DL, TII->get(AMDGPU::S_CMP_EQ_U32))
         .addReg(RegHi1)
         .addReg(RegHi2);
@@ -5207,8 +5205,8 @@ MachineBasicBlock *SITargetLowering::EmitInstrWithCustomInserter(
     // FIXME: This could be predicates on the immediate, but tablegen doesn't
     // allow you to have a no side effect instruction in the output of a
     // sideeffecting pattern.
-    unsigned ID, Offset, Width;
-    AMDGPU::Hwreg::decodeHwreg(MI.getOperand(1).getImm(), ID, Offset, Width);
+    auto [ID, Offset, Width] =
+        AMDGPU::Hwreg::HwregEncoding::decode(MI.getOperand(1).getImm());
     if (ID != AMDGPU::Hwreg::ID_MODE)
       return BB;
 
@@ -10495,9 +10493,8 @@ SDValue SITargetLowering::LowerFDIV32(SDValue Op, SelectionDAG &DAG) const {
   SDValue NegDivScale0 = DAG.getNode(ISD::FNEG, SL, MVT::f32,
                                      DenominatorScaled, Flags);
 
-  const unsigned Denorm32Reg = AMDGPU::Hwreg::ID_MODE |
-                               (4 << AMDGPU::Hwreg::OFFSET_SHIFT_) |
-                               (1 << AMDGPU::Hwreg::WIDTH_M1_SHIFT_);
+  using namespace AMDGPU::Hwreg;
+  const unsigned Denorm32Reg = HwregEncoding::encode(ID_MODE, 4, 2);
   const SDValue BitField = DAG.getTargetConstant(Denorm32Reg, SL, MVT::i32);
 
   const MachineFunction &MF = DAG.getMachineFunction();

llvm/lib/Target/AMDGPU/SIModeRegister.cpp

@@ -225,11 +225,10 @@ void SIModeRegister::insertSetreg(MachineBasicBlock &MBB, MachineInstr *MI,
     unsigned Offset = llvm::countr_zero<unsigned>(InstrMode.Mask);
     unsigned Width = llvm::countr_one<unsigned>(InstrMode.Mask >> Offset);
     unsigned Value = (InstrMode.Mode >> Offset) & ((1 << Width) - 1);
+    using namespace AMDGPU::Hwreg;
     BuildMI(MBB, MI, nullptr, TII->get(AMDGPU::S_SETREG_IMM32_B32))
         .addImm(Value)
-        .addImm(((Width - 1) << AMDGPU::Hwreg::WIDTH_M1_SHIFT_) |
-                (Offset << AMDGPU::Hwreg::OFFSET_SHIFT_) |
-                (AMDGPU::Hwreg::ID_MODE << AMDGPU::Hwreg::ID_SHIFT_));
+        .addImm(HwregEncoding::encode(ID_MODE, Offset, Width));
     ++NumSetregInserted;
     Changed = true;
     InstrMode.Mask &= ~(((1 << Width) - 1) << Offset);
@@ -276,15 +275,11 @@ void SIModeRegister::processBlockPhase1(MachineBasicBlock &MBB,
       // as we assume it has been inserted by a higher authority (this is
       // likely to be a very rare occurrence).
       unsigned Dst = TII->getNamedOperand(MI, AMDGPU::OpName::simm16)->getImm();
-      if (((Dst & AMDGPU::Hwreg::ID_MASK_) >> AMDGPU::Hwreg::ID_SHIFT_) !=
-          AMDGPU::Hwreg::ID_MODE)
+      using namespace AMDGPU::Hwreg;
+      auto [Id, Offset, Width] = HwregEncoding::decode(Dst);
+      if (Id != ID_MODE)
         continue;
 
-      unsigned Width = ((Dst & AMDGPU::Hwreg::WIDTH_M1_MASK_) >>
-                        AMDGPU::Hwreg::WIDTH_M1_SHIFT_) +
-                       1;
-      unsigned Offset =
-          (Dst & AMDGPU::Hwreg::OFFSET_MASK_) >> AMDGPU::Hwreg::OFFSET_SHIFT_;
       unsigned Mask = maskTrailingOnes<unsigned>(Width) << Offset;
 
       // If an InsertionPoint is set we will insert a setreg there.

llvm/lib/Target/AMDGPU/Utils/AMDGPUBaseInfo.cpp

@@ -1698,35 +1698,21 @@ int64_t getHwregId(const StringRef Name, const MCSubtargetInfo &STI) {
   return (Idx < 0) ? Idx : Opr[Idx].Encoding;
 }
 
