1 //===------ LiveDebugValues.cpp - Tracking Debug Value MIs ----------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 /// This pass implements a data flow analysis that propagates debug location
11 /// information by inserting additional DBG_VALUE instructions into the machine
12 /// instruction stream. The pass internally builds debug location liveness
13 /// ranges to determine the points where additional DBG_VALUEs need to be
16 /// This is a separate pass from DbgValueHistoryCalculator to facilitate
17 /// testing and improve modularity.
19 //===----------------------------------------------------------------------===//
21 #include "llvm/ADT/Statistic.h"
22 #include "llvm/ADT/SmallVector.h"
23 #include "llvm/CodeGen/MachineFunction.h"
24 #include "llvm/CodeGen/MachineFunctionPass.h"
25 #include "llvm/CodeGen/MachineInstrBuilder.h"
26 #include "llvm/CodeGen/Passes.h"
27 #include "llvm/Support/CommandLine.h"
28 #include "llvm/Support/Debug.h"
29 #include "llvm/Support/raw_ostream.h"
30 #include "llvm/Target/TargetInstrInfo.h"
31 #include "llvm/Target/TargetRegisterInfo.h"
32 #include "llvm/Target/TargetSubtargetInfo.h"
38 #define DEBUG_TYPE "live-debug-values"
40 STATISTIC(NumInserted, "Number of DBG_VALUE instructions inserted");
44 class LiveDebugValues : public MachineFunctionPass {
47 const TargetRegisterInfo *TRI;
48 const TargetInstrInfo *TII;
50 typedef std::pair<const DILocalVariable *, const DILocation *>
53 /// A potentially inlined instance of a variable.
54 struct DebugVariable {
55 const DILocalVariable *Var;
56 const DILocation *InlinedAt;
58 DebugVariable(const DILocalVariable *_var, const DILocation *_inlinedAt)
59 : Var(_var), InlinedAt(_inlinedAt) {}
61 bool operator==(const DebugVariable &DV) const {
62 return (Var == DV.Var) && (InlinedAt == DV.InlinedAt);
66 /// Member variables and functions for Range Extension across basic blocks.
69 const MachineInstr *MI; // MachineInstr should be a DBG_VALUE instr.
71 VarLoc(DebugVariable _var, const MachineInstr *_mi) : Var(_var), MI(_mi) {}
73 bool operator==(const VarLoc &V) const;
76 typedef std::list<VarLoc> VarLocList;
77 typedef SmallDenseMap<const MachineBasicBlock *, VarLocList> VarLocInMBB;
79 void transferDebugValue(MachineInstr &MI, VarLocList &OpenRanges);
80 void transferRegisterDef(MachineInstr &MI, VarLocList &OpenRanges);
81 bool transferTerminatorInst(MachineInstr &MI, VarLocList &OpenRanges,
82 VarLocInMBB &OutLocs);
83 bool transfer(MachineInstr &MI, VarLocList &OpenRanges, VarLocInMBB &OutLocs);
85 bool join(MachineBasicBlock &MBB, VarLocInMBB &OutLocs, VarLocInMBB &InLocs);
87 bool ExtendRanges(MachineFunction &MF);
92 /// Default construct and initialize the pass.
95 /// Tell the pass manager which passes we depend on and what
96 /// information we preserve.
97 void getAnalysisUsage(AnalysisUsage &AU) const override;
99 /// Print to ostream with a message.
100 void printVarLocInMBB(const VarLocInMBB &V, const char *msg,
101 raw_ostream &Out) const;
103 /// Calculate the liveness information for the given machine function.
104 bool runOnMachineFunction(MachineFunction &MF) override;
108 //===----------------------------------------------------------------------===//
110 //===----------------------------------------------------------------------===//
112 char LiveDebugValues::ID = 0;
113 char &llvm::LiveDebugValuesID = LiveDebugValues::ID;
114 INITIALIZE_PASS(LiveDebugValues, "livedebugvalues", "Live DEBUG_VALUE analysis",
117 /// Default construct and initialize the pass.
118 LiveDebugValues::LiveDebugValues() : MachineFunctionPass(ID) {
119 initializeLiveDebugValuesPass(*PassRegistry::getPassRegistry());
122 /// Tell the pass manager which passes we depend on and what information we
124 void LiveDebugValues::getAnalysisUsage(AnalysisUsage &AU) const {
125 MachineFunctionPass::getAnalysisUsage(AU);
128 // \brief If @MI is a DBG_VALUE with debug value described by a defined
129 // register, returns the number of this register. In the other case, returns 0.
130 static unsigned isDescribedByReg(const MachineInstr &MI) {
131 assert(MI.isDebugValue());
132 assert(MI.getNumOperands() == 4);
133 // If location of variable is described using a register (directly or
134 // indirecltly), this register is always a first operand.
