llvm/llvm/lib/CodeGen/RemoveRedundantDebugValues.cpp

//===- RemoveRedundantDebugValues.cpp - Remove Redundant Debug Value MIs --===//
//
// 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 "llvm/ADT/DenseMap.h"
#include "llvm/ADT/DenseSet.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/CodeGen/MachineBasicBlock.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/TargetSubtargetInfo.h"
#include "llvm/IR/DebugInfoMetadata.h"
#include "llvm/IR/Function.h"
#include "llvm/InitializePasses.h"
#include "llvm/Pass.h"
#include "llvm/PassRegistry.h"

/// \file RemoveRedundantDebugValues.cpp
///
/// The RemoveRedundantDebugValues pass removes redundant DBG_VALUEs that
/// appear in MIR after the register allocator.

#define DEBUG_TYPE …

usingnamespacellvm;

STATISTIC(NumRemovedBackward, "Number of DBG_VALUEs removed (backward scan)");
STATISTIC(NumRemovedForward, "Number of DBG_VALUEs removed (forward scan)");

namespace {

class RemoveRedundantDebugValues : public MachineFunctionPass { … };

} // namespace

//===----------------------------------------------------------------------===//
//            Implementation
//===----------------------------------------------------------------------===//

char RemoveRedundantDebugValues::ID = …;

char &llvm::RemoveRedundantDebugValuesID = …;

INITIALIZE_PASS(…)

/// Default construct and initialize the pass.
RemoveRedundantDebugValues::RemoveRedundantDebugValues()
    : … { … }

// This analysis aims to remove redundant DBG_VALUEs by going forward
// in the basic block by considering the first DBG_VALUE as a valid
// until its first (location) operand is not clobbered/modified.
// For example:
//   (1) DBG_VALUE $edi, !"var1", ...
//   (2) <block of code that does affect $edi>
//   (3) DBG_VALUE $edi, !"var1", ...
//   ...
// in this case, we can remove (3).
// TODO: Support DBG_VALUE_LIST and other debug instructions.
static bool reduceDbgValsForwardScan(MachineBasicBlock &MBB) { … }

// This analysis aims to remove redundant DBG_VALUEs by going backward
// in the basic block and removing all but the last DBG_VALUE for any
// given variable in a set of consecutive DBG_VALUE instructions.
// For example:
//   (1) DBG_VALUE $edi, !"var1", ...
//   (2) DBG_VALUE $esi, !"var2", ...
//   (3) DBG_VALUE $edi, !"var1", ...
//   ...
// in this case, we can remove (1).
static bool reduceDbgValsBackwardScan(MachineBasicBlock &MBB) { … }

bool RemoveRedundantDebugValues::reduceDbgValues(MachineFunction &MF) { … }

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