1//===-- FuncletLayout.cpp - Contiguously lay out funclets -----------------===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10// This file implements basic block placement transformations which result in
11// funclets being contiguous.
12//
13//===----------------------------------------------------------------------===//
14#include "llvm/CodeGen/Passes.h"
15#include "llvm/CodeGen/Analysis.h"
16#include "llvm/CodeGen/MachineFunction.h"
17#include "llvm/CodeGen/MachineFunctionPass.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};
32}
33
34char FuncletLayout::ID = 0;
35char &llvm::FuncletLayoutID = FuncletLayout::ID;
36INITIALIZE_PASS(FuncletLayout, "funclet-layout",
37                "Contiguously Lay Out Funclets", false, false)
38
39bool FuncletLayout::runOnMachineFunction(MachineFunction &F) {
40  DenseMap<const MachineBasicBlock *, int> FuncletMembership =
41      getFuncletMembership(F);
42  if (FuncletMembership.empty())
43    return false;
44
45  F.sort([&](MachineBasicBlock &X, MachineBasicBlock &Y) {
46    auto FuncletX = FuncletMembership.find(&X);
47    auto FuncletY = FuncletMembership.find(&Y);
48    assert(FuncletX != FuncletMembership.end());
49    assert(FuncletY != FuncletMembership.end());
50    return FuncletX->second < FuncletY->second;
51  });
52
53  // Conservatively assume we changed something.
54  return true;
55}
56