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"
18 using namespace llvm;
19
20 #define DEBUG_TYPE "funclet-layout"
21
22 namespace {
23 class FuncletLayout : public MachineFunctionPass {
24 public:
25 static char ID; // Pass identification, replacement for typeid
FuncletLayout()26 FuncletLayout() : MachineFunctionPass(ID) {
27 initializeFuncletLayoutPass(*PassRegistry::getPassRegistry());
28 }
29
30 bool runOnMachineFunction(MachineFunction &F) override;
getRequiredProperties() const31 MachineFunctionProperties getRequiredProperties() const override {
32 return MachineFunctionProperties().set(
33 MachineFunctionProperties::Property::NoVRegs);
34 }
35 };
36 }
37
38 char FuncletLayout::ID = 0;
39 char &llvm::FuncletLayoutID = FuncletLayout::ID;
40 INITIALIZE_PASS(FuncletLayout, DEBUG_TYPE,
41 "Contiguously Lay Out Funclets", false, false)
42
runOnMachineFunction(MachineFunction & F)43 bool 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