예제 #1
0
static bool MaybeRewriteToFallthrough(MachineInstr &MI, MachineBasicBlock &MBB,
                                      const MachineFunction &MF,
                                      WebAssemblyFunctionInfo &MFI,
                                      MachineRegisterInfo &MRI,
                                      const WebAssemblyInstrInfo &TII,
                                      unsigned FallthroughOpc,
                                      unsigned CopyLocalOpc) {
  if (DisableWebAssemblyFallthroughReturnOpt)
    return false;
  if (&MBB != &MF.back())
    return false;
  if (&MI != &MBB.back())
    return false;

  // If the operand isn't stackified, insert a COPY to read the operand and
  // stackify it.
  MachineOperand &MO = MI.getOperand(0);
  unsigned Reg = MO.getReg();
  if (!MFI.isVRegStackified(Reg)) {
    unsigned NewReg = MRI.createVirtualRegister(MRI.getRegClass(Reg));
    BuildMI(MBB, MI, MI.getDebugLoc(), TII.get(CopyLocalOpc), NewReg)
        .addReg(Reg);
    MO.setReg(NewReg);
    MFI.stackifyVReg(NewReg);
  }

  // Rewrite the return.
  MI.setDesc(TII.get(FallthroughOpc));
  return true;
}
예제 #2
0
/// Test whether OneUse, a use of Reg, dominates all of Reg's other uses.
static bool OneUseDominatesOtherUses(unsigned Reg, const MachineOperand &OneUse,
                                     const MachineBasicBlock &MBB,
                                     const MachineRegisterInfo &MRI,
                                     const MachineDominatorTree &MDT,
                                     LiveIntervals &LIS,
                                     WebAssemblyFunctionInfo &MFI) {
  const LiveInterval &LI = LIS.getInterval(Reg);

  const MachineInstr *OneUseInst = OneUse.getParent();
  VNInfo *OneUseVNI = LI.getVNInfoBefore(LIS.getInstructionIndex(*OneUseInst));

  for (const MachineOperand &Use : MRI.use_nodbg_operands(Reg)) {
    if (&Use == &OneUse)
      continue;

    const MachineInstr *UseInst = Use.getParent();
    VNInfo *UseVNI = LI.getVNInfoBefore(LIS.getInstructionIndex(*UseInst));

    if (UseVNI != OneUseVNI)
      continue;

    const MachineInstr *OneUseInst = OneUse.getParent();
    if (UseInst == OneUseInst) {
      // Another use in the same instruction. We need to ensure that the one
      // selected use happens "before" it.
      if (&OneUse > &Use)
        return false;
    } else {
      // Test that the use is dominated by the one selected use.
      while (!MDT.dominates(OneUseInst, UseInst)) {
        // Actually, dominating is over-conservative. Test that the use would
        // happen after the one selected use in the stack evaluation order.
        //
        // This is needed as a consequence of using implicit get_locals for
        // uses and implicit set_locals for defs.
        if (UseInst->getDesc().getNumDefs() == 0)
          return false;
        const MachineOperand &MO = UseInst->getOperand(0);
        if (!MO.isReg())
          return false;
        unsigned DefReg = MO.getReg();
        if (!TargetRegisterInfo::isVirtualRegister(DefReg) ||
            !MFI.isVRegStackified(DefReg))
          return false;
        assert(MRI.hasOneUse(DefReg));
        const MachineOperand &NewUse = *MRI.use_begin(DefReg);
        const MachineInstr *NewUseInst = NewUse.getParent();
        if (NewUseInst == OneUseInst) {
          if (&OneUse > &NewUse)
            return false;
          break;
        }
        UseInst = NewUseInst;
      }
    }
  }
  return true;
}
예제 #3
0
/// Test whether MI is a child of some other node in an expression tree.
static bool IsChild(const MachineInstr *MI,
                    const WebAssemblyFunctionInfo &MFI) {
  if (MI->getNumOperands() == 0)
    return false;
  const MachineOperand &MO = MI->getOperand(0);
  if (!MO.isReg() || MO.isImplicit() || !MO.isDef())
    return false;
  unsigned Reg = MO.getReg();
  return TargetRegisterInfo::isVirtualRegister(Reg) &&
         MFI.isVRegStackified(Reg);
}