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//===- LoopRotation.cpp - Loop Rotation Pass ------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file implements Loop Rotation Pass.
//
//===----------------------------------------------------------------------===//
#include "llvm/Transforms/Scalar/LoopRotation.h"
#include "llvm/Analysis/AssumptionCache.h"
#include "llvm/Analysis/InstructionSimplify.h"
#include "llvm/Analysis/LazyBlockFrequencyInfo.h"
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Analysis/LoopPass.h"
#include "llvm/Analysis/MemorySSA.h"
#include "llvm/Analysis/MemorySSAUpdater.h"
#include "llvm/Analysis/ScalarEvolution.h"
#include "llvm/Analysis/TargetTransformInfo.h"
#include "llvm/InitializePasses.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Transforms/Scalar.h"
#include "llvm/Transforms/Utils/LoopRotationUtils.h"
#include "llvm/Transforms/Utils/LoopUtils.h"
#include <optional>
using namespace llvm;
#define DEBUG_TYPE "loop-rotate"
static cl::opt<unsigned> DefaultRotationThreshold(
"rotation-max-header-size", cl::init(16), cl::Hidden,
cl::desc("The default maximum header size for automatic loop rotation"));
static cl::opt<bool> PrepareForLTOOption(
"rotation-prepare-for-lto", cl::init(false), cl::Hidden,
cl::desc("Run loop-rotation in the prepare-for-lto stage. This option "
"should be used for testing only."));
LoopRotatePass::LoopRotatePass(bool EnableHeaderDuplication, bool PrepareForLTO)
: EnableHeaderDuplication(EnableHeaderDuplication),
PrepareForLTO(PrepareForLTO) {}
void LoopRotatePass::printPipeline(
raw_ostream &OS, function_ref<StringRef(StringRef)> MapClassName2PassName) {
static_cast<PassInfoMixin<LoopRotatePass> *>(this)->printPipeline(
OS, MapClassName2PassName);
OS << "<";
if (!EnableHeaderDuplication)
OS << "no-";
OS << "header-duplication;";
if (!PrepareForLTO)
OS << "no-";
OS << "prepare-for-lto";
OS << ">";
}
PreservedAnalyses LoopRotatePass::run(Loop &L, LoopAnalysisManager &AM,
LoopStandardAnalysisResults &AR,
LPMUpdater &) {
// Vectorization requires loop-rotation. Use default threshold for loops the
// user explicitly marked for vectorization, even when header duplication is
// disabled.
int Threshold =
(EnableHeaderDuplication && !L.getHeader()->getParent()->hasMinSize()) ||
hasVectorizeTransformation(&L) == TM_ForcedByUser
? DefaultRotationThreshold
: 0;
const DataLayout &DL = L.getHeader()->getDataLayout();
const SimplifyQuery SQ = getBestSimplifyQuery(AR, DL);
std::optional<MemorySSAUpdater> MSSAU;
if (AR.MSSA)
MSSAU = MemorySSAUpdater(AR.MSSA);
bool Changed = LoopRotation(&L, &AR.LI, &AR.TTI, &AR.AC, &AR.DT, &AR.SE,
MSSAU ? &*MSSAU : nullptr, SQ, false, Threshold,
false, PrepareForLTO || PrepareForLTOOption);
if (!Changed)
return PreservedAnalyses::all();
if (AR.MSSA && VerifyMemorySSA)
AR.MSSA->verifyMemorySSA();
auto PA = getLoopPassPreservedAnalyses();
if (AR.MSSA)
PA.preserve<MemorySSAAnalysis>();
return PA;
}
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