MDBuilder.h

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//===---- llvm/MDBuilder.h - Builder for LLVM metadata ----------*- C++ -*-===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file defines the MDBuilder class, which is used as a convenient way to
// create LLVM metadata with a consistent and simplified interface.
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_IR_MDBUILDER_H
#define LLVM_IR_MDBUILDER_H

#include "llvm/IR/Constants.h"
#include "llvm/IR/DerivedTypes.h"
#include "llvm/IR/Metadata.h"

namespace llvm {

class APInt;
class LLVMContext;

class MDBuilder {
  LLVMContext &Context;

public:
  MDBuilder(LLVMContext &context) : Context(context) {}

  /// \brief Return the given string as metadata.
  MDString *createString(StringRef Str) {
    return MDString::get(Context, Str);
  }

  //===------------------------------------------------------------------===//
  // FPMath metadata.
  //===------------------------------------------------------------------===//

  /// \brief Return metadata with the given settings.  The special value 0.0
  /// for the Accuracy parameter indicates the default (maximal precision)
  /// setting.
  MDNode *createFPMath(float Accuracy) {
    if (Accuracy == 0.0)
      return 0;
    assert(Accuracy > 0.0 && "Invalid fpmath accuracy!");
    Value *Op = ConstantFP::get(Type::getFloatTy(Context), Accuracy);
    return MDNode::get(Context, Op);
  }

  //===------------------------------------------------------------------===//
  // Prof metadata.
  //===------------------------------------------------------------------===//

  /// \brief Return metadata containing two branch weights.
  MDNode *createBranchWeights(uint32_t TrueWeight, uint32_t FalseWeight) {
    uint32_t Weights[] = { TrueWeight, FalseWeight };
    return createBranchWeights(Weights);
  }

  /// \brief Return metadata containing a number of branch weights.
  MDNode *createBranchWeights(ArrayRef<uint32_t> Weights) {
    assert(Weights.size() >= 2 && "Need at least two branch weights!");

    SmallVector<Value *, 4> Vals(Weights.size()+1);
    Vals[0] = createString("branch_weights");

    Type *Int32Ty = Type::getInt32Ty(Context);
    for (unsigned i = 0, e = Weights.size(); i != e; ++i)
      Vals[i+1] = ConstantInt::get(Int32Ty, Weights[i]);

    return MDNode::get(Context, Vals);
  }

  //===------------------------------------------------------------------===//
  // Range metadata.
  //===------------------------------------------------------------------===//

  /// \brief Return metadata describing the range [Lo, Hi).
  MDNode *createRange(const APInt &Lo, const APInt &Hi) {
    assert(Lo.getBitWidth() == Hi.getBitWidth() && "Mismatched bitwidths!");
    // If the range is everything then it is useless.
    if (Hi == Lo)
      return 0;

    // Return the range [Lo, Hi).
    Type *Ty = IntegerType::get(Context, Lo.getBitWidth());
    Value *Range[2] = { ConstantInt::get(Ty, Lo), ConstantInt::get(Ty, Hi) };
    return MDNode::get(Context, Range);
  }


  //===------------------------------------------------------------------===//
  // TBAA metadata.
  //===------------------------------------------------------------------===//

  /// \brief Return metadata appropriate for a TBAA root node.  Each returned
  /// node is distinct from all other metadata and will never be identified
  /// (uniqued) with anything else.
  MDNode *createAnonymousTBAARoot() {
    // To ensure uniqueness the root node is self-referential.
    MDNode *Dummy = MDNode::getTemporary(Context, ArrayRef<Value*>());
    MDNode *Root = MDNode::get(Context, Dummy);
    // At this point we have
    //   !0 = metadata !{}            <- dummy
    //   !1 = metadata !{metadata !0} <- root
    // Replace the dummy operand with the root node itself and delete the dummy.
    Root->replaceOperandWith(0, Root);
    MDNode::deleteTemporary(Dummy);
    // We now have
    //   !1 = metadata !{metadata !1} <- self-referential root
    return Root;
  }

  /// \brief Return metadata appropriate for a TBAA root node with the given
  /// name.  This may be identified (uniqued) with other roots with the same
  /// name.
  MDNode *createTBAARoot(StringRef Name) {
    return MDNode::get(Context, createString(Name));
  }

  /// \brief Return metadata for a non-root TBAA node with the given name,
  /// parent in the TBAA tree, and value for 'pointsToConstantMemory'.
  MDNode *createTBAANode(StringRef Name, MDNode *Parent,
                         bool isConstant = false) {
    if (isConstant) {
      Constant *Flags = ConstantInt::get(Type::getInt64Ty(Context), 1);
      Value *Ops[3] = { createString(Name), Parent, Flags };
      return MDNode::get(Context, Ops);
    } else {
      Value *Ops[2] = { createString(Name), Parent };
      return MDNode::get(Context, Ops);
    }
  }

  struct TBAAStructField {
    uint64_t Offset;
    uint64_t Size;
    MDNode *TBAA;
    TBAAStructField(uint64_t Offset, uint64_t Size, MDNode *TBAA) :
      Offset(Offset), Size(Size), TBAA(TBAA) {}
  };

  /// \brief Return metadata for a tbaa.struct node with the given
  /// struct field descriptions.
  MDNode *createTBAAStructNode(ArrayRef<TBAAStructField> Fields) {
    SmallVector<Value *, 4> Vals(Fields.size() * 3);
    Type *Int64 = IntegerType::get(Context, 64);
    for (unsigned i = 0, e = Fields.size(); i != e; ++i) {
      Vals[i * 3 + 0] = ConstantInt::get(Int64, Fields[i].Offset);
      Vals[i * 3 + 1] = ConstantInt::get(Int64, Fields[i].Size);
      Vals[i * 3 + 2] = Fields[i].TBAA;
    }
    return MDNode::get(Context, Vals);
  }

  /// \brief Return metadata for a TBAA struct node in the type DAG
  /// with the given name, a list of pairs (offset, field type in the type DAG).
  MDNode *createTBAAStructTypeNode(StringRef Name,
             ArrayRef<std::pair<MDNode*, uint64_t> > Fields) {
    SmallVector<Value *, 4> Ops(Fields.size() * 2 + 1);
    Type *Int64 = IntegerType::get(Context, 64);
    Ops[0] = createString(Name);
    for (unsigned i = 0, e = Fields.size(); i != e; ++i) {
      Ops[i * 2 + 1] = Fields[i].first;
      Ops[i * 2 + 2] = ConstantInt::get(Int64, Fields[i].second);
    }
    return MDNode::get(Context, Ops);
  }

  /// \brief Return metadata for a TBAA scalar type node with the
  /// given name, an offset and a parent in the TBAA type DAG.
  MDNode *createTBAAScalarTypeNode(StringRef Name, MDNode *Parent,
                                   uint64_t Offset = 0) {
    SmallVector<Value *, 4> Ops(3);
    Type *Int64 = IntegerType::get(Context, 64);
    Ops[0] = createString(Name);
    Ops[1] = Parent;
    Ops[2] = ConstantInt::get(Int64, Offset);
    return MDNode::get(Context, Ops);
  }

  /// \brief Return metadata for a TBAA tag node with the given
  /// base type, access type and offset relative to the base type.
  MDNode *createTBAAStructTagNode(MDNode *BaseType, MDNode *AccessType,
                                  uint64_t Offset) {
    Type *Int64 = IntegerType::get(Context, 64);
    Value *Ops[3] = { BaseType, AccessType, ConstantInt::get(Int64, Offset) };
    return MDNode::get(Context, Ops);
  }

};

} // end namespace llvm

#endif