LangRef and basic memory-representation/reading/writing for 'cmpxchg' and

'atomicrmw' instructions, which allow representing all the current atomic
rmw intrinsics.

The allowed operands for these instructions are heavily restricted at the
moment; we can probably loosen it a bit, but supporting general
first-class types (where it makes sense) might get a bit complicated,
given how SelectionDAG works.

As an initial cut, these operations do not support specifying an alignment,
but it would be possible to add if we think it's useful. Specifying an
alignment lower than the natural alignment would be essentially
impossible to support on anything other than x86, but specifying a greater
alignment would be possible.  I can't think of any useful optimizations which
would use that information, but maybe someone else has ideas.

Optimizer/codegen support coming soon.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@136404 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 253 insertions, 0 deletions

diff --git a/include/llvm/Instructions.h b/include/llvm/Instructions.h
index 3e250d8..cb21e63 100644
--- a/include/llvm/Instructions.h
+++ b/include/llvm/Instructions.h
@@ -362,6 +362,259 @@ private:
 };
 
 //===----------------------------------------------------------------------===//
+//                                AtomicCmpXchgInst Class
+//===----------------------------------------------------------------------===//
+
+/// AtomicCmpXchgInst - an instruction that atomically checks whether a
+/// specified value is in a memory location, and, if it is, stores a new value
+/// there.  Returns the value that was loaded.
+///
+class AtomicCmpXchgInst : public Instruction {
+  void *operator new(size_t, unsigned);  // DO NOT IMPLEMENT
+  void Init(Value *Ptr, Value *Cmp, Value *NewVal,
+            AtomicOrdering Ordering, SynchronizationScope SynchScope);
+protected:
+  virtual AtomicCmpXchgInst *clone_impl() const;
+public:
+  // allocate space for exactly three operands
+  void *operator new(size_t s) {
+    return User::operator new(s, 3);
+  }
+  AtomicCmpXchgInst(Value *Ptr, Value *Cmp, Value *NewVal,
+                    AtomicOrdering Ordering, SynchronizationScope SynchScope,
+                    Instruction *InsertBefore = 0);
+  AtomicCmpXchgInst(Value *Ptr, Value *Cmp, Value *NewVal,
+                    AtomicOrdering Ordering, SynchronizationScope SynchScope,
+                    BasicBlock *InsertAtEnd);
+
+  /// isVolatile - Return true if this is a cmpxchg from a volatile memory
+  /// location.
+  ///
+  bool isVolatile() const {
+    return getSubclassDataFromInstruction() & 1;
+  }
+
+  /// setVolatile - Specify whether this is a volatile cmpxchg.
+  ///
+  void setVolatile(bool V) {
+     setInstructionSubclassData((getSubclassDataFromInstruction() & ~1) |
+                                (unsigned)V);
+  }
+
+  /// Transparently provide more efficient getOperand methods.
+  DECLARE_TRANSPARENT_OPERAND_ACCESSORS(Value);
+
+  /// Set the ordering constraint on this cmpxchg.
+  void setOrdering(AtomicOrdering Ordering) {
+    assert(Ordering != NotAtomic &&
+           "CmpXchg instructions can only be atomic.");
+    setInstructionSubclassData((getSubclassDataFromInstruction() & 3) |
+                               (Ordering << 2));
+  }
+
+  /// Specify whether this cmpxchg is atomic and orders other operations with
+  /// respect to all concurrently executing threads, or only with respect to
+  /// signal handlers executing in the same thread.
+  void setSynchScope(SynchronizationScope SynchScope) {
+    setInstructionSubclassData((getSubclassDataFromInstruction() & ~2) |
+                               (SynchScope << 1));
+  }
+
+  /// Returns the ordering constraint on this cmpxchg.
+  AtomicOrdering getOrdering() const {
+    return AtomicOrdering(getSubclassDataFromInstruction() >> 2);
+  }
+
+  /// Returns whether this cmpxchg is atomic between threads or only within a
+  /// single thread.
+  SynchronizationScope getSynchScope() const {
+    return SynchronizationScope((getSubclassDataFromInstruction() & 2) >> 1);
+  }
+
+  Value *getPointerOperand() { return getOperand(0); }
+  const Value *getPointerOperand() const { return getOperand(0); }
+  static unsigned getPointerOperandIndex() { return 0U; }
+
+  Value *getCompareOperand() { return getOperand(1); }
+  const Value *getCompareOperand() const { return getOperand(1); }
+  
+  Value *getNewValOperand() { return getOperand(2); }
+  const Value *getNewValOperand() const { return getOperand(2); }
+  
+  unsigned getPointerAddressSpace() const {
+    return cast<PointerType>(getPointerOperand()->getType())->getAddressSpace();
+  }
+  
+  // Methods for support type inquiry through isa, cast, and dyn_cast:
+  static inline bool classof(const AtomicCmpXchgInst *) { return true; }
+  static inline bool classof(const Instruction *I) {
+    return I->getOpcode() == Instruction::AtomicCmpXchg;
+  }
+  static inline 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 <>
+struct OperandTraits<AtomicCmpXchgInst> :
+    public FixedNumOperandTraits<AtomicCmpXchgInst, 3> {
+};
+
+DEFINE_TRANSPARENT_OPERAND_ACCESSORS(AtomicCmpXchgInst, Value)
