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
28 using namespace llvm;
29
30 #define DEBUG_TYPE "stackmaps"
31
32 static cl::opt<bool> EnablePatchPointLiveness(
33 "enable-patchpoint-liveness", cl::Hidden, cl::init(true),
34 cl::desc("Enable PatchPoint Liveness Analysis Pass"));
35
36 STATISTIC(NumStackMapFuncVisited, "Number of functions visited");
37 STATISTIC(NumStackMapFuncSkipped, "Number of functions skipped");
38 STATISTIC(NumBBsVisited, "Number of basic blocks visited");
39 STATISTIC(NumBBsHaveNoStackmap, "Number of basic blocks with no stackmap");
40 STATISTIC(NumStackMaps, "Number of StackMaps visited");
41
42 namespace {
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.
51 class StackMapLiveness : public MachineFunctionPass {
52 const TargetRegisterInfo *TRI;
53 LivePhysRegs LiveRegs;
54
55 public:
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
getRequiredProperties() const65 MachineFunctionProperties getRequiredProperties() const override {
66 return MachineFunctionProperties().set(
67 MachineFunctionProperties::Property::AllVRegsAllocated);
68 }
69
70 /// \brief Calculate the liveness information for the given machine function.
71 bool runOnMachineFunction(MachineFunction &MF) override;
72
73 private:
74 /// \brief Performs the actual liveness calculation for the function.
75 bool calculateLiveness(MachineFunction &MF);
76
77 /// \brief Add the current register live set to the instruction.
78 void addLiveOutSetToMI(MachineFunction &MF, MachineInstr &MI);
79
80 /// \brief Create a register mask and initialize it with the registers from
81 /// the register live set.
82 uint32_t *createRegisterMask(MachineFunction &MF) const;
83 };
84 } // namespace
85
86 char StackMapLiveness::ID = 0;
87 char &llvm::StackMapLivenessID = StackMapLiveness::ID;
88 INITIALIZE_PASS(StackMapLiveness, "stackmap-liveness",
89 "StackMap Liveness Analysis", false, false)
90
91 /// Default construct and initialize the pass.
StackMapLiveness()92 StackMapLiveness::StackMapLiveness() : MachineFunctionPass(ID) {
93 initializeStackMapLivenessPass(*PassRegistry::getPassRegistry());
94 }
95
96 /// Tell the pass manager which passes we depend on and what information we
97 /// preserve.
getAnalysisUsage(AnalysisUsage & AU) const98 void StackMapLiveness::getAnalysisUsage(AnalysisUsage &AU) const {
99 // We preserve all information.
100 AU.setPreservesAll();
101 AU.setPreservesCFG();
102 MachineFunctionPass::getAnalysisUsage(AU);
103 }
104
105 /// Calculate the liveness information for the given machine function.
runOnMachineFunction(MachineFunction & MF)106 bool StackMapLiveness::runOnMachineFunction(MachineFunction &MF) {
107 if (!EnablePatchPointLiveness)
108 return false;
109
110 DEBUG(dbgs() << "********** COMPUTING STACKMAP LIVENESS: " << MF.getName()
111 << " **********\n");
112 TRI = MF.getSubtarget().getRegisterInfo();
113 ++NumStackMapFuncVisited;
114
115 // Skip this function if there are no patchpoints to process.
116 if (!MF.getFrameInfo()->hasPatchPoint()) {
117 ++NumStackMapFuncSkipped;
118 return false;
119 }
120 return calculateLiveness(MF);
121 }
122
123 /// Performs the actual liveness calculation for the function.
calculateLiveness(MachineFunction & MF)124 bool StackMapLiveness::calculateLiveness(MachineFunction &MF) {
125 bool HasChanged = false;
126 // For all basic blocks in the function.
127 for (auto &MBB : MF) {
128 DEBUG(dbgs() << "****** BB " << MBB.getName() << " ******\n");
129 LiveRegs.init(TRI);
130 // FIXME: This should probably be addLiveOuts().
131 LiveRegs.addLiveOutsNoPristines(MBB);
132 bool HasStackMap = false;
133 // Reverse iterate over all instructions and add the current live register
134 // set to an instruction if we encounter a patchpoint instruction.
135 for (auto I = MBB.rbegin(), E = MBB.rend(); I != E; ++I) {
136 if (I->getOpcode() == TargetOpcode::PATCHPOINT) {
137 addLiveOutSetToMI(MF, *I);
138 HasChanged = true;
139 HasStackMap = true;
140 ++NumStackMaps;
141 }
142 DEBUG(dbgs() << " " << LiveRegs << " " << *I);
143 LiveRegs.stepBackward(*I);
144 }
145 ++NumBBsVisited;
146 if (!HasStackMap)
147 ++NumBBsHaveNoStackmap;
148 }
149 return HasChanged;
150 }
151
152 /// Add the current register live set to the instruction.
addLiveOutSetToMI(MachineFunction & MF,MachineInstr & MI)153 void StackMapLiveness::addLiveOutSetToMI(MachineFunction &MF,
154 MachineInstr &MI) {
155 uint32_t *Mask = createRegisterMask(MF);
156 MachineOperand MO = MachineOperand::CreateRegLiveOut(Mask);
157 MI.addOperand(MF, MO);
158 }
159
160 /// Create a register mask and initialize it with the registers from the
161 /// register live set.
createRegisterMask(MachineFunction & MF) const162 uint32_t *StackMapLiveness::createRegisterMask(MachineFunction &MF) const {
163 // The mask is owned and cleaned up by the Machine Function.
164 uint32_t *Mask = MF.allocateRegisterMask(TRI->getNumRegs());
165 for (auto Reg : LiveRegs)
166 Mask[Reg / 32] |= 1U << (Reg % 32);
167
168 // Give the target a chance to adjust the mask.
169 TRI->adjustStackMapLiveOutMask(Mask);
170
171 return Mask;
172 }
173