[NFC] Use ADT/Bitfields in Instructions

[gchatelet]

Summary

This is an example patch for D81580.

[gchatelet]

llvm/include/llvm/IR/InstrTypes.h

1099

Previous code was not explicit about the size of the packed bit, so it was possible to pass in values that would be truncated when stored (values >=8192)
Additionally the first two bits were left unused which would force a shift operation for both get and set.

I believe we can just make the bitfield start at 0

llvm/include/llvm/IR/Instructions.h

429

The first bit is unused, this leads to an additional shift operation for both get and set.
Also the field was not bounded, making it impossible to know which bits are available.

534

The bit in position 1 is unused?

569

The masking pattern here is dubious.

582

The masking pattern here is dubious.

734

Same here the bit in position 1 is unused.

748

The Operation field is not bounded making it impossible to know which next bit is usable.

llvm/lib/IR/Instructions.cpp

1401

Here only the lower bits are masked so theoretically encode(Align) could occupy more than 6 bits and start overrun the next field storing AtomicOrdering

1480

ditto.

[craig.topper]

llvm/include/llvm/IR/InstrTypes.h

1099

Isn't TailCallKind from CallInst in bits 0 and 1?

[craig.topper]

llvm/include/llvm/IR/Instructions.h

534

It used to be syncscope before that was extended to support arbitrary scopes instead of just single thread and system

734

Same as above

[serge-sans-paille]

I really like the extra abstraction layer! Some reviews inline.

llvm/include/llvm/ADT/Bitfields.h

75 ↗

(On Diff #270144)

Shouldn't this be (8 * sizeof(type)) instead of 64?

76 ↗

(On Diff #270144)

if sizeof(1ULL) == 64 and size == 64 then you're doomed. what about ~static_cast<type>(0) >> (8 * sizeof(type) - size)` ?

llvm/include/llvm/IR/InstrTypes.h

1361

Looks like this is breaking the abstraction. Make this a (static) method?

[gchatelet]

• Handle bounds and signed integer, redesign the implementation

[gchatelet]

llvm/include/llvm/ADT/Bitfields.h

76 ↗

(On Diff #270144)

Thx for your comment, I had to be more careful about signed-ness but I believe the new implementation is much better,

llvm/include/llvm/IR/InstrTypes.h

1099

You're right, thx for pointing this out it was not obvious.

1361

The abstraction will now check bounds for enums.

llvm/include/llvm/IR/Instructions.h

534

Thank you, I've updated the patch to reflect this knowledge.

[gchatelet]

• Update style.

[gchatelet]

• Modify all enums to be unsigned

[gchatelet]

Fix style and rebase

[gchatelet]

rebase

[gchatelet]

Fix style.

[nhaehnle]

llvm/lib/Target/AMDGPU/SIISelLowering.cpp

4556

This change and the one below don't look wrong, but they seem unrelated to what this patch is claiming to achieve.

[gchatelet]

llvm/lib/Target/AMDGPU/SIISelLowering.cpp

4556

They seem unrelated but they are : )
This has to do with ICmpInst::Predicate now being explicitly unsigned for efficiency reasons.
The comparison below in the if statement would then trigger a warning because we compare signed and unsigned types.
Changing Condcode to unsigned makes sure the compiler is happy.

[gchatelet]

• Fix misaligned documentation

[aprantl]

Can you add a comment that explains when and why to use this over actual C(++) bitfields?

llvm/include/llvm/ADT/Bitfields.h

25 ↗

(On Diff #272719)

Does this doxygen comment just hang in open space? It would be unfortunate if it didn't make it into the documentation just because it's not attached to a syntax node.

[gchatelet]

In D81662#2109849, @aprantl wrote:

Can you add a comment that explains when and why to use this over actual C(++) bitfields?

Last version of the design is here https://reviews.llvm.org/D82454#change-SB8sVbudjRwc
I've updated the documentation. WDYT?

[gchatelet]

• rebase with the new API

[gchatelet]

Use the optimized test method

[gchatelet]

LGTY @serge-sans-paille?

[gchatelet]

rebase

[gchatelet]

I'll submit this if nobody objects

llvm/include/llvm/IR/InstrTypes.h

public:
   /// This enumeration lists the possible predicates for CmpInst subclasses.
   /// Values in the range 0-31 are reserved for FCmpInst, while values in the
   /// range 32-64 are reserved for ICmpInst. This is necessary to ensure the
   /// predicate values are not overlapping between the classes.
   ///
   /// Some passes (e.g. InstCombine) depend on the bit-wise characteristics of
   /// FCMP_* values. Changing the bit patterns requires a potential change to
   /// those passes.
-  enum Predicate {
-    // Opcode              U L G E    Intuitive operation
-    FCMP_FALSE =  0,  ///< 0 0 0 0    Always false (always folded)
-    FCMP_OEQ   =  1,  ///< 0 0 0 1    True if ordered and equal
-    FCMP_OGT   =  2,  ///< 0 0 1 0    True if ordered and greater than
-    FCMP_OGE   =  3,  ///< 0 0 1 1    True if ordered and greater than or equal
-    FCMP_OLT   =  4,  ///< 0 1 0 0    True if ordered and less than
-    FCMP_OLE   =  5,  ///< 0 1 0 1    True if ordered and less than or equal
-    FCMP_ONE   =  6,  ///< 0 1 1 0    True if ordered and operands are unequal
-    FCMP_ORD   =  7,  ///< 0 1 1 1    True if ordered (no nans)
-    FCMP_UNO   =  8,  ///< 1 0 0 0    True if unordered: isnan(X) | isnan(Y)
-    FCMP_UEQ   =  9,  ///< 1 0 0 1    True if unordered or equal
-    FCMP_UGT   = 10,  ///< 1 0 1 0    True if unordered or greater than
-    FCMP_UGE   = 11,  ///< 1 0 1 1    True if unordered, greater than, or equal
-    FCMP_ULT   = 12,  ///< 1 1 0 0    True if unordered or less than
-    FCMP_ULE   = 13,  ///< 1 1 0 1    True if unordered, less than, or equal
-    FCMP_UNE   = 14,  ///< 1 1 1 0    True if unordered or not equal
-    FCMP_TRUE  = 15,  ///< 1 1 1 1    Always true (always folded)
+  enum Predicate : unsigned {
+    // Opcode            U L G E    Intuitive operation
+    FCMP_FALSE = 0, ///< 0 0 0 0    Always false (always folded)
+    FCMP_OEQ = 1,   ///< 0 0 0 1    True if ordered and equal
+    FCMP_OGT = 2,   ///< 0 0 1 0    True if ordered and greater than
+    FCMP_OGE = 3,   ///< 0 0 1 1    True if ordered and greater than or equal
+    FCMP_OLT = 4,   ///< 0 1 0 0    True if ordered and less than
+    FCMP_OLE = 5,   ///< 0 1 0 1    True if ordered and less than or equal
+    FCMP_ONE = 6,   ///< 0 1 1 0    True if ordered and operands are unequal
+    FCMP_ORD = 7,   ///< 0 1 1 1    True if ordered (no nans)
+    FCMP_UNO = 8,   ///< 1 0 0 0    True if unordered: isnan(X) | isnan(Y)
+    FCMP_UEQ = 9,   ///< 1 0 0 1    True if unordered or equal
+    FCMP_UGT = 10,  ///< 1 0 1 0    True if unordered or greater than
+    FCMP_UGE = 11,  ///< 1 0 1 1    True if unordered, greater than, or equal
+    FCMP_ULT = 12,  ///< 1 1 0 0    True if unordered or less than
+    FCMP_ULE = 13,  ///< 1 1 0 1    True if unordered, less than, or equal
+    FCMP_UNE = 14,  ///< 1 1 1 0    True if unordered or not equal
+    FCMP_TRUE = 15, ///< 1 1 1 1    Always true (always folded)
     FIRST_FCMP_PREDICATE = FCMP_FALSE,
     LAST_FCMP_PREDICATE = FCMP_TRUE,
     BAD_FCMP_PREDICATE = FCMP_TRUE + 1,
-    ICMP_EQ    = 32,  ///< equal
-    ICMP_NE    = 33,  ///< not equal
-    ICMP_UGT   = 34,  ///< unsigned greater than
-    ICMP_UGE   = 35,  ///< unsigned greater or equal
-    ICMP_ULT   = 36,  ///< unsigned less than
-    ICMP_ULE   = 37,  ///< unsigned less or equal
-    ICMP_SGT   = 38,  ///< signed greater than
-    ICMP_SGE   = 39,  ///< signed greater or equal
-    ICMP_SLT   = 40,  ///< signed less than
-    ICMP_SLE   = 41,  ///< signed less or equal
+    ICMP_EQ = 32,  ///< equal
+    ICMP_NE = 33,  ///< not equal
+    ICMP_UGT = 34, ///< unsigned greater than
+    ICMP_UGE = 35, ///< unsigned greater or equal
+    ICMP_ULT = 36, ///< unsigned less than
+    ICMP_ULE = 37, ///< unsigned less or equal
+    ICMP_SGT = 38, ///< signed greater than
+    ICMP_SGE = 39, ///< signed greater or equal
+    ICMP_SLT = 40, ///< signed less than
+    ICMP_SLE = 41, ///< signed less or equal
     FIRST_ICMP_PREDICATE = ICMP_EQ,
     LAST_ICMP_PREDICATE = ICMP_SLE,
     BAD_ICMP_PREDICATE = ICMP_SLE + 1
   };
+  using PredicateField =
+      Bitfield::Element<Predicate, 0, 6, LAST_ICMP_PREDICATE>; // Next bit:6
 
