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+//===-- SpeculateAnalyses.cpp --*- C++ -*-===//
+//
+// 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 "llvm/ExecutionEngine/Orc/SpeculateAnalyses.h"
+#include "llvm/ADT/ArrayRef.h"
+#include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/STLExtras.h"
+#include "llvm/ADT/SmallPtrSet.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/Analysis/BlockFrequencyInfo.h"
+#include "llvm/Analysis/BranchProbabilityInfo.h"
+#include "llvm/Analysis/CFG.h"
+#include "llvm/IR/PassManager.h"
+#include "llvm/Passes/PassBuilder.h"
+#include "llvm/Support/ErrorHandling.h"
+
+#include <algorithm>
+
+namespace {
+using namespace llvm;
+SmallVector<const BasicBlock *, 8> findBBwithCalls(const Function &F,
+ bool IndirectCall = false) {
+ SmallVector<const BasicBlock *, 8> BBs;
+
+ auto findCallInst = [&IndirectCall](const Instruction &I) {
+ if (auto Call = dyn_cast<CallBase>(&I))
+ return Call->isIndirectCall() ? IndirectCall : true;
+ else
+ return false;
+ };
+ for (auto &BB : F)
+ if (findCallInst(*BB.getTerminator()) ||
+ llvm::any_of(BB.instructionsWithoutDebug(), findCallInst))
+ BBs.emplace_back(&BB);
+
+ return BBs;
+}
+} // namespace
+
+// Implementations of Queries shouldn't need to lock the resources
+// such as LLVMContext, each argument (function) has a non-shared LLVMContext
+// Plus, if Queries contain states necessary locking scheme should be provided.
+namespace llvm {
+namespace orc {
+
+// Collect direct calls only
+void SpeculateQuery::findCalles(const BasicBlock *BB,
+ DenseSet<StringRef> &CallesNames) {
+ assert(BB != nullptr && "Traversing Null BB to find calls?");
+
+ auto getCalledFunction = [&CallesNames](const CallBase *Call) {
+ auto CalledValue = Call->getCalledOperand()->stripPointerCasts();
+ if (auto DirectCall = dyn_cast<Function>(CalledValue))
+ CallesNames.insert(DirectCall->getName());
+ };
+ for (auto &I : BB->instructionsWithoutDebug())
+ if (auto CI = dyn_cast<CallInst>(&I))
+ getCalledFunction(CI);
+
+ if (auto II = dyn_cast<InvokeInst>(BB->getTerminator()))
+ getCalledFunction(II);
+}
+
+bool SpeculateQuery::isStraightLine(const Function &F) {
+ return llvm::all_of(F.getBasicBlockList(), [](const BasicBlock &BB) {
+ return BB.getSingleSuccessor() != nullptr;
+ });
+}
+
+// BlockFreqQuery Implementations
+
+size_t BlockFreqQuery::numBBToGet(size_t numBB) {
+ // small CFG
+ if (numBB < 4)
+ return numBB;
+ // mid-size CFG
+ else if (numBB < 20)
+ return (numBB / 2);
+ else
+ return (numBB / 2) + (numBB / 4);
+}
+
+BlockFreqQuery::ResultTy BlockFreqQuery::operator()(Function &F) {
+ DenseMap<StringRef, DenseSet<StringRef>> CallerAndCalles;
+ DenseSet<StringRef> Calles;
+ SmallVector<std::pair<const BasicBlock *, uint64_t>, 8> BBFreqs;
+
+ PassBuilder PB;
+ FunctionAnalysisManager FAM;
+ PB.registerFunctionAnalyses(FAM);
+
+ auto IBBs = findBBwithCalls(F);
+
+ if (IBBs.empty())
+ return None;
+
+ auto &BFI = FAM.getResult<BlockFrequencyAnalysis>(F);
+
+ for (const auto I : IBBs)
+ BBFreqs.push_back({I, BFI.getBlockFreq(I).getFrequency()});
+
+ assert(IBBs.size() == BBFreqs.size() && "BB Count Mismatch");
+
+ llvm::sort(BBFreqs.begin(), BBFreqs.end(),
+ [](decltype(BBFreqs)::const_reference BBF,
+ decltype(BBFreqs)::const_reference BBS) {
+ return BBF.second > BBS.second ? true : false;
+ });
+
+ // ignoring number of direct calls in a BB
+ auto Topk = numBBToGet(BBFreqs.size());
+
+ for (size_t i = 0; i < Topk; i++)
+ findCalles(BBFreqs[i].first, Calles);
+
+ assert(!Calles.empty() && "Running Analysis on Function with no calls?");
+
+ CallerAndCalles.insert({F.getName(), std::move(Calles)});
+
+ return CallerAndCalles;
+}
+
+// SequenceBBQuery Implementation
+std::size_t SequenceBBQuery::getHottestBlocks(std::size_t TotalBlocks) {
+ if (TotalBlocks == 1)
+ return TotalBlocks;
+ return TotalBlocks / 2;
+}
+
+// FIXME : find good implementation.
