SimplifyCFGPass.cpp | Explore in Territory

//===- SimplifyCFGPass.cpp - CFG Simplification 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 dead code elimination and basic block merging, along
// with a collection of other peephole control flow optimizations.  For example:
//
//   * Removes basic blocks with no predecessors.
//   * Merges a basic block into its predecessor if there is only one and the
//     predecessor only has one successor.
//   * Eliminates PHI nodes for basic blocks with a single predecessor.
//   * Eliminates a basic block that only contains an unconditional branch.
//   * Changes invoke instructions to nounwind functions to be calls.
//   * Change things like "if (x) if (y)" into "if (x&y)".
//   * etc..
//
//===----------------------------------------------------------------------===//

#include "llvm/ADT/MapVector.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/AssumptionCache.h"
#include "llvm/Analysis/CFG.h"
#include "llvm/Analysis/DomTreeUpdater.h"
#include "llvm/Analysis/GlobalsModRef.h"
#include "llvm/Analysis/TargetTransformInfo.h"
#include "llvm/IR/Attributes.h"
#include "llvm/IR/CFG.h"
#include "llvm/IR/DebugInfoMetadata.h"
#include "llvm/IR/Dominators.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/ValueHandle.h"
#include "llvm/InitializePasses.h"
#include "llvm/Pass.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Transforms/Scalar.h"
#include "llvm/Transforms/Scalar/SimplifyCFG.h"
#include "llvm/Transforms/Utils/Local.h"
#include "llvm/Transforms/Utils/SimplifyCFGOptions.h"
#include <utility>
usingnamespacellvm;

#define DEBUG_TYPE …

static cl::opt<unsigned> UserBonusInstThreshold(
    "bonus-inst-threshold", cl::Hidden, cl::init(1),
    cl::desc("Control the number of bonus instructions (default = 1)"));

static cl::opt<bool> UserKeepLoops(
    "keep-loops", cl::Hidden, cl::init(true),
    cl::desc("Preserve canonical loop structure (default = true)"));

static cl::opt<bool> UserSwitchRangeToICmp(
    "switch-range-to-icmp", cl::Hidden, cl::init(false),
    cl::desc(
        "Convert switches into an integer range comparison (default = false)"));

static cl::opt<bool> UserSwitchToLookup(
    "switch-to-lookup", cl::Hidden, cl::init(false),
    cl::desc("Convert switches to lookup tables (default = false)"));

static cl::opt<bool> UserForwardSwitchCond(
    "forward-switch-cond", cl::Hidden, cl::init(false),
    cl::desc("Forward switch condition to phi ops (default = false)"));

static cl::opt<bool> UserHoistCommonInsts(
    "hoist-common-insts", cl::Hidden, cl::init(false),
    cl::desc("hoist common instructions (default = false)"));

static cl::opt<bool> UserHoistLoadsStoresWithCondFaulting(
    "hoist-loads-stores-with-cond-faulting", cl::Hidden, cl::init(false),
    cl::desc("Hoist loads/stores if the target supports conditional faulting "
             "(default = false)"));

static cl::opt<bool> UserSinkCommonInsts(
    "sink-common-insts", cl::Hidden, cl::init(false),
    cl::desc("Sink common instructions (default = false)"));

static cl::opt<bool> UserSpeculateUnpredictables(
    "speculate-unpredictables", cl::Hidden, cl::init(false),
    cl::desc("Speculate unpredictable branches (default = false)"));

STATISTIC(NumSimpl, "Number of blocks simplified");

static bool
performBlockTailMerging(Function &F, ArrayRef<BasicBlock *> BBs,
                        std::vector<DominatorTree::UpdateType> *Updates) { … }

static bool tailMergeBlocksWithSimilarFunctionTerminators(Function &F,
                                                          DomTreeUpdater *DTU) { … }

/// Call SimplifyCFG on all the blocks in the function,
/// iterating until no more changes are made.
static bool iterativelySimplifyCFG(Function &F, const TargetTransformInfo &TTI,
                                   DomTreeUpdater *DTU,
                                   const SimplifyCFGOptions &Options) { … }

static bool simplifyFunctionCFGImpl(Function &F, const TargetTransformInfo &TTI,
                                    DominatorTree *DT,
                                    const SimplifyCFGOptions &Options) { … }

static bool simplifyFunctionCFG(Function &F, const TargetTransformInfo &TTI,
                                DominatorTree *DT,
                                const SimplifyCFGOptions &Options) { … }

// Command-line settings override compile-time settings.
static void applyCommandLineOverridesToOptions(SimplifyCFGOptions &Options) { … }

SimplifyCFGPass::SimplifyCFGPass() { … }

SimplifyCFGPass::SimplifyCFGPass(const SimplifyCFGOptions &Opts)
    : … { … }

void SimplifyCFGPass::printPipeline(
    raw_ostream &OS, function_ref<StringRef(StringRef)> MapClassName2PassName) { … }

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

namespace {
struct CFGSimplifyPass : public FunctionPass { … };
}

char CFGSimplifyPass::ID = …;
INITIALIZE_PASS_BEGIN(CFGSimplifyPass, "simplifycfg", "Simplify the CFG", false,
                      false)
INITIALIZE_PASS_DEPENDENCY(TargetTransformInfoWrapperPass)
INITIALIZE_PASS_DEPENDENCY(AssumptionCacheTracker)
INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
INITIALIZE_PASS_END(CFGSimplifyPass, "simplifycfg", "Simplify the CFG", false,
                    false)

// Public interface to the CFGSimplification pass
FunctionPass *
llvm::createCFGSimplificationPass(SimplifyCFGOptions Options,
                                  std::function<bool(const Function &)> Ftor) { … }
llvm/llvm/lib/Transforms/Scalar/SimplifyCFGPass.cpp