 protected:
   CmpInst(Type *ty, Instruction::OtherOps op, Predicate pred,
           Value *LHS, Value *RHS, const Twine &Name = "",
           Instruction *InsertBefore = nullptr,
           Instruction *FlagsSource = nullptr);
 
   CmpInst(Type *ty, Instruction::OtherOps op, Predicate pred,
static CmpInst *Create(OtherOps Op, Predicate predicate, Value *S1,
                          Value *S2, const Twine &Name, BasicBlock *InsertAtEnd);
 
   /// Get the opcode casted to the right type
   OtherOps getOpcode() const {
     return static_cast<OtherOps>(Instruction::getOpcode());
   }
 
   /// Return the predicate for this instruction.
-  Predicate getPredicate() const {
-    return Predicate(getSubclassDataFromInstruction());
-  }
+  Predicate getPredicate() const { return getSubclassData<PredicateField>(); }
 
   /// Set the predicate for this instruction to the specified value.
-  void setPredicate(Predicate P) { setInstructionSubclassData(P); }
+  void setPredicate(Predicate P) { setSubclassData<PredicateField>(P); }
 
   static bool isFPPredicate(Predicate P) {
     return P >= FIRST_FCMP_PREDICATE && P <= LAST_FCMP_PREDICATE;
   }
 
   static bool isIntPredicate(Predicate P) {
     return P >= FIRST_ICMP_PREDICATE && P <= LAST_ICMP_PREDICATE;
   }

 /// - Zero or more subclass controlled operands
 /// - The called function.
 ///
 /// This allows this base class to easily access the called function and the
 /// start of the arguments without knowing how many other operands a particular
 /// subclass requires. Note that accessing the end of the argument list isn't
 /// as cheap as most other operations on the base class.
 class CallBase : public Instruction {
+  // The first two bits are reserved by CallInst for fast retrieving,
+  using CallInstReservedField = Bitfield::Element<unsigned, 0, 2>; // Next bit:2
+  using CallingConvField = Bitfield::Element<CallingConv::ID, 2, 10,
+                                             CallingConv::MaxID>; // Next bit:12
+
 protected:
   /// The last operand is the called operand.
   static constexpr int CalledOperandOpEndIdx = -1;
 
   AttributeList Attrs; ///< parameter attributes for callable
   FunctionType *FTy;
 
   template <class... ArgsTy>
assert(FTy == cast<FunctionType>(
                       cast<PointerType>(Fn->getType())->getElementType()));
     // This function doesn't mutate the return type, only the function
     // type. Seems broken, but I'm just gonna stick an assert in for now.
     assert(getType() == FTy->getReturnType());
     setCalledOperand(Fn);
   }
 
   CallingConv::ID getCallingConv() const {
-    return static_cast<CallingConv::ID>(getSubclassDataFromInstruction() >> 2);
+    return getSubclassData<CallingConvField>();
   }
 
   void setCallingConv(CallingConv::ID CC) {
-    auto ID = static_cast<unsigned>(CC);
-    assert(!(ID & ~CallingConv::MaxID) && "Unsupported calling convention");
-    setInstructionSubclassData((getSubclassDataFromInstruction() & 3) |
-                               (ID << 2));
+    setSubclassData<CallingConvField>(CC);
   }
 
   /// Check if this call is an inline asm statement.
   bool isInlineAsm() const { return isa<InlineAsm>(getCalledOperand()); }
 
   /// \name Attribute API
   ///
   /// These methods access and modify attributes on this call (including

llvm/include/llvm/IR/Instruction.h

 // base class for all of the LLVM instructions.
 //
 //===----------------------------------------------------------------------===//
 
 #ifndef LLVM_IR_INSTRUCTION_H
 #define LLVM_IR_INSTRUCTION_H
 
 #include "llvm/ADT/ArrayRef.h"
+#include "llvm/ADT/Bitfields.h"
 #include "llvm/ADT/None.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/ADT/ilist_node.h"
 #include "llvm/IR/DebugLoc.h"
 #include "llvm/IR/SymbolTableListTraits.h"
 #include "llvm/IR/User.h"
 #include "llvm/IR/Value.h"
 #include "llvm/Support/Casting.h"
class Instruction : public User,
                     public ilist_node_with_parent<Instruction, BasicBlock> {
   BasicBlock *Parent;
   DebugLoc DbgLoc;                         // 'dbg' Metadata cache.
 
   /// Relative order of this instruction in its parent basic block. Used for
   /// O(1) local dominance checks between instructions.
   mutable unsigned Order = 0;
 
-  enum {
-    /// This is a bit stored in the SubClassData field which indicates whether
-    /// this instruction has metadata attached to it or not.
-    HasMetadataBit = 1 << 15
-  };
+protected:
+  // The 15 first bits of `Value::SubclassData` are available for subclasses of
+  // `Instruction` to use.
+  using OpaqueField = Bitfield::Element<uint16_t, 0, 15>; // Next bit:15
+private:
+  // The last bit is used to store whether the instruction has metadata attached
+  // or not.
+  using HasMetadataField = Bitfield::Element<bool, 15, 1>;
 
 protected:
   ~Instruction(); // Use deleteValue() to delete a generic Instruction.
 
 public:
   Instruction(const Instruction &) = delete;
   Instruction &operator=(const Instruction &) = delete;
 
public:
   ///     applications, thus the N-way merging should be in code path.
   /// The DebugLoc attached to this instruction will be overwritten by the
   /// merged DebugLoc.
   void applyMergedLocation(const DILocation *LocA, const DILocation *LocB);
 
 private:
   /// Return true if we have an entry in the on-the-side metadata hash.
   bool hasMetadataHashEntry() const {
-    return (getSubclassDataFromValue() & HasMetadataBit) != 0;
+    return Bitfield::test<HasMetadataField>(getSubclassDataFromValue());
   }
 
   // These are all implemented in Metadata.cpp.
   MDNode *getMetadataImpl(unsigned KindID) const;
   MDNode *getMetadataImpl(StringRef Kind) const;
   void
   getAllMetadataImpl(SmallVectorImpl<std::pair<unsigned, MDNode *>> &) const;
   void getAllMetadataOtherThanDebugLocImpl(
private:
   void setValueSubclassData(unsigned short D) {
     Value::setValueSubclassData(D);
   }
 
   unsigned short getSubclassDataFromValue() const {
     return Value::getSubclassDataFromValue();
   }
 
-  void setHasMetadataHashEntry(bool V) {
-    setValueSubclassData((getSubclassDataFromValue() & ~HasMetadataBit) |
-                         (V ? HasMetadataBit : 0));
-  }
+  void setHasMetadataHashEntry(bool V) { setSubclassData<HasMetadataField>(V); }
 
   void setParent(BasicBlock *P);
 
 protected:
   // Instruction subclasses can stick up to 15 bits of stuff into the
   // SubclassData field of instruction with these members.
 