+SequenceBBQuery::BlockListTy
+SequenceBBQuery::rearrangeBB(const Function &F, const BlockListTy &BBList) {
+ BlockListTy RearrangedBBSet;
+
+ for (auto &Block : F.getBasicBlockList())
+ if (llvm::is_contained(BBList, &Block))
+ RearrangedBBSet.push_back(&Block);
+
+ assert(RearrangedBBSet.size() == BBList.size() &&
+ "BasicBlock missing while rearranging?");
+ return RearrangedBBSet;
+}
+
+void SequenceBBQuery::traverseToEntryBlock(const BasicBlock *AtBB,
+ const BlockListTy &CallerBlocks,
+ const BackEdgesInfoTy &BackEdgesInfo,
+ const BranchProbabilityInfo *BPI,
+ VisitedBlocksInfoTy &VisitedBlocks) {
+ auto Itr = VisitedBlocks.find(AtBB);
+ if (Itr != VisitedBlocks.end()) { // already visited.
+ if (!Itr->second.Upward)
+ return;
+ Itr->second.Upward = false;
+ } else {
+ // Create hint for newly discoverd blocks.
+ WalkDirection BlockHint;
+ BlockHint.Upward = false;
+ // FIXME: Expensive Check
+ if (llvm::is_contained(CallerBlocks, AtBB))
+ BlockHint.CallerBlock = true;
+ VisitedBlocks.insert(std::make_pair(AtBB, BlockHint));
+ }
+
+ const_pred_iterator PIt = pred_begin(AtBB), EIt = pred_end(AtBB);
+ // Move this check to top, when we have code setup to launch speculative
+ // compiles for function in entry BB, this triggers the speculative compiles
+ // before running the program.
+ if (PIt == EIt) // No Preds.
+ return;
+
+ DenseSet<const BasicBlock *> PredSkipNodes;
+
+ // Since we are checking for predecessor's backedges, this Block
+ // occurs in second position.
+ for (auto &I : BackEdgesInfo)
+ if (I.second == AtBB)
+ PredSkipNodes.insert(I.first);
+
+ // Skip predecessors which source of back-edges.
+ for (; PIt != EIt; ++PIt)
+ // checking EdgeHotness is cheaper
+ if (BPI->isEdgeHot(*PIt, AtBB) && !PredSkipNodes.count(*PIt))
+ traverseToEntryBlock(*PIt, CallerBlocks, BackEdgesInfo, BPI,
+ VisitedBlocks);
+}
+
+void SequenceBBQuery::traverseToExitBlock(const BasicBlock *AtBB,
+ const BlockListTy &CallerBlocks,
+ const BackEdgesInfoTy &BackEdgesInfo,
+ const BranchProbabilityInfo *BPI,
+ VisitedBlocksInfoTy &VisitedBlocks) {
+ auto Itr = VisitedBlocks.find(AtBB);
+ if (Itr != VisitedBlocks.end()) { // already visited.
+ if (!Itr->second.Downward)
+ return;
+ Itr->second.Downward = false;
+ } else {
+ // Create hint for newly discoverd blocks.
