forked from OSchip/llvm-project
1084 lines
42 KiB
C++
1084 lines
42 KiB
C++
//===---- MachineOutliner.cpp - Outline instructions -----------*- C++ -*-===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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///
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/// \file
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/// Replaces repeated sequences of instructions with function calls.
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///
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/// This works by placing every instruction from every basic block in a
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/// suffix tree, and repeatedly querying that tree for repeated sequences of
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/// instructions. If a sequence of instructions appears often, then it ought
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/// to be beneficial to pull out into a function.
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///
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/// The MachineOutliner communicates with a given target using hooks defined in
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/// TargetInstrInfo.h. The target supplies the outliner with information on how
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/// a specific sequence of instructions should be outlined. This information
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/// is used to deduce the number of instructions necessary to
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///
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/// * Create an outlined function
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/// * Call that outlined function
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///
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/// Targets must implement
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/// * getOutliningCandidateInfo
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/// * buildOutlinedFrame
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/// * insertOutlinedCall
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/// * isFunctionSafeToOutlineFrom
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///
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/// in order to make use of the MachineOutliner.
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///
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/// This was originally presented at the 2016 LLVM Developers' Meeting in the
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/// talk "Reducing Code Size Using Outlining". For a high-level overview of
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/// how this pass works, the talk is available on YouTube at
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///
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/// https://www.youtube.com/watch?v=yorld-WSOeU
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///
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/// The slides for the talk are available at
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///
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/// http://www.llvm.org/devmtg/2016-11/Slides/Paquette-Outliner.pdf
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///
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/// The talk provides an overview of how the outliner finds candidates and
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/// ultimately outlines them. It describes how the main data structure for this
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/// pass, the suffix tree, is queried and purged for candidates. It also gives
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/// a simplified suffix tree construction algorithm for suffix trees based off
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/// of the algorithm actually used here, Ukkonen's algorithm.
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///
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/// For the original RFC for this pass, please see
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///
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/// http://lists.llvm.org/pipermail/llvm-dev/2016-August/104170.html
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///
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/// For more information on the suffix tree data structure, please see
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/// https://www.cs.helsinki.fi/u/ukkonen/SuffixT1withFigs.pdf
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///
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//===----------------------------------------------------------------------===//
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#include "llvm/CodeGen/MachineOutliner.h"
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#include "llvm/ADT/DenseMap.h"
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#include "llvm/ADT/SmallSet.h"
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#include "llvm/ADT/Statistic.h"
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#include "llvm/ADT/Twine.h"
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#include "llvm/CodeGen/MachineModuleInfo.h"
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#include "llvm/CodeGen/MachineOptimizationRemarkEmitter.h"
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#include "llvm/CodeGen/Passes.h"
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#include "llvm/CodeGen/TargetInstrInfo.h"
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#include "llvm/CodeGen/TargetSubtargetInfo.h"
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#include "llvm/IR/DIBuilder.h"
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#include "llvm/IR/IRBuilder.h"
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#include "llvm/IR/Mangler.h"
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#include "llvm/InitializePasses.h"
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#include "llvm/Support/CommandLine.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/Support/SuffixTree.h"
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#include "llvm/Support/raw_ostream.h"
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#include <functional>
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#include <tuple>
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#include <vector>
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#define DEBUG_TYPE "machine-outliner"
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using namespace llvm;
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using namespace ore;
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using namespace outliner;
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// Statistics for outlined functions.
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STATISTIC(NumOutlined, "Number of candidates outlined");
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STATISTIC(FunctionsCreated, "Number of functions created");
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// Statistics for instruction mapping.
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STATISTIC(NumLegalInUnsignedVec, "Number of legal instrs in unsigned vector");
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STATISTIC(NumIllegalInUnsignedVec,
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"Number of illegal instrs in unsigned vector");
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STATISTIC(NumInvisible, "Number of invisible instrs in unsigned vector");
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STATISTIC(UnsignedVecSize, "Size of unsigned vector");
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// Set to true if the user wants the outliner to run on linkonceodr linkage
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// functions. This is false by default because the linker can dedupe linkonceodr
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// functions. Since the outliner is confined to a single module (modulo LTO),
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// this is off by default. It should, however, be the default behaviour in
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// LTO.
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static cl::opt<bool> EnableLinkOnceODROutlining(
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"enable-linkonceodr-outlining", cl::Hidden,
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cl::desc("Enable the machine outliner on linkonceodr functions"),
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cl::init(false));
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/// Number of times to re-run the outliner. This is not the total number of runs
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/// as the outliner will run at least one time. The default value is set to 0,
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/// meaning the outliner will run one time and rerun zero times after that.
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static cl::opt<unsigned> OutlinerReruns(
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"machine-outliner-reruns", cl::init(0), cl::Hidden,
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cl::desc(
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"Number of times to rerun the outliner after the initial outline"));
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namespace {
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/// Maps \p MachineInstrs to unsigned integers and stores the mappings.
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struct InstructionMapper {
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/// The next available integer to assign to a \p MachineInstr that
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/// cannot be outlined.
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///
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/// Set to -3 for compatability with \p DenseMapInfo<unsigned>.
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unsigned IllegalInstrNumber = -3;
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/// The next available integer to assign to a \p MachineInstr that can
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/// be outlined.
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unsigned LegalInstrNumber = 0;
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/// Correspondence from \p MachineInstrs to unsigned integers.
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DenseMap<MachineInstr *, unsigned, MachineInstrExpressionTrait>
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InstructionIntegerMap;
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/// Correspondence between \p MachineBasicBlocks and target-defined flags.
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DenseMap<MachineBasicBlock *, unsigned> MBBFlagsMap;
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/// The vector of unsigned integers that the module is mapped to.
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std::vector<unsigned> UnsignedVec;
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/// Stores the location of the instruction associated with the integer
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/// at index i in \p UnsignedVec for each index i.
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std::vector<MachineBasicBlock::iterator> InstrList;
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// Set if we added an illegal number in the previous step.
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// Since each illegal number is unique, we only need one of them between
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// each range of legal numbers. This lets us make sure we don't add more
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// than one illegal number per range.
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bool AddedIllegalLastTime = false;
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/// Maps \p *It to a legal integer.
