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/Passes.h"
  15 #include "llvm/CodeGen/Analysis.h"
  16 #include "llvm/CodeGen/MachineFunction.h"
  17 #include "llvm/CodeGen/MachineFunctionPass.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 };
  32 }
  33
  34 char FuncletLayout::ID = 0;
  35 char &llvm::FuncletLayoutID = FuncletLayout::ID;
  36 INITIALIZE_PASS(FuncletLayout, "funclet-layout",
  37                 "Contiguously Lay Out Funclets", false, false)
  38
  39 bool 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 }