path: root/lib/CodeGen/CGAtomic.cpp

//===--- CGAtomic.cpp - Emit LLVM IR for atomic operations ----------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file contains the code for emitting atomic operations.
//
//===----------------------------------------------------------------------===//

#include "CodeGenFunction.h"
#include "CGCall.h"
#include "CodeGenModule.h"
#include "clang/AST/ASTContext.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/Intrinsics.h"
#include "llvm/IR/Operator.h"

using namespace clang;
using namespace CodeGen;

// The ABI values for various atomic memory orderings.
enum AtomicOrderingKind {
  AO_ABI_memory_order_relaxed = 0,
  AO_ABI_memory_order_consume = 1,
  AO_ABI_memory_order_acquire = 2,
  AO_ABI_memory_order_release = 3,
  AO_ABI_memory_order_acq_rel = 4,
  AO_ABI_memory_order_seq_cst = 5
};

namespace {
  class AtomicInfo {
    CodeGenFunction &CGF;
    QualType AtomicTy;
    QualType ValueTy;
    uint64_t AtomicSizeInBits;
    uint64_t ValueSizeInBits;
    CharUnits AtomicAlign;
    CharUnits ValueAlign;
    CharUnits LValueAlign;
    TypeEvaluationKind EvaluationKind;
    bool UseLibcall;
  public:
    AtomicInfo(CodeGenFunction &CGF, LValue &lvalue) : CGF(CGF) {
      assert(lvalue.isSimple());

      AtomicTy = lvalue.getType();
      ValueTy = AtomicTy->castAs<AtomicType>()->getValueType();
      EvaluationKind = CGF.getEvaluationKind(ValueTy);

      ASTContext &C = CGF.getContext();

      uint64_t valueAlignInBits;
      llvm::tie(ValueSizeInBits, valueAlignInBits) = C.getTypeInfo(ValueTy);

      uint64_t atomicAlignInBits;
      llvm::tie(AtomicSizeInBits, atomicAlignInBits) = C.getTypeInfo(AtomicTy);

      assert(ValueSizeInBits <= AtomicSizeInBits);
      assert(valueAlignInBits <= atomicAlignInBits);

      AtomicAlign = C.toCharUnitsFromBits(atomicAlignInBits);
      ValueAlign = C.toCharUnitsFromBits(valueAlignInBits);
      if (lvalue.getAlignment().isZero())
        lvalue.setAlignment(AtomicAlign);

      UseLibcall =
        (AtomicSizeInBits > uint64_t(C.toBits(lvalue.getAlignment())) ||
         AtomicSizeInBits > C.getTargetInfo().getMaxAtomicInlineWidth());
    }

    QualType getAtomicType() const { return AtomicTy; }
    QualType getValueType() const { return ValueTy; }
    CharUnits getAtomicAlignment() const { return AtomicAlign; }
    CharUnits getValueAlignment() const { return ValueAlign; }
    uint64_t getAtomicSizeInBits() const { return AtomicSizeInBits; }
    uint64_t getValueSizeInBits() const { return AtomicSizeInBits; }
    TypeEvaluationKind getEvaluationKind() const { return EvaluationKind; }
    bool shouldUseLibcall() const { return UseLibcall; }

    /// Is the atomic size larger than the underlying value type?
    ///
    /// Note that the absence of padding does not mean that atomic
    /// objects are completely interchangeable with non-atomic
    /// objects: we might have promoted the alignment of a type
    /// without making it bigger.
    bool hasPadding() const {
      return (ValueSizeInBits != AtomicSizeInBits);
    }

    void emitMemSetZeroIfNecessary(LValue dest) const;

    llvm::Value *getAtomicSizeValue() const {
      CharUnits size = CGF.getContext().toCharUnitsFromBits(AtomicSizeInBits);
      return CGF.CGM.getSize(size);
    }

    /// Cast the given pointer to an integer pointer suitable for
    /// atomic operations.
    llvm::Value *emitCastToAtomicIntPointer(llvm::Value *addr) const;

    /// Turn an atomic-layout object into an r-value.
    RValue convertTempToRValue(llvm::Value *addr,
                               AggValueSlot resultSlot) const;

    /// Copy an atomic r-value into atomic-layout memory.
    void emitCopyIntoMemory(RValue rvalue, LValue lvalue) const;

    /// Project an l-value down to the value field.
    LValue projectValue(LValue lvalue) const {
      llvm::Value *addr = lvalue.getAddress();
      if (hasPadding())
        addr = CGF.Builder.CreateStructGEP(addr, 0);

      return LValue::MakeAddr(addr, getValueType(), lvalue.getAlignment(),
                              CGF.getContext(), lvalue.getTBAAInfo());
    }

    /// Materialize an atomic r-value in atomic-layout memory.
    llvm::Value *materializeRValue(RValue rvalue) const;

  private:
    bool requiresMemSetZero(llvm::Type *type) const;
  };
}

static RValue emitAtomicLibcall(CodeGenFunction &CGF,
                                StringRef fnName,
                                QualType resultType,
                                CallArgList &args) {
  const CGFunctionInfo &fnInfo =
    CGF.CGM.getTypes().arrangeFreeFunctionCall(resultType, args,
            FunctionType::ExtInfo(), RequiredArgs::All);
  llvm::FunctionType *fnTy = CGF.CGM.getTypes().GetFunctionType(fnInfo);
  llvm::Constant *fn = CGF.CGM.CreateRuntimeFunction(fnTy, </