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///
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/// Updates \p CanOutlineWithPrevInstr, \p HaveLegalRange, \p InstrListForMBB,
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/// \p UnsignedVecForMBB, \p InstructionIntegerMap, and \p LegalInstrNumber.
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///
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/// \returns The integer that \p *It was mapped to.
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unsigned mapToLegalUnsigned(
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MachineBasicBlock::iterator &It, bool &CanOutlineWithPrevInstr,
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bool &HaveLegalRange, unsigned &NumLegalInBlock,
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std::vector<unsigned> &UnsignedVecForMBB,
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std::vector<MachineBasicBlock::iterator> &InstrListForMBB) {
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// We added something legal, so we should unset the AddedLegalLastTime
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// flag.
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AddedIllegalLastTime = false;
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// If we have at least two adjacent legal instructions (which may have
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// invisible instructions in between), remember that.
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if (CanOutlineWithPrevInstr)
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HaveLegalRange = true;
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CanOutlineWithPrevInstr = true;
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// Keep track of the number of legal instructions we insert.
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NumLegalInBlock++;
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// Get the integer for this instruction or give it the current
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// LegalInstrNumber.
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InstrListForMBB.push_back(It);
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MachineInstr &MI = *It;
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bool WasInserted;
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DenseMap<MachineInstr *, unsigned, MachineInstrExpressionTrait>::iterator
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ResultIt;
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std::tie(ResultIt, WasInserted) =
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InstructionIntegerMap.insert(std::make_pair(&MI, LegalInstrNumber));
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unsigned MINumber = ResultIt->second;
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// There was an insertion.
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if (WasInserted)
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LegalInstrNumber++;
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UnsignedVecForMBB.push_back(MINumber);
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// Make sure we don't overflow or use any integers reserved by the DenseMap.
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if (LegalInstrNumber >= IllegalInstrNumber)
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report_fatal_error("Instruction mapping overflow!");
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assert(LegalInstrNumber != DenseMapInfo<unsigned>::getEmptyKey() &&
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"Tried to assign DenseMap tombstone or empty key to instruction.");
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assert(LegalInstrNumber != DenseMapInfo<unsigned>::getTombstoneKey() &&
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"Tried to assign DenseMap tombstone or empty key to instruction.");
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// Statistics.
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++NumLegalInUnsignedVec;
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return MINumber;
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}
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/// Maps \p *It to an illegal integer.
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///
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/// Updates \p InstrListForMBB, \p UnsignedVecForMBB, and \p
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/// IllegalInstrNumber.
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///
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/// \returns The integer that \p *It was mapped to.
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unsigned mapToIllegalUnsigned(
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MachineBasicBlock::iterator &It, bool &CanOutlineWithPrevInstr,
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std::vector<unsigned> &UnsignedVecForMBB,
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std::vector<MachineBasicBlock::iterator> &InstrListForMBB) {
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// Can't outline an illegal instruction. Set the flag.
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CanOutlineWithPrevInstr = false;
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// Only add one illegal number per range of legal numbers.
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if (AddedIllegalLastTime)
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return IllegalInstrNumber;
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// Remember that we added an illegal number last time.
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AddedIllegalLastTime = true;
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unsigned MINumber = IllegalInstrNumber;
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InstrListForMBB.push_back(It);
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UnsignedVecForMBB.push_back(IllegalInstrNumber);
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IllegalInstrNumber--;
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// Statistics.
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++NumIllegalInUnsignedVec;
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assert(LegalInstrNumber < IllegalInstrNumber &&
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"Instruction mapping overflow!");
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assert(IllegalInstrNumber != DenseMapInfo<unsigned>::getEmptyKey() &&
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"IllegalInstrNumber cannot be DenseMap tombstone or empty key!");
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assert(IllegalInstrNumber != DenseMapInfo<unsigned>::getTombstoneKey() &&
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"IllegalInstrNumber cannot be DenseMap tombstone or empty key!");
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return MINumber;
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}
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/// Transforms a \p MachineBasicBlock into a \p vector of \p unsigneds
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/// and appends it to \p UnsignedVec and \p InstrList.
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///
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/// Two instructions are assigned the same integer if they are identical.
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/// If an instruction is deemed unsafe to outline, then it will be assigned an
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/// unique integer. The resulting mapping is placed into a suffix tree and
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/// queried for candidates.
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///
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/// \param MBB The \p MachineBasicBlock to be translated into integers.
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/// \param TII \p TargetInstrInfo for the function.
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void convertToUnsignedVec(MachineBasicBlock &MBB,
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const TargetInstrInfo &TII) {
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unsigned Flags = 0;
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// Don't even map in this case.
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if (!TII.isMBBSafeToOutlineFrom(MBB, Flags))
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return;
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// Store info for the MBB for later outlining.
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MBBFlagsMap[&MBB] = Flags;
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MachineBasicBlock::iterator It = MBB.begin();
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// The number of instructions in this block that will be considered for
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// outlining.
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unsigned NumLegalInBlock = 0;
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// True if we have at least two legal instructions which aren't separated
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// by an illegal instruction.
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bool HaveLegalRange = false;
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// True if we can perform outlining given the last mapped (non-invisible)
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// instruction. This lets us know if we have a legal range.
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bool CanOutlineWithPrevInstr = false;
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// FIXME: Should this all just be handled in the target, rather than using
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// repeated calls to getOutliningType?
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std::vector<unsigned> UnsignedVecForMBB;
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std::vector<MachineBasicBlock::iterator> InstrListForMBB;
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for (MachineBasicBlock::iterator Et = MBB.end(); It != Et; ++It) {
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// Keep track of where this instruction is in the module.
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switch (TII.getOutliningType(It, Flags)) {
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case InstrType::Illegal:
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mapToIllegalUnsigned(It, CanOutlineWithPrevInstr, UnsignedVecForMBB,
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InstrListForMBB);
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break;
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case InstrType::Legal:
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mapToLegalUnsigned(It, CanOutlineWithPrevInstr, HaveLegalRange,
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NumLegalInBlock, UnsignedVecForMBB, InstrListForMBB);
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break;
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case InstrType::LegalTerminator:
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mapToLegalUnsigned(It, CanOutlineWithPrevInstr, HaveLegalRange,
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NumLegalInBlock, UnsignedVecForMBB, InstrListForMBB);
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// The instruction also acts as a terminator, so we have to record that
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// in the string.