+ WalkDirection BlockHint;
+ BlockHint.Downward = false;
+ // FIXME: Expensive Check
+ if (llvm::is_contained(CallerBlocks, AtBB))
+ BlockHint.CallerBlock = true;
+ VisitedBlocks.insert(std::make_pair(AtBB, BlockHint));
+ }
+
+ succ_const_iterator PIt = succ_begin(AtBB), EIt = succ_end(AtBB);
+ if (PIt == EIt) // No succs.
+ return;
+
+ // If there are hot edges, then compute SuccSkipNodes.
+ DenseSet<const BasicBlock *> SuccSkipNodes;
+
+ // Since we are checking for successor's backedges, this Block
+ // occurs in first position.
+ for (auto &I : BackEdgesInfo)
+ if (I.first == AtBB)
+ SuccSkipNodes.insert(I.second);
+
+ for (; PIt != EIt; ++PIt)
+ if (BPI->isEdgeHot(AtBB, *PIt) && !SuccSkipNodes.count(*PIt))
+ traverseToExitBlock(*PIt, CallerBlocks, BackEdgesInfo, BPI,
+ VisitedBlocks);
+}
+
+// Get Block frequencies for blocks and take most frquently executed block,
+// walk towards the entry block from those blocks and discover the basic blocks
+// with call.
+SequenceBBQuery::BlockListTy
+SequenceBBQuery::queryCFG(Function &F, const BlockListTy &CallerBlocks) {
+
+ BlockFreqInfoTy BBFreqs;
+ VisitedBlocksInfoTy VisitedBlocks;
+ BackEdgesInfoTy BackEdgesInfo;
+
+ PassBuilder PB;
+ FunctionAnalysisManager FAM;
+ PB.registerFunctionAnalyses(FAM);
+
+ auto &BFI = FAM.getResult<BlockFrequencyAnalysis>(F);
+
+ llvm::FindFunctionBackedges(F, BackEdgesInfo);
+
+ for (const auto I : CallerBlocks)
+ BBFreqs.push_back({I, BFI.getBlockFreq(I).getFrequency()});
+
+ llvm::sort(BBFreqs, [](decltype(BBFreqs)::const_reference Bbf,
+ decltype(BBFreqs)::const_reference Bbs) {
+ return Bbf.second > Bbs.second;
+ });
+
+ ArrayRef<std::pair<const BasicBlock *, uint64_t>> HotBlocksRef(BBFreqs);
+ HotBlocksRef =
+ HotBlocksRef.drop_back(BBFreqs.size() - getHottestBlocks(BBFreqs.size()));
+
+ BranchProbabilityInfo *BPI =
+ FAM.getCachedResult<BranchProbabilityAnalysis>(F);
+
+ // visit NHotBlocks,
+ // traverse upwards to entry
+ // traverse downwards to end.
+
+ for (auto I : HotBlocksRef) {
+ traverseToEntryBlock(I.first, CallerBlocks, BackEdgesInfo, BPI,
+ VisitedBlocks);
+ traverseToExitBlock(I.first, CallerBlocks, BackEdgesInfo, BPI,
+ VisitedBlocks);
+ }
+
+ BlockListTy MinCallerBlocks;
+ for (auto &I : VisitedBlocks)
+ if (I.second.CallerBlock)
+ MinCallerBlocks.push_back(std::move(I.first));
+
+ return rearrangeBB(F, MinCallerBlocks);
+}
+
+SpeculateQuery::ResultTy SequenceBBQuery::operator()(Function &F) {
+ // reduce the number of lists!
+ DenseMap<StringRef, DenseSet<StringRef>> CallerAndCalles;
+ DenseSet<StringRef> Calles;
+ BlockListTy SequencedBlocks;
+ BlockListTy CallerBlocks;
+
+ CallerBlocks = findBBwithCalls(F);
+ if (CallerBlocks.empty())
+ return None;
+
+ if (isStraightLine(F))
+ SequencedBlocks = rearrangeBB(F, CallerBlocks);
+ else
+ SequencedBlocks = queryCFG(F, CallerBlocks);
+
+ for (auto BB : SequencedBlocks)
+ findCalles(BB, Calles);
+
+ CallerAndCalles.insert({F.getName(), std::move(Calles)});
+ return CallerAndCalles;
+}
+
+} // namespace orc
+} // namespace llvm
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