LeonPasses.cpp

//===------ LeonPasses.cpp - Define passes specific to LEON ---------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
//
//===----------------------------------------------------------------------===//

#include "LeonPasses.h"
#include "SparcSubtarget.h"
#include "llvm/CodeGen/MachineBasicBlock.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/Support/raw_ostream.h"

using namespace llvm;

LEONMachineFunctionPass::LEONMachineFunctionPass(char &ID)
    : MachineFunctionPass(ID) {}

//*****************************************************************************
//**** InsertNOPLoad pass
//*****************************************************************************
// This pass fixes the incorrectly working Load instructions that exists for
// some earlier versions of the LEON processor line. NOP instructions must
// be inserted after the load instruction to ensure that the Load instruction
// behaves as expected for these processors.
//
// This pass inserts a NOP after any LD or LDF instruction.
//
char InsertNOPLoad::ID = 0;

InsertNOPLoad::InsertNOPLoad() : LEONMachineFunctionPass(ID) {}

bool InsertNOPLoad::runOnMachineFunction(MachineFunction &MF) {
  Subtarget = &MF.getSubtarget<SparcSubtarget>();
  if (!Subtarget->insertNOPLoad())
    return false;

  const TargetInstrInfo &TII = *Subtarget->getInstrInfo();
  DebugLoc DL = DebugLoc();

  bool Modified = false;
  for (MachineBasicBlock &MBB : MF) {
    for (auto MBBI = MBB.begin(), E = MBB.end(); MBBI != E; ++MBBI) {
      MachineInstr &MI = *MBBI;
      unsigned Opcode = MI.getOpcode();
      if (Opcode >= SP::LDDArr && Opcode <= SP::LDrr) {
        MachineBasicBlock::iterator NMBBI = std::next(MBBI);
        BuildMI(MBB, NMBBI, DL, TII.get(SP::NOP));
        Modified = true;
      }
    }
  }

  return Modified;
}



//*****************************************************************************
//**** DetectRoundChange pass
//*****************************************************************************
// To prevent any explicit change of the default rounding mode, this pass
// detects any call of the fesetround function.
// A warning is generated to ensure the user knows this has happened.
//
// Detects an erratum in UT699 LEON 3 processor

char DetectRoundChange::ID = 0;

DetectRoundChange::DetectRoundChange() : LEONMachineFunctionPass(ID) {}

bool DetectRoundChange::runOnMachineFunction(MachineFunction &MF) {
  Subtarget = &MF.getSubtarget<SparcSubtarget>();
  if (!Subtarget->detectRoundChange())
    return false;

  bool Modified = false;
  for (MachineBasicBlock &MBB : MF) {
    for (MachineInstr &MI : MBB) {
      unsigned Opcode = MI.getOpcode();
      if (Opcode == SP::CALL && MI.getNumOperands() > 0) {
        MachineOperand &MO = MI.getOperand(0);

        if (MO.isGlobal()) {
          StringRef FuncName = MO.getGlobal()->getName();
          if (FuncName.compare_insensitive("fesetround") == 0) {
            errs() << "Error: You are using the detectroundchange "
                      "option to detect rounding changes that will "
                      "cause LEON errata. The only way to fix this "
                      "is to remove the call to fesetround from "
                      "the source code.\n";
          }
        }
      }
    }
  }

  return Modified;
}

//*****************************************************************************
//**** FixAllFDIVSQRT pass
//*****************************************************************************
// This pass fixes the incorrectly working FDIVx and FSQRTx instructions that
// exist for some earlier versions of the LEON processor line. Five NOP
// instructions need to be inserted after these instructions to ensure the
// correct result is placed in the destination registers before they are used.
//
// This pass implements two fixes:
//  1) fixing the FSQRTS and FSQRTD instructions.
//  2) fixing the FDIVS and FDIVD instructions.
//
// FSQRTS and FDIVS are converted to FDIVD and FSQRTD respectively earlier in
// the pipeline when this option is enabled, so this pass needs only to deal
// with the changes that still need implementing for the "double" versions
// of these instructions.
//
char FixAllFDIVSQRT::ID = 0;

FixAllFDIVSQRT::FixAllFDIVSQRT() : LEONMachineFunctionPass(ID) {}

bool FixAllFDIVSQRT::runOnMachineFunction(MachineFunction &MF) {
  Subtarget = &MF.getSubtarget<SparcSubtarget>();
  if (!Subtarget->fixAllFDIVSQRT())
    return false;

  const TargetInstrInfo &TII = *Subtarget->getInstrInfo();
  DebugLoc DL = DebugLoc();

  bool Modified = false;
  for (MachineBasicBlock &MBB : MF) {
    for (auto MBBI = MBB.begin(), E = MBB.end(); MBBI != E; ++MBBI) {
      MachineInstr &MI = *MBBI;
      unsigned Opcode = MI.getOpcode();

      // Note: FDIVS and FSQRTS cannot be generated when this erratum fix is
      // switched on so we don't need to check for them here. They will
      // already have been converted to FSQRTD or FDIVD earlier in the
      // pipeline.
      if (Opcode == SP::FSQRTD || Opcode == SP::FDIVD) {
        for (int InsertedCount = 0; InsertedCount < 5; InsertedCount++)
          BuildMI(MBB, MBBI, DL, TII.get(SP::NOP));

        MachineBasicBlock::iterator NMBBI = std::next(MBBI);
        for (int InsertedCount = 0; InsertedCount < 28; InsertedCount++)
          BuildMI(MBB, NMBBI, DL, TII.get(SP::NOP));

        Modified = true;
      }
    }
  }

  return Modified;
}