135 return MI.getOperand(0).isReg() ? MI.getOperand(0).getReg() : 0;
138 // \brief This function takes two DBG_VALUE instructions and returns true
139 // if their offsets are equal; otherwise returns false.
140 static bool areOffsetsEqual(const MachineInstr &MI1, const MachineInstr &MI2) {
141 assert(MI1.isDebugValue());
142 assert(MI1.getNumOperands() == 4);
144 assert(MI2.isDebugValue());
145 assert(MI2.getNumOperands() == 4);
147 if (!MI1.isIndirectDebugValue() && !MI2.isIndirectDebugValue())
150 // Check if both MIs are indirect and they are equal.
151 if (MI1.isIndirectDebugValue() && MI2.isIndirectDebugValue())
152 return MI1.getOperand(1).getImm() == MI2.getOperand(1).getImm();
157 //===----------------------------------------------------------------------===//
158 // Debug Range Extension Implementation
159 //===----------------------------------------------------------------------===//
161 void LiveDebugValues::printVarLocInMBB(const VarLocInMBB &V, const char *msg,
162 raw_ostream &Out) const {
163 Out << "Printing " << msg << ":\n";
164 for (const auto &L : V) {
165 Out << "MBB: " << L.first->getName() << ":\n";
166 for (const auto &VLL : L.second) {
167 Out << " Var: " << VLL.Var.Var->getName();
176 bool LiveDebugValues::VarLoc::operator==(const VarLoc &V) const {
177 return (Var == V.Var) && (isDescribedByReg(*MI) == isDescribedByReg(*V.MI)) &&
178 (areOffsetsEqual(*MI, *V.MI));
181 /// End all previous ranges related to @MI and start a new range from @MI
182 /// if it is a DBG_VALUE instr.
183 void LiveDebugValues::transferDebugValue(MachineInstr &MI,
184 VarLocList &OpenRanges) {
185 if (!MI.isDebugValue())
187 const DILocalVariable *RawVar = MI.getDebugVariable();
188 assert(RawVar->isValidLocationForIntrinsic(MI.getDebugLoc()) &&
189 "Expected inlined-at fields to agree");
190 DebugVariable Var(RawVar, MI.getDebugLoc()->getInlinedAt());
192 // End all previous ranges of Var.
194 std::remove_if(OpenRanges.begin(), OpenRanges.end(),
195 [&](const VarLoc &V) { return (Var == V.Var); }),
198 // Add Var to OpenRanges from this DBG_VALUE.
199 // TODO: Currently handles DBG_VALUE which has only reg as location.
200 if (isDescribedByReg(MI)) {
202 OpenRanges.push_back(std::move(V));
206 /// A definition of a register may mark the end of a range.
207 void LiveDebugValues::transferRegisterDef(MachineInstr &MI,
208 VarLocList &OpenRanges) {
209 for (const MachineOperand &MO : MI.operands()) {
210 if (!(MO.isReg() && MO.isDef() && MO.getReg() &&
211 TRI->isPhysicalRegister(MO.getReg())))
213 // Remove ranges of all aliased registers.
214 for (MCRegAliasIterator RAI(MO.getReg(), TRI, true); RAI.isValid(); ++RAI)
215 OpenRanges.erase(std::remove_if(OpenRanges.begin(), OpenRanges.end(),
216 [&](const VarLoc &V) {
218 isDescribedByReg(*V.MI));
224 /// Terminate all open ranges at the end of the current basic block.
225 bool LiveDebugValues::transferTerminatorInst(MachineInstr &MI,
226 VarLocList &OpenRanges,
227 VarLocInMBB &OutLocs) {
228 bool Changed = false;
229 const MachineBasicBlock *CurMBB = MI.getParent();
230 if (!(MI.isTerminator() || (&MI == &CurMBB->instr_back())))
233 if (OpenRanges.empty())
236 VarLocList &VLL = OutLocs[CurMBB];
238 for (auto OR : OpenRanges) {
239 // Copy OpenRanges to OutLocs, if not already present.
240 assert(OR.MI->isDebugValue());
241 DEBUG(dbgs() << "Add to OutLocs: "; OR.MI->dump(););
242 if (std::find_if(VLL.begin(), VLL.end(),
243 [&](const VarLoc &V) { return (OR == V); }) == VLL.end()) {
244 VLL.push_back(std::move(OR));
252 /// This routine creates OpenRanges and OutLocs.
253 bool LiveDebugValues::transfer(MachineInstr &MI, VarLocList &OpenRanges,
254 VarLocInMBB &OutLocs) {
255 bool Changed = false;
256 transferDebugValue(MI, OpenRanges);
257 transferRegisterDef(MI, OpenRanges);
258 Changed = transferTerminatorInst(MI, OpenRanges, OutLocs);
262 /// This routine joins the analysis results of all incoming edges in @MBB by
263 /// inserting a new DBG_VALUE instruction at the start of the @MBB - if the same
264 /// source variable in all the predecessors of @MBB reside in the same location.
