llvm/llvm/lib/Target/Mips/MipsMulMulBugPass.cpp

//===- MipsMulMulBugPass.cpp - Mips VR4300 mulmul bugfix pass -------------===//
//
// 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
//
//===----------------------------------------------------------------------===//
//
// Early revisions of the VR4300 have a hardware bug where two consecutive
// multiplications can produce an incorrect result in the second multiply.
//
// This pass scans for mul instructions in each basic block and inserts
// a nop whenever the following conditions are met:
//
// - The current instruction is a single or double-precision floating-point
//   mul instruction.
// - The next instruction is either a mul instruction (any kind)
//   or a branch instruction.
//===----------------------------------------------------------------------===//

#include "Mips.h"
#include "MipsInstrInfo.h"
#include "MipsSubtarget.h"
#include "llvm/CodeGen/MachineBasicBlock.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Target/TargetMachine.h"

#define DEBUG_TYPE …

usingnamespacellvm;

namespace {

class MipsMulMulBugFix : public MachineFunctionPass { … };

} // namespace

INITIALIZE_PASS(…)

char MipsMulMulBugFix::ID = …;

bool MipsMulMulBugFix::runOnMachineFunction(MachineFunction &MF) { … }

static bool isFirstMul(const MachineInstr &MI) { … }

static bool isSecondMulOrBranch(const MachineInstr &MI) { … }

bool MipsMulMulBugFix::fixMulMulBB(MachineBasicBlock &MBB,
                                   const MipsInstrInfo &MipsII) { … }

FunctionPass *llvm::createMipsMulMulBugPass() { … }