llvm/llvm/lib/CodeGen/IndirectBrExpandPass.cpp

//===- IndirectBrExpandPass.cpp - Expand indirectbr to switch -------------===//
//
// 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
//
//===----------------------------------------------------------------------===//
/// \file
///
/// Implements an expansion pass to turn `indirectbr` instructions in the IR
/// into `switch` instructions. This works by enumerating the basic blocks in
/// a dense range of integers, replacing each `blockaddr` constant with the
/// corresponding integer constant, and then building a switch that maps from
/// the integers to the actual blocks. All of the indirectbr instructions in the
/// function are redirected to this common switch.
///
/// While this is generically useful if a target is unable to codegen
/// `indirectbr` natively, it is primarily useful when there is some desire to
/// get the builtin non-jump-table lowering of a switch even when the input
/// source contained an explicit indirect branch construct.
///
/// Note that it doesn't make any sense to enable this pass unless a target also
/// disables jump-table lowering of switches. Doing that is likely to pessimize
/// the code.
///
//===----------------------------------------------------------------------===//

#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/Sequence.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/Analysis/DomTreeUpdater.h"
#include "llvm/CodeGen/IndirectBrExpand.h"
#include "llvm/CodeGen/TargetPassConfig.h"
#include "llvm/CodeGen/TargetSubtargetInfo.h"
#include "llvm/IR/BasicBlock.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/Dominators.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/Instructions.h"
#include "llvm/InitializePasses.h"
#include "llvm/Pass.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Target/TargetMachine.h"
#include <optional>

usingnamespacellvm;

#define DEBUG_TYPE …

namespace {

class IndirectBrExpandLegacyPass : public FunctionPass { … };

} // end anonymous namespace

static bool runImpl(Function &F, const TargetLowering *TLI,
                    DomTreeUpdater *DTU);

PreservedAnalyses IndirectBrExpandPass::run(Function &F,
                                            FunctionAnalysisManager &FAM) { … }

char IndirectBrExpandLegacyPass::ID = …;

INITIALIZE_PASS_BEGIN(IndirectBrExpandLegacyPass, DEBUG_TYPE,
                      "Expand indirectbr instructions", false, false)
INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
INITIALIZE_PASS_END(IndirectBrExpandLegacyPass, DEBUG_TYPE,
                    "Expand indirectbr instructions", false, false)

FunctionPass *llvm::createIndirectBrExpandPass() { … }

bool runImpl(Function &F, const TargetLowering *TLI, DomTreeUpdater *DTU) { … }

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