-bool isValidHwreg(int64_t Id) {
-  return 0 <= Id && isUInt<ID_WIDTH_>(Id);
-}
+bool isValidHwreg(int64_t Id) { return 0 <= Id && isUInt<HwregId::Width>(Id); }
 
 bool isValidHwregOffset(int64_t Offset) {
-  return 0 <= Offset && isUInt<OFFSET_WIDTH_>(Offset);
+  return 0 <= Offset && isUInt<HwregOffset::Width>(Offset);
 }
 
 bool isValidHwregWidth(int64_t Width) {
-  return 0 <= (Width - 1) && isUInt<WIDTH_M1_WIDTH_>(Width - 1);
-}
-
-uint64_t encodeHwreg(uint64_t Id, uint64_t Offset, uint64_t Width) {
-  return (Id << ID_SHIFT_) |
-         (Offset << OFFSET_SHIFT_) |
-         ((Width - 1) << WIDTH_M1_SHIFT_);
+  return 0 <= (Width - 1) && isUInt<HwregSize::Width>(Width - 1);
 }
 
 StringRef getHwreg(unsigned Id, const MCSubtargetInfo &STI) {
   int Idx = getOprIdx<const MCSubtargetInfo &>(Id, Opr, OPR_SIZE, STI);
   return (Idx < 0) ? "" : Opr[Idx].Name;
 }
 
-void decodeHwreg(unsigned Val, unsigned &Id, unsigned &Offset, unsigned &Width) {
-  Id = (Val & ID_MASK_) >> ID_SHIFT_;
-  Offset = (Val & OFFSET_MASK_) >> OFFSET_SHIFT_;
-  Width = ((Val & WIDTH_M1_MASK_) >> WIDTH_M1_SHIFT_) + 1;
-}
-
 } // namespace Hwreg
 
 //===----------------------------------------------------------------------===//

llvm/lib/Target/AMDGPU/Utils/AMDGPUBaseInfo.h

@@ -322,6 +322,35 @@ getNumVGPRBlocks(const MCSubtargetInfo *STI, unsigned NumSGPRs,
 
 } // end namespace IsaInfo
 
+// Represents a field in an encoded value.
+template <unsigned HighBit, unsigned LowBit, unsigned D = 0>
+struct EncodingField {
+  static_assert(HighBit >= LowBit, "Invalid bit range!");
+  static constexpr unsigned Offset = LowBit;
+  static constexpr unsigned Width = HighBit - LowBit + 1;
+
+  using ValueType = unsigned;
+  static constexpr ValueType Default = D;
+
+  ValueType Value;
+  constexpr EncodingField(ValueType Value) : Value(Value) {}
+
+  constexpr uint64_t encode() const { return Value; }
+  static ValueType decode(uint64_t Encoded) { return Encoded; }
+};
+
+// A helper for encoding and decoding multiple fields.
+template <typename... Fields> struct EncodingFields {
+  static constexpr uint64_t encode(Fields... Values) {
+    return ((Values.encode() << Values.Offset) | ...);
+  }
+
+  static std::tuple<typename Fields::ValueType...> decode(uint64_t Encoded) {
+    return {Fields::decode((Encoded >> Fields::Offset) &
+                           maxUIntN(Fields::Width))...};
+  }
+};
+
 LLVM_READONLY
 int16_t getNamedOperandIdx(uint16_t Opcode, uint16_t NamedIdx);
 
@@ -1021,6 +1050,17 @@ unsigned encodeStorecntDscnt(const IsaVersion &Version, const Waitcnt &Decoded);
 
 namespace Hwreg {
 
+using HwregId = EncodingField<5, 0>;
+using HwregOffset = EncodingField<10, 6>;
+
+struct HwregSize : EncodingField<15, 11, 32> {
+  using EncodingField::EncodingField;
+  constexpr uint64_t encode() const { return Value - 1; }
+  static ValueType decode(uint64_t Encoded) { return Encoded + 1; }
+};
+
+using HwregEncoding = EncodingFields<HwregId, HwregOffset, HwregSize>;
+
 LLVM_READONLY
 int64_t getHwregId(const StringRef Name, const MCSubtargetInfo &STI);
 
@@ -1033,14 +1073,9 @@ bool isValidHwregOffset(int64_t Offset);
 LLVM_READNONE
 bool isValidHwregWidth(int64_t Width);
 
-LLVM_READNONE
-uint64_t encodeHwreg(uint64_t Id, uint64_t Offset, uint64_t Width);
-
 LLVM_READNONE
 StringRef getHwreg(unsigned Id, const MCSubtargetInfo &STI);
 
-void decodeHwreg(unsigned Val, unsigned &Id, unsigned &Offset, unsigned &Width);
-
 } // namespace Hwreg
 
 namespace DepCtr {