+
+//===----------------------------------------------------------------------===//
+//                                AtomicRMWInst Class
+//===----------------------------------------------------------------------===//
+
+/// AtomicRMWInst - an instruction that atomically reads a memory location,
+/// combines it with another value, and then stores the result back.  Returns
+/// the old value.
+///
+class AtomicRMWInst : public Instruction {
+  void *operator new(size_t, unsigned);  // DO NOT IMPLEMENT
+protected:
+  virtual AtomicRMWInst *clone_impl() 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 {
+    /// *p = v
+    Xchg,
+    /// *p = old + v
+    Add,
+    /// *p = old - v
+    Sub,
+    /// *p = old & v
+    And,
+    /// *p = ~old & v
+    Nand,
+    /// *p = old | v
+    Or,
+    /// *p = old ^ v
+    Xor,
+    /// *p = old >signed v ? old : v
+    Max,
+    /// *p = old <signed v ? old : v
+    Min,
+    /// *p = old >unsigned v ? old : v
+    UMax,
+    /// *p = old <unsigned v ? old : v
+    UMin,
+
+    FIRST_BINOP = Xchg,
+    LAST_BINOP = UMin,
+    BAD_BINOP
+  };
+
+  // allocate space for exactly two operands
+  void *operator new(size_t s) {
+    return User::operator new(s, 2);
+  }
+  AtomicRMWInst(BinOp Operation, Value *Ptr, Value *Val,
+                AtomicOrdering Ordering, SynchronizationScope SynchScope,
+                Instruction *InsertBefore = 0);
+  AtomicRMWInst(BinOp Operation, Value *Ptr, Value *Val,
+                AtomicOrdering Ordering, SynchronizationScope SynchScope,
+                BasicBlock *InsertAtEnd);
+
+  BinOp getOperation() const {
+    return static_cast<BinOp>(getSubclassDataFromInstruction() >> 5);
+  }
+
+  void setOperation(BinOp Operation) {
+    unsigned short SubclassData = getSubclassDataFromInstruction();
+    setInstructionSubclassData((SubclassData & 31) |
+                               (Operation << 5));
+  }
+
+  /// isVolatile - Return true if this is a RMW on a volatile memory location.
+  ///
+  bool isVolatile() const {
+    return getSubclassDataFromInstruction() & 1;
+  }
+
+  /// setVolatile - Specify whether this is a volatile RMW or not.
+  ///
+  void setVolatile(bool V) {
+     setInstructionSubclassData((getSubclassDataFromInstruction() & ~1) |
+                                (unsigned)V);
+  }
+
+  /// Transparently provide more efficient getOperand methods.
+  DECLARE_TRANSPARENT_OPERAND_ACCESSORS(Value);
+
+  /// Set the ordering constraint on this RMW.
+  void setOrdering(AtomicOrdering Ordering) {
+    assert(Ordering != NotAtomic &&
+           "atomicrmw instructions can only be atomic.");
+    setInstructionSubclassData((getSubclassDataFromInstruction() & ~28) |
+                               (Ordering << 2));
+  }
+
+  /// Specify whether this RMW orders other operations with respect to all
+  /// concurrently executing threads, or only with respect to signal handlers
+  /// executing in the same thread.
+  void setSynchScope(SynchronizationScope SynchScope) {
+    setInstructionSubclassData((getSubclassDataFromInstruction() & ~2) |
+                               (SynchScope << 1));
+  }
+
+  /// Returns the ordering constraint on this RMW.
+  AtomicOrdering getOrdering() const {
+    return AtomicOrdering((getSubclassDataFromInstruction() & 28) >> 2);
+  }
+
+  /// Returns whether this RMW is atomic between threads or only within a
+  /// single thread.
+  SynchronizationScope getSynchScope() const {
+    return SynchronizationScope((getSubclassDataFromInstruction() & 2) >> 1);
+  }
+
+  Value *getPointerOperand() { return getOperand(0); }
+  const Value *getPointerOperand() const { return getOperand(0); }
+  static unsigned getPointerOperandIndex() { return 0U; }
+
+  Value *getValOperand() { return getOperand(1); }
+  const Value *getValOperand() const { return getOperand(1); }
+
+  unsigned getPointerAddressSpace() const {
+    return cast<PointerType>(getPointerOperand()->getType())->getAddressSpace();
+  }
+
+  // Methods for support type inquiry through isa, cast, and dyn_cast:
+  static inline bool classof(const AtomicRMWInst *) { return true; }
+  static inline bool classof(const Instruction *I) {
+    return I->getOpcode() == Instruction::AtomicRMW;
+  }
+  static inline bool classof(const Value *V) {
+    return isa<Instruction>(V) && classof(cast<Instruction>(V));
+  }
+private:
+  void Init(BinOp Operation, Value *Ptr, Value *Val,
+            AtomicOrdering Ordering, SynchronizationScope SynchScope);
+  // Shadow Instruction::setInstructionSubclassData with a private forwarding
+  // method so that subclasses cannot accidentally use it.
+  void setInstructionSubclassData(unsigned short D) {
+    Instruction::setInstructionSubclassData(D);
+  }
+};
+
+template <>
+struct OperandTraits<AtomicRMWInst>
+    : public FixedNumOperandTraits<AtomicRMWInst,2> {
+};
+
+DEFINE_TRANSPARENT_OPERAND_ACCESSORS(AtomicRMWInst, Value)
+
+//===----------------------------------------------------------------------===//
 //                             GetElementPtrInst Class
 //===----------------------------------------------------------------------===//