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
65 /// \brief Calculate the liveness information for the given machine function.
66 bool runOnMachineFunction(MachineFunction &MF) override;
67
68 private:
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
81 char StackMapLiveness::ID = 0;
82 char &llvm::StackMapLivenessID = StackMapLiveness::ID;
83 INITIALIZE_PASS(StackMapLiveness, "stackmap-liveness",
84 "StackMap Liveness Analysis", false, false)
85
86 /// Default construct and initialize the pass.
StackMapLiveness()87 StackMapLiveness::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.
getAnalysisUsage(AnalysisUsage & AU) const93 void 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.
runOnMachineFunction(MachineFunction & MF)101 bool 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.
calculateLiveness(MachineFunction & MF)119 bool 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.
addLiveOutSetToMI(MachineFunction & MF,MachineInstr & MI)147 void 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.
createRegisterMask(MachineFunction & MF) const156 uint32_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