-  // Verify that only the low 15 bits are used.
-  void setInstructionSubclassData(unsigned short D) {
-    assert((D & HasMetadataBit) == 0 && "Out of range value put into field");
-    setValueSubclassData((getSubclassDataFromValue() & HasMetadataBit) | D);
-  }
-
-  unsigned getSubclassDataFromInstruction() const {
-    return getSubclassDataFromValue() & ~HasMetadataBit;
+  template <typename BitfieldElement>
+  typename BitfieldElement::Type getSubclassData() const {
+    static_assert(
+        std::is_same<BitfieldElement, HasMetadataField>::value ||
+            !Bitfield::isOverlapping<BitfieldElement, HasMetadataField>(),
+        "Must not overlap with the metadata bit");
+    return Bitfield::get<BitfieldElement>(getSubclassDataFromValue());
+  }
+
+  template <typename BitfieldElement>
+  void setSubclassData(typename BitfieldElement::Type Value) {
+    static_assert(
+        std::is_same<BitfieldElement, HasMetadataField>::value ||
+            !Bitfield::isOverlapping<BitfieldElement, HasMetadataField>(),
+        "Must not overlap with the metadata bit");
+    auto Storage = getSubclassDataFromValue();
+    Bitfield::set<BitfieldElement>(Storage, Value);
+    setValueSubclassData(Storage);
   }
 
   Instruction(Type *Ty, unsigned iType, Use *Ops, unsigned NumOps,
               Instruction *InsertBefore = nullptr);
   Instruction(Type *Ty, unsigned iType, Use *Ops, unsigned NumOps,
               BasicBlock *InsertAtEnd);
 
 private:

llvm/include/llvm/IR/Instructions.h

 // instruction subclasses.
 //
 //===----------------------------------------------------------------------===//
 
 #ifndef LLVM_IR_INSTRUCTIONS_H
 #define LLVM_IR_INSTRUCTIONS_H
 
 #include "llvm/ADT/ArrayRef.h"
+#include "llvm/ADT/Bitfields.h"
 #include "llvm/ADT/None.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/ADT/Twine.h"
 #include "llvm/ADT/iterator.h"
 #include "llvm/ADT/iterator_range.h"
 #include "llvm/IR/Attributes.h"

 //===----------------------------------------------------------------------===//
 //                                AllocaInst Class
 //===----------------------------------------------------------------------===//
 
 /// an instruction to allocate memory on the stack
 class AllocaInst : public UnaryInstruction {
   Type *AllocatedType;
 
+  using AlignmentField = Bitfield::Element<unsigned, 0, 5>;    // Next bit:5
+  using UsedWithInAllocaField = Bitfield::Element<bool, 5, 1>; // Next bit:6
+  using SwiftErrorField = Bitfield::Element<bool, 6, 1>;       // Next bit:7
+
 protected:
   // Note: Instruction needs to be a friend here to call cloneImpl.
   friend class Instruction;
 
   AllocaInst *cloneImpl() const;
 
 public:
   explicit AllocaInst(Type *Ty, unsigned AddrSpace, Value *ArraySize,
public:
   Type *getAllocatedType() const { return AllocatedType; }
   /// for use only in special circumstances that need to generically
   /// transform a whole instruction (eg: IR linking and vectorization).
   void setAllocatedType(Type *Ty) { AllocatedType = Ty; }
 
   /// Return the alignment of the memory that is being allocated by the
   /// instruction.
   Align getAlign() const {
-    return *decodeMaybeAlign(getSubclassDataFromInstruction() & 31);
+    return *decodeMaybeAlign(getSubclassData<AlignmentField>());
   }
   // FIXME: Remove this one transition to Align is over.
   unsigned getAlignment() const { return getAlign().value(); }
   void setAlignment(Align Align);
 
   /// Return true if this alloca is in the entry block of the function and is a
   /// constant size. If so, the code generator will fold it into the
   /// prolog/epilog code, so it is basically free.
   bool isStaticAlloca() const;
 
   /// Return true if this alloca is used as an inalloca argument to a call. Such
   /// allocas are never considered static even if they are in the entry block.
   bool isUsedWithInAlloca() const {
-    return getSubclassDataFromInstruction() & 32;
+    return getSubclassData<UsedWithInAllocaField>();
   }
 
   /// Specify whether this alloca is used to represent the arguments to a call.
   void setUsedWithInAlloca(bool V) {
-    setInstructionSubclassData((getSubclassDataFromInstruction() & ~32) |
-                               (V ? 32 : 0));
+    setSubclassData<UsedWithInAllocaField>(V);
   }
 
   /// Return true if this alloca is used as a swifterror argument to a call.
-  bool isSwiftError() const {
-    return getSubclassDataFromInstruction() & 64;
-  }
-
+  bool isSwiftError() const { return getSubclassData<SwiftErrorField>(); }
   /// Specify whether this alloca is used to represent a swifterror.
-  void setSwiftError(bool V) {
-    setInstructionSubclassData((getSubclassDataFromInstruction() & ~64) |
-                               (V ? 64 : 0));
-  }
+  void setSwiftError(bool V) { setSubclassData<SwiftErrorField>(V); }
 
   // Methods for support type inquiry through isa, cast, and dyn_cast:
   static bool classof(const Instruction *I) {
     return (I->getOpcode() == Instruction::Alloca);
   }
   static bool classof(const Value *V) {
     return isa<Instruction>(V) && classof(cast<Instruction>(V));
   }
 
 private:
   // Shadow Instruction::setInstructionSubclassData with a private forwarding
   // method so that subclasses cannot accidentally use it.
-  void setInstructionSubclassData(unsigned short D) {
-    Instruction::setInstructionSubclassData(D);
+  template <typename Bitfield>
+  void setSubclassData(typename Bitfield::Type Value) {
+    Instruction::setSubclassData<Bitfield>(Value);
   }
 };
 
 //===----------------------------------------------------------------------===//
 //                                LoadInst Class
 //===----------------------------------------------------------------------===//
 
 /// An instruction for reading from memory. This uses the SubclassData field in
 /// Value to store whether or not the load is volatile.
 class LoadInst : public UnaryInstruction {
+  using VolatileField = Bitfield::Element<bool, 0, 1>;      // Next bit:1
+  using AlignmentField = Bitfield::Element<unsigned, 1, 6>; // Next bit:7
+  using OrderingField = Bitfield::Element<AtomicOrdering, 7, 3,
+                                          AtomicOrdering::LAST>; // Next bit:10
+
   void AssertOK();
 
 protected:
   // Note: Instruction needs to be a friend here to call cloneImpl.
   friend class Instruction;
 
   LoadInst *cloneImpl() const;
 
LoadInst(Type *Ty, Value *Ptr, const Twine &NameStr, bool isVolatile,
            Align Align, AtomicOrdering Order,
            SyncScope::ID SSID = SyncScope::System,
            Instruction *InsertBefore = nullptr);
   LoadInst(Type *Ty, Value *Ptr, const Twine &NameStr, bool isVolatile,
            Align Align, AtomicOrdering Order, SyncScope::ID SSID,
            BasicBlock *InsertAtEnd);
 
   /// Return true if this is a load from a volatile memory location.
-  bool isVolatile() const { return getSubclassDataFromInstruction() & 1; }
+  bool isVolatile() const { return getSubclassData<VolatileField>(); }
 
   /// Specify whether this is a volatile load or not.
-  void setVolatile(bool V) {
-    setInstructionSubclassData((getSubclassDataFromInstruction() & ~1) |
-                               (V ? 1 : 0));
-  }
+  void setVolatile(bool V) { setSubclassData<VolatileField>(V); }
 
   /// Return the alignment of the access that is being performed.
   /// FIXME: Remove this function once transition to Align is over.
   /// Use getAlign() instead.
   unsigned getAlignment() const { return getAlign().value(); }
 
   /// Return the alignment of the access that is being performed.
   Align getAlign() const {
-    return *decodeMaybeAlign((getSubclassDataFromInstruction() >> 1) & 31);
+    return *decodeMaybeAlign(getSubclassData<AlignmentField>());
   }
 
   void setAlignment(Align Alignment);
 