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mapToIllegalUnsigned(It, CanOutlineWithPrevInstr, UnsignedVecForMBB,
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InstrListForMBB);
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break;
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case InstrType::Invisible:
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// Normally this is set by mapTo(Blah)Unsigned, but we just want to
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// skip this instruction. So, unset the flag here.
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++NumInvisible;
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AddedIllegalLastTime = false;
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break;
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}
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}
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// Are there enough legal instructions in the block for outlining to be
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// possible?
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if (HaveLegalRange) {
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// After we're done every insertion, uniquely terminate this part of the
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// "string". This makes sure we won't match across basic block or function
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// boundaries since the "end" is encoded uniquely and thus appears in no
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// repeated substring.
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mapToIllegalUnsigned(It, CanOutlineWithPrevInstr, UnsignedVecForMBB,
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InstrListForMBB);
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llvm::append_range(InstrList, InstrListForMBB);
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llvm::append_range(UnsignedVec, UnsignedVecForMBB);
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}
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}
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InstructionMapper() {
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// Make sure that the implementation of DenseMapInfo<unsigned> hasn't
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// changed.
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assert(DenseMapInfo<unsigned>::getEmptyKey() == (unsigned)-1 &&
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"DenseMapInfo<unsigned>'s empty key isn't -1!");
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assert(DenseMapInfo<unsigned>::getTombstoneKey() == (unsigned)-2 &&
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"DenseMapInfo<unsigned>'s tombstone key isn't -2!");
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}
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};
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/// An interprocedural pass which finds repeated sequences of
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/// instructions and replaces them with calls to functions.
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///
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/// Each instruction is mapped to an unsigned integer and placed in a string.
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/// The resulting mapping is then placed in a \p SuffixTree. The \p SuffixTree
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/// is then repeatedly queried for repeated sequences of instructions. Each
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/// non-overlapping repeated sequence is then placed in its own
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/// \p MachineFunction and each instance is then replaced with a call to that
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/// function.
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struct MachineOutliner : public ModulePass {
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static char ID;
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/// Set to true if the outliner should consider functions with
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/// linkonceodr linkage.
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bool OutlineFromLinkOnceODRs = false;
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/// The current repeat number of machine outlining.
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unsigned OutlineRepeatedNum = 0;
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/// Set to true if the outliner should run on all functions in the module
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/// considered safe for outlining.
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/// Set to true by default for compatibility with llc's -run-pass option.
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/// Set when the pass is constructed in TargetPassConfig.
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bool RunOnAllFunctions = true;
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StringRef getPassName() const override { return "Machine Outliner"; }
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void getAnalysisUsage(AnalysisUsage &AU) const override {
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AU.addRequired<MachineModuleInfoWrapperPass>();
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AU.addPreserved<MachineModuleInfoWrapperPass>();
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AU.setPreservesAll();
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ModulePass::getAnalysisUsage(AU);
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}
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MachineOutliner() : ModulePass(ID) {
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initializeMachineOutlinerPass(*PassRegistry::getPassRegistry());
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}
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/// Remark output explaining that not outlining a set of candidates would be
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/// better than outlining that set.
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void emitNotOutliningCheaperRemark(
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unsigned StringLen, std::vector<Candidate> &CandidatesForRepeatedSeq,
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OutlinedFunction &OF);
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/// Remark output explaining that a function was outlined.
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void emitOutlinedFunctionRemark(OutlinedFunction &OF);
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/// Find all repeated substrings that satisfy the outlining cost model by
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/// constructing a suffix tree.
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///
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/// If a substring appears at least twice, then it must be represented by
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/// an internal node which appears in at least two suffixes. Each suffix
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/// is represented by a leaf node. To do this, we visit each internal node
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/// in the tree, using the leaf children of each internal node. If an
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/// internal node represents a beneficial substring, then we use each of
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/// its leaf children to find the locations of its substring.
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///
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/// \param Mapper Contains outlining mapping information.
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/// \param[out] FunctionList Filled with a list of \p OutlinedFunctions
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/// each type of candidate.
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void findCandidates(InstructionMapper &Mapper,
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std::vector<OutlinedFunction> &FunctionList);
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/// Replace the sequences of instructions represented by \p OutlinedFunctions
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/// with calls to functions.
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///
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/// \param M The module we are outlining from.
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/// \param FunctionList A list of functions to be inserted into the module.
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/// \param Mapper Contains the instruction mappings for the module.
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bool outline(Module &M, std::vector<OutlinedFunction> &FunctionList,
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InstructionMapper &Mapper, unsigned &OutlinedFunctionNum);
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/// Creates a function for \p OF and inserts it into the module.
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MachineFunction *createOutlinedFunction(Module &M, OutlinedFunction &OF,
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InstructionMapper &Mapper,
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unsigned Name);
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/// Calls 'doOutline()' 1 + OutlinerReruns times.
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bool runOnModule(Module &M) override;
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/// Construct a suffix tree on the instructions in \p M and outline repeated
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/// strings from that tree.
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bool doOutline(Module &M, unsigned &OutlinedFunctionNum);
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/// Return a DISubprogram for OF if one exists, and null otherwise. Helper
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/// function for remark emission.
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DISubprogram *getSubprogramOrNull(const OutlinedFunction &OF) {
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for (const Candidate &C : OF.Candidates)
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if (MachineFunction *MF = C.getMF())
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if (DISubprogram *SP = MF->getFunction().getSubprogram())
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return SP;
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return nullptr;
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}
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/// Populate and \p InstructionMapper with instruction-to-integer mappings.
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/// These are used to construct a suffix tree.
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void populateMapper(InstructionMapper &Mapper, Module &M,
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MachineModuleInfo &MMI);
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/// Initialize information necessary to output a size remark.
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/// FIXME: This should be handled by the pass manager, not the outliner.
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/// FIXME: This is nearly identical to the initSizeRemarkInfo in the legacy
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/// pass manager.
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void initSizeRemarkInfo(const Module &M, const MachineModuleInfo &MMI,
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StringMap<unsigned> &FunctionToInstrCount);
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/// Emit the remark.
