src/llvm-project/llvm/lib/Transforms/IPO/AlwaysInliner.cpp

//===- AlwaysInliner.cpp - Code to inline always_inline functions ----------===//
//
// 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 file implements a custom inliner that handles only functions that
// are marked as "always inline".
//
//===----------------------------------------------------------------------===//

#include "llvm/Transforms/IPO/AlwaysInliner.h"
#include "llvm/ADT/SetVector.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/Analysis/AssumptionCache.h"
#include "llvm/Analysis/InlineCost.h"
#include "llvm/Analysis/OptimizationRemarkEmitter.h"
#include "llvm/Analysis/ProfileSummaryInfo.h"
#include "llvm/IR/Module.h"
#include "llvm/InitializePasses.h"
#include "llvm/Transforms/IPO/Inliner.h"
#include "llvm/Transforms/Utils/Cloning.h"
#include "llvm/Transforms/Utils/ModuleUtils.h"

using namespace llvm;

#define DEBUG_TYPE "inline"

namespace {

bool AlwaysInlineImpl(
    Module &M, bool InsertLifetime, ProfileSummaryInfo &PSI,
    function_ref<AssumptionCache &(Function &)> GetAssumptionCache,
    function_ref<AAResults &(Function &)> GetAAR,
    function_ref<BlockFrequencyInfo &(Function &)> GetBFI) {
  SmallSetVector<CallBase *, 16> Calls;
  bool Changed = false;
  SmallVector<Function *, 16> InlinedFunctions;
  for (Function &F : M) {
    // When callee coroutine function is inlined into caller coroutine function
    // before coro-split pass,
    // coro-early pass can not handle this quiet well.
    // So we won't inline the coroutine function if it have not been unsplited
    if (F.isPresplitCoroutine())
      continue;

    if (!F.isDeclaration() && isInlineViable(F).isSuccess()) {
      Calls.clear();

      for (User *U : F.users())
        if (auto *CB = dyn_cast<CallBase>(U))
          if (CB->getCalledFunction() == &F &&
                CB->hasFnAttr(Attribute::AlwaysInline) &&
                !CB->getAttributes().hasFnAttr(Attribute::NoInline))
              Calls.insert(CB);

      for (CallBase *CB : Calls) {
        Function *Caller = CB->getCaller();
        OptimizationRemarkEmitter ORE(Caller);
        DebugLoc DLoc = CB->getDebugLoc();
        BasicBlock *Block = CB->getParent();

        InlineFunctionInfo IFI(GetAssumptionCache, &PSI,
                               GetBFI ? &GetBFI(*Caller) : nullptr,
                               GetBFI ? &GetBFI(F) : nullptr);

        InlineResult Res = InlineFunction(*CB, IFI, /*MergeAttributes=*/true,
                                          &GetAAR(F), InsertLifetime);
        if (!Res.isSuccess()) {
          ORE.emit([&]() {
            return OptimizationRemarkMissed(DEBUG_TYPE, "NotInlined", DLoc,
                                            Block)
                   << "'" << ore::NV("Callee", &F) << "' is not inlined into '"
                   << ore::NV("Caller", Caller)
                   << "': " << ore::NV("Reason", Res.getFailureReason());
          });
          continue;
        }

        emitInlinedIntoBasedOnCost(
            ORE, DLoc, Block, F, *Caller,
            InlineCost::getAlways("always inline attribute"),
            /*ForProfileContext=*/false, DEBUG_TYPE);

        Changed = true;
      }

      if (F.hasFnAttribute(Attribute::AlwaysInline)) {
        // Remember to try and delete this function afterward. This both avoids
        // re-walking the rest of the module and avoids dealing with any
        // iterator invalidation issues while deleting functions.
        InlinedFunctions.push_back(&F);
      }
    }
  }

  // Remove any live functions.
  erase_if(InlinedFunctions, [&](Function *F) {
    F->removeDeadConstantUsers();
    return !F->isDefTriviallyDead();
  });

