C++ RegDescribedVarsMap类代码示例

// \brief Terminate the location range for variables described by register
// @RegNo by inserting @ClobberingInstr to their history.
static void clobberRegisterUses(RegDescribedVarsMap &RegVars, unsigned RegNo,
                                DbgValueHistoryMap &HistMap,
                                const MachineInstr &ClobberingInstr) {
  const auto &I = RegVars.find(RegNo);
  if (I == RegVars.end())
    return;
  clobberRegisterUses(RegVars, I, HistMap, ClobberingInstr);
}

// \brief Claim that @Var is not described by @RegNo anymore.
static void dropRegDescribedVar(RegDescribedVarsMap &RegVars, unsigned RegNo,
                                InlinedVariable Var) {
  const auto &I = RegVars.find(RegNo);
  assert(RegNo != 0U && I != RegVars.end());
  auto &VarSet = I->second;
  const auto &VarPos = std::find(VarSet.begin(), VarSet.end(), Var);
  assert(VarPos != VarSet.end());
  VarSet.erase(VarPos);
  // Don't keep empty sets in a map to keep it as small as possible.
  if (VarSet.empty())
    RegVars.erase(I);
}

// \brief Terminate the location range for variables described by register
// @RegNo by inserting @ClobberingInstr to their history.
static void clobberRegisterUses(RegDescribedVarsMap &RegVars, unsigned RegNo,
                                DbgValueHistoryMap &HistMap,
                                const MachineInstr &ClobberingInstr) {
  const auto &I = RegVars.find(RegNo);
  if (I == RegVars.end())
    return;
  // Iterate over all variables described by this register and add this
  // instruction to their history, clobbering it.
  for (const auto &Var : I->second)
    clobberVariableLocation(HistMap[Var], ClobberingInstr);
  RegVars.erase(I);
}

void llvm::calculateDbgValueHistory(const MachineFunction *MF,
                                    const TargetRegisterInfo *TRI,
                                    DbgValueHistoryMap &Result) {
  BitVector ChangingRegs(TRI->getNumRegs());
  collectChangingRegs(MF, TRI, ChangingRegs);

  RegDescribedVarsMap RegVars;
  for (const auto &MBB : *MF) {
    for (const auto &MI : MBB) {
      if (!MI.isDebugValue()) {
        // Not a DBG_VALUE instruction. It may clobber registers which describe
        // some variables.
        applyToClobberedRegisters(MI, TRI, [&](unsigned RegNo) {
          if (ChangingRegs.test(RegNo))
            clobberRegisterUses(RegVars, RegNo, Result, MI);
        });
        continue;
      }

      assert(MI.getNumOperands() > 1 && "Invalid DBG_VALUE instruction!");
      // Use the base variable (without any DW_OP_piece expressions)
      // as index into History. The full variables including the
      // piece expressions are attached to the MI.
      const DILocalVariable *RawVar = MI.getDebugVariable();
      assert(RawVar->isValidLocationForIntrinsic(MI.getDebugLoc()) &&
             "Expected inlined-at fields to agree");
      InlinedVariable Var(RawVar, MI.getDebugLoc()->getInlinedAt());

      if (unsigned PrevReg = Result.getRegisterForVar(Var))
        dropRegDescribedVar(RegVars, PrevReg, Var);

      Result.startInstrRange(Var, MI);

      if (unsigned NewReg = isDescribedByReg(MI))
        addRegDescribedVar(RegVars, NewReg, Var);
    }

    // Make sure locations for register-described variables are valid only
    // until the end of the basic block (unless it's the last basic block, in
    // which case let their liveness run off to the end of the function).
    if (!MBB.empty() && &MBB != &MF->back()) {
      for (auto I = RegVars.begin(), E = RegVars.end(); I != E;) {
        auto CurElem = I++; // CurElem can be erased below.
        if (ChangingRegs.test(CurElem->first))
          clobberRegisterUses(RegVars, CurElem, Result, MBB.back());
      }
    }
  }
}

