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().setNoVRegs();
33 }
34};
35}
36
37char FuncletLayout::ID = 0;
38char &llvm::FuncletLayoutID = FuncletLayout::ID;
39INITIALIZE_PASS(FuncletLayout, DEBUG_TYPE,
40 "Contiguously Lay Out Funclets", false, false)
41
42bool FuncletLayout::runOnMachineFunction(MachineFunction &F) {
43 // Even though this gets information from getEHScopeMembership(), this pass is
44 // only necessary for funclet-based EH personalities, in which these EH scopes
45 // are outlined at the end.
46 DenseMap<const MachineBasicBlock *, int> FuncletMembership =
47 getEHScopeMembership(MF: F);
48 if (FuncletMembership.empty())
49 return false;
50
51 F.sort(comp: [&](MachineBasicBlock &X, MachineBasicBlock &Y) {
52 auto FuncletX = FuncletMembership.find(Val: &X);
53 auto FuncletY = FuncletMembership.find(Val: &Y);
54 assert(FuncletX != FuncletMembership.end());
55 assert(FuncletY != FuncletMembership.end());
56 return FuncletX->second < FuncletY->second;
57 });
58
59 // Conservatively assume we changed something.
60 return true;
61}
62