//===- RegUsageInfoCollector.cpp - Register Usage Informartion Collector --===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
///
/// This pass is required to take advantage of the interprocedural register
/// allocation infrastructure.
///
/// This pass is simple MachineFunction pass which collects register usage
/// details by iterating through each physical registers and checking
/// MRI::isPhysRegUsed() then creates a RegMask based on this details.
/// The pass then stores this RegMask in PhysicalRegisterUsageInfo.cpp
///
//===----------------------------------------------------------------------===//

#include "llvm/CodeGen/MachineBasicBlock.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/MachineOperand.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/Passes.h"
#include "llvm/CodeGen/RegisterUsageInfo.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"

using namespace llvm;

#define DEBUG_TYPE "ip-regalloc"

namespace llvm {
void initializeRegUsageInfoCollectorPass(PassRegistry &);
}

namespace {
class RegUsageInfoCollector : public MachineFunctionPass {
public:
  RegUsageInfoCollector() : MachineFunctionPass(ID) {
    PassRegistry &Registry = *PassRegistry::getPassRegistry();
    initializeRegUsageInfoCollectorPass(Registry);
  }

  const char *getPassName() const override {
    return "Register Usage Information Collector Pass";
  }

  void getAnalysisUsage(AnalysisUsage &AU) const override;

  bool runOnMachineFunction(MachineFunction &MF) override;

  static char ID;

private:
  void markRegClobbered(const TargetRegisterInfo *TRI, uint32_t *RegMask,
                        unsigned PReg);
};
} // end of anonymous namespace

char RegUsageInfoCollector::ID = 0;

INITIALIZE_PASS_BEGIN(RegUsageInfoCollector, "RegUsageInfoCollector",
                      "Register Usage Information Collector", false, false)
INITIALIZE_PASS_DEPENDENCY(PhysicalRegisterUsageInfo)
INITIALIZE_PASS_END(RegUsageInfoCollector, "RegUsageInfoCollector",
                    "Register Usage Information Collector", false, false)

FunctionPass *llvm::createRegUsageInfoCollector() {
  return new RegUsageInfoCollector();
}

void RegUsageInfoCollector::markRegClobbered(const TargetRegisterInfo *TRI,
                                             uint32_t *RegMask, unsigned PReg) {
  // If PReg is clobbered then all of its alias are also clobbered.
  for (MCRegAliasIterator AI(PReg, TRI, true); AI.isValid(); ++AI)
    RegMask[*AI / 32] &= ~(1u << *AI % 32);
}

void RegUsageInfoCollector::getAnalysisUsage(AnalysisUsage &AU) const {
  AU.addRequired<PhysicalRegisterUsageInfo>();
  AU.setPreservesAll();
  MachineFunctionPass::getAnalysisUsage(AU);
}

bool RegUsageInfoCollector::runOnMachineFunction(MachineFunction &MF) {
  MachineRegisterInfo *MRI = &MF.getRegInfo();
  const TargetRegisterInfo *TRI = MF.getSubtarget().getRegisterInfo();
  const TargetMachine &TM = MF.getTarget();

  DEBUG(dbgs() << " -------------------- " << getPassName()
               << " -------------------- \n");
  DEBUG(dbgs() << "Function Name : " << MF.getName() << "\n");

  std::vector<uint32_t> RegMask;

  // Compute the size of the bit vector to represent all the registers.
  // The bit vector is broken into 32-bit chunks, thus takes the ceil of
  // the number of registers divided by 32 for the size.
  unsigned regMaskSize = (TRI->getNumRegs() + 31) / 32;
  RegMask.resize(regMaskSize, 0xFFFFFFFF);

  PhysicalRegisterUsageInfo *PRUI = &getAnalysis<PhysicalRegisterUsageInfo>();

  PRUI->setTargetMachine(&TM);

  DEBUG(dbgs() << "Clobbered Registers: ");
  for (unsigned PReg = 1, PRegE = TRI->getNumRegs(); PReg < PRegE; ++PReg) {
    if (!MRI->reg_nodbg_empty(PReg) && MRI->isPhysRegUsed(PReg))
      markRegClobbered(TRI, &RegMask[0], PReg);
  }

  const uint32_t *CallPreservedMask =
      TRI->getCallPreservedMask(MF, MF.getFunction()->getCallingConv());
  // Set callee saved register as preserved.
  for (unsigned index = 0; index < regMaskSize; index++) {
    RegMask[index] = RegMask[index] | CallPreservedMask[index];
  }
  for (unsigned PReg = 1, PRegE = TRI->getNumRegs(); PReg < PRegE; ++PReg) {
    if (MachineOperand::clobbersPhysReg(&(RegMask[0]), PReg))
      DEBUG(dbgs() << TRI->getName(PReg) << " ");
  }

  DEBUG(dbgs() << " \n----------------------------------------\n");

  PRUI->storeUpdateRegUsageInfo(MF.getFunction(), std::move(RegMask));

  return false;
}