lib/Target/ARM/ARMMachineFunctionInfo.cpp

//===-- ARMMachineFunctionInfo.cpp - ARM machine function info ------------===//
//
// 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 "ARMMachineFunctionInfo.h"
#include "ARMSubtarget.h"

using namespace llvm;

void ARMFunctionInfo::anchor() {}

static bool GetBranchTargetEnforcement(MachineFunction &MF) {
  const auto &Subtarget = MF.getSubtarget<ARMSubtarget>();
  if (!Subtarget.isMClass() || !Subtarget.hasV7Ops())
    return false;

  const Function &F = MF.getFunction();
  if (!F.hasFnAttribute("branch-target-enforcement")) {
    if (const auto *BTE = mdconst::extract_or_null<ConstantInt>(
            F.getParent()->getModuleFlag("branch-target-enforcement")))
      return BTE->getZExtValue();
    return false;
  }

  const StringRef BTIEnable =
      F.getFnAttribute("branch-target-enforcement").getValueAsString();
  assert(BTIEnable.equals_insensitive("true") ||
         BTIEnable.equals_insensitive("false"));
  return BTIEnable.equals_insensitive("true");
}

// The pair returns values for the ARMFunctionInfo members
// SignReturnAddress and SignReturnAddressAll respectively.
static std::pair<bool, bool> GetSignReturnAddress(const Function &F) {
  if (!F.hasFnAttribute("sign-return-address")) {
    const Module &M = *F.getParent();
    if (const auto *Sign = mdconst::extract_or_null<ConstantInt>(
            M.getModuleFlag("sign-return-address"))) {
      if (Sign->getZExtValue()) {
        if (const auto *All = mdconst::extract_or_null<ConstantInt>(
                M.getModuleFlag("sign-return-address-all")))
          return {true, All->getZExtValue()};
        return {true, false};
      }
    }
    return {false, false};
  }

  StringRef Scope = F.getFnAttribute("sign-return-address").getValueAsString();
  if (Scope.equals("none"))
    return {false, false};

  if (Scope.equals("all"))
    return {true, true};

  assert(Scope.equals("non-leaf"));
  return {true, false};
}

ARMFunctionInfo::ARMFunctionInfo(MachineFunction &MF)
    : isThumb(MF.getSubtarget<ARMSubtarget>().isThumb()),
      hasThumb2(MF.getSubtarget<ARMSubtarget>().hasThumb2()),
      IsCmseNSEntry(MF.getFunction().hasFnAttribute("cmse_nonsecure_entry")),
      IsCmseNSCall(MF.getFunction().hasFnAttribute("cmse_nonsecure_call")),
      BranchTargetEnforcement(GetBranchTargetEnforcement(MF)) {

  const auto &Subtarget = MF.getSubtarget<ARMSubtarget>();
  if (Subtarget.isMClass() && Subtarget.hasV7Ops())
    std::tie(SignReturnAddress, SignReturnAddressAll) =
        GetSignReturnAddress(MF.getFunction());
}