lib/Support/RegisterPasses.cpp

//===------ RegisterPasses.cpp - Add the Polly Passes to default passes  --===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file composes the individual LLVM-IR passes provided by Polly to a
// functional polyhedral optimizer. The polyhedral optimizer is automatically
// made available to LLVM based compilers by loading the Polly shared library
// into such a compiler.
//
// The Polly optimizer is made available by executing a static constructor that
// registers the individual Polly passes in the LLVM pass manager builder. The
// passes are registered such that the default behaviour of the compiler is not
// changed, but that the flag '-polly' provided at optimization level '-O3'
// enables additional polyhedral optimizations.
//===----------------------------------------------------------------------===//

#include "polly/RegisterPasses.h"
#include "polly/Canonicalization.h"
#include "polly/CodeGen/CodeGeneration.h"
#include "polly/CodeGen/CodegenCleanup.h"
#include "polly/DependenceInfo.h"
#include "polly/LinkAllPasses.h"
#include "polly/Options.h"
#include "polly/ScopDetection.h"
#include "polly/ScopInfo.h"
#include "llvm/Analysis/CFGPrinter.h"
#include "llvm/IR/LegacyPassManager.h"
#include "llvm/Transforms/IPO.h"
#include "llvm/Transforms/IPO/PassManagerBuilder.h"
#include "llvm/Transforms/Scalar.h"
#include "llvm/Transforms/Vectorize.h"

using namespace llvm;
using namespace polly;

cl::OptionCategory PollyCategory("Polly Options",
                                 "Configure the polly loop optimizer");

static cl::opt<bool>
    PollyEnabled("polly", cl::desc("Enable the polly optimizer (only at -O3)"),
                 cl::init(false), cl::ZeroOrMore, cl::cat(PollyCategory));

static cl::opt<bool> PollyDetectOnly(
    "polly-only-scop-detection",
    cl::desc("Only run scop detection, but no other optimizations"),
    cl::init(false), cl::ZeroOrMore, cl::cat(PollyCategory));

enum PassPositionChoice {
  POSITION_EARLY,
  POSITION_AFTER_LOOPOPT,
  POSITION_BEFORE_VECTORIZER
};

enum OptimizerChoice { OPTIMIZER_NONE, OPTIMIZER_ISL };

static cl::opt<PassPositionChoice> PassPosition(
    "polly-position", cl::desc("Where to run polly in the pass pipeline"),
    cl::values(
        clEnumValN(POSITION_EARLY, "early", "Before everything"),
        clEnumValN(POSITION_AFTER_LOOPOPT, "after-loopopt",
                   "After the loop optimizer (but within the inline cycle)"),
        clEnumValN(POSITION_BEFORE_VECTORIZER, "before-vectorizer",
                   "Right before the vectorizer"),
        clEnumValEnd),
    cl::Hidden, cl::init(POSITION_EARLY), cl::ZeroOrMore,
    cl::cat(PollyCategory));

static cl::opt<OptimizerChoice> Optimizer(
    "polly-optimizer", cl::desc("Select the scheduling optimizer"),
    cl::values(clEnumValN(OPTIMIZER_NONE, "none", "No optimizer"),
               clEnumValN(OPTIMIZER_ISL, "isl", "The isl scheduling optimizer"),
               clEnumValEnd),
    cl::Hidden, cl::init(OPTIMIZER_ISL), cl::ZeroOrMore,
    cl::cat(PollyCategory));

enum CodeGenChoice { CODEGEN_ISL, CODEGEN_NONE };
static cl::opt<CodeGenChoice> CodeGenerator(
    "polly-code-generator", cl::desc("Select the code generator"),
    cl::values(clEnumValN(CODEGEN_ISL, "isl", "isl code generator"),
               clEnumValN(CODEGEN_NONE, "none", "no code generation"),
               clEnumValEnd),
    cl::Hidden, cl::init(CODEGEN_ISL), cl::ZeroOrMore, cl::cat(PollyCategory));

VectorizerChoice polly::PollyVectorizerChoice;
static cl::opt<polly::VectorizerChoice, true> Vectorizer(
    "polly-vectorizer", cl::desc("Select the vectorization strategy"),
    cl::values(
        clEnumValN(polly::VECTORIZER_NONE, "none", "No Vectorization"),
        clEnumValN(polly::VECTORIZER_POLLY, "polly",
                   "Polly internal vectorizer"),
        clEnumValN(polly::VECTORIZER_STRIPMINE, "stripmine",
                   "Strip-mine outer loops for the loop-vectorizer to trigger"),
        clEnumValEnd),
    cl::location(PollyVectorizerChoice), cl::init(polly::VECTORIZER_NONE),
    cl::ZeroOrMore, cl::cat(PollyCategory));

