lib/CodeGen/FuncletLayout.cpp

   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/Analysis.h"
  15 #include "llvm/CodeGen/MachineFunction.h"
  16 #include "llvm/CodeGen/MachineFunctionPass.h"
  17 #include "llvm/CodeGen/Passes.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
  26   FuncletLayout() : MachineFunctionPass(ID) {
  27     initializeFuncletLayoutPass(*PassRegistry::getPassRegistry());
  28   }
  29
  30   bool runOnMachineFunction(MachineFunction &F) override;
  31   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
  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 }