  // Delete the non-comdat ones from the module and also from our vector.
  auto NonComdatBegin = partition(
      InlinedFunctions, [&](Function *F) { return F->hasComdat(); });
  for (Function *F : make_range(NonComdatBegin, InlinedFunctions.end())) {
    M.getFunctionList().erase(F);
    Changed = true;
  }
  InlinedFunctions.erase(NonComdatBegin, InlinedFunctions.end());

  if (!InlinedFunctions.empty()) {
    // Now we just have the comdat functions. Filter out the ones whose comdats
    // are not actually dead.
    filterDeadComdatFunctions(InlinedFunctions);
    // The remaining functions are actually dead.
    for (Function *F : InlinedFunctions) {
      M.getFunctionList().erase(F);
      Changed = true;
    }
  }

  return Changed;
}

struct AlwaysInlinerLegacyPass : public ModulePass {
  bool InsertLifetime;

  AlwaysInlinerLegacyPass()
      : AlwaysInlinerLegacyPass(/*InsertLifetime*/ true) {}

  AlwaysInlinerLegacyPass(bool InsertLifetime)
      : ModulePass(ID), InsertLifetime(InsertLifetime) {
    initializeAlwaysInlinerLegacyPassPass(*PassRegistry::getPassRegistry());
  }

  /// Main run interface method.  We override here to avoid calling skipSCC().
  bool runOnModule(Module &M) override {

    auto &PSI = getAnalysis<ProfileSummaryInfoWrapperPass>().getPSI();
    auto GetAAR = [&](Function &F) -> AAResults & {
      return getAnalysis<AAResultsWrapperPass>(F).getAAResults();
    };
    auto GetAssumptionCache = [&](Function &F) -> AssumptionCache & {
      return getAnalysis<AssumptionCacheTracker>().getAssumptionCache(F);
    };

    return AlwaysInlineImpl(M, InsertLifetime, PSI, GetAssumptionCache, GetAAR,
                            /*GetBFI*/ nullptr);
  }

  static char ID; // Pass identification, replacement for typeid

  void getAnalysisUsage(AnalysisUsage &AU) const override {
    AU.addRequired<AssumptionCacheTracker>();
    AU.addRequired<AAResultsWrapperPass>();
    AU.addRequired<ProfileSummaryInfoWrapperPass>();
  }
};

} // namespace

char AlwaysInlinerLegacyPass::ID = 0;
INITIALIZE_PASS_BEGIN(AlwaysInlinerLegacyPass, "always-inline",
                      "Inliner for always_inline functions", false, false)
INITIALIZE_PASS_DEPENDENCY(AAResultsWrapperPass)
INITIALIZE_PASS_DEPENDENCY(AssumptionCacheTracker)
INITIALIZE_PASS_DEPENDENCY(ProfileSummaryInfoWrapperPass)
INITIALIZE_PASS_END(AlwaysInlinerLegacyPass, "always-inline",
                    "Inliner for always_inline functions", false, false)

Pass *llvm::createAlwaysInlinerLegacyPass(bool InsertLifetime) {
  return new AlwaysInlinerLegacyPass(InsertLifetime);
}

PreservedAnalyses AlwaysInlinerPass::run(Module &M,
                                         ModuleAnalysisManager &MAM) {
  FunctionAnalysisManager &FAM =
      MAM.getResult<FunctionAnalysisManagerModuleProxy>(M).getManager();
  auto GetAssumptionCache = [&](Function &F) -> AssumptionCache & {
    return FAM.getResult<AssumptionAnalysis>(F);
  };
  auto GetBFI = [&](Function &F) -> BlockFrequencyInfo & {
    return FAM.getResult<BlockFrequencyAnalysis>(F);
  };
  auto GetAAR = [&](Function &F) -> AAResults & {
    return FAM.getResult<AAManager>(F);
  };
  auto &PSI = MAM.getResult<ProfileSummaryAnalysis>(M);

  bool Changed = AlwaysInlineImpl(M, InsertLifetime, PSI, GetAssumptionCache,
                                  GetAAR, GetBFI);

  return Changed ? PreservedAnalyses::none() : PreservedAnalyses::all();
}