265 bool LiveDebugValues::join(MachineBasicBlock &MBB, VarLocInMBB &OutLocs,
266 VarLocInMBB &InLocs) {
267 DEBUG(dbgs() << "join MBB: " << MBB.getName() << "\n");
268 bool Changed = false;
270 VarLocList InLocsT; // Temporary incoming locations.
272 // For all predecessors of this MBB, find the set of VarLocs that can be
274 for (auto p : MBB.predecessors()) {
275 auto OL = OutLocs.find(p);
276 // Join is null in case of empty OutLocs from any of the pred.
277 if (OL == OutLocs.end())
280 // Just copy over the Out locs to incoming locs for the first predecessor.
281 if (p == *MBB.pred_begin()) {
282 InLocsT = OL->second;
286 // Join with this predecessor.
287 VarLocList &VLL = OL->second;
289 std::remove_if(InLocsT.begin(), InLocsT.end(), [&](VarLoc &ILT) {
290 return (std::find_if(VLL.begin(), VLL.end(), [&](const VarLoc &V) {
299 VarLocList &ILL = InLocs[&MBB];
301 // Insert DBG_VALUE instructions, if not already inserted.
302 for (auto ILT : InLocsT) {
303 if (std::find_if(ILL.begin(), ILL.end(), [&](const VarLoc &I) {
306 // This VarLoc is not found in InLocs i.e. it is not yet inserted. So, a
307 // new range is started for the var from the mbb's beginning by inserting
308 // a new DBG_VALUE. transfer() will end this range however appropriate.
309 const MachineInstr *DMI = ILT.MI;
311 BuildMI(MBB, MBB.instr_begin(), DMI->getDebugLoc(), DMI->getDesc(),
312 DMI->isIndirectDebugValue(), DMI->getOperand(0).getReg(), 0,
313 DMI->getDebugVariable(), DMI->getDebugExpression());
314 if (DMI->isIndirectDebugValue())
315 MI->getOperand(1).setImm(DMI->getOperand(1).getImm());
316 DEBUG(dbgs() << "Inserted: "; MI->dump(););
320 VarLoc V(ILT.Var, MI);
321 ILL.push_back(std::move(V));
327 /// Calculate the liveness information for the given machine function and
328 /// extend ranges across basic blocks.
329 bool LiveDebugValues::ExtendRanges(MachineFunction &MF) {
331 DEBUG(dbgs() << "\nDebug Range Extension\n");
333 bool Changed = false;
334 bool OLChanged = false;
335 bool MBBJoined = false;
337 VarLocList OpenRanges; // Ranges that are open until end of bb.
338 VarLocInMBB OutLocs; // Ranges that exist beyond bb.
339 VarLocInMBB InLocs; // Ranges that are incoming after joining.
341 std::deque<MachineBasicBlock *> BBWorklist;
343 // Initialize every mbb with OutLocs.
346 transfer(MI, OpenRanges, OutLocs);
347 DEBUG(printVarLocInMBB(OutLocs, "OutLocs after initialization", dbgs()));
349 // Construct a worklist of MBBs.
351 BBWorklist.push_back(&MBB);
353 // Perform join() and transfer() using the worklist until the ranges converge
354 // Ranges have converged when the worklist is empty.
355 while (!BBWorklist.empty()) {
356 MachineBasicBlock *MBB = BBWorklist.front();
357 BBWorklist.pop_front();
359 MBBJoined = join(*MBB, OutLocs, InLocs);
364 for (auto &MI : *MBB)
365 OLChanged |= transfer(MI, OpenRanges, OutLocs);
366 DEBUG(printVarLocInMBB(OutLocs, "OutLocs after propagating", dbgs()));
367 DEBUG(printVarLocInMBB(InLocs, "InLocs after propagating", dbgs()));
371 for (auto s : MBB->successors())
372 if (std::find(BBWorklist.begin(), BBWorklist.end(), s) ==
373 BBWorklist.end()) // add if not already present.
374 BBWorklist.push_back(s);
378 DEBUG(printVarLocInMBB(OutLocs, "Final OutLocs", dbgs()));
379 DEBUG(printVarLocInMBB(InLocs, "Final InLocs", dbgs()));
383 bool LiveDebugValues::runOnMachineFunction(MachineFunction &MF) {
384 TRI = MF.getSubtarget().getRegisterInfo();
385 TII = MF.getSubtarget().getInstrInfo();
387 bool Changed = false;
389 Changed |= ExtendRanges(MF);