lib/CodeGen/FuncletLayout.cpp

   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 using namespace llvm;
  18
  19 #define DEBUG_TYPE "funclet-layout"
  20
  21 namespace {
  22 class FuncletLayout : public MachineFunctionPass {
  23 public:
  24   static char ID; // Pass identification, replacement for typeid
  25   FuncletLayout() : MachineFunctionPass(ID) {
  26     initializeFuncletLayoutPass(*PassRegistry::getPassRegistry());
  27   }
  28
  29   bool runOnMachineFunction(MachineFunction &F) override;
  30   MachineFunctionProperties getRequiredProperties() const override {
  31     return MachineFunctionProperties().set(
  32         MachineFunctionProperties::Property::NoVRegs);
  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
  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 }