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399 lines
13 KiB
399 lines
13 KiB
//===- LoopPass.cpp - Loop Pass and Loop Pass Manager ---------------------===//
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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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// This file implements LoopPass and LPPassManager. All loop optimization
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// and transformation passes are derived from LoopPass. LPPassManager is
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// responsible for managing LoopPasses.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Analysis/LoopPass.h"
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#include "llvm/Analysis/LoopAnalysisManager.h"
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#include "llvm/IR/Dominators.h"
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#include "llvm/IR/LLVMContext.h"
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#include "llvm/IR/OptBisect.h"
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#include "llvm/IR/PassManager.h"
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#include "llvm/IR/PassTimingInfo.h"
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#include "llvm/IR/PrintPasses.h"
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#include "llvm/IR/StructuralHash.h"
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#include "llvm/InitializePasses.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/Support/TimeProfiler.h"
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#include "llvm/Support/Timer.h"
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#include "llvm/Support/raw_ostream.h"
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using namespace llvm;
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#define DEBUG_TYPE "loop-pass-manager"
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namespace {
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/// PrintLoopPass - Print a Function corresponding to a Loop.
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///
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class PrintLoopPassWrapper : public LoopPass {
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raw_ostream &OS;
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std::string Banner;
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public:
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static char ID;
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PrintLoopPassWrapper() : LoopPass(ID), OS(dbgs()) {}
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PrintLoopPassWrapper(raw_ostream &OS, const std::string &Banner)
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: LoopPass(ID), OS(OS), Banner(Banner) {}
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void getAnalysisUsage(AnalysisUsage &AU) const override {
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AU.setPreservesAll();
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}
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bool runOnLoop(Loop *L, LPPassManager &) override {
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auto BBI = llvm::find_if(L->blocks(), [](BasicBlock *BB) { return BB; });
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if (BBI != L->blocks().end() &&
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isFunctionInPrintList((*BBI)->getParent()->getName())) {
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printLoop(*L, OS, Banner);
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}
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return false;
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}
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StringRef getPassName() const override { return "Print Loop IR"; }
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};
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char PrintLoopPassWrapper::ID = 0;
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}
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//===----------------------------------------------------------------------===//
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// LPPassManager
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//
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char LPPassManager::ID = 0;
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LPPassManager::LPPassManager()
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: FunctionPass(ID), PMDataManager() {
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LI = nullptr;
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CurrentLoop = nullptr;
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}
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// Insert loop into loop nest (LoopInfo) and loop queue (LQ).
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void LPPassManager::addLoop(Loop &L) {
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if (L.isOutermost()) {
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// This is the top level loop.
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LQ.push_front(&L);
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return;
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}
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// Insert L into the loop queue after the parent loop.
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for (auto I = LQ.begin(), E = LQ.end(); I != E; ++I) {
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if (*I == L.getParentLoop()) {
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// deque does not support insert after.
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++I;
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LQ.insert(I, 1, &L);
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return;
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}
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}
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}
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// Recurse through all subloops and all loops into LQ.
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static void addLoopIntoQueue(Loop *L, std::deque<Loop *> &LQ) {
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LQ.push_back(L);
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for (Loop *I : reverse(*L))
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addLoopIntoQueue(I, LQ);
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}
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/// Pass Manager itself does not invalidate any analysis info.
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void LPPassManager::getAnalysisUsage(AnalysisUsage &Info) const {
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// LPPassManager needs LoopInfo. In the long term LoopInfo class will
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// become part of LPPassManager.
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Info.addRequired<LoopInfoWrapperPass>();
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Info.addRequired<DominatorTreeWrapperPass>();
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Info.setPreservesAll();
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}
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void LPPassManager::markLoopAsDeleted(Loop &L) {
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assert((&L == CurrentLoop || CurrentLoop->contains(&L)) &&
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"Must not delete loop outside the current loop tree!");
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// If this loop appears elsewhere within the queue, we also need to remove it
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// there. However, we have to be careful to not remove the back of the queue
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// as that is assumed to match the current loop.
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assert(LQ.back() == CurrentLoop && "Loop queue back isn't the current loop!");
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LQ.erase(std::remove(LQ.begin(), LQ.end(), &L), LQ.end());
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if (&L == CurrentLoop) {
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CurrentLoopDeleted = true;
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// Add this loop back onto the back of the queue to preserve our invariants.
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LQ.push_back(&L);
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}
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}
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/// run - Execute all of the passes scheduled for execution. Keep track of
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/// whether any of the passes modifies the function, and if so, return true.
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bool LPPassManager::runOnFunction(Function &F) {
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auto &LIWP = getAnalysis<LoopInfoWrapperPass>();
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LI = &LIWP.getLoopInfo();
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Module &M = *F.getParent();
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#if 0
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DominatorTree *DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
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#endif
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bool Changed = false;
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// Collect inherited analysis from Module level pass manager.
