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 MachineFunction *MF;
53 const TargetRegisterInfo *TRI;
54 LivePhysRegs LiveRegs;
55
56 public:
57 static char ID;
58
59 /// \brief Default construct and initialize the pass.
60 StackMapLiveness();
61
62 /// \brief Tell the pass manager which passes we depend on and what
63 /// information we preserve.
64 void getAnalysisUsage(AnalysisUsage &AU) const override;
65
66 /// \brief Calculate the liveness information for the given machine function.
67 bool runOnMachineFunction(MachineFunction &MF) override;
68
69 private:
70 /// \brief Performs the actual liveness calculation for the function.
71 bool calculateLiveness();
72
73 /// \brief Add the current register live set to the instruction.
74 void addLiveOutSetToMI(MachineInstr &MI);
75
76 /// \brief Create a register mask and initialize it with the registers from
77 /// the register live set.
78 uint32_t *createRegisterMask() const;
79 };
80 } // namespace
81
82 char StackMapLiveness::ID = 0;
83 char &llvm::StackMapLivenessID = StackMapLiveness::ID;
84 INITIALIZE_PASS(StackMapLiveness, "stackmap-liveness",
85 "StackMap Liveness Analysis", false, false)
86
87 /// Default construct and initialize the pass.
StackMapLiveness()88 StackMapLiveness::StackMapLiveness() : MachineFunctionPass(ID) {
89 initializeStackMapLivenessPass(*PassRegistry::getPassRegistry());
90 }
91
92 /// Tell the pass manager which passes we depend on and what information we
93 /// preserve.
getAnalysisUsage(AnalysisUsage & AU) const94 void StackMapLiveness::getAnalysisUsage(AnalysisUsage &AU) const {
95 // We preserve all information.
96 AU.setPreservesAll();
97 AU.setPreservesCFG();
98 // Default dependencie for all MachineFunction passes.
99 AU.addRequired<MachineFunctionAnalysis>();
100 }
101
102 /// Calculate the liveness information for the given machine function.
runOnMachineFunction(MachineFunction & MF)103 bool StackMapLiveness::runOnMachineFunction(MachineFunction &MF) {
104 if (!EnablePatchPointLiveness)
105 return false;
106
107 DEBUG(dbgs() << "********** COMPUTING STACKMAP LIVENESS: " << MF.getName()
108 << " **********\n");
109 this->MF = &MF;
110 TRI = MF.getSubtarget().getRegisterInfo();
111 ++NumStackMapFuncVisited;
112
113 // Skip this function if there are no patchpoints to process.
114 if (!MF.getFrameInfo()->hasPatchPoint()) {
115 ++NumStackMapFuncSkipped;
116 return false;
117 }
118 return calculateLiveness();
119 }
120
121 /// Performs the actual liveness calculation for the function.
calculateLiveness()122 bool StackMapLiveness::calculateLiveness() {
123 bool HasChanged = false;
124 // For all basic blocks in the function.
125 for (MachineFunction::iterator MBBI = MF->begin(), MBBE = MF->end();
126 MBBI != MBBE; ++MBBI) {
127 DEBUG(dbgs() << "****** BB " << MBBI->getName() << " ******\n");
128 LiveRegs.init(TRI);
129 LiveRegs.addLiveOuts(MBBI);
130 bool HasStackMap = false;
131 // Reverse iterate over all instructions and add the current live register
132 // set to an instruction if we encounter a patchpoint instruction.
133 for (MachineBasicBlock::reverse_iterator I = MBBI->rbegin(),
134 E = MBBI->rend(); I != E; ++I) {
135 if (I->getOpcode() == TargetOpcode::PATCHPOINT) {
136 addLiveOutSetToMI(*I);
137 HasChanged = true;
138 HasStackMap = true;
139 ++NumStackMaps;
140 }
141 DEBUG(dbgs() << " " << LiveRegs << " " << *I);
142 LiveRegs.stepBackward(*I);
143 }
144 ++NumBBsVisited;
145 if (!HasStackMap)
146 ++NumBBsHaveNoStackmap;
147 }
148 return HasChanged;
149 }
150
151 /// Add the current register live set to the instruction.
addLiveOutSetToMI(MachineInstr & MI)152 void StackMapLiveness::addLiveOutSetToMI(MachineInstr &MI) {
153 uint32_t *Mask = createRegisterMask();
154 MachineOperand MO = MachineOperand::CreateRegLiveOut(Mask);
155 MI.addOperand(*MF, MO);
156 }
157
158 /// Create a register mask and initialize it with the registers from the
159 /// register live set.
createRegisterMask() const160 uint32_t *StackMapLiveness::createRegisterMask() const {
161 // The mask is owned and cleaned up by the Machine Function.
162 uint32_t *Mask = MF->allocateRegisterMask(TRI->getNumRegs());
163 for (LivePhysRegs::const_iterator RI = LiveRegs.begin(), RE = LiveRegs.end();
164 RI != RE; ++RI)
165 Mask[*RI / 32] |= 1U << (*RI % 32);
166
167 TRI->adjustStackMapLiveOutMask(Mask);
168 return Mask;
169 }
170