StackMapLivenessAnalysis.cpp revision 274955 
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/MachineFrameInfo.h"
18#include "llvm/CodeGen/MachineFunction.h"
19#include "llvm/CodeGen/MachineFunctionAnalysis.h"
20#include "llvm/CodeGen/Passes.h"
21#include "llvm/CodeGen/StackMapLivenessAnalysis.h"
22#include "llvm/Support/CommandLine.h"
23#include "llvm/Support/Debug.h"
24
25
26using namespace llvm;
27
28#define DEBUG_TYPE "stackmaps"
29
30namespace llvm {
31cl::opt<bool> EnablePatchPointLiveness("enable-patchpoint-liveness",
32  cl::Hidden, cl::init(true),
33  cl::desc("Enable PatchPoint Liveness Analysis Pass"));
34}
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
42char StackMapLiveness::ID = 0;
43char &llvm::StackMapLivenessID = StackMapLiveness::ID;
44INITIALIZE_PASS(StackMapLiveness, "stackmap-liveness",
45                "StackMap Liveness Analysis", false, false)
46
47/// Default construct and initialize the pass.
48StackMapLiveness::StackMapLiveness() : MachineFunctionPass(ID) {
49  initializeStackMapLivenessPass(*PassRegistry::getPassRegistry());
50}
51
52/// Tell the pass manager which passes we depend on and what information we
53/// preserve.
54void StackMapLiveness::getAnalysisUsage(AnalysisUsage &AU) const {
55  // We preserve all information.
56  AU.setPreservesAll();
57  AU.setPreservesCFG();
58  // Default dependencie for all MachineFunction passes.
59  AU.addRequired<MachineFunctionAnalysis>();
60}
61
62/// Calculate the liveness information for the given machine function.
63bool StackMapLiveness::runOnMachineFunction(MachineFunction &_MF) {
64  if (!EnablePatchPointLiveness)
65    return false;
66
67  DEBUG(dbgs() << "********** COMPUTING STACKMAP LIVENESS: "
68               << _MF.getName() << " **********\n");
69  MF = &_MF;
70  TRI = MF->getTarget().getRegisterInfo();
71  ++NumStackMapFuncVisited;
72
73  // Skip this function if there are no patchpoints to process.
74  if (!MF->getFrameInfo()->hasPatchPoint()) {
75    ++NumStackMapFuncSkipped;
76    return false;
77  }
78  return calculateLiveness();
79}
80
81/// Performs the actual liveness calculation for the function.
82bool StackMapLiveness::calculateLiveness() {
83  bool HasChanged = false;
84  // For all basic blocks in the function.
85  for (MachineFunction::iterator MBBI = MF->begin(), MBBE = MF->end();
86       MBBI != MBBE; ++MBBI) {
87    DEBUG(dbgs() << "****** BB " << MBBI->getName() << " ******\n");
88    LiveRegs.init(TRI);
89    LiveRegs.addLiveOuts(MBBI);
90    bool HasStackMap = false;
91    // Reverse iterate over all instructions and add the current live register
92    // set to an instruction if we encounter a patchpoint instruction.
93    for (MachineBasicBlock::reverse_iterator I = MBBI->rbegin(),
94         E = MBBI->rend(); I != E; ++I) {
95      if (I->getOpcode() == TargetOpcode::PATCHPOINT) {
96        addLiveOutSetToMI(*I);
97        HasChanged = true;
98        HasStackMap = true;
99        ++NumStackMaps;
100      }
101      DEBUG(dbgs() << "   " << LiveRegs << "   " << *I);
102      LiveRegs.stepBackward(*I);
103    }
104    ++NumBBsVisited;
105    if (!HasStackMap)
106      ++NumBBsHaveNoStackmap;
107  }
108  return HasChanged;
109}
110
111/// Add the current register live set to the instruction.
112void StackMapLiveness::addLiveOutSetToMI(MachineInstr &MI) {
113  uint32_t *Mask = createRegisterMask();
114  MachineOperand MO = MachineOperand::CreateRegLiveOut(Mask);
115  MI.addOperand(*MF, MO);
116}
117
118/// Create a register mask and initialize it with the registers from the
119/// register live set.
120uint32_t *StackMapLiveness::createRegisterMask() const {
121  // The mask is owned and cleaned up by the Machine Function.
122  uint32_t *Mask = MF->allocateRegisterMask(TRI->getNumRegs());
123  for (LivePhysRegs::const_iterator RI = LiveRegs.begin(), RE = LiveRegs.end();
124       RI != RE; ++RI)
125    Mask[*RI / 32] |= 1U << (*RI % 32);
126  return Mask;
127}
128