llvm/llvm/lib/CodeGen/BranchRelaxation.cpp

//===- BranchRelaxation.cpp -----------------------------------------------===//
//
// 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/SmallVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/CodeGen/LivePhysRegs.h"
#include "llvm/CodeGen/MachineBasicBlock.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/RegisterScavenging.h"
#include "llvm/CodeGen/TargetInstrInfo.h"
#include "llvm/CodeGen/TargetRegisterInfo.h"
#include "llvm/CodeGen/TargetSubtargetInfo.h"
#include "llvm/Config/llvm-config.h"
#include "llvm/IR/DebugLoc.h"
#include "llvm/InitializePasses.h"
#include "llvm/Pass.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/Format.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Target/TargetMachine.h"
#include <cassert>
#include <cstdint>
#include <iterator>
#include <memory>

usingnamespacellvm;

#define DEBUG_TYPE …

STATISTIC(NumSplit, "Number of basic blocks split");
STATISTIC(NumConditionalRelaxed, "Number of conditional branches relaxed");
STATISTIC(NumUnconditionalRelaxed, "Number of unconditional branches relaxed");

#define BRANCH_RELAX_NAME …

namespace {

class BranchRelaxation : public MachineFunctionPass { … };

} // end anonymous namespace

char BranchRelaxation::ID = …;

char &llvm::BranchRelaxationPassID = …;

INITIALIZE_PASS(…)

/// verify - check BBOffsets, BBSizes, alignment of islands
void BranchRelaxation::verify() { … }

#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
/// print block size and offset information - debugging
LLVM_DUMP_METHOD void BranchRelaxation::dumpBBs() {
  for (auto &MBB : *MF) {
    const BasicBlockInfo &BBI = BlockInfo[MBB.getNumber()];
    dbgs() << format("%%bb.%u\toffset=%08x\t", MBB.getNumber(), BBI.Offset)
           << format("size=%#x\n", BBI.Size);
  }
}
#endif

/// scanFunction - Do the initial scan of the function, building up
/// information about each block.
void BranchRelaxation::scanFunction() { … }

/// computeBlockSize - Compute the size for MBB.
uint64_t
BranchRelaxation::computeBlockSize(const MachineBasicBlock &MBB) const { … }

/// getInstrOffset - Return the current offset of the specified machine
/// instruction from the start of the function.  This offset changes as stuff is
/// moved around inside the function.
unsigned BranchRelaxation::getInstrOffset(const MachineInstr &MI) const { … }

void BranchRelaxation::adjustBlockOffsets(MachineBasicBlock &Start) { … }

void BranchRelaxation::adjustBlockOffsets(MachineBasicBlock &Start,
                                          MachineFunction::iterator End) { … }

/// Insert a new empty MachineBasicBlock and insert it after \p OrigMBB
MachineBasicBlock *
BranchRelaxation::createNewBlockAfter(MachineBasicBlock &OrigBB) { … }

/// Insert a new empty MachineBasicBlock with \p BB as its BasicBlock
/// and insert it after \p OrigMBB
MachineBasicBlock *
BranchRelaxation::createNewBlockAfter(MachineBasicBlock &OrigMBB,
                                      const BasicBlock *BB) { … }

/// Split the basic block containing MI into two blocks, which are joined by
/// an unconditional branch.  Update data structures and renumber blocks to
/// account for this change and returns the newly created block.
MachineBasicBlock *
BranchRelaxation::splitBlockBeforeInstr(MachineInstr &MI,
                                        MachineBasicBlock *DestBB) { … }

/// isBlockInRange - Returns true if the distance between specific MI and
/// specific BB can fit in MI's displacement field.
bool BranchRelaxation::isBlockInRange(const MachineInstr &MI,
                                      const MachineBasicBlock &DestBB) const { … }

/// fixupConditionalBranch - Fix up a conditional branch whose destination is
/// too far away to fit in its displacement field. It is converted to an inverse
/// conditional branch + an unconditional branch to the destination.
bool BranchRelaxation::fixupConditionalBranch(MachineInstr &MI) { … }

bool BranchRelaxation::fixupUnconditionalBranch(MachineInstr &MI) { … }

bool BranchRelaxation::relaxBranchInstructions() { … }

bool BranchRelaxation::runOnMachineFunction(MachineFunction &mf) { … }