   /// Returns the ordering constraint of this load instruction.
   AtomicOrdering getOrdering() const {
-    return AtomicOrdering((getSubclassDataFromInstruction() >> 7) & 7);
+    return getSubclassData<OrderingField>();
   }
-
   /// Sets the ordering constraint of this load instruction.  May not be Release
   /// or AcquireRelease.
   void setOrdering(AtomicOrdering Ordering) {
-    setInstructionSubclassData((getSubclassDataFromInstruction() & ~(7 << 7)) |
-                               ((unsigned)Ordering << 7));
+    setSubclassData<OrderingField>(Ordering);
   }
 
   /// Returns the synchronization scope ID of this load instruction.
   SyncScope::ID getSyncScopeID() const {
     return SSID;
   }
 
   /// Sets the synchronization scope ID of this load instruction.
public:
   }
   static bool classof(const Value *V) {
     return isa<Instruction>(V) && classof(cast<Instruction>(V));
   }
 
 private:
   // Shadow Instruction::setInstructionSubclassData with a private forwarding
   // method so that subclasses cannot accidentally use it.
-  void setInstructionSubclassData(unsigned short D) {
-    Instruction::setInstructionSubclassData(D);
+  template <typename Bitfield>
+  void setSubclassData(typename Bitfield::Type Value) {
+    Instruction::setSubclassData<Bitfield>(Value);
   }
 
   /// The synchronization scope ID of this load instruction.  Not quite enough
   /// room in SubClassData for everything, so synchronization scope ID gets its
   /// own field.
   SyncScope::ID SSID;
 };
 
 //===----------------------------------------------------------------------===//
 //                                StoreInst Class
 //===----------------------------------------------------------------------===//
 
 /// An instruction for storing to memory.
 class StoreInst : public Instruction {
+  using VolatileField = Bitfield::Element<bool, 0, 1>;      // Next bit:1
+  using AlignmentField = Bitfield::Element<unsigned, 1, 6>; // Next bit:7
+  using OrderingField = Bitfield::Element<AtomicOrdering, 7, 3,
+                                          AtomicOrdering::LAST>; // Next bit:10
+
   void AssertOK();
 
 protected:
   // Note: Instruction needs to be a friend here to call cloneImpl.
   friend class Instruction;
 
   StoreInst *cloneImpl() const;
 
StoreInst(Value *Val, Value *Ptr, bool isVolatile, Align Align,
             AtomicOrdering Order, SyncScope::ID SSID, BasicBlock *InsertAtEnd);
 
   // allocate space for exactly two operands
   void *operator new(size_t s) {
     return User::operator new(s, 2);
   }
 
   /// Return true if this is a store to a volatile memory location.
-  bool isVolatile() const { return getSubclassDataFromInstruction() & 1; }
+  bool isVolatile() const { return getSubclassData<VolatileField>(); }
 
   /// Specify whether this is a volatile store or not.
-  void setVolatile(bool V) {
-    setInstructionSubclassData((getSubclassDataFromInstruction() & ~1) |
-                               (V ? 1 : 0));
-  }
+  void setVolatile(bool V) { setSubclassData<VolatileField>(V); }
 
   /// Transparently provide more efficient getOperand methods.
   DECLARE_TRANSPARENT_OPERAND_ACCESSORS(Value);
 
   /// Return the alignment of the access that is being performed
   /// FIXME: Remove this function once transition to Align is over.
   /// Use getAlign() instead.
   unsigned getAlignment() const { return getAlign().value(); }
 
   Align getAlign() const {
-    return *decodeMaybeAlign((getSubclassDataFromInstruction() >> 1) & 31);
+    return *decodeMaybeAlign(getSubclassData<AlignmentField>());
   }
 
   void setAlignment(Align Alignment);
 
   /// Returns the ordering constraint of this store instruction.
   AtomicOrdering getOrdering() const {
-    return AtomicOrdering((getSubclassDataFromInstruction() >> 7) & 7);
+    return getSubclassData<OrderingField>();
   }
 
   /// Sets the ordering constraint of this store instruction.  May not be
   /// Acquire or AcquireRelease.
   void setOrdering(AtomicOrdering Ordering) {
-    setInstructionSubclassData((getSubclassDataFromInstruction() & ~(7 << 7)) |
-                               ((unsigned)Ordering << 7));
+    setSubclassData<OrderingField>(Ordering);
   }
 
   /// Returns the synchronization scope ID of this store instruction.
   SyncScope::ID getSyncScopeID() const {
     return SSID;
   }
 
   /// Sets the synchronization scope ID of this store instruction.
public:
   }
   static bool classof(const Value *V) {
     return isa<Instruction>(V) && classof(cast<Instruction>(V));
   }
 
 private:
   // Shadow Instruction::setInstructionSubclassData with a private forwarding
   // method so that subclasses cannot accidentally use it.
-  void setInstructionSubclassData(unsigned short D) {
-    Instruction::setInstructionSubclassData(D);
+  template <typename Bitfield>
+  void setSubclassData(typename Bitfield::Type Value) {
+    Instruction::setSubclassData<Bitfield>(Value);
   }
 
   /// The synchronization scope ID of this store instruction.  Not quite enough
   /// room in SubClassData for everything, so synchronization scope ID gets its
   /// own field.
   SyncScope::ID SSID;
 };
 
 template <>
 struct OperandTraits<StoreInst> : public FixedNumOperandTraits<StoreInst, 2> {
 };
 
 DEFINE_TRANSPARENT_OPERAND_ACCESSORS(StoreInst, Value)
 
 //===----------------------------------------------------------------------===//
 //                                FenceInst Class
 //===----------------------------------------------------------------------===//
 
 /// An instruction for ordering other memory operations.
 class FenceInst : public Instruction {
+  using OrderingField = Bitfield::Element<AtomicOrdering, 1, 3,
+                                          AtomicOrdering::LAST>; // Next bit:4
+
   void Init(AtomicOrdering Ordering, SyncScope::ID SSID);
 
 protected:
   // Note: Instruction needs to be a friend here to call cloneImpl.
   friend class Instruction;
 
   FenceInst *cloneImpl() const;
 
 public:
   // Ordering may only be Acquire, Release, AcquireRelease, or
   // SequentiallyConsistent.
   FenceInst(LLVMContext &C, AtomicOrdering Ordering,
             SyncScope::ID SSID = SyncScope::System,
             Instruction *InsertBefore = nullptr);
   FenceInst(LLVMContext &C, AtomicOrdering Ordering, SyncScope::ID SSID,
             BasicBlock *InsertAtEnd);
 
   // allocate space for exactly zero operands
   void *operator new(size_t s) {
     return User::operator new(s, 0);
   }
 
   /// Returns the ordering constraint of this fence instruction.
   AtomicOrdering getOrdering() const {
-    return AtomicOrdering(getSubclassDataFromInstruction() >> 1);
+    return getSubclassData<OrderingField>();
   }
 
   /// Sets the ordering constraint of this fence instruction.  May only be
   /// Acquire, Release, AcquireRelease, or SequentiallyConsistent.
   void setOrdering(AtomicOrdering Ordering) {
-    setInstructionSubclassData((getSubclassDataFromInstruction() & 1) |
-                               ((unsigned)Ordering << 1));
+    setSubclassData<OrderingField>(Ordering);
   }
 
   /// Returns the synchronization scope ID of this fence instruction.
   SyncScope::ID getSyncScopeID() const {
     return SSID;
   }
 
   /// Sets the synchronization scope ID of this fence instruction.
   void setSyncScopeID(SyncScope::ID SSID) {
     this->SSID = SSID;
   }
 
   // Methods for support type inquiry through isa, cast, and dyn_cast:
   static bool classof(const Instruction *I) {
     return I->getOpcode() == Instruction::Fence;
   }
   static bool classof(const Value *V) {
     return isa<Instruction>(V) && classof(cast<Instruction>(V));
   }
 
 private:
   // Shadow Instruction::setInstructionSubclassData with a private forwarding
   // method so that subclasses cannot accidentally use it.
-  void setInstructionSubclassData(unsigned short D) {
-    Instruction::setInstructionSubclassData(D);
+  template <typename Bitfield>
+  void setSubclassData(typename Bitfield::Type Value) {
+    Instruction::setSubclassData<Bitfield>(Value);
   }
 