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// FIXME: This should be handled by the pass manager, not the outliner.
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void
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emitInstrCountChangedRemark(const Module &M, const MachineModuleInfo &MMI,
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const StringMap<unsigned> &FunctionToInstrCount);
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};
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} // Anonymous namespace.
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char MachineOutliner::ID = 0;
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namespace llvm {
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ModulePass *createMachineOutlinerPass(bool RunOnAllFunctions) {
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MachineOutliner *OL = new MachineOutliner();
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OL->RunOnAllFunctions = RunOnAllFunctions;
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return OL;
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}
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} // namespace llvm
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INITIALIZE_PASS(MachineOutliner, DEBUG_TYPE, "Machine Function Outliner", false,
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false)
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void MachineOutliner::emitNotOutliningCheaperRemark(
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unsigned StringLen, std::vector<Candidate> &CandidatesForRepeatedSeq,
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OutlinedFunction &OF) {
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// FIXME: Right now, we arbitrarily choose some Candidate from the
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// OutlinedFunction. This isn't necessarily fixed, nor does it have to be.
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// We should probably sort these by function name or something to make sure
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// the remarks are stable.
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Candidate &C = CandidatesForRepeatedSeq.front();
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MachineOptimizationRemarkEmitter MORE(*(C.getMF()), nullptr);
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MORE.emit([&]() {
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MachineOptimizationRemarkMissed R(DEBUG_TYPE, "NotOutliningCheaper",
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C.front()->getDebugLoc(), C.getMBB());
|
|
R << "Did not outline " << NV("Length", StringLen) << " instructions"
|
|
<< " from " << NV("NumOccurrences", CandidatesForRepeatedSeq.size())
|
|
<< " locations."
|
|
<< " Bytes from outlining all occurrences ("
|
|
<< NV("OutliningCost", OF.getOutliningCost()) << ")"
|
|
<< " >= Unoutlined instruction bytes ("
|
|
<< NV("NotOutliningCost", OF.getNotOutlinedCost()) << ")"
|
|
<< " (Also found at: ";
|
|
|
|
// Tell the user the other places the candidate was found.
|
|
for (unsigned i = 1, e = CandidatesForRepeatedSeq.size(); i < e; i++) {
|
|
R << NV((Twine("OtherStartLoc") + Twine(i)).str(),
|
|
CandidatesForRepeatedSeq[i].front()->getDebugLoc());
|
|
if (i != e - 1)
|
|
R << ", ";
|
|
}
|
|
|
|
R << ")";
|
|
return R;
|
|
});
|
|
}
|
|
|
|
void MachineOutliner::emitOutlinedFunctionRemark(OutlinedFunction &OF) {
|
|
MachineBasicBlock *MBB = &*OF.MF->begin();
|
|
MachineOptimizationRemarkEmitter MORE(*OF.MF, nullptr);
|
|
MachineOptimizationRemark R(DEBUG_TYPE, "OutlinedFunction",
|
|
MBB->findDebugLoc(MBB->begin()), MBB);
|
|
R << "Saved " << NV("OutliningBenefit", OF.getBenefit()) << " bytes by "
|
|
<< "outlining " << NV("Length", OF.getNumInstrs()) << " instructions "
|
|
<< "from " << NV("NumOccurrences", OF.getOccurrenceCount())
|
|
<< " locations. "
|
|
<< "(Found at: ";
|
|
|
|
// Tell the user the other places the candidate was found.
|
|
for (size_t i = 0, e = OF.Candidates.size(); i < e; i++) {
|
|
|
|
R << NV((Twine("StartLoc") + Twine(i)).str(),
|
|
OF.Candidates[i].front()->getDebugLoc());
|
|
if (i != e - 1)
|
|
R << ", ";
|
|
}
|
|
|
|
R << ")";
|
|
|
|
MORE.emit(R);
|
|
}
|
|
|
|
void MachineOutliner::findCandidates(
|
|
InstructionMapper &Mapper, std::vector<OutlinedFunction> &FunctionList) {
|
|
FunctionList.clear();
|
|
SuffixTree ST(Mapper.UnsignedVec);
|
|
|
|
// First, find all of the repeated substrings in the tree of minimum length
|
|
// 2.
|
|
std::vector<Candidate> CandidatesForRepeatedSeq;
|
|
for (const SuffixTree::RepeatedSubstring &RS : ST) {
|
|
CandidatesForRepeatedSeq.clear();
|
|
unsigned StringLen = RS.Length;
|
|
for (const unsigned &StartIdx : RS.StartIndices) {
|
|
unsigned EndIdx = StartIdx + StringLen - 1;
|
|
// Trick: Discard some candidates that would be incompatible with the
|
|
// ones we've already found for this sequence. This will save us some
|
|
// work in candidate selection.
|
|
//
|
|
// If two candidates overlap, then we can't outline them both. This
|
|
// happens when we have candidates that look like, say
|
|
//
|
|
// AA (where each "A" is an instruction).
|
|
//
|
|
// We might have some portion of the module that looks like this:
|
|
// AAAAAA (6 A's)
|
|
//
|
|
// In this case, there are 5 different copies of "AA" in this range, but
|
|
// at most 3 can be outlined. If only outlining 3 of these is going to
|
|
// be unbeneficial, then we ought to not bother.
|
|
//
|
|
// Note that two things DON'T overlap when they look like this:
|
|
// start1...end1 .... start2...end2
|
|
// That is, one must either
|
|
// * End before the other starts
|
|
// * Start after the other ends
|
|
if (llvm::all_of(CandidatesForRepeatedSeq, [&StartIdx,
|
|
&EndIdx](const Candidate &C) {
|
|
return (EndIdx < C.getStartIdx() || StartIdx > C.getEndIdx());
|
|
})) {
|
|
// It doesn't overlap with anything, so we can outline it.
|
|
// Each sequence is over [StartIt, EndIt].
|
|
// Save the candidate and its location.
