LoopDataPrefetch.cpp | Explore in Territory

//===-------- LoopDataPrefetch.cpp - Loop Data Prefetching 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 a Loop Data Prefetching Pass.
//
//===----------------------------------------------------------------------===//

#include "llvm/Transforms/Scalar/LoopDataPrefetch.h"
#include "llvm/InitializePasses.h"

#include "llvm/ADT/DepthFirstIterator.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/AssumptionCache.h"
#include "llvm/Analysis/CodeMetrics.h"
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Analysis/OptimizationRemarkEmitter.h"
#include "llvm/Analysis/ScalarEvolution.h"
#include "llvm/Analysis/ScalarEvolutionExpressions.h"
#include "llvm/Analysis/TargetTransformInfo.h"
#include "llvm/IR/Dominators.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/Module.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Transforms/Scalar.h"
#include "llvm/Transforms/Utils.h"
#include "llvm/Transforms/Utils/ScalarEvolutionExpander.h"

#define DEBUG_TYPE …

usingnamespacellvm;

// By default, we limit this to creating 16 PHIs (which is a little over half
// of the allocatable register set).
static cl::opt<bool>
PrefetchWrites("loop-prefetch-writes", cl::Hidden, cl::init(false),
               cl::desc("Prefetch write addresses"));

static cl::opt<unsigned>
    PrefetchDistance("prefetch-distance",
                     cl::desc("Number of instructions to prefetch ahead"),
                     cl::Hidden);

static cl::opt<unsigned>
    MinPrefetchStride("min-prefetch-stride",
                      cl::desc("Min stride to add prefetches"), cl::Hidden);

static cl::opt<unsigned> MaxPrefetchIterationsAhead(
    "max-prefetch-iters-ahead",
    cl::desc("Max number of iterations to prefetch ahead"), cl::Hidden);

STATISTIC(NumPrefetches, "Number of prefetches inserted");

namespace {

/// Loop prefetch implementation class.
class LoopDataPrefetch { … };

/// Legacy class for inserting loop data prefetches.
class LoopDataPrefetchLegacyPass : public FunctionPass { … };
}

char LoopDataPrefetchLegacyPass::ID = …;
INITIALIZE_PASS_BEGIN(LoopDataPrefetchLegacyPass, "loop-data-prefetch",
                      "Loop Data Prefetch", false, false)
INITIALIZE_PASS_DEPENDENCY(AssumptionCacheTracker)
INITIALIZE_PASS_DEPENDENCY(TargetTransformInfoWrapperPass)
INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass)
INITIALIZE_PASS_DEPENDENCY(LoopSimplify)
INITIALIZE_PASS_DEPENDENCY(OptimizationRemarkEmitterWrapperPass)
INITIALIZE_PASS_DEPENDENCY(ScalarEvolutionWrapperPass)
INITIALIZE_PASS_END(LoopDataPrefetchLegacyPass, "loop-data-prefetch",
                    "Loop Data Prefetch", false, false)

FunctionPass *llvm::createLoopDataPrefetchPass() { … }

bool LoopDataPrefetch::isStrideLargeEnough(const SCEVAddRecExpr *AR,
                                           unsigned TargetMinStride) { … }

PreservedAnalyses LoopDataPrefetchPass::run(Function &F,
                                            FunctionAnalysisManager &AM) { … }

bool LoopDataPrefetchLegacyPass::runOnFunction(Function &F) { … }

bool LoopDataPrefetch::run() { … }

/// A record for a potential prefetch made during the initial scan of the
/// loop. This is used to let a single prefetch target multiple memory accesses.
struct Prefetch { … };

bool LoopDataPrefetch::runOnLoop(Loop *L) { … }
llvm/llvm/lib/Transforms/Scalar/LoopDataPrefetch.cpp