   /// The synchronization scope ID of this fence instruction.  Not quite enough
   /// room in SubClassData for everything, so synchronization scope ID gets its
   /// own field.
   SyncScope::ID SSID;
 };
 
AtomicCmpXchgInst(Value *Ptr, Value *Cmp, Value *NewVal,
                     AtomicOrdering FailureOrdering,
                     SyncScope::ID SSID, BasicBlock *InsertAtEnd);
 
   // allocate space for exactly three operands
   void *operator new(size_t s) {
     return User::operator new(s, 3);
   }
 
+  // FIXME: Reuse bit 1 that was used by `syncscope.`
+  using VolatileField = Bitfield::Element<bool, 0, 1>; // Next bit:1
+  using SuccessOrderingField =
+      Bitfield::Element<AtomicOrdering, 2, 3,
+                        AtomicOrdering::LAST>; // Next bit:5
+  using FailureOrderingField =
+      Bitfield::Element<AtomicOrdering, 5, 3,
+                        AtomicOrdering::LAST>;     // Next bit:8
+  using WeakField = Bitfield::Element<bool, 8, 1>; // Next bit:9
+
   /// Always returns the natural type alignment.
   /// FIXME: Introduce a proper alignment
   /// https://bugs.llvm.org/show_bug.cgi?id=27168
   Align getAlign() const;
 
   /// Return true if this is a cmpxchg from a volatile memory
   /// location.
   ///
-  bool isVolatile() const {
-    return getSubclassDataFromInstruction() & 1;
-  }
+  bool isVolatile() const { return getSubclassData<VolatileField>(); }
 
   /// Specify whether this is a volatile cmpxchg.
   ///
-  void setVolatile(bool V) {
-     setInstructionSubclassData((getSubclassDataFromInstruction() & ~1) |
-                                (unsigned)V);
-  }
+  void setVolatile(bool V) { setSubclassData<VolatileField>(V); }
 
   /// Return true if this cmpxchg may spuriously fail.
-  bool isWeak() const {
-    return getSubclassDataFromInstruction() & 0x100;
-  }
+  bool isWeak() const { return getSubclassData<WeakField>(); }
 
-  void setWeak(bool IsWeak) {
-    setInstructionSubclassData((getSubclassDataFromInstruction() & ~0x100) |
-                               (IsWeak << 8));
-  }
+  void setWeak(bool IsWeak) { setSubclassData<WeakField>(IsWeak); }
 
   /// Transparently provide more efficient getOperand methods.
   DECLARE_TRANSPARENT_OPERAND_ACCESSORS(Value);
 
   /// Returns the success ordering constraint of this cmpxchg instruction.
   AtomicOrdering getSuccessOrdering() const {
-    return AtomicOrdering((getSubclassDataFromInstruction() >> 2) & 7);
+    return getSubclassData<SuccessOrderingField>();
   }
 
   /// Sets the success ordering constraint of this cmpxchg instruction.
   void setSuccessOrdering(AtomicOrdering Ordering) {
     assert(Ordering != AtomicOrdering::NotAtomic &&
            "CmpXchg instructions can only be atomic.");
-    setInstructionSubclassData((getSubclassDataFromInstruction() & ~0x1c) |
-                               ((unsigned)Ordering << 2));
+    setSubclassData<SuccessOrderingField>(Ordering);
   }
 
   /// Returns the failure ordering constraint of this cmpxchg instruction.
   AtomicOrdering getFailureOrdering() const {
-    return AtomicOrdering((getSubclassDataFromInstruction() >> 5) & 7);
+    return getSubclassData<FailureOrderingField>();
   }
 
   /// Sets the failure ordering constraint of this cmpxchg instruction.
   void setFailureOrdering(AtomicOrdering Ordering) {
     assert(Ordering != AtomicOrdering::NotAtomic &&
            "CmpXchg instructions can only be atomic.");
-    setInstructionSubclassData((getSubclassDataFromInstruction() & ~0xe0) |
-                               ((unsigned)Ordering << 5));
+    setSubclassData<FailureOrderingField>(Ordering);
   }
 
   /// Returns the synchronization scope ID of this cmpxchg instruction.
   SyncScope::ID getSyncScopeID() const {
     return SSID;
   }
 
   /// Sets the synchronization scope ID of this cmpxchg instruction.
public:
   }
   static bool classof(const Value *V) {
     return isa<Instruction>(V) && classof(cast<Instruction>(V));
   }
 
 private:
   // Shadow Instruction::setInstructionSubclassData with a private forwarding
   // method so that subclasses cannot accidentally use it.
-  void setInstructionSubclassData(unsigned short D) {
-    Instruction::setInstructionSubclassData(D);
+  template <typename Bitfield>
+  void setSubclassData(typename Bitfield::Type Value) {
+    Instruction::setSubclassData<Bitfield>(Value);
   }
 
   /// The synchronization scope ID of this cmpxchg instruction.  Not quite
   /// enough room in SubClassData for everything, so synchronization scope ID
   /// gets its own field.
   SyncScope::ID SSID;
 };
 
protected:
 
   AtomicRMWInst *cloneImpl() const;
 
 public:
   /// This enumeration lists the possible modifications atomicrmw can make.  In
   /// the descriptions, 'p' is the pointer to the instruction's memory location,
   /// 'old' is the initial value of *p, and 'v' is the other value passed to the
   /// instruction.  These instructions always return 'old'.
-  enum BinOp {
+  enum BinOp : unsigned {
     /// *p = v
     Xchg,
     /// *p = old + v
     Add,
     /// *p = old - v
     Sub,
     /// *p = old & v
     And,
AtomicRMWInst(BinOp Operation, Value *Ptr, Value *Val,
                 AtomicOrdering Ordering, SyncScope::ID SSID,
                 BasicBlock *InsertAtEnd);
 
   // allocate space for exactly two operands
   void *operator new(size_t s) {
     return User::operator new(s, 2);
   }
 
-  BinOp getOperation() const {
-    return static_cast<BinOp>(getSubclassDataFromInstruction() >> 5);
-  }
+  // FIXME: Reuse bit 1 that was used by `syncscope.`
+  using VolatileField = Bitfield::Element<bool, 0, 1>; // Next bit:1
+  using AtomicOrderingField =
+      Bitfield::Element<AtomicOrdering, 2, 3,
+                        AtomicOrdering::LAST>; // Next bit:5
+  using OperationField = Bitfield::Element<BinOp, 5, 4,
+                                           BinOp::LAST_BINOP>; // Next bit:9
+
+  BinOp getOperation() const { return getSubclassData<OperationField>(); }
 
   static StringRef getOperationName(BinOp Op);
 
   static bool isFPOperation(BinOp Op) {
     switch (Op) {
     case AtomicRMWInst::FAdd:
     case AtomicRMWInst::FSub:
       return true;
     default:
       return false;
     }
   }
 
   void setOperation(BinOp Operation) {
-    unsigned short SubclassData = getSubclassDataFromInstruction();
-    setInstructionSubclassData((SubclassData & 31) |
-                               (Operation << 5));
+    setSubclassData<OperationField>(Operation);
   }
 
   /// Always returns the natural type alignment.
   /// FIXME: Introduce a proper alignment
   /// https://bugs.llvm.org/show_bug.cgi?id=27168
   Align getAlign() const;
 
   /// Return true if this is a RMW on a volatile memory location.
   ///
-  bool isVolatile() const {
-    return getSubclassDataFromInstruction() & 1;
-  }
+  bool isVolatile() const { return getSubclassData<VolatileField>(); }
 
   /// Specify whether this is a volatile RMW or not.
   ///
-  void setVolatile(bool V) {
-     setInstructionSubclassData((getSubclassDataFromInstruction() & ~1) |
-                                (unsigned)V);
-  }
+  void setVolatile(bool V) { setSubclassData<VolatileField>(V); }
 
