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().setNoVRegs();
33 }
34 };
35 }
36
37 char FuncletLayout::ID = 0;
38 char &llvm::FuncletLayoutID = FuncletLayout::ID;
39 INITIALIZE_PASS(FuncletLayout, DEBUG_TYPE,
40 "Contiguously Lay Out Funclets", false, false)
41
runOnMachineFunction(MachineFunction & F)42 bool 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(F);
48 if (FuncletMembership.empty())
49 return false;
50
51 F.sort([&](MachineBasicBlock &X, MachineBasicBlock &Y) {
52 auto FuncletX = FuncletMembership.find(&X);
53 auto FuncletY = FuncletMembership.find(&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