|
|
|
|
MachineBasicBlock::iterator StartIt = Mapper.InstrList[StartIdx];
|
|
MachineBasicBlock::iterator EndIt = Mapper.InstrList[EndIdx];
|
|
MachineBasicBlock *MBB = StartIt->getParent();
|
|
|
|
CandidatesForRepeatedSeq.emplace_back(StartIdx, StringLen, StartIt,
|
|
EndIt, MBB, FunctionList.size(),
|
|
Mapper.MBBFlagsMap[MBB]);
|
|
}
|
|
}
|
|
|
|
// We've found something we might want to outline.
|
|
// Create an OutlinedFunction to store it and check if it'd be beneficial
|
|
// to outline.
|
|
if (CandidatesForRepeatedSeq.size() < 2)
|
|
continue;
|
|
|
|
// Arbitrarily choose a TII from the first candidate.
|
|
// FIXME: Should getOutliningCandidateInfo move to TargetMachine?
|
|
const TargetInstrInfo *TII =
|
|
CandidatesForRepeatedSeq[0].getMF()->getSubtarget().getInstrInfo();
|
|
|
|
OutlinedFunction OF =
|
|
TII->getOutliningCandidateInfo(CandidatesForRepeatedSeq);
|
|
|
|
// If we deleted too many candidates, then there's nothing worth outlining.
|
|
// FIXME: This should take target-specified instruction sizes into account.
|
|
if (OF.Candidates.size() < 2)
|
|
continue;
|
|
|
|
// Is it better to outline this candidate than not?
|
|
if (OF.getBenefit() < 1) {
|
|
emitNotOutliningCheaperRemark(StringLen, CandidatesForRepeatedSeq, OF);
|
|
continue;
|
|
}
|
|
|
|
FunctionList.push_back(OF);
|
|
}
|
|
}
|
|
|
|
MachineFunction *MachineOutliner::createOutlinedFunction(
|
|
Module &M, OutlinedFunction &OF, InstructionMapper &Mapper, unsigned Name) {
|
|
|
|
// Create the function name. This should be unique.
|
|
// FIXME: We should have a better naming scheme. This should be stable,
|
|
// regardless of changes to the outliner's cost model/traversal order.
|
|
std::string FunctionName = "OUTLINED_FUNCTION_";
|
|
if (OutlineRepeatedNum > 0)
|
|
FunctionName += std::to_string(OutlineRepeatedNum + 1) + "_";
|
|
FunctionName += std::to_string(Name);
|
|
|
|
// Create the function using an IR-level function.
|
|
LLVMContext &C = M.getContext();
|
|
Function *F = Function::Create(FunctionType::get(Type::getVoidTy(C), false),
|
|
Function::ExternalLinkage, FunctionName, M);
|
|
|
|
// NOTE: If this is linkonceodr, then we can take advantage of linker deduping
|
|
// which gives us better results when we outline from linkonceodr functions.
|
|
F->setLinkage(GlobalValue::InternalLinkage);
|
|
F->setUnnamedAddr(GlobalValue::UnnamedAddr::Global);
|
|
|
|
// Set optsize/minsize, so we don't insert padding between outlined
|
|
// functions.
|
|
F->addFnAttr(Attribute::OptimizeForSize);
|
|
F->addFnAttr(Attribute::MinSize);
|
|
|
|
Candidate &FirstCand = OF.Candidates.front();
|
|
const TargetInstrInfo &TII =
|
|
*FirstCand.getMF()->getSubtarget().getInstrInfo();
|
|
|
|
TII.mergeOutliningCandidateAttributes(*F, OF.Candidates);
|
|
|
|
// Set uwtable, so we generate eh_frame.
|
|
UWTableKind UW = std::accumulate(
|
|
OF.Candidates.cbegin(), OF.Candidates.cend(), UWTableKind::None,
|
|
[](UWTableKind K, const outliner::Candidate &C) {
|
|
return std::max(K, C.getMF()->getFunction().getUWTableKind());
|
|
});
|
|
if (UW != UWTableKind::None)
|
|
F->setUWTableKind(UW);
|
|
|
|
BasicBlock *EntryBB = BasicBlock::Create(C, "entry", F);
|
|
IRBuilder<> Builder(EntryBB);
|
|
Builder.CreateRetVoid();
|
|
|
|
MachineModuleInfo &MMI = getAnalysis<MachineModuleInfoWrapperPass>().getMMI();
|
|
MachineFunction &MF = MMI.getOrCreateMachineFunction(*F);
|
|
MachineBasicBlock &MBB = *MF.CreateMachineBasicBlock();
|
|
|
|
// Insert the new function into the module.
|
|
MF.insert(MF.begin(), &MBB);
|
|
|
|
MachineFunction *OriginalMF = FirstCand.front()->getMF();
|
|
const std::vector<MCCFIInstruction> &Instrs =
|
|
OriginalMF->getFrameInstructions();
|
|
for (auto I = FirstCand.front(), E = std::next(FirstCand.back()); I != E;
|
|
++I) {
|
|
if (I->isDebugInstr())
|
|
continue;
|
|
MachineInstr *NewMI = MF.CloneMachineInstr(&*I);
|
|
if (I->isCFIInstruction()) {
|
|
unsigned CFIIndex = NewMI->getOperand(0).getCFIIndex();
|
|
MCCFIInstruction CFI = Instrs[CFIIndex];
|
|
(void)MF.addFrameInst(CFI);
|
|
}
|
|
NewMI->dropMemRefs(MF);
|
|
|
|
// Don't keep debug information for outlined instructions.
|
|
NewMI->setDebugLoc(DebugLoc());
|
|
MBB.insert(MBB.end(), NewMI);
|
|
}
|
|
|
|
// Set normal properties for a late MachineFunction.
|
|
MF.getProperties().reset(MachineFunctionProperties::Property::IsSSA);
|
|
MF.getProperties().set(MachineFunctionProperties::Property::NoPHIs);
|
|
MF.getProperties().set(MachineFunctionProperties::Property::NoVRegs);
|
|
MF.getProperties().set(MachineFunctionProperties::Property::TracksLiveness);
|
|
MF.getRegInfo().freezeReservedRegs(MF);
|
|
|
|
// Compute live-in set for outlined fn
|
|
const MachineRegisterInfo &MRI = MF.getRegInfo();
|
|
const TargetRegisterInfo &TRI = *MRI.getTargetRegisterInfo();
|
|
LivePhysRegs LiveIns(TRI);
|
|
for (auto &Cand : OF.Candidates) {
|
|
// Figure out live-ins at the first instruction.