static cl::opt<bool> ImportJScop(
    "polly-import",
    cl::desc("Export the polyhedral description of the detected Scops"),
    cl::Hidden, cl::init(false), cl::ZeroOrMore, cl::cat(PollyCategory));

static cl::opt<bool> ExportJScop(
    "polly-export",
    cl::desc("Export the polyhedral description of the detected Scops"),
    cl::Hidden, cl::init(false), cl::ZeroOrMore, cl::cat(PollyCategory));

static cl::opt<bool> DeadCodeElim("polly-run-dce",
                                  cl::desc("Run the dead code elimination"),
                                  cl::Hidden, cl::init(false), cl::ZeroOrMore,
                                  cl::cat(PollyCategory));

static cl::opt<bool> PollyViewer(
    "polly-show",
    cl::desc("Highlight the code regions that will be optimized in a "
             "(CFG BBs and LLVM-IR instructions)"),
    cl::init(false), cl::ZeroOrMore, cl::cat(PollyCategory));

static cl::opt<bool> PollyOnlyViewer(
    "polly-show-only",
    cl::desc("Highlight the code regions that will be optimized in "
             "a (CFG only BBs)"),
    cl::init(false), cl::cat(PollyCategory));

static cl::opt<bool>
    PollyPrinter("polly-dot", cl::desc("Enable the Polly DOT printer in -O3"),
                 cl::Hidden, cl::value_desc("Run the Polly DOT printer at -O3"),
                 cl::init(false), cl::cat(PollyCategory));

static cl::opt<bool> PollyOnlyPrinter(
    "polly-dot-only",
    cl::desc("Enable the Polly DOT printer in -O3 (no BB content)"), cl::Hidden,
    cl::value_desc("Run the Polly DOT printer at -O3 (no BB content"),
    cl::init(false), cl::cat(PollyCategory));

static cl::opt<bool>
    CFGPrinter("polly-view-cfg",
               cl::desc("Show the Polly CFG right after code generation"),
               cl::Hidden, cl::init(false), cl::cat(PollyCategory));

namespace polly {
void initializePollyPasses(PassRegistry &Registry) {
  initializeCodeGenerationPass(Registry);
  initializeCodePreparationPass(Registry);
  initializeDeadCodeElimPass(Registry);
  initializeDependenceInfoPass(Registry);
  initializeJSONExporterPass(Registry);
  initializeJSONImporterPass(Registry);
  initializeIslAstInfoPass(Registry);
  initializeIslScheduleOptimizerPass(Registry);
  initializePollyCanonicalizePass(Registry);
  initializeScopDetectionPass(Registry);
  initializeScopInfoRegionPassPass(Registry);
  initializeCodegenCleanupPass(Registry);
}

/// @brief Register Polly passes such that they form a polyhedral optimizer.
///
/// The individual Polly passes are registered in the pass manager such that
/// they form a full polyhedral optimizer. The flow of the optimizer starts with
/// a set of preparing transformations that canonicalize the LLVM-IR such that
/// the LLVM-IR is easier for us to understand and to optimizes. On the
/// canonicalized LLVM-IR we first run the ScopDetection pass, which detects
/// static control flow regions. Those regions are then translated by the
/// ScopInfo pass into a polyhedral representation. As a next step, a scheduling
/// optimizer is run on the polyhedral representation and finally the optimized
/// polyhedral representation is code generated back to LLVM-IR.
///
/// Besides this core functionality, we optionally schedule passes that provide
/// a graphical view of the scops (Polly[Only]Viewer, Polly[Only]Printer), that
/// allow the export/import of the polyhedral representation
/// (JSCON[Exporter|Importer]) or that show the cfg after code generation.
///
/// For certain parts of the Polly optimizer, several alternatives are provided:
///
/// As scheduling optimizer we support the isl scheduling optimizer
/// (http://freecode.com/projects/isl).
/// It is also possible to run Polly with no optimizer. This mode is mainly
/// provided to analyze the run and compile time changes caused by the
/// scheduling optimizer.
///
/// Polly supports the isl internal code generator.
void registerPollyPasses(llvm::legacy::PassManagerBase &PM) {
  PM.add(polly::createScopDetectionPass());

  if (PollyDetectOnly)
    return;

  if (PollyViewer)
    PM.add(polly::createDOTViewerPass());
  if (PollyOnlyViewer)
    PM.add(polly::createDOTOnlyViewerPass());
  if (PollyPrinter)
    PM.add(polly::createDOTPrinterPass());
  if (PollyOnlyPrinter)
    PM.add(polly::createDOTOnlyPrinterPass());

