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authorvitalyisaev <vitalyisaev@yandex-team.com>2023-06-29 10:00:50 +0300
committervitalyisaev <vitalyisaev@yandex-team.com>2023-06-29 10:00:50 +0300
commit6ffe9e53658409f212834330e13564e4952558f6 (patch)
tree85b1e00183517648b228aafa7c8fb07f5276f419 /contrib/libs/llvm14/lib/CodeGen/MachineFunctionSplitter.cpp
parent726057070f9c5a91fc10fde0d5024913d10f1ab9 (diff)
downloadydb-6ffe9e53658409f212834330e13564e4952558f6.tar.gz
YQ Connector: support managed ClickHouse
Со стороны dqrun можно обратиться к инстансу коннектора, который работает на streaming стенде, и извлечь данные из облачного CH.
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+//===-- MachineFunctionSplitter.cpp - Split machine 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
+//
+//===----------------------------------------------------------------------===//
+//
+// \file
+// Uses profile information to split out cold blocks.
+//
+// This pass splits out cold machine basic blocks from the parent function. This
+// implementation leverages the basic block section framework. Blocks marked
+// cold by this pass are grouped together in a separate section prefixed with
+// ".text.unlikely.*". The linker can then group these together as a cold
+// section. The split part of the function is a contiguous region identified by
+// the symbol "foo.cold". Grouping all cold blocks across functions together
+// decreases fragmentation and improves icache and itlb utilization. Note that
+// the overall changes to the binary size are negligible; only a small number of
+// additional jump instructions may be introduced.
+//
+// For the original RFC of this pass please see
+// https://groups.google.com/d/msg/llvm-dev/RUegaMg-iqc/wFAVxa6fCgAJ
+//===----------------------------------------------------------------------===//
+
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/ADT/Statistic.h"
+#include "llvm/Analysis/ProfileSummaryInfo.h"
+#include "llvm/CodeGen/BasicBlockSectionUtils.h"
+#include "llvm/CodeGen/MachineBasicBlock.h"
+#include "llvm/CodeGen/MachineBlockFrequencyInfo.h"
+#include "llvm/CodeGen/MachineFunction.h"
+#include "llvm/CodeGen/MachineFunctionPass.h"
+#include "llvm/CodeGen/MachineModuleInfo.h"
+#include "llvm/CodeGen/Passes.h"
+#include "llvm/IR/Function.h"
+#include "llvm/IR/Module.h"
+#include "llvm/InitializePasses.h"
+#include "llvm/Support/CommandLine.h"
+
+using namespace llvm;
+
+// FIXME: This cutoff value is CPU dependent and should be moved to
+// TargetTransformInfo once we consider enabling this on other platforms.
+// The value is expressed as a ProfileSummaryInfo integer percentile cutoff.
+// Defaults to 999950, i.e. all blocks colder than 99.995 percentile are split.
+// The default was empirically determined to be optimal when considering cutoff
+// values between 99%-ile to 100%-ile with respect to iTLB and icache metrics on
+// Intel CPUs.
+static cl::opt<unsigned>
+ PercentileCutoff("mfs-psi-cutoff",
+ cl::desc("Percentile profile summary cutoff used to "
+ "determine cold blocks. Unused if set to zero."),
+ cl::init(999950), cl::Hidden);
+
+static cl::opt<unsigned> ColdCountThreshold(
+ "mfs-count-threshold",
+ cl::desc(
+ "Minimum number of times a block must be executed to be retained."),
+ cl::init(1), cl::Hidden);
+
+namespace {
+
+class MachineFunctionSplitter : public MachineFunctionPass {
+public:
+ static char ID;
+ MachineFunctionSplitter() : MachineFunctionPass(ID) {
+ initializeMachineFunctionSplitterPass(*PassRegistry::getPassRegistry());
+ }
+
+ StringRef getPassName() const override {
+ return "Machine Function Splitter Transformation";
+ }
+
+ void getAnalysisUsage(AnalysisUsage &AU) const override;
+
+ bool runOnMachineFunction(MachineFunction &F) override;
+};
+} // end anonymous namespace
+
+static bool isColdBlock(const MachineBasicBlock &MBB,
+ const MachineBlockFrequencyInfo *MBFI,
+ ProfileSummaryInfo *PSI) {
+ Optional<uint64_t> Count = MBFI->getBlockProfileCount(&MBB);
+ if (!Count.hasValue())
+ return true;
+
+ if (PercentileCutoff > 0) {
+ return PSI->isColdCountNthPercentile(PercentileCutoff, *Count);
+ }
+ return (*Count < ColdCountThreshold);
+}
+
+bool MachineFunctionSplitter::runOnMachineFunction(MachineFunction &MF) {
+ // TODO: We only target functions with profile data. Static information may
+ // also be considered but we don't see performance improvements yet.
