path: root/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp

//===-- SelectionDAGISel.cpp - Implement the SelectionDAGISel class -------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file was developed by the LLVM research group and is distributed under
// the University of Illinois Open Source License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This implements the SelectionDAGISel class.
//
//===----------------------------------------------------------------------===//

#define DEBUG_TYPE "isel"
#include "llvm/CodeGen/SelectionDAGISel.h"
#include "llvm/Constants.h"
#include "llvm/DerivedTypes.h"
#include "llvm/Function.h"
#include "llvm/Instructions.h"
#include "llvm/Intrinsics.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/SelectionDAG.h"
#include "llvm/CodeGen/SSARegMap.h"
#include "llvm/Target/TargetData.h"
#include "llvm/Target/TargetFrameInfo.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Target/TargetLowering.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include <map>
#include <iostream>
using namespace llvm;

#ifndef _NDEBUG
static cl::opt<bool>
ViewDAGs("view-isel-dags", cl::Hidden,
         cl::desc("Pop up a window to show isel dags as they are selected"));
#else
static const bool ViewDAGS = 0;
#endif

namespace llvm {
  //===--------------------------------------------------------------------===//
  /// FunctionLoweringInfo - This contains information that is global to a
  /// function that is used when lowering a region of the function.
  class FunctionLoweringInfo {
  public:
    TargetLowering &TLI;
    Function &Fn;
    MachineFunction &MF;
    SSARegMap *RegMap;

    FunctionLoweringInfo(TargetLowering &TLI, Function &Fn,MachineFunction &MF);

    /// MBBMap - A mapping from LLVM basic blocks to their machine code entry.
    std::map<const BasicBlock*, MachineBasicBlock *> MBBMap;

    /// ValueMap - Since we emit code for the function a basic block at a time,
    /// we must remember which virtual registers hold the values for
    /// cross-basic-block values.
    std::map<const Value*, unsigned> ValueMap;

    /// StaticAllocaMap - Keep track of frame indices for fixed sized allocas in
    /// the entry block.  This allows the allocas to be efficiently referenced
    /// anywhere in the function.
    std::map<const AllocaInst*, int> StaticAllocaMap;

    /// BlockLocalArguments - If any arguments are only used in a single basic
    /// block, and if the target can access the arguments without side-effects,
    /// avoid emitting CopyToReg nodes for those arguments.  This map keeps
    /// track of which arguments are local to each BB.
    std::multimap<BasicBlock*, std::pair<Argument*,
                                         unsigned> > BlockLocalArguments;


    unsigned MakeReg(MVT::ValueType VT) {
      return RegMap->createVirtualRegister(TLI.getRegClassFor(VT));
    }

    unsigned CreateRegForValue(const Value *V) {
      MVT::ValueType VT = TLI.getValueType(V->getType());
      // The common case is that we will only create one register for this
      // value.  If we have that case, create and return the virtual register.
      unsigned NV = TLI.getNumElements(VT);
      if (NV == 1) {
        // If we are promoting this value, pick the next largest supported type.
        return MakeReg(TLI.getTypeToTransformTo(VT));
      }

      // If this value is represented with multiple target registers, make sure
      // to create enough consequtive registers of the right (smaller) type.
      unsigned NT = VT-1;  // Find the type to use.
      while (TLI.getNumElements((MVT::ValueType)NT) != 1)
        --NT;

      unsigned R = MakeReg((MVT::ValueType)NT);
      for (unsigned i = 1; i != NV; ++i)
        MakeReg((MVT::ValueType)NT);
      return R;
    }

    unsigned InitializeRegForValue(const Value *V) {
      unsigned &R = ValueMap[V];
      assert(R == 0 && "Already initialized this value register!");
      return R = CreateRegForValue(V);
    }
  };
}

/// isUsedOutsideOfDefiningBlock - Return true if this instruction is used by
/// PHI nodes or outside of the basic block that defines it.
static bool isUsedOutsideOfDefiningBlock(Instruction *I) {
  if (isa<PHINode>(I))