llvm/llvm/lib/Target/ARM/Thumb2SizeReduction.cpp

//===-- Thumb2SizeReduction.cpp - Thumb2 code size reduction pass -*- C++ -*-=//
//
// 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 "ARM.h"
#include "ARMBaseInstrInfo.h"
#include "ARMSubtarget.h"
#include "MCTargetDesc/ARMBaseInfo.h"
#include "Thumb2InstrInfo.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/PostOrderIterator.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SmallSet.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/CodeGen/MachineBasicBlock.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineOperand.h"
#include "llvm/CodeGen/TargetInstrInfo.h"
#include "llvm/IR/DebugLoc.h"
#include "llvm/IR/Function.h"
#include "llvm/MC/MCAsmInfo.h"
#include "llvm/MC/MCInstrDesc.h"
#include "llvm/MC/MCRegisterInfo.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/raw_ostream.h"
#include <algorithm>
#include <cassert>
#include <cstdint>
#include <functional>
#include <iterator>
#include <utility>

usingnamespacellvm;

#define DEBUG_TYPE …
#define THUMB2_SIZE_REDUCE_NAME …

STATISTIC(NumNarrows,  "Number of 32-bit instrs reduced to 16-bit ones");
STATISTIC(Num2Addrs,   "Number of 32-bit instrs reduced to 2addr 16-bit ones");
STATISTIC(NumLdSts,    "Number of 32-bit load / store reduced to 16-bit ones");

static cl::opt<int> ReduceLimit("t2-reduce-limit",
                                cl::init(-1), cl::Hidden);
static cl::opt<int> ReduceLimit2Addr("t2-reduce-limit2",
                                     cl::init(-1), cl::Hidden);
static cl::opt<int> ReduceLimitLdSt("t2-reduce-limit3",
                                     cl::init(-1), cl::Hidden);

namespace {

  /// ReduceTable - A static table with information on mapping from wide
  /// opcodes to narrow
  struct ReduceEntry { … };

  static const ReduceEntry ReduceTable[] = …;

  class Thumb2SizeReduce : public MachineFunctionPass { … };

  char Thumb2SizeReduce::ID = …;

} // end anonymous namespace

INITIALIZE_PASS(…)

Thumb2SizeReduce::Thumb2SizeReduce(std::function<bool(const Function &)> Ftor)
    : … { … }

static bool HasImplicitCPSRDef(const MCInstrDesc &MCID) { … }

// Check for a likely high-latency flag def.
static bool isHighLatencyCPSR(MachineInstr *Def) { … }

/// canAddPseudoFlagDep - For A9 (and other out-of-order) implementations,
/// the 's' 16-bit instruction partially update CPSR. Abort the
/// transformation to avoid adding false dependency on last CPSR setting
/// instruction which hurts the ability for out-of-order execution engine
/// to do register renaming magic.
/// This function checks if there is a read-of-write dependency between the
/// last instruction that defines the CPSR and the current instruction. If there
/// is, then there is no harm done since the instruction cannot be retired
/// before the CPSR setting instruction anyway.
/// Note, we are not doing full dependency analysis here for the sake of compile
/// time. We're not looking for cases like:
/// r0 = muls ...
/// r1 = add.w r0, ...
/// ...
///    = mul.w r1
/// In this case it would have been ok to narrow the mul.w to muls since there
/// are indirect RAW dependency between the muls and the mul.w
bool
Thumb2SizeReduce::canAddPseudoFlagDep(MachineInstr *Use, bool FirstInSelfLoop) { … }

bool
Thumb2SizeReduce::VerifyPredAndCC(MachineInstr *MI, const ReduceEntry &Entry,
                                  bool is2Addr, ARMCC::CondCodes Pred,
                                  bool LiveCPSR, bool &HasCC, bool &CCDead) { … }

static bool VerifyLowRegs(MachineInstr *MI) { … }

bool
Thumb2SizeReduce::ReduceLoadStore(MachineBasicBlock &MBB, MachineInstr *MI,
                                  const ReduceEntry &Entry) { … }

bool
Thumb2SizeReduce::ReduceSpecial(MachineBasicBlock &MBB, MachineInstr *MI,
                                const ReduceEntry &Entry,
                                bool LiveCPSR, bool IsSelfLoop) { … }

bool
Thumb2SizeReduce::ReduceTo2Addr(MachineBasicBlock &MBB, MachineInstr *MI,
                                const ReduceEntry &Entry,
                                bool LiveCPSR, bool IsSelfLoop) { … }

bool
Thumb2SizeReduce::ReduceToNarrow(MachineBasicBlock &MBB, MachineInstr *MI,
                                 const ReduceEntry &Entry,
                                 bool LiveCPSR, bool IsSelfLoop) { … }

static bool UpdateCPSRDef(MachineInstr &MI, bool LiveCPSR, bool &DefCPSR) { … }

static bool UpdateCPSRUse(MachineInstr &MI, bool LiveCPSR) { … }

bool Thumb2SizeReduce::ReduceMI(MachineBasicBlock &MBB, MachineInstr *MI,
                                bool LiveCPSR, bool IsSelfLoop,
                                bool SkipPrologueEpilogue) { … }

bool Thumb2SizeReduce::ReduceMBB(MachineBasicBlock &MBB,
                                 bool SkipPrologueEpilogue) { … }

bool Thumb2SizeReduce::runOnMachineFunction(MachineFunction &MF) { … }

/// createThumb2SizeReductionPass - Returns an instance of the Thumb2 size
/// reduction pass.
FunctionPass *llvm::createThumb2SizeReductionPass(
    std::function<bool(const Function &)> Ftor) { … }