   /// Transparently provide more efficient getOperand methods.
   DECLARE_TRANSPARENT_OPERAND_ACCESSORS(Value);
 
   /// Returns the ordering constraint of this rmw instruction.
   AtomicOrdering getOrdering() const {
-    return AtomicOrdering((getSubclassDataFromInstruction() >> 2) & 7);
+    return getSubclassData<AtomicOrderingField>();
   }
 
   /// Sets the ordering constraint of this rmw instruction.
   void setOrdering(AtomicOrdering Ordering) {
     assert(Ordering != AtomicOrdering::NotAtomic &&
            "atomicrmw instructions can only be atomic.");
-    setInstructionSubclassData((getSubclassDataFromInstruction() & ~(7 << 2)) |
-                               ((unsigned)Ordering << 2));
+    setSubclassData<AtomicOrderingField>(Ordering);
   }
 
   /// Returns the synchronization scope ID of this rmw instruction.
   SyncScope::ID getSyncScopeID() const {
     return SSID;
   }
 
   /// Sets the synchronization scope ID of this rmw instruction.
public:
   }
 
 private:
   void Init(BinOp Operation, Value *Ptr, Value *Val,
             AtomicOrdering Ordering, SyncScope::ID SSID);
 
   // Shadow Instruction::setInstructionSubclassData with a private forwarding
   // method so that subclasses cannot accidentally use it.
-  void setInstructionSubclassData(unsigned short D) {
-    Instruction::setInstructionSubclassData(D);
+  template <typename Bitfield>
+  void setSubclassData(typename Bitfield::Type Value) {
+    Instruction::setSubclassData<Bitfield>(Value);
   }
 
   /// The synchronization scope ID of this rmw instruction.  Not quite enough
   /// room in SubClassData for everything, so synchronization scope ID gets its
   /// own field.
   SyncScope::ID SSID;
 };
 
public:
   static Instruction *CreateFree(Value *Source,
                                  ArrayRef<OperandBundleDef> Bundles,
                                  Instruction *InsertBefore);
   static Instruction *CreateFree(Value *Source,
                                  ArrayRef<OperandBundleDef> Bundles,
                                  BasicBlock *InsertAtEnd);
 
   // Note that 'musttail' implies 'tail'.
-  enum TailCallKind {
+  enum TailCallKind : unsigned {
     TCK_None = 0,
     TCK_Tail = 1,
     TCK_MustTail = 2,
-    TCK_NoTail = 3
+    TCK_NoTail = 3,
+    TCK_LAST = TCK_NoTail
   };
+
+  using TailCallKindField = Bitfield::Element<TailCallKind, 0, 2, TCK_LAST>;
+
   TailCallKind getTailCallKind() const {
-    return TailCallKind(getSubclassDataFromInstruction() & 3);
+    return getSubclassData<TailCallKindField>();
   }
 
   bool isTailCall() const {
-    unsigned Kind = getSubclassDataFromInstruction() & 3;
+    TailCallKind Kind = getTailCallKind();
     return Kind == TCK_Tail || Kind == TCK_MustTail;
   }
 
-  bool isMustTailCall() const {
-    return (getSubclassDataFromInstruction() & 3) == TCK_MustTail;
-  }
+  bool isMustTailCall() const { return getTailCallKind() == TCK_MustTail; }
 
-  bool isNoTailCall() const {
-    return (getSubclassDataFromInstruction() & 3) == TCK_NoTail;
-  }
+  bool isNoTailCall() const { return getTailCallKind() == TCK_NoTail; }
 
-  void setTailCall(bool isTC = true) {
-    setInstructionSubclassData((getSubclassDataFromInstruction() & ~3) |
-                               unsigned(isTC ? TCK_Tail : TCK_None));
+  void setTailCallKind(TailCallKind TCK) {
+    setSubclassData<TailCallKindField>(TCK);
   }
 
-  void setTailCallKind(TailCallKind TCK) {
-    setInstructionSubclassData((getSubclassDataFromInstruction() & ~3) |
-                               unsigned(TCK));
+  void setTailCall(bool IsTc = true) {
+    setTailCallKind(IsTc ? TCK_Tail : TCK_None);
   }
 
   /// Return true if the call can return twice
   bool canReturnTwice() const { return hasFnAttr(Attribute::ReturnsTwice); }
   void setCanReturnTwice() {
     addAttribute(AttributeList::FunctionIndex, Attribute::ReturnsTwice);
   }
 
   // Methods for support type inquiry through isa, cast, and dyn_cast:
   static bool classof(const Instruction *I) {
     return I->getOpcode() == Instruction::Call;
   }
   static bool classof(const Value *V) {
     return isa<Instruction>(V) && classof(cast<Instruction>(V));
   }
 
   /// Updates profile metadata by scaling it by \p S / \p T.
   void updateProfWeight(uint64_t S, uint64_t T);
 
 private:
   // Shadow Instruction::setInstructionSubclassData with a private forwarding
   // method so that subclasses cannot accidentally use it.
-  void setInstructionSubclassData(unsigned short D) {
-    Instruction::setInstructionSubclassData(D);
+  template <typename Bitfield>
+  void setSubclassData(typename Bitfield::Type Value) {
+    Instruction::setSubclassData<Bitfield>(Value);
   }
 };
 
 CallInst::CallInst(FunctionType *Ty, Value *Func, ArrayRef<Value *> Args,
                    ArrayRef<OperandBundleDef> Bundles, const Twine &NameStr,
                    BasicBlock *InsertAtEnd)
     : CallBase(Ty->getReturnType(), Instruction::Call,
                OperandTraits<CallBase>::op_end(this) -

 /// The landingpad instruction holds all of the information
 /// necessary to generate correct exception handling. The landingpad instruction
 /// cannot be moved from the top of a landing pad block, which itself is
 /// accessible only from the 'unwind' edge of an invoke. This uses the
 /// SubclassData field in Value to store whether or not the landingpad is a
 /// cleanup.
 ///
 class LandingPadInst : public Instruction {
+  using CleanupField = Bitfield::Element<bool, 0, 1>;
+
   /// The number of operands actually allocated.  NumOperands is
   /// the number actually in use.
   unsigned ReservedSpace;
 
   LandingPadInst(const LandingPadInst &LP);
 
 public:
   enum ClauseType { Catch, Filter };
static LandingPadInst *Create(Type *RetTy, unsigned NumReservedClauses,
                                 const Twine &NameStr, BasicBlock *InsertAtEnd);
 
   /// Provide fast operand accessors
   DECLARE_TRANSPARENT_OPERAND_ACCESSORS(Value);
 
   /// Return 'true' if this landingpad instruction is a
   /// cleanup. I.e., it should be run when unwinding even if its landing pad
   /// doesn't catch the exception.
-  bool isCleanup() const { return getSubclassDataFromInstruction() & 1; }
+  bool isCleanup() const { return getSubclassData<CleanupField>(); }
 
   /// Indicate that this landingpad instruction is a cleanup.
-  void setCleanup(bool V) {
-    setInstructionSubclassData((getSubclassDataFromInstruction() & ~1) |
-                               (V ? 1 : 0));
-  }
+  void setCleanup(bool V) { setSubclassData<CleanupField>(V); }
 
   /// Add a catch or filter clause to the landing pad.
   void addClause(Constant *ClauseVal);
 
   /// Get the value of the clause at index Idx. Use isCatch/isFilter to
   /// determine what type of clause this is.
   Constant *getClause(unsigned Idx) const {
     return cast<Constant>(getOperandList()[Idx]);
public:
   static bool classof(const Instruction *I) {
     return (I->getOpcode() == Instruction::Invoke);
   }
   static bool classof(const Value *V) {
     return isa<Instruction>(V) && classof(cast<Instruction>(V));
   }
 
 private:
-
   // Shadow Instruction::setInstructionSubclassData with a private forwarding
   // method so that subclasses cannot accidentally use it.
-  void setInstructionSubclassData(unsigned short D) {
-    Instruction::setInstructionSubclassData(D);
+  template <typename Bitfield>
+  void setSubclassData(typename Bitfield::Type Value) {
+    Instruction::setSubclassData<Bitfield>(Value);
   }
 };
 