+ if (!MF.getFunction().hasProfileData())
+ return false;
+
+ // TODO: We don't split functions where a section attribute has been set
+ // since the split part may not be placed in a contiguous region. It may also
+ // be more beneficial to augment the linker to ensure contiguous layout of
+ // split functions within the same section as specified by the attribute.
+ if (MF.getFunction().hasSection() ||
+ MF.getFunction().hasFnAttribute("implicit-section-name"))
+ return false;
+
+ // We don't want to proceed further for cold functions
+ // or functions of unknown hotness. Lukewarm functions have no prefix.
+ Optional<StringRef> SectionPrefix = MF.getFunction().getSectionPrefix();
+ if (SectionPrefix.hasValue() &&
+ (SectionPrefix.getValue().equals("unlikely") ||
+ SectionPrefix.getValue().equals("unknown"))) {
+ return false;
+ }
+
+ // Renumbering blocks here preserves the order of the blocks as
+ // sortBasicBlocksAndUpdateBranches uses the numeric identifier to sort
+ // blocks. Preserving the order of blocks is essential to retaining decisions
+ // made by prior passes such as MachineBlockPlacement.
+ MF.RenumberBlocks();
+ MF.setBBSectionsType(BasicBlockSection::Preset);
+ auto *MBFI = &getAnalysis<MachineBlockFrequencyInfo>();
+ auto *PSI = &getAnalysis<ProfileSummaryInfoWrapperPass>().getPSI();
+
+ SmallVector<MachineBasicBlock *, 2> LandingPads;
+ for (auto &MBB : MF) {
+ if (MBB.isEntryBlock())
+ continue;
+
+ if (MBB.isEHPad())
+ LandingPads.push_back(&MBB);
+ else if (isColdBlock(MBB, MBFI, PSI))
+ MBB.setSectionID(MBBSectionID::ColdSectionID);
+ }
+
+ // We only split out eh pads if all of them are cold.
+ bool HasHotLandingPads = false;
+ for (const MachineBasicBlock *LP : LandingPads) {
+ if (!isColdBlock(*LP, MBFI, PSI))
+ HasHotLandingPads = true;
+ }
+ if (!HasHotLandingPads) {
+ for (MachineBasicBlock *LP : LandingPads)
+ LP->setSectionID(MBBSectionID::ColdSectionID);
+ }
+
+ auto Comparator = [](const MachineBasicBlock &X, const MachineBasicBlock &Y) {
+ return X.getSectionID().Type < Y.getSectionID().Type;
+ };
+ llvm::sortBasicBlocksAndUpdateBranches(MF, Comparator);
+
+ return true;
+}
+
+void MachineFunctionSplitter::getAnalysisUsage(AnalysisUsage &AU) const {
+ AU.addRequired<MachineModuleInfoWrapperPass>();
+ AU.addRequired<MachineBlockFrequencyInfo>();
+ AU.addRequired<ProfileSummaryInfoWrapperPass>();
+}
+
+char MachineFunctionSplitter::ID = 0;
+INITIALIZE_PASS(MachineFunctionSplitter, "machine-function-splitter",
+ "Split machine functions using profile information", false,
+ false)
+
+MachineFunctionPass *llvm::createMachineFunctionSplitterPass() {
+ return new MachineFunctionSplitter();
+}