llvm/llvm/lib/Target/X86/X86FixupInstTuning.cpp

//===-- X86FixupInstTunings.cpp - replace instructions -----------===//
//
// 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
//
//===----------------------------------------------------------------------===//
//
// This file does a tuning pass replacing slower machine instructions
// with faster ones. We do this here, as opposed to during normal ISel, as
// attempting to get the "right" instruction can break patterns. This pass
// is not meant search for special cases where an instruction can be transformed
// to another, it is only meant to do transformations where the old instruction
// is always replacable with the new instructions. For example:
//
//      `vpermq ymm` -> `vshufd ymm`
//          -- BAD, not always valid (lane cross/non-repeated mask)
//
//      `vpermilps ymm` -> `vshufd ymm`
//          -- GOOD, always replaceable
//
//===----------------------------------------------------------------------===//

#include "X86.h"
#include "X86InstrInfo.h"
#include "X86Subtarget.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"

usingnamespacellvm;

#define DEBUG_TYPE …

STATISTIC(NumInstChanges, "Number of instructions changes");

namespace {
class X86FixupInstTuningPass : public MachineFunctionPass { … };
} // end anonymous namespace

char X86FixupInstTuningPass::ID = …;

INITIALIZE_PASS(…)

FunctionPass *llvm::createX86FixupInstTuning() { … }

template <typename T>
static std::optional<bool> CmpOptionals(T NewVal, T CurVal) { … }

bool X86FixupInstTuningPass::processInstruction(
    MachineFunction &MF, MachineBasicBlock &MBB,
    MachineBasicBlock::iterator &I) { … }

bool X86FixupInstTuningPass::runOnMachineFunction(MachineFunction &MF) { … }