|
|
MachineBasicBlock &OutlineBB = *Cand.front()->getParent();
|
|
LivePhysRegs CandLiveIns(TRI);
|
|
CandLiveIns.addLiveOuts(OutlineBB);
|
|
for (const MachineInstr &MI :
|
|
reverse(make_range(Cand.front(), OutlineBB.end())))
|
|
CandLiveIns.stepBackward(MI);
|
|
|
|
// The live-in set for the outlined function is the union of the live-ins
|
|
// from all the outlining points.
|
|
for (MCPhysReg Reg : CandLiveIns)
|
|
LiveIns.addReg(Reg);
|
|
}
|
|
addLiveIns(MBB, LiveIns);
|
|
|
|
TII.buildOutlinedFrame(MBB, MF, OF);
|
|
|
|
// If there's a DISubprogram associated with this outlined function, then
|
|
// emit debug info for the outlined function.
|
|
if (DISubprogram *SP = getSubprogramOrNull(OF)) {
|
|
// We have a DISubprogram. Get its DICompileUnit.
|
|
DICompileUnit *CU = SP->getUnit();
|
|
DIBuilder DB(M, true, CU);
|
|
DIFile *Unit = SP->getFile();
|
|
Mangler Mg;
|
|
// Get the mangled name of the function for the linkage name.
|
|
std::string Dummy;
|
|
llvm::raw_string_ostream MangledNameStream(Dummy);
|
|
Mg.getNameWithPrefix(MangledNameStream, F, false);
|
|
|
|
DISubprogram *OutlinedSP = DB.createFunction(
|
|
Unit /* Context */, F->getName(), StringRef(MangledNameStream.str()),
|
|
Unit /* File */,
|
|
0 /* Line 0 is reserved for compiler-generated code. */,
|
|
DB.createSubroutineType(DB.getOrCreateTypeArray(None)), /* void type */
|
|
0, /* Line 0 is reserved for compiler-generated code. */
|
|
DINode::DIFlags::FlagArtificial /* Compiler-generated code. */,
|
|
/* Outlined code is optimized code by definition. */
|
|
DISubprogram::SPFlagDefinition | DISubprogram::SPFlagOptimized);
|
|
|
|
// Don't add any new variables to the subprogram.
|
|
DB.finalizeSubprogram(OutlinedSP);
|
|
|
|
// Attach subprogram to the function.
|
|
F->setSubprogram(OutlinedSP);
|
|
// We're done with the DIBuilder.
|
|
DB.finalize();
|
|
}
|
|
|
|
return &MF;
|
|
}
|
|
|
|
bool MachineOutliner::outline(Module &M,
|
|
std::vector<OutlinedFunction> &FunctionList,
|
|
InstructionMapper &Mapper,
|
|
unsigned &OutlinedFunctionNum) {
|
|
|
|
bool OutlinedSomething = false;
|
|
|
|
// Sort by benefit. The most beneficial functions should be outlined first.
|
|
llvm::stable_sort(FunctionList, [](const OutlinedFunction &LHS,
|
|
const OutlinedFunction &RHS) {
|
|
return LHS.getBenefit() > RHS.getBenefit();
|
|
});
|
|
|
|
// Walk over each function, outlining them as we go along. Functions are
|
|
// outlined greedily, based off the sort above.
|
|
for (OutlinedFunction &OF : FunctionList) {
|
|
// If we outlined something that overlapped with a candidate in a previous
|
|
// step, then we can't outline from it.
|
|
erase_if(OF.Candidates, [&Mapper](Candidate &C) {
|
|
return std::any_of(
|
|
Mapper.UnsignedVec.begin() + C.getStartIdx(),
|
|
Mapper.UnsignedVec.begin() + C.getEndIdx() + 1,
|
|
[](unsigned I) { return (I == static_cast<unsigned>(-1)); });
|
|
});
|
|
|
|
// If we made it unbeneficial to outline this function, skip it.
|
|
if (OF.getBenefit() < 1)
|
|
continue;
|
|
|
|
// It's beneficial. Create the function and outline its sequence's
|
|
// occurrences.
|
|
OF.MF = createOutlinedFunction(M, OF, Mapper, OutlinedFunctionNum);
|
|
emitOutlinedFunctionRemark(OF);
|
|
FunctionsCreated++;
|
|
OutlinedFunctionNum++; // Created a function, move to the next name.
|
|
MachineFunction *MF = OF.MF;
|
|
const TargetSubtargetInfo &STI = MF->getSubtarget();
|
|
const TargetInstrInfo &TII = *STI.getInstrInfo();
|
|
|
|
// Replace occurrences of the sequence with calls to the new function.
|
|
for (Candidate &C : OF.Candidates) {
|
|
MachineBasicBlock &MBB = *C.getMBB();
|
|
MachineBasicBlock::iterator StartIt = C.front();
|
|
MachineBasicBlock::iterator EndIt = C.back();
|
|
|
|
// Insert the call.
|
|
auto CallInst = TII.insertOutlinedCall(M, MBB, StartIt, *MF, C);
|
|
|
|
// If the caller tracks liveness, then we need to make sure that
|
|
// anything we outline doesn't break liveness assumptions. The outlined
|
|
// functions themselves currently don't track liveness, but we should
|
|
// make sure that the ranges we yank things out of aren't wrong.
|
|
if (MBB.getParent()->getProperties().hasProperty(
|
|
MachineFunctionProperties::Property::TracksLiveness)) {
|
|
// The following code is to add implicit def operands to the call
|
|
// instruction. It also updates call site information for moved
|
|
// code.
|
|
SmallSet<Register, 2> UseRegs, DefRegs;
|
|
// Copy over the defs in the outlined range.
|
|
// First inst in outlined range <-- Anything that's defined in this
|
|
// ... .. range has to be added as an
|
|
// implicit Last inst in outlined range <-- def to the call
|
|
// instruction. Also remove call site information for outlined block
|
|
// of code. The exposed uses need to be copied in the outlined range.