  PM.add(polly::createScopInfoRegionPassPass());

  if (ImportJScop)
    PM.add(polly::createJSONImporterPass());

  if (DeadCodeElim)
    PM.add(polly::createDeadCodeElimPass());

  switch (Optimizer) {
  case OPTIMIZER_NONE:
    break; /* Do nothing */

  case OPTIMIZER_ISL:
    PM.add(polly::createIslScheduleOptimizerPass());
    break;
  }

  if (ExportJScop)
    PM.add(polly::createJSONExporterPass());

  switch (CodeGenerator) {
  case CODEGEN_ISL:
    PM.add(polly::createCodeGenerationPass());
    break;
  case CODEGEN_NONE:
    break;
  }

  // FIXME: This dummy ModulePass keeps some programs from miscompiling,
  // probably some not correctly preserved analyses. It acts as a barrier to
  // force all analysis results to be recomputed.
  PM.add(createBarrierNoopPass());

  if (CFGPrinter)
    PM.add(llvm::createCFGPrinterPass());
}

static bool shouldEnablePolly() {
  if (PollyOnlyPrinter || PollyPrinter || PollyOnlyViewer || PollyViewer)
    PollyTrackFailures = true;

  if (PollyOnlyPrinter || PollyPrinter || PollyOnlyViewer || PollyViewer ||
      ExportJScop || ImportJScop)
    PollyEnabled = true;

  return PollyEnabled;
}

static void
registerPollyEarlyAsPossiblePasses(const llvm::PassManagerBuilder &Builder,
                                   llvm::legacy::PassManagerBase &PM) {
  if (!polly::shouldEnablePolly())
    return;

  if (PassPosition != POSITION_EARLY)
    return;

  registerCanonicalicationPasses(PM);
  polly::registerPollyPasses(PM);
}

static void
registerPollyLoopOptimizerEndPasses(const llvm::PassManagerBuilder &Builder,
                                    llvm::legacy::PassManagerBase &PM) {
  if (!polly::shouldEnablePolly())
    return;

  if (PassPosition != POSITION_AFTER_LOOPOPT)
    return;

  PM.add(polly::createCodePreparationPass());
  polly::registerPollyPasses(PM);
  PM.add(createCodegenCleanupPass());
}

static void
registerPollyScalarOptimizerLatePasses(const llvm::PassManagerBuilder &Builder,
                                       llvm::legacy::PassManagerBase &PM) {
  if (!polly::shouldEnablePolly())
    return;

  if (PassPosition != POSITION_BEFORE_VECTORIZER)
    return;

  PM.add(polly::createCodePreparationPass());
  polly::registerPollyPasses(PM);
  PM.add(createCodegenCleanupPass());
}

/// @brief Register Polly to be available as an optimizer
///
///
/// We can currently run Polly at three different points int the pass manager.
/// a) very early, b) after the canonicalizing loop transformations and c) right
/// before the vectorizer.
///
/// The default is currently a), to register Polly such that it runs as early as
/// possible. This has several implications:
///
///   1) We need to schedule more canonicalization passes
///
///   As nothing is run before Polly, it is necessary to run a set of preparing
///   transformations before Polly to canonicalize the LLVM-IR and to allow
///   Polly to detect and understand the code.
///
///   2) LICM and LoopIdiom pass have not yet been run
///
///   Loop invariant code motion as well as the loop idiom recognition pass make
///   it more difficult for Polly to transform code. LICM may introduce
///   additional data dependences that are hard to eliminate and the loop idiom
///   recognition pass may introduce calls to memset that we currently do not
///   understand. By running Polly early enough (meaning before these passes) we
///   avoid difficulties that may be introduced by these passes.
///
///   3) We get the full -O3 optimization sequence after Polly
///
///   The LLVM-IR that is generated by Polly has been optimized on a high level,
///   but it may be rather inefficient on the lower/scalar level. By scheduling
///   Polly before all other passes, we have the full sequence of -O3
///   optimizations behind us, such that inefficiencies on the low level can
///   be optimized away.
///
/// We are currently evaluating the benefit or running Polly at position b) or
/// c). b) is likely to early as it interacts with the inliner. c) is nice
/// as everything is fully inlined and canonicalized, but we need to be able
/// to handle LICMed code to make it useful.
static llvm::RegisterStandardPasses RegisterPollyOptimizerEarly(
    llvm::PassManagerBuilder::EP_ModuleOptimizerEarly,
    registerPollyEarlyAsPossiblePasses);

static llvm::RegisterStandardPasses
    RegisterPollyOptimizerLoopEnd(llvm::PassManagerBuilder::EP_LoopOptimizerEnd,
                                  registerPollyLoopOptimizerEndPasses);

static llvm::RegisterStandardPasses RegisterPollyOptimizerScalarLate(
    llvm::PassManagerBuilder::EP_VectorizerStart,
    registerPollyScalarOptimizerLatePasses);
}