llvm/llvm/lib/Target/ARM/ARMBlockPlacement.cpp

//===-- ARMBlockPlacement.cpp - ARM block placement 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
//
//===----------------------------------------------------------------------===//
//
// This pass re-arranges machine basic blocks to suit target requirements.
// Currently it only moves blocks to fix backwards WLS branches.
//
//===----------------------------------------------------------------------===//

#include "ARM.h"
#include "ARMBaseInstrInfo.h"
#include "ARMBasicBlockInfo.h"
#include "ARMSubtarget.h"
#include "MVETailPredUtils.h"
#include "llvm/CodeGen/LivePhysRegs.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineLoopInfo.h"

usingnamespacellvm;

#define DEBUG_TYPE …
#define DEBUG_PREFIX …

namespace llvm {
class ARMBlockPlacement : public MachineFunctionPass { … };

} // namespace llvm

FunctionPass *llvm::createARMBlockPlacementPass() { … }

char ARMBlockPlacement::ID = …;

INITIALIZE_PASS(…)

static MachineInstr *findWLSInBlock(MachineBasicBlock *MBB) { … }

/// Find WhileLoopStart in the loop predecessor BB or otherwise in its only
/// predecessor. If found, returns (BB, WLS Instr) pair, otherwise a null pair.
static MachineInstr *findWLS(MachineLoop *ML) { … }

// Revert a WhileLoopStart to an equivalent DoLoopStart and branch. Note that
// because of the branches this requires an extra block to be created.
bool ARMBlockPlacement::revertWhileToDoLoop(MachineInstr *WLS) { … }

/// Checks if loop has a backwards branching WLS, and if possible, fixes it.
/// This requires checking the predecessor (ie. preheader or it's predecessor)
/// for a WLS and if its loopExit/target is before it.
/// If moving the predecessor won't convert a WLS (to the predecessor) from
/// a forward to a backward branching WLS, then move the predecessor block
/// to before the loopExit/target.
bool ARMBlockPlacement::fixBackwardsWLS(MachineLoop *ML) { … }

/// Updates ordering (of WLS BB and their loopExits) in inner loops first
/// Returns true if any change was made in any of the loops
bool ARMBlockPlacement::processPostOrderLoops(MachineLoop *ML) { … }

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

bool ARMBlockPlacement::blockIsBefore(MachineBasicBlock *BB,
                                      MachineBasicBlock *Other) { … }

// Moves a BasicBlock before another, without changing the control flow
void ARMBlockPlacement::moveBasicBlock(MachineBasicBlock *BB,
                                       MachineBasicBlock *Before) { … }