|
|
for (MachineBasicBlock::reverse_iterator
|
|
Iter = EndIt.getReverse(),
|
|
Last = std::next(CallInst.getReverse());
|
|
Iter != Last; Iter++) {
|
|
MachineInstr *MI = &*Iter;
|
|
SmallSet<Register, 2> InstrUseRegs;
|
|
for (MachineOperand &MOP : MI->operands()) {
|
|
// Skip over anything that isn't a register.
|
|
if (!MOP.isReg())
|
|
continue;
|
|
|
|
if (MOP.isDef()) {
|
|
// Introduce DefRegs set to skip the redundant register.
|
|
DefRegs.insert(MOP.getReg());
|
|
if (UseRegs.count(MOP.getReg()) &&
|
|
!InstrUseRegs.count(MOP.getReg()))
|
|
// Since the regiester is modeled as defined,
|
|
// it is not necessary to be put in use register set.
|
|
UseRegs.erase(MOP.getReg());
|
|
} else if (!MOP.isUndef()) {
|
|
// Any register which is not undefined should
|
|
// be put in the use register set.
|
|
UseRegs.insert(MOP.getReg());
|
|
InstrUseRegs.insert(MOP.getReg());
|
|
}
|
|
}
|
|
if (MI->isCandidateForCallSiteEntry())
|
|
MI->getMF()->eraseCallSiteInfo(MI);
|
|
}
|
|
|
|
for (const Register &I : DefRegs)
|
|
// If it's a def, add it to the call instruction.
|
|
CallInst->addOperand(
|
|
MachineOperand::CreateReg(I, true, /* isDef = true */
|
|
true /* isImp = true */));
|
|
|
|
for (const Register &I : UseRegs)
|
|
// If it's a exposed use, add it to the call instruction.
|
|
CallInst->addOperand(
|
|
MachineOperand::CreateReg(I, false, /* isDef = false */
|
|
true /* isImp = true */));
|
|
}
|
|
|
|
// Erase from the point after where the call was inserted up to, and
|
|
// including, the final instruction in the sequence.
|
|
// Erase needs one past the end, so we need std::next there too.
|
|
MBB.erase(std::next(StartIt), std::next(EndIt));
|
|
|
|
// Keep track of what we removed by marking them all as -1.
|
|
std::for_each(Mapper.UnsignedVec.begin() + C.getStartIdx(),
|
|
Mapper.UnsignedVec.begin() + C.getEndIdx() + 1,
|
|
[](unsigned &I) { I = static_cast<unsigned>(-1); });
|
|
OutlinedSomething = true;
|
|
|
|
// Statistics.
|
|
NumOutlined++;
|
|
}
|
|
}
|
|
|
|
LLVM_DEBUG(dbgs() << "OutlinedSomething = " << OutlinedSomething << "\n";);
|
|
return OutlinedSomething;
|
|
}
|
|
|
|
void MachineOutliner::populateMapper(InstructionMapper &Mapper, Module &M,
|
|
MachineModuleInfo &MMI) {
|
|
// Build instruction mappings for each function in the module. Start by
|
|
// iterating over each Function in M.
|
|
for (Function &F : M) {
|
|
|
|
// If there's nothing in F, then there's no reason to try and outline from
|
|
// it.
|
|
if (F.empty())
|
|
continue;
|
|
|
|
// There's something in F. Check if it has a MachineFunction associated with
|
|
// it.
|
|
MachineFunction *MF = MMI.getMachineFunction(F);
|
|
|
|
// If it doesn't, then there's nothing to outline from. Move to the next
|
|
// Function.
|
|
if (!MF)
|
|
continue;
|
|
|
|
const TargetInstrInfo *TII = MF->getSubtarget().getInstrInfo();
|
|
|
|
if (!RunOnAllFunctions && !TII->shouldOutlineFromFunctionByDefault(*MF))
|
|
continue;
|
|
|
|
// We have a MachineFunction. Ask the target if it's suitable for outlining.
|
|
// If it isn't, then move on to the next Function in the module.
|
|
if (!TII->isFunctionSafeToOutlineFrom(*MF, OutlineFromLinkOnceODRs))
|
|
continue;
|
|
|
|
// We have a function suitable for outlining. Iterate over every
|
|
// MachineBasicBlock in MF and try to map its instructions to a list of
|
|
// unsigned integers.
|
|
for (MachineBasicBlock &MBB : *MF) {
|
|
// If there isn't anything in MBB, then there's no point in outlining from
|
|
// it.
|
|
// If there are fewer than 2 instructions in the MBB, then it can't ever
|
|
// contain something worth outlining.
|
|
// FIXME: This should be based off of the maximum size in B of an outlined
|
|
// call versus the size in B of the MBB.
|
|
if (MBB.empty() || MBB.size() < 2)
|
|
continue;
|
|
|
|
// Check if MBB could be the target of an indirect branch. If it is, then
|
|
// we don't want to outline from it.
|
|
if (MBB.hasAddressTaken())
|
|
continue;
|
|
|
|
// MBB is suitable for outlining. Map it to a list of unsigneds.
|
|
Mapper.convertToUnsignedVec(MBB, *TII);
|
|
}
|
|
|
|
// Statistics.
|
|
UnsignedVecSize = Mapper.UnsignedVec.size();
|
|
}
|
|
}
|
|
|
|
void MachineOutliner::initSizeRemarkInfo(
|
|
const Module &M, const MachineModuleInfo &MMI,
|
|
StringMap<unsigned> &FunctionToInstrCount) {
|
|
// Collect instruction counts for every function. We'll use this to emit
|
|
// per-function size remarks later.
|
|
for (const Function &F : M) {
|
|
MachineFunction *MF = MMI.getMachineFunction(F);
|
|
|
|
// We only care about MI counts here. If there's no MachineFunction at this
|
|
// point, then there won't be after the outliner runs, so let's move on.
|
|
if (!MF)
|
|
continue;
|
|
FunctionToInstrCount[F.getName().str()] = MF->getInstructionCount();
|
|
}
|
|
}
|
|
|
|
void MachineOutliner::emitInstrCountChangedRemark(
|
|
const Module &M, const MachineModuleInfo &MMI,
|
|
const StringMap<unsigned> &FunctionToInstrCount) {
|
|
// Iterate over each function in the module and emit remarks.
|
|
// Note that we won't miss anything by doing this, because the outliner never
|
|
// deletes functions.
