llvm/llvm/lib/Target/Hexagon/HexagonFixupHwLoops.cpp

//===---- HexagonFixupHwLoops.cpp - Fixup HW loops too far from LOOPn. ----===//
//
// 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
//
// The loop start address in the LOOPn instruction is encoded as a distance
// from the LOOPn instruction itself. If the start address is too far from
// the LOOPn instruction, the instruction needs to use a constant extender.
// This pass will identify and convert such LOOPn instructions to a proper
// form.
//===----------------------------------------------------------------------===//

#include "Hexagon.h"
#include "HexagonTargetMachine.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/Passes.h"
#include "llvm/CodeGen/TargetInstrInfo.h"
#include "llvm/Support/MathExtras.h"
#include "llvm/Pass.h"

usingnamespacellvm;

static cl::opt<unsigned> MaxLoopRange(
    "hexagon-loop-range", cl::Hidden, cl::init(200),
    cl::desc("Restrict range of loopN instructions (testing only)"));

namespace llvm {
  FunctionPass *createHexagonFixupHwLoops();
  void initializeHexagonFixupHwLoopsPass(PassRegistry&);
}

namespace {
  struct HexagonFixupHwLoops : public MachineFunctionPass { … };

  char HexagonFixupHwLoops::ID = …;
}

INITIALIZE_PASS(…)

FunctionPass *llvm::createHexagonFixupHwLoops() { … }

/// Returns true if the instruction is a hardware loop instruction.
static bool isHardwareLoop(const MachineInstr &MI) { … }

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

/// For Hexagon, if the loop label is to far from the
/// loop instruction then we need to set the LC0 and SA0 registers
/// explicitly instead of using LOOP(start,count).  This function
/// checks the distance, and generates register assignments if needed.
///
/// This function makes two passes over the basic blocks.  The first
/// pass computes the offset of the basic block from the start.
/// The second pass checks all the loop instructions.
bool HexagonFixupHwLoops::fixupLoopInstrs(MachineFunction &MF) { … }

/// Replace loop instructions with the constant extended version.
void HexagonFixupHwLoops::useExtLoopInstr(MachineFunction &MF,
                                          MachineBasicBlock::iterator &MII) { … }