1//===-- FuncletLayout.cpp - Contiguously lay out funclets -----------------===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9// This file implements basic block placement transformations which result in
10// funclets being contiguous.
11//
12//===----------------------------------------------------------------------===//
13#include "llvm/CodeGen/Analysis.h"
14#include "llvm/CodeGen/MachineFunction.h"
15#include "llvm/CodeGen/MachineFunctionPass.h"
16#include "llvm/CodeGen/Passes.h"
17#include "llvm/InitializePasses.h"
18using namespace llvm;
19
20#define DEBUG_TYPE "funclet-layout"
21
22namespace {
23class FuncletLayout : public MachineFunctionPass {
24public:
25  static char ID; // Pass identification, replacement for typeid
26  FuncletLayout() : MachineFunctionPass(ID) {
27    initializeFuncletLayoutPass(*PassRegistry::getPassRegistry());
28  }
29
30  bool runOnMachineFunction(MachineFunction &F) override;
31  MachineFunctionProperties getRequiredProperties() const override {
32    return MachineFunctionProperties().set(
33        MachineFunctionProperties::Property::NoVRegs);
34  }
35};
36}
37
38char FuncletLayout::ID = 0;
39char &llvm::FuncletLayoutID = FuncletLayout::ID;
40INITIALIZE_PASS(FuncletLayout, DEBUG_TYPE,
41                "Contiguously Lay Out Funclets", false, false)
42
43bool FuncletLayout::runOnMachineFunction(MachineFunction &F) {
44  // Even though this gets information from getEHScopeMembership(), this pass is
45  // only necessary for funclet-based EH personalities, in which these EH scopes
46  // are outlined at the end.
47  DenseMap<const MachineBasicBlock *, int> FuncletMembership =
48      getEHScopeMembership(F);
49  if (FuncletMembership.empty())
50    return false;
51
52  F.sort([&](MachineBasicBlock &X, MachineBasicBlock &Y) {
53    auto FuncletX = FuncletMembership.find(&X);
54    auto FuncletY = FuncletMembership.find(&Y);
55    assert(FuncletX != FuncletMembership.end());
56    assert(FuncletY != FuncletMembership.end());
57    return FuncletX->second < FuncletY->second;
58  });
59
60  // Conservatively assume we changed something.
61  return true;
62}
63