|
|
for (const Function &F : M) {
|
|
MachineFunction *MF = MMI.getMachineFunction(F);
|
|
|
|
// The outliner never deletes functions. If we don't have a MF here, then we
|
|
// didn't have one prior to outlining either.
|
|
if (!MF)
|
|
continue;
|
|
|
|
std::string Fname = std::string(F.getName());
|
|
unsigned FnCountAfter = MF->getInstructionCount();
|
|
unsigned FnCountBefore = 0;
|
|
|
|
// Check if the function was recorded before.
|
|
auto It = FunctionToInstrCount.find(Fname);
|
|
|
|
// Did we have a previously-recorded size? If yes, then set FnCountBefore
|
|
// to that.
|
|
if (It != FunctionToInstrCount.end())
|
|
FnCountBefore = It->second;
|
|
|
|
// Compute the delta and emit a remark if there was a change.
|
|
int64_t FnDelta = static_cast<int64_t>(FnCountAfter) -
|
|
static_cast<int64_t>(FnCountBefore);
|
|
if (FnDelta == 0)
|
|
continue;
|
|
|
|
MachineOptimizationRemarkEmitter MORE(*MF, nullptr);
|
|
MORE.emit([&]() {
|
|
MachineOptimizationRemarkAnalysis R("size-info", "FunctionMISizeChange",
|
|
DiagnosticLocation(), &MF->front());
|
|
R << DiagnosticInfoOptimizationBase::Argument("Pass", "Machine Outliner")
|
|
<< ": Function: "
|
|
<< DiagnosticInfoOptimizationBase::Argument("Function", F.getName())
|
|
<< ": MI instruction count changed from "
|
|
<< DiagnosticInfoOptimizationBase::Argument("MIInstrsBefore",
|
|
FnCountBefore)
|
|
<< " to "
|
|
<< DiagnosticInfoOptimizationBase::Argument("MIInstrsAfter",
|
|
FnCountAfter)
|
|
<< "; Delta: "
|
|
<< DiagnosticInfoOptimizationBase::Argument("Delta", FnDelta);
|
|
return R;
|
|
});
|
|
}
|
|
}
|
|
|
|
bool MachineOutliner::runOnModule(Module &M) {
|
|
// Check if there's anything in the module. If it's empty, then there's
|
|
// nothing to outline.
|
|
if (M.empty())
|
|
return false;
|
|
|
|
// Number to append to the current outlined function.
|
|
unsigned OutlinedFunctionNum = 0;
|
|
|
|
OutlineRepeatedNum = 0;
|
|
if (!doOutline(M, OutlinedFunctionNum))
|
|
return false;
|
|
|
|
for (unsigned I = 0; I < OutlinerReruns; ++I) {
|
|
OutlinedFunctionNum = 0;
|
|
OutlineRepeatedNum++;
|
|
if (!doOutline(M, OutlinedFunctionNum)) {
|
|
LLVM_DEBUG({
|
|
dbgs() << "Did not outline on iteration " << I + 2 << " out of "
|
|
<< OutlinerReruns + 1 << "\n";
|
|
});
|
|
break;
|
|
}
|
|
}
|
|
|
|
return true;
|
|
}
|
|
|
|
bool MachineOutliner::doOutline(Module &M, unsigned &OutlinedFunctionNum) {
|
|
MachineModuleInfo &MMI = getAnalysis<MachineModuleInfoWrapperPass>().getMMI();
|
|
|
|
// If the user passed -enable-machine-outliner=always or
|
|
// -enable-machine-outliner, the pass will run on all functions in the module.
|
|
// Otherwise, if the target supports default outlining, it will run on all
|
|
// functions deemed by the target to be worth outlining from by default. Tell
|
|
// the user how the outliner is running.
|
|
LLVM_DEBUG({
|
|
dbgs() << "Machine Outliner: Running on ";
|
|
if (RunOnAllFunctions)
|
|
dbgs() << "all functions";
|
|
else
|
|
dbgs() << "target-default functions";
|
|
dbgs() << "\n";
|
|
});
|
|
|
|
// If the user specifies that they want to outline from linkonceodrs, set
|
|
// it here.
|
|
OutlineFromLinkOnceODRs = EnableLinkOnceODROutlining;
|
|
InstructionMapper Mapper;
|
|
|
|
// Prepare instruction mappings for the suffix tree.
|
|
populateMapper(Mapper, M, MMI);
|
|
std::vector<OutlinedFunction> FunctionList;
|
|
|
|
// Find all of the outlining candidates.
|
|
findCandidates(Mapper, FunctionList);
|
|
|
|
// If we've requested size remarks, then collect the MI counts of every
|
|
// function before outlining, and the MI counts after outlining.
|
|
// FIXME: This shouldn't be in the outliner at all; it should ultimately be
|
|
// the pass manager's responsibility.
|
|
// This could pretty easily be placed in outline instead, but because we
|
|
// really ultimately *don't* want this here, it's done like this for now
|
|
// instead.
|
|
|
|
// Check if we want size remarks.
|
|
bool ShouldEmitSizeRemarks = M.shouldEmitInstrCountChangedRemark();
|
|
StringMap<unsigned> FunctionToInstrCount;
|
|
if (ShouldEmitSizeRemarks)
|
|
initSizeRemarkInfo(M, MMI, FunctionToInstrCount);
|
|
|
|
// Outline each of the candidates and return true if something was outlined.
|
|
bool OutlinedSomething =
|
|
outline(M, FunctionList, Mapper, OutlinedFunctionNum);
|
|
|
|
// If we outlined something, we definitely changed the MI count of the
|
|
// module. If we've asked for size remarks, then output them.
|
|
// FIXME: This should be in the pass manager.
|
|
if (ShouldEmitSizeRemarks && OutlinedSomething)
|
|
emitInstrCountChangedRemark(M, MMI, FunctionToInstrCount);
|
|
|
|
LLVM_DEBUG({
|
|
if (!OutlinedSomething)
|
|
dbgs() << "Stopped outlining at iteration " << OutlineRepeatedNum
|
|
<< " because no changes were found.\n";
|
|
});
|
|
|
|
return OutlinedSomething;
|
|
}
|