1//===-- StackMapLivenessAnalysis.cpp - StackMap live Out Analysis ----------===//
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 the StackMap Liveness analysis pass. The pass calculates
11// the liveness for each basic block in a function and attaches the register
12// live-out information to a stackmap or patchpoint intrinsic if present.
13//
14//===----------------------------------------------------------------------===//
15
16#include "llvm/ADT/Statistic.h"
17#include "llvm/CodeGen/LivePhysRegs.h"
18#include "llvm/CodeGen/MachineFrameInfo.h"
19#include "llvm/CodeGen/MachineFunction.h"
20#include "llvm/CodeGen/MachineFunctionAnalysis.h"
21#include "llvm/CodeGen/MachineFunctionPass.h"
22#include "llvm/CodeGen/Passes.h"
23#include "llvm/Support/CommandLine.h"
24#include "llvm/Support/Debug.h"
25#include "llvm/Support/raw_ostream.h"
26#include "llvm/Target/TargetSubtargetInfo.h"
27
28using namespace llvm;
29
30#define DEBUG_TYPE "stackmaps"
31
32static cl::opt<bool> EnablePatchPointLiveness(
33    "enable-patchpoint-liveness", cl::Hidden, cl::init(true),
34    cl::desc("Enable PatchPoint Liveness Analysis Pass"));
35
36STATISTIC(NumStackMapFuncVisited, "Number of functions visited");
37STATISTIC(NumStackMapFuncSkipped, "Number of functions skipped");
38STATISTIC(NumBBsVisited,          "Number of basic blocks visited");
39STATISTIC(NumBBsHaveNoStackmap,   "Number of basic blocks with no stackmap");
40STATISTIC(NumStackMaps,           "Number of StackMaps visited");
41
42namespace {
43/// \brief This pass calculates the liveness information for each basic block in
44/// a function and attaches the register live-out information to a patchpoint
45/// intrinsic if present.
46///
47/// This pass can be disabled via the -enable-patchpoint-liveness=false flag.
48/// The pass skips functions that don't have any patchpoint intrinsics. The
49/// information provided by this pass is optional and not required by the
50/// aformentioned intrinsic to function.
51class StackMapLiveness : public MachineFunctionPass {
52  const TargetRegisterInfo *TRI;
53  LivePhysRegs LiveRegs;
54
55public:
56  static char ID;
57
58  /// \brief Default construct and initialize the pass.
59  StackMapLiveness();
60
61  /// \brief Tell the pass manager which passes we depend on and what
62  /// information we preserve.
63  void getAnalysisUsage(AnalysisUsage &AU) const override;
64
65  /// \brief Calculate the liveness information for the given machine function.
66  bool runOnMachineFunction(MachineFunction &MF) override;
67
68private:
69  /// \brief Performs the actual liveness calculation for the function.
70  bool calculateLiveness(MachineFunction &MF);
71
72  /// \brief Add the current register live set to the instruction.
73  void addLiveOutSetToMI(MachineFunction &MF, MachineInstr &MI);
74
75  /// \brief Create a register mask and initialize it with the registers from
76  /// the register live set.
77  uint32_t *createRegisterMask(MachineFunction &MF) const;
78};
79} // namespace
80
81char StackMapLiveness::ID = 0;
82char &llvm::StackMapLivenessID = StackMapLiveness::ID;
83INITIALIZE_PASS(StackMapLiveness, "stackmap-liveness",
84                "StackMap Liveness Analysis", false, false)
85
86/// Default construct and initialize the pass.
87StackMapLiveness::StackMapLiveness() : MachineFunctionPass(ID) {
88  initializeStackMapLivenessPass(*PassRegistry::getPassRegistry());
89}
90
91/// Tell the pass manager which passes we depend on and what information we
92/// preserve.
93void StackMapLiveness::getAnalysisUsage(AnalysisUsage &AU) const {
94  // We preserve all information.
95  AU.setPreservesAll();
96  AU.setPreservesCFG();
97  MachineFunctionPass::getAnalysisUsage(AU);
98}
99
100/// Calculate the liveness information for the given machine function.
101bool StackMapLiveness::runOnMachineFunction(MachineFunction &MF) {
102  if (!EnablePatchPointLiveness)
103    return false;
104
105  DEBUG(dbgs() << "********** COMPUTING STACKMAP LIVENESS: " << MF.getName()
106               << " **********\n");
107  TRI = MF.getSubtarget().getRegisterInfo();
108  ++NumStackMapFuncVisited;
109
110  // Skip this function if there are no patchpoints to process.
111  if (!MF.getFrameInfo()->hasPatchPoint()) {
112    ++NumStackMapFuncSkipped;
113    return false;
114  }
115  return calculateLiveness(MF);
116}
117
118/// Performs the actual liveness calculation for the function.
119bool StackMapLiveness::calculateLiveness(MachineFunction &MF) {
120  bool HasChanged = false;
121  // For all basic blocks in the function.
122  for (auto &MBB : MF) {
123    DEBUG(dbgs() << "****** BB " << MBB.getName() << " ******\n");
124    LiveRegs.init(TRI);
125    LiveRegs.addLiveOuts(&MBB);
126    bool HasStackMap = false;
127    // Reverse iterate over all instructions and add the current live register
128    // set to an instruction if we encounter a patchpoint instruction.
129    for (auto I = MBB.rbegin(), E = MBB.rend(); I != E; ++I) {
130      if (I->getOpcode() == TargetOpcode::PATCHPOINT) {
131        addLiveOutSetToMI(MF, *I);
132        HasChanged = true;
133        HasStackMap = true;
134        ++NumStackMaps;
135      }
136      DEBUG(dbgs() << "   " << LiveRegs << "   " << *I);
137      LiveRegs.stepBackward(*I);
138    }
139    ++NumBBsVisited;
140    if (!HasStackMap)
141      ++NumBBsHaveNoStackmap;
142  }
143  return HasChanged;
144}
145
146/// Add the current register live set to the instruction.
147void StackMapLiveness::addLiveOutSetToMI(MachineFunction &MF,
148                                         MachineInstr &MI) {
149  uint32_t *Mask = createRegisterMask(MF);
150  MachineOperand MO = MachineOperand::CreateRegLiveOut(Mask);
151  MI.addOperand(MF, MO);
152}
153
154/// Create a register mask and initialize it with the registers from the
155/// register live set.
156uint32_t *StackMapLiveness::createRegisterMask(MachineFunction &MF) const {
157  // The mask is owned and cleaned up by the Machine Function.
158  uint32_t *Mask = MF.allocateRegisterMask(TRI->getNumRegs());
159  for (auto Reg : LiveRegs)
160    Mask[Reg / 32] |= 1U << (Reg % 32);
161
162  // Give the target a chance to adjust the mask.
163  TRI->adjustStackMapLiveOutMask(Mask);
164
165  return Mask;
166}
167