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
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().set(
33         MachineFunctionProperties::Property::AllVRegsAllocated);
34   }
35 };
36 }
37 
38 char FuncletLayout::ID = 0;
39 char &llvm::FuncletLayoutID = FuncletLayout::ID;
40 INITIALIZE_PASS(FuncletLayout, "funclet-layout",
41                 "Contiguously Lay Out Funclets", false, false)
42 
runOnMachineFunction(MachineFunction & F)43 bool FuncletLayout::runOnMachineFunction(MachineFunction &F) {
44   DenseMap<const MachineBasicBlock *, int> FuncletMembership =
45       getFuncletMembership(F);
46   if (FuncletMembership.empty())
47     return false;
48 
49   F.sort([&](MachineBasicBlock &X, MachineBasicBlock &Y) {
50     auto FuncletX = FuncletMembership.find(&X);
51     auto FuncletY = FuncletMembership.find(&Y);
52     assert(FuncletX != FuncletMembership.end());
53     assert(FuncletY != FuncletMembership.end());
54     return FuncletX->second < FuncletY->second;
55   });
56 
57   // Conservatively assume we changed something.
58   return true;
59 }
60