StackMapLivenessAnalysis.cpp revision 36b56886974eae4f9c5ebc96befd3e7bfe5de338 
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#define DEBUG_TYPE "stackmaps"
17#include "llvm/ADT/Statistic.h"
18#include "llvm/CodeGen/MachineFrameInfo.h"
19#include "llvm/CodeGen/MachineFunction.h"
20#include "llvm/CodeGen/MachineFunctionAnalysis.h"
21#include "llvm/CodeGen/Passes.h"
22#include "llvm/CodeGen/StackMapLivenessAnalysis.h"
23#include "llvm/Support/CommandLine.h"
24#include "llvm/Support/Debug.h"
25
26
27using namespace llvm;
28
29namespace llvm {
30cl::opt<bool> EnableStackMapLiveness("enable-stackmap-liveness",
31  cl::Hidden, cl::desc("Enable StackMap Liveness Analysis Pass"));
32cl::opt<bool> EnablePatchPointLiveness("enable-patchpoint-liveness",
33  cl::Hidden, 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  DEBUG(dbgs() << "********** COMPUTING STACKMAP LIVENESS: "
65               << _MF.getName() << " **********\n");
66  MF = &_MF;
67  TRI = MF->getTarget().getRegisterInfo();
68  ++NumStackMapFuncVisited;
69
70  // Skip this function if there are no stackmaps or patchpoints to process.
71  if (!((MF->getFrameInfo()->hasStackMap() && EnableStackMapLiveness) ||
72        (MF->getFrameInfo()->hasPatchPoint() && EnablePatchPointLiveness))) {
73    ++NumStackMapFuncSkipped;
74    return false;
75  }
76  return calculateLiveness();
77}
78
79/// Performs the actual liveness calculation for the function.
80bool StackMapLiveness::calculateLiveness() {
81  bool HasChanged = false;
82  // For all basic blocks in the function.
83  for (MachineFunction::iterator MBBI = MF->begin(), MBBE = MF->end();
84       MBBI != MBBE; ++MBBI) {
85    DEBUG(dbgs() << "****** BB " << MBBI->getName() << " ******\n");
86    LiveRegs.init(TRI);
87    LiveRegs.addLiveOuts(MBBI);
88    bool HasStackMap = false;
89    // Reverse iterate over all instructions and add the current live register
90    // set to an instruction if we encounter a stackmap or patchpoint
91    // instruction.
92    for (MachineBasicBlock::reverse_iterator I = MBBI->rbegin(),
93         E = MBBI->rend(); I != E; ++I) {
94      int Opc = I->getOpcode();
95      if ((EnableStackMapLiveness && (Opc == TargetOpcode::STACKMAP)) ||
96          (EnablePatchPointLiveness && (Opc == TargetOpcode::PATCHPOINT))) {
97        addLiveOutSetToMI(*I);
98        HasChanged = true;
99        HasStackMap = true;
100        ++NumStackMaps;
101      }
102      DEBUG(dbgs() << "   " << *I << "   " << LiveRegs);
103      LiveRegs.stepBackward(*I);
104    }
105    ++NumBBsVisited;
106    if (!HasStackMap)
107      ++NumBBsHaveNoStackmap;
108  }
109  return HasChanged;
110}
111
112/// Add the current register live set to the instruction.
113void StackMapLiveness::addLiveOutSetToMI(MachineInstr &MI) {
114  uint32_t *Mask = createRegisterMask();
115  MachineOperand MO = MachineOperand::CreateRegLiveOut(Mask);
116  MI.addOperand(*MF, MO);
117}
118
119/// Create a register mask and initialize it with the registers from the
120/// register live set.
121uint32_t *StackMapLiveness::createRegisterMask() const {
122  // The mask is owned and cleaned up by the Machine Function.
123  uint32_t *Mask = MF->allocateRegisterMask(TRI->getNumRegs());
124  for (LivePhysRegs::const_iterator RI = LiveRegs.begin(), RE = LiveRegs.end();
125       RI != RE; ++RI)
126    Mask[*RI / 32] |= 1U << (*RI % 32);
127  return Mask;
128}
129