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populateInheritedAnalysis(TPM->activeStack);
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// Populate the loop queue in reverse program order. There is no clear need to
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// process sibling loops in either forward or reverse order. There may be some
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// advantage in deleting uses in a later loop before optimizing the
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// definitions in an earlier loop. If we find a clear reason to process in
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// forward order, then a forward variant of LoopPassManager should be created.
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//
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// Note that LoopInfo::iterator visits loops in reverse program
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// order. Here, reverse_iterator gives us a forward order, and the LoopQueue
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// reverses the order a third time by popping from the back.
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for (Loop *L : reverse(*LI))
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addLoopIntoQueue(L, LQ);
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if (LQ.empty()) // No loops, skip calling finalizers
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return false;
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// Initialization
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for (Loop *L : LQ) {
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for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
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LoopPass *P = getContainedPass(Index);
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Changed |= P->doInitialization(L, *this);
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}
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}
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// Walk Loops
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unsigned InstrCount, FunctionSize = 0;
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StringMap<std::pair<unsigned, unsigned>> FunctionToInstrCount;
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bool EmitICRemark = M.shouldEmitInstrCountChangedRemark();
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// Collect the initial size of the module and the function we're looking at.
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if (EmitICRemark) {
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InstrCount = initSizeRemarkInfo(M, FunctionToInstrCount);
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FunctionSize = F.getInstructionCount();
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}
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while (!LQ.empty()) {
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CurrentLoopDeleted = false;
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CurrentLoop = LQ.back();
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// Run all passes on the current Loop.
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for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
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LoopPass *P = getContainedPass(Index);
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llvm::TimeTraceScope LoopPassScope("RunLoopPass", P->getPassName());
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dumpPassInfo(P, EXECUTION_MSG, ON_LOOP_MSG,
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CurrentLoop->getHeader()->getName());
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dumpRequiredSet(P);
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initializeAnalysisImpl(P);
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bool LocalChanged = false;
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{
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PassManagerPrettyStackEntry X(P, *CurrentLoop->getHeader());
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TimeRegion PassTimer(getPassTimer(P));
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#ifdef EXPENSIVE_CHECKS
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uint64_t RefHash = StructuralHash(F);
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#endif
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LocalChanged = P->runOnLoop(CurrentLoop, *this);
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#ifdef EXPENSIVE_CHECKS
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if (!LocalChanged && (RefHash != StructuralHash(F))) {
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llvm::errs() << "Pass modifies its input and doesn't report it: "
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<< P->getPassName() << "\n";
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llvm_unreachable("Pass modifies its input and doesn't report it");
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}
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#endif
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Changed |= LocalChanged;
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if (EmitICRemark) {
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unsigned NewSize = F.getInstructionCount();
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// Update the size of the function, emit a remark, and update the
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// size of the module.
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if (NewSize != FunctionSize) {
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int64_t Delta = static_cast<int64_t>(NewSize) -
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static_cast<int64_t>(FunctionSize);
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emitInstrCountChangedRemark(P, M, Delta, InstrCount,
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FunctionToInstrCount, &F);
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InstrCount = static_cast<int64_t>(InstrCount) + Delta;
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FunctionSize = NewSize;
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}
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}
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}
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if (LocalChanged)
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dumpPassInfo(P, MODIFICATION_MSG, ON_LOOP_MSG,
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CurrentLoopDeleted ? "<deleted loop>"
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: CurrentLoop->getName());
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dumpPreservedSet(P);
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if (!CurrentLoopDeleted) {
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// Manually check that this loop is still healthy. This is done
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// instead of relying on LoopInfo::verifyLoop since LoopInfo
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// is a function pass and it's really expensive to verify every
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// loop in the function every time. That level of checking can be
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// enabled with the -verify-loop-info option.
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{
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TimeRegion PassTimer(getPassTimer(&LIWP));
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CurrentLoop->verifyLoop();
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}
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// Here we apply same reasoning as in the above case. Only difference
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// is that LPPassManager might run passes which do not require LCSSA
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// form (LoopPassPrinter for example). We should skip verification for
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// such passes.
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// FIXME: Loop-sink currently break LCSSA. Fix it and reenable the
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// verification!
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#if 0
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if (mustPreserveAnalysisID(LCSSAVerificationPass::ID))
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assert(CurrentLoop->isRecursivelyLCSSAForm(*DT, *LI));
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#endif
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// Then call the regular verifyAnalysis functions.
