llvm/llvm/include/llvm/Transforms/Vectorize/LoopVectorize.h

//===- LoopVectorize.h ------------------------------------------*- C++ -*-===//
//
// 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 is the LLVM loop vectorizer. This pass modifies 'vectorizable' loops
// and generates target-independent LLVM-IR.
// The vectorizer uses the TargetTransformInfo analysis to estimate the costs
// of instructions in order to estimate the profitability of vectorization.
//
// The loop vectorizer combines consecutive loop iterations into a single
// 'wide' iteration. After this transformation the index is incremented
// by the SIMD vector width, and not by one.
//
// This pass has four parts:
// 1. The main loop pass that drives the different parts.
// 2. LoopVectorizationLegality - A unit that checks for the legality
//    of the vectorization.
// 3. InnerLoopVectorizer - A unit that performs the actual
//    widening of instructions.
// 4. LoopVectorizationCostModel - A unit that checks for the profitability
//    of vectorization. It decides on the optimal vector width, which
//    can be one, if vectorization is not profitable.
//
// There is a development effort going on to migrate loop vectorizer to the
// VPlan infrastructure and to introduce outer loop vectorization support (see
// docs/VectorizationPlan.rst and
// http://lists.llvm.org/pipermail/llvm-dev/2017-December/119523.html). For this
// purpose, we temporarily introduced the VPlan-native vectorization path: an
// alternative vectorization path that is natively implemented on top of the
// VPlan infrastructure. See EnableVPlanNativePath for enabling.
//
//===----------------------------------------------------------------------===//
//
// The reduction-variable vectorization is based on the paper:
//  D. Nuzman and R. Henderson. Multi-platform Auto-vectorization.
//
// Variable uniformity checks are inspired by:
//  Karrenberg, R. and Hack, S. Whole Function Vectorization.
//
// The interleaved access vectorization is based on the paper:
//  Dorit Nuzman, Ira Rosen and Ayal Zaks.  Auto-Vectorization of Interleaved
//  Data for SIMD
//
// Other ideas/concepts are from:
//  A. Zaks and D. Nuzman. Autovectorization in GCC-two years later.
//
//  S. Maleki, Y. Gao, M. Garzaran, T. Wong and D. Padua.  An Evaluation of
//  Vectorizing Compilers.
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_TRANSFORMS_VECTORIZE_LOOPVECTORIZE_H
#define LLVM_TRANSFORMS_VECTORIZE_LOOPVECTORIZE_H

#include "llvm/IR/PassManager.h"
#include "llvm/Support/CommandLine.h"
#include <functional>

namespace llvm {

class AssumptionCache;
class BlockFrequencyInfo;
class DemandedBits;
class DominatorTree;
class Function;
class Instruction;
class Loop;
class LoopAccessInfoManager;
class LoopInfo;
class OptimizationRemarkEmitter;
class ProfileSummaryInfo;
class ScalarEvolution;
class TargetLibraryInfo;
class TargetTransformInfo;

extern cl::opt<bool> EnableLoopInterleaving;
extern cl::opt<bool> EnableLoopVectorization;

/// A marker to determine if extra passes after loop vectorization should be
/// run.
struct ShouldRunExtraVectorPasses
    : public AnalysisInfoMixin<ShouldRunExtraVectorPasses> { … };

/// A pass manager to run a set of extra function simplification passes after
/// vectorization, if requested. LoopVectorize caches the
/// ShouldRunExtraVectorPasses analysis to request extra simplifications, if
/// they could be beneficial.
struct ExtraVectorPassManager : public FunctionPassManager { … };

struct LoopVectorizeOptions { … };

/// Storage for information about made changes.
struct LoopVectorizeResult { … };

/// The LoopVectorize Pass.
struct LoopVectorizePass : public PassInfoMixin<LoopVectorizePass> { … };

/// Reports a vectorization failure: print \p DebugMsg for debugging
/// purposes along with the corresponding optimization remark \p RemarkName.
/// If \p I is passed, it is an instruction that prevents vectorization.
/// Otherwise, the loop \p TheLoop is used for the location of the remark.
void reportVectorizationFailure(const StringRef DebugMsg,
    const StringRef OREMsg, const StringRef ORETag,
    OptimizationRemarkEmitter *ORE, Loop *TheLoop, Instruction *I = nullptr);

} // end namespace llvm

#endif // LLVM_TRANSFORMS_VECTORIZE_LOOPVECTORIZE_H