 InvokeInst::InvokeInst(FunctionType *Ty, Value *Func, BasicBlock *IfNormal,
                        BasicBlock *IfException, ArrayRef<Value *> Args,
                        ArrayRef<OperandBundleDef> Bundles, int NumOperands,
                        const Twine &NameStr, Instruction *InsertBefore)
     : CallBase(Ty->getReturnType(), Instruction::Invoke,
public:
   static bool classof(const Instruction *I) {
     return (I->getOpcode() == Instruction::CallBr);
   }
   static bool classof(const Value *V) {
     return isa<Instruction>(V) && classof(cast<Instruction>(V));
   }
 
 private:
-
   // Shadow Instruction::setInstructionSubclassData with a private forwarding
   // method so that subclasses cannot accidentally use it.
-  void setInstructionSubclassData(unsigned short D) {
-    Instruction::setInstructionSubclassData(D);
+  template <typename Bitfield>
+  void setSubclassData(typename Bitfield::Type Value) {
+    Instruction::setSubclassData<Bitfield>(Value);
   }
 };
 
 CallBrInst::CallBrInst(FunctionType *Ty, Value *Func, BasicBlock *DefaultDest,
                        ArrayRef<BasicBlock *> IndirectDests,
                        ArrayRef<Value *> Args,
                        ArrayRef<OperandBundleDef> Bundles, int NumOperands,
                        const Twine &NameStr, Instruction *InsertBefore)

 };
 
 DEFINE_TRANSPARENT_OPERAND_ACCESSORS(ResumeInst, Value)
 
 //===----------------------------------------------------------------------===//
 //                         CatchSwitchInst Class
 //===----------------------------------------------------------------------===//
 class CatchSwitchInst : public Instruction {
+  using UnwindDestField = Bitfield::Element<unsigned, 0, 1>; // Next bit:1
+
   /// The number of operands actually allocated.  NumOperands is
   /// the number actually in use.
   unsigned ReservedSpace;
 
   // Operand[0] = Outer scope
   // Operand[1] = Unwind block destination
   // Operand[n] = BasicBlock to go to on match
   CatchSwitchInst(const CatchSwitchInst &CSI);
public:
   /// Provide fast operand accessors
   DECLARE_TRANSPARENT_OPERAND_ACCESSORS(Value);
 
   // Accessor Methods for CatchSwitch stmt
   Value *getParentPad() const { return getOperand(0); }
   void setParentPad(Value *ParentPad) { setOperand(0, ParentPad); }
 
   // Accessor Methods for CatchSwitch stmt
-  bool hasUnwindDest() const { return getSubclassDataFromInstruction() & 1; }
+  bool hasUnwindDest() const { return getSubclassData<UnwindDestField>(); }
   bool unwindsToCaller() const { return !hasUnwindDest(); }
   BasicBlock *getUnwindDest() const {
     if (hasUnwindDest())
       return cast<BasicBlock>(getOperand(1));
     return nullptr;
   }
   void setUnwindDest(BasicBlock *UnwindDest) {
     assert(UnwindDest);

 
 DEFINE_TRANSPARENT_OPERAND_ACCESSORS(CatchReturnInst, Value)
 
 //===----------------------------------------------------------------------===//
 //                               CleanupReturnInst Class
 //===----------------------------------------------------------------------===//
 
 class CleanupReturnInst : public Instruction {
+  using UnwindDestField = Bitfield::Element<unsigned, 0, 1>; // Next bit:1
 private:
   CleanupReturnInst(const CleanupReturnInst &RI);
   CleanupReturnInst(Value *CleanupPad, BasicBlock *UnwindBB, unsigned Values,
                     Instruction *InsertBefore = nullptr);
   CleanupReturnInst(Value *CleanupPad, BasicBlock *UnwindBB, unsigned Values,
                     BasicBlock *InsertAtEnd);
 
   void init(Value *CleanupPad, BasicBlock *UnwindBB);
if (UnwindBB)
       ++Values;
     return new (Values)
         CleanupReturnInst(CleanupPad, UnwindBB, Values, InsertAtEnd);
   }
 
   /// Provide fast operand accessors
   DECLARE_TRANSPARENT_OPERAND_ACCESSORS(Value);
 
-  bool hasUnwindDest() const { return getSubclassDataFromInstruction() & 1; }
+  bool hasUnwindDest() const { return getSubclassData<UnwindDestField>(); }
   bool unwindsToCaller() const { return !hasUnwindDest(); }
 
   /// Convenience accessor.
   CleanupPadInst *getCleanupPad() const {
     return cast<CleanupPadInst>(Op<0>());
   }
   void setCleanupPad(CleanupPadInst *CleanupPad) {
     assert(CleanupPad);
private:
 
   void setSuccessor(unsigned Idx, BasicBlock *B) {
     assert(Idx == 0);
     setUnwindDest(B);
   }
 
   // Shadow Instruction::setInstructionSubclassData with a private forwarding
   // method so that subclasses cannot accidentally use it.
-  void setInstructionSubclassData(unsigned short D) {
-    Instruction::setInstructionSubclassData(D);
+  template <typename Bitfield>
+  void setSubclassData(typename Bitfield::Type Value) {
+    Instruction::setSubclassData<Bitfield>(Value);
   }
 };
 
 template <>
 struct OperandTraits<CleanupReturnInst>
     : public VariadicOperandTraits<CleanupReturnInst, /*MINARITY=*/1> {};
 
 DEFINE_TRANSPARENT_OPERAND_ACCESSORS(CleanupReturnInst, Value)

llvm/include/llvm/Support/AtomicOrdering.h

 
 /// Atomic ordering for LLVM's memory model.
 ///
 /// C++ defines ordering as a lattice. LLVM supplements this with NotAtomic and
 /// Unordered, which are both below the C++ orders.
 ///
 /// not_atomic-->unordered-->relaxed-->release--------------->acq_rel-->seq_cst
 ///                                   \-->consume-->acquire--/
-enum class AtomicOrdering {
+enum class AtomicOrdering : unsigned {
   NotAtomic = 0,
   Unordered = 1,
   Monotonic = 2, // Equivalent to C++'s relaxed.
   // Consume = 3,  // Not specified yet.
   Acquire = 4,
   Release = 5,
   AcquireRelease = 6,
-  SequentiallyConsistent = 7
+  SequentiallyConsistent = 7,
+  LAST = SequentiallyConsistent
 };
 
 bool operator<(AtomicOrdering, AtomicOrdering) = delete;
 bool operator>(AtomicOrdering, AtomicOrdering) = delete;
 bool operator<=(AtomicOrdering, AtomicOrdering) = delete;
 bool operator>=(AtomicOrdering, AtomicOrdering) = delete;
 
 // Validate an integral value which isn't known to fit within the enum's range

llvm/lib/IR/Instructions.cpp

 //                        CleanupReturnInst Implementation
 //===----------------------------------------------------------------------===//
 
 CleanupReturnInst::CleanupReturnInst(const CleanupReturnInst &CRI)
     : Instruction(CRI.getType(), Instruction::CleanupRet,
                   OperandTraits<CleanupReturnInst>::op_end(this) -
                       CRI.getNumOperands(),
                   CRI.getNumOperands()) {
-  setInstructionSubclassData(CRI.getSubclassDataFromInstruction());
+  setSubclassData<Instruction::OpaqueField>(
+      CRI.getSubclassData<Instruction::OpaqueField>());
   Op<0>() = CRI.Op<0>();
   if (CRI.hasUnwindDest())
     Op<1>() = CRI.Op<1>();
 }
 
 void CleanupReturnInst::init(Value *CleanupPad, BasicBlock *UnwindBB) {
   if (UnwindBB)
-    setInstructionSubclassData(getSubclassDataFromInstruction() | 1);
+    setSubclassData<UnwindDestField>(true);
 
   Op<0>() = CleanupPad;
   if (UnwindBB)
     Op<1>() = UnwindBB;
 }
 
 CleanupReturnInst::CleanupReturnInst(Value *CleanupPad, BasicBlock *UnwindBB,
                                      unsigned Values, Instruction *InsertBefore)
void CatchSwitchInst::init(Value *ParentPad, BasicBlock *UnwindDest,
   assert(ParentPad && NumReservedValues);
 