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verifyPreservedAnalysis(P);
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F.getContext().yield();
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}
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if (LocalChanged)
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removeNotPreservedAnalysis(P);
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recordAvailableAnalysis(P);
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removeDeadPasses(P,
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CurrentLoopDeleted ? "<deleted>"
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: CurrentLoop->getHeader()->getName(),
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ON_LOOP_MSG);
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if (CurrentLoopDeleted)
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// Do not run other passes on this loop.
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break;
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}
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// If the loop was deleted, release all the loop passes. This frees up
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// some memory, and avoids trouble with the pass manager trying to call
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// verifyAnalysis on them.
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if (CurrentLoopDeleted) {
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for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
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Pass *P = getContainedPass(Index);
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freePass(P, "<deleted>", ON_LOOP_MSG);
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}
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}
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// Pop the loop from queue after running all passes.
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LQ.pop_back();
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}
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// Finalization
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for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
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LoopPass *P = getContainedPass(Index);
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Changed |= P->doFinalization();
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}
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return Changed;
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}
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/// Print passes managed by this manager
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void LPPassManager::dumpPassStructure(unsigned Offset) {
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errs().indent(Offset*2) << "Loop Pass Manager\n";
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for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
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Pass *P = getContainedPass(Index);
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P->dumpPassStructure(Offset + 1);
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dumpLastUses(P, Offset+1);
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}
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}
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//===----------------------------------------------------------------------===//
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// LoopPass
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Pass *LoopPass::createPrinterPass(raw_ostream &O,
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const std::string &Banner) const {
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return new PrintLoopPassWrapper(O, Banner);
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}
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// Check if this pass is suitable for the current LPPassManager, if
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// available. This pass P is not suitable for a LPPassManager if P
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// is not preserving higher level analysis info used by other
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// LPPassManager passes. In such case, pop LPPassManager from the
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// stack. This will force assignPassManager() to create new
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// LPPassManger as expected.
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void LoopPass::preparePassManager(PMStack &PMS) {
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// Find LPPassManager
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while (!PMS.empty() &&
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PMS.top()->getPassManagerType() > PMT_LoopPassManager)
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PMS.pop();
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// If this pass is destroying high level information that is used
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// by other passes that are managed by LPM then do not insert
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// this pass in current LPM. Use new LPPassManager.
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if (PMS.top()->getPassManagerType() == PMT_LoopPassManager &&
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!PMS.top()->preserveHigherLevelAnalysis(this))
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PMS.pop();
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}
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/// Assign pass manager to manage this pass.
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void LoopPass::assignPassManager(PMStack &PMS,
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PassManagerType PreferredType) {
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// Find LPPassManager
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while (!PMS.empty() &&
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PMS.top()->getPassManagerType() > PMT_LoopPassManager)
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PMS.pop();
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LPPassManager *LPPM;
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if (PMS.top()->getPassManagerType() == PMT_LoopPassManager)
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LPPM = (LPPassManager*)PMS.top();
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else {
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// Create new Loop Pass Manager if it does not exist.
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assert (!PMS.empty() && "Unable to create Loop Pass Manager");
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PMDataManager *PMD = PMS.top();
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// [1] Create new Loop Pass Manager
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LPPM = new LPPassManager();
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LPPM->populateInheritedAnalysis(PMS);
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// [2] Set up new manager's top level manager
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PMTopLevelManager *TPM = PMD->getTopLevelManager();
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TPM->addIndirectPassManager(LPPM);
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// [3] Assign manager to manage this new manager. This may create
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// and push new managers into PMS
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Pass *P = LPPM->getAsPass();
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TPM->schedulePass(P);
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// [4] Push new manager into PMS
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PMS.push(LPPM);
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}
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LPPM->add(this);
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}
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static std::string getDescription(const Loop &L) {
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return "loop";
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}
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bool LoopPass::skipLoop(const Loop *L) const {
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const Function *F = L->getHeader()->getParent();
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if (!F)
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return false;
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// Check the opt bisect limit.
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OptPassGate &Gate = F->getContext().getOptPassGate();
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if (Gate.isEnabled() && !Gate.shouldRunPass(this, getDescription(*L)))
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return true;
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// Check for the OptimizeNone attribute.
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if (F->hasOptNone()) {
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// FIXME: Report this to dbgs() only once per function.
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LLVM_DEBUG(dbgs() << "Skipping pass '" << getPassName() << "' in function "
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<< F->getName() << "\n");
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// FIXME: Delete loop from pass manager's queue?
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return true;
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}
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return false;
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}
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LCSSAVerificationPass::LCSSAVerificationPass() : FunctionPass(ID) {
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initializeLCSSAVerificationPassPass(*PassRegistry::getPassRegistry());
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}
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char LCSSAVerificationPass::ID = 0;
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INITIALIZE_PASS(LCSSAVerificationPass, "lcssa-verification", "LCSSA Verifier",
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false, false)
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