// \brief Terminate the location range for all register-described variables
// by inserting @ClobberingInstr to their history.
static void clobberAllRegistersUses(RegDescribedVarsMap &RegVars,
                                    DbgValueHistoryMap &HistMap,
                                    const MachineInstr &ClobberingInstr) {
  for (const auto &I : RegVars)
    for (const auto &Var : I.second)
      clobberVariableLocation(HistMap[Var], ClobberingInstr);
  RegVars.clear();
}

void llvm::calculateDbgValueHistory(const MachineFunction *MF,
                                    const TargetRegisterInfo *TRI,
                                    DbgValueHistoryMap &Result) {
  BitVector ChangingRegs(TRI->getNumRegs());
  collectChangingRegs(MF, TRI, ChangingRegs);

  const TargetLowering *TLI = MF->getSubtarget().getTargetLowering();
  unsigned SP = TLI->getStackPointerRegisterToSaveRestore();
  RegDescribedVarsMap RegVars;
  for (const auto &MBB : *MF) {
    for (const auto &MI : MBB) {
      if (!MI.isDebugValue()) {
        // Not a DBG_VALUE instruction. It may clobber registers which describe
        // some variables.
        for (const MachineOperand &MO : MI.operands()) {
          if (MO.isReg() && MO.isDef() && MO.getReg()) {
            // If this is a virtual register, only clobber it since it doesn't
            // have aliases.
            if (TRI->isVirtualRegister(MO.getReg()))
              clobberRegisterUses(RegVars, MO.getReg(), Result, MI);
            // If this is a register def operand, it may end a debug value
            // range.
            else {
              for (MCRegAliasIterator AI(MO.getReg(), TRI, true); AI.isValid();
                   ++AI)
                if (ChangingRegs.test(*AI))
                  clobberRegisterUses(RegVars, *AI, Result, MI);
            }
          } else if (MO.isRegMask()) {
            // If this is a register mask operand, clobber all debug values in
            // non-CSRs.
            for (int I = ChangingRegs.find_first(); I != -1;
                 I = ChangingRegs.find_next(I)) {
              // Don't consider SP to be clobbered by register masks.
              if (unsigned(I) != SP && TRI->isPhysicalRegister(I) &&
                  MO.clobbersPhysReg(I)) {
                clobberRegisterUses(RegVars, I, Result, MI);
              }
            }
          }
        }
        continue;
      }

      assert(MI.getNumOperands() > 1 && "Invalid DBG_VALUE instruction!");
      // Use the base variable (without any DW_OP_piece expressions)
      // as index into History. The full variables including the
      // piece expressions are attached to the MI.
      const DILocalVariable *RawVar = MI.getDebugVariable();
      assert(RawVar->isValidLocationForIntrinsic(MI.getDebugLoc()) &&
             "Expected inlined-at fields to agree");
      InlinedVariable Var(RawVar, MI.getDebugLoc()->getInlinedAt());

      if (unsigned PrevReg = Result.getRegisterForVar(Var))
        dropRegDescribedVar(RegVars, PrevReg, Var);

      Result.startInstrRange(Var, MI);

      if (unsigned NewReg = isDescribedByReg(MI))
        addRegDescribedVar(RegVars, NewReg, Var);
    }

    // Make sure locations for register-described variables are valid only
    // until the end of the basic block (unless it's the last basic block, in
    // which case let their liveness run off to the end of the function).
    if (!MBB.empty() && &MBB != &MF->back()) {
      for (auto I = RegVars.begin(), E = RegVars.end(); I != E;) {
        auto CurElem = I++; // CurElem can be erased below.
        if (TRI->isVirtualRegister(CurElem->first) ||
            ChangingRegs.test(CurElem->first))
          clobberRegisterUses(RegVars, CurElem, Result, MBB.back());
      }
    }
  }
}