   ReservedSpace = NumReservedValues;
   setNumHungOffUseOperands(UnwindDest ? 2 : 1);
   allocHungoffUses(ReservedSpace);
 
   Op<0>() = ParentPad;
   if (UnwindDest) {
-    setInstructionSubclassData(getSubclassDataFromInstruction() | 1);
+    setSubclassData<UnwindDestField>(true);
     setUnwindDest(UnwindDest);
   }
 }
 
 /// growOperands - grow operands - This grows the operand list in response to a
 /// push_back style of operation. This grows the number of ops by 2 times.
 void CatchSwitchInst::growOperands(unsigned Size) {
   unsigned NumOperands = getNumOperands();
AllocaInst::AllocaInst(Type *Ty, unsigned AddrSpace, Value *ArraySize,
   setAlignment(Align);
   assert(!Ty->isVoidTy() && "Cannot allocate void!");
   setName(Name);
 }
 
 void AllocaInst::setAlignment(Align Align) {
   assert(Align <= MaximumAlignment &&
          "Alignment is greater than MaximumAlignment!");
-  setInstructionSubclassData((getSubclassDataFromInstruction() & ~31) |
-                             encode(Align));
-  assert(getAlignment() == Align.value() && "Alignment representation error!");
+  setSubclassData<AlignmentField>(encode(Align));
 }
 
 bool AllocaInst::isArrayAllocation() const {
   if (ConstantInt *CI = dyn_cast<ConstantInt>(getOperand(0)))
     return !CI->isOne();
   return true;
 }
 
LoadInst::LoadInst(Type *Ty, Value *Ptr, const Twine &Name, bool isVolatile,
   setAtomic(Order, SSID);
   AssertOK();
   setName(Name);
 }
 
 void LoadInst::setAlignment(Align Align) {
   assert(Align <= MaximumAlignment &&
          "Alignment is greater than MaximumAlignment!");
-  setInstructionSubclassData((getSubclassDataFromInstruction() & ~(31 << 1)) |
-                             (encode(Align) << 1));
-  assert(getAlign() == Align && "Alignment representation error!");
+  setSubclassData<AlignmentField>(encode(Align));
 }
 
 //===----------------------------------------------------------------------===//
 //                           StoreInst Implementation
 //===----------------------------------------------------------------------===//
 
 void StoreInst::AssertOK() {
   assert(getOperand(0) && getOperand(1) && "Both operands must be non-null!");
StoreInst::StoreInst(Value *val, Value *addr, bool isVolatile, Align Align,
   setAlignment(Align);
   setAtomic(Order, SSID);
   AssertOK();
 }
 
 void StoreInst::setAlignment(Align Alignment) {
   assert(Alignment <= MaximumAlignment &&
          "Alignment is greater than MaximumAlignment!");
-  setInstructionSubclassData((getSubclassDataFromInstruction() & ~(31 << 1)) |
-                             (encode(Alignment) << 1));
-  assert(getAlign() == Alignment && "Alignment representation error!");
+  setSubclassData<AlignmentField>(encode(Alignment));
 }
 
 //===----------------------------------------------------------------------===//
 //                       AtomicCmpXchgInst Implementation
 //===----------------------------------------------------------------------===//
 
 void AtomicCmpXchgInst::Init(Value *Ptr, Value *Cmp, Value *NewVal,
                              AtomicOrdering SuccessOrdering,

llvm/lib/Target/AMDGPU/SIISelLowering.cpp

return DAG.getMergeValues(
       {DAG.getNode(ISD::BITCAST, DL, LoadVT, MemNode), MemNode.getValue(1)},
       DL);
 }
 
 static SDValue lowerICMPIntrinsic(const SITargetLowering &TLI,
                                   SDNode *N, SelectionDAG &DAG) {
   EVT VT = N->getValueType(0);
   const auto *CD = cast<ConstantSDNode>(N->getOperand(3));
-  int CondCode = CD->getSExtValue();
+  unsigned CondCode = CD->getZExtValue();
   if (CondCode < ICmpInst::Predicate::FIRST_ICMP_PREDICATE ||
       CondCode > ICmpInst::Predicate::LAST_ICMP_PREDICATE)
     return DAG.getUNDEF(VT);
 
   ICmpInst::Predicate IcInput = static_cast<ICmpInst::Predicate>(CondCode);
 
   SDValue LHS = N->getOperand(1);
   SDValue RHS = N->getOperand(2);
static SDValue lowerICMPIntrinsic(const SITargetLowering &TLI,
   return DAG.getZExtOrTrunc(SetCC, DL, VT);
 }
 
 static SDValue lowerFCMPIntrinsic(const SITargetLowering &TLI,
                                   SDNode *N, SelectionDAG &DAG) {
   EVT VT = N->getValueType(0);
   const auto *CD = cast<ConstantSDNode>(N->getOperand(3));
 
-  int CondCode = CD->getSExtValue();
+  unsigned CondCode = CD->getZExtValue();
   if (CondCode < FCmpInst::Predicate::FIRST_FCMP_PREDICATE ||
       CondCode > FCmpInst::Predicate::LAST_FCMP_PREDICATE) {
     return DAG.getUNDEF(VT);
   }
 
   SDValue Src0 = N->getOperand(1);
   SDValue Src1 = N->getOperand(2);
   EVT CmpVT = Src0.getValueType();

llvm/lib/Transforms/Instrumentation/ThreadSanitizer.cpp

for (size_t i = 0; i < kNumberOfAccessSizes; ++i) {
     SmallString<32> AtomicLoadName("__tsan_atomic" + BitSizeStr + "_load");
     TsanAtomicLoad[i] =
         M.getOrInsertFunction(AtomicLoadName, Attr, Ty, PtrTy, OrdTy);
 
     SmallString<32> AtomicStoreName("__tsan_atomic" + BitSizeStr + "_store");
     TsanAtomicStore[i] = M.getOrInsertFunction(
         AtomicStoreName, Attr, IRB.getVoidTy(), PtrTy, Ty, OrdTy);
 
-    for (int op = AtomicRMWInst::FIRST_BINOP;
-        op <= AtomicRMWInst::LAST_BINOP; ++op) {
-      TsanAtomicRMW[op][i] = nullptr;
+    for (unsigned Op = AtomicRMWInst::FIRST_BINOP;
+         Op <= AtomicRMWInst::LAST_BINOP; ++Op) {
+      TsanAtomicRMW[Op][i] = nullptr;
       const char *NamePart = nullptr;
-      if (op == AtomicRMWInst::Xchg)
+      if (Op == AtomicRMWInst::Xchg)
         NamePart = "_exchange";
-      else if (op == AtomicRMWInst::Add)
+      else if (Op == AtomicRMWInst::Add)
         NamePart = "_fetch_add";
-      else if (op == AtomicRMWInst::Sub)
+      else if (Op == AtomicRMWInst::Sub)
         NamePart = "_fetch_sub";
-      else if (op == AtomicRMWInst::And)
+      else if (Op == AtomicRMWInst::And)
         NamePart = "_fetch_and";
-      else if (op == AtomicRMWInst::Or)
+      else if (Op == AtomicRMWInst::Or)
         NamePart = "_fetch_or";
-      else if (op == AtomicRMWInst::Xor)
+      else if (Op == AtomicRMWInst::Xor)
         NamePart = "_fetch_xor";
-      else if (op == AtomicRMWInst::Nand)
+      else if (Op == AtomicRMWInst::Nand)
         NamePart = "_fetch_nand";
       else
         continue;
       SmallString<32> RMWName("__tsan_atomic" + itostr(BitSize) + NamePart);
-      TsanAtomicRMW[op][i] =
+      TsanAtomicRMW[Op][i] =
           M.getOrInsertFunction(RMWName, Attr, Ty, PtrTy, Ty, OrdTy);
     }
 
     SmallString<32> AtomicCASName("__tsan_atomic" + BitSizeStr +
                                   "_compare_exchange_val");
     TsanAtomicCAS[i] = M.getOrInsertFunction(AtomicCASName, Attr, Ty, PtrTy, Ty,
                                              Ty, OrdTy, OrdTy);
   }