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llvm-project/llvm/lib/CodeGen/LiveDebugValues.cpp

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//===------ LiveDebugValues.cpp - Tracking Debug Value MIs ----------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
///
/// This pass implements a data flow analysis that propagates debug location
/// information by inserting additional DBG_VALUE instructions into the machine
/// instruction stream. The pass internally builds debug location liveness
/// ranges to determine the points where additional DBG_VALUEs need to be
/// inserted.
///
/// This is a separate pass from DbgValueHistoryCalculator to facilitate
/// testing and improve modularity.
///
//===----------------------------------------------------------------------===//
#include "llvm/ADT/PostOrderIterator.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/SparseBitVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/UniqueVector.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/Passes.h"
#include "llvm/IR/DebugInfo.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Target/TargetLowering.h"
#include "llvm/Target/TargetRegisterInfo.h"
#include "llvm/Target/TargetSubtargetInfo.h"
#include <list>
#include <queue>
using namespace llvm;
#define DEBUG_TYPE "live-debug-values"
STATISTIC(NumInserted, "Number of DBG_VALUE instructions inserted");
namespace {
// \brief If @MI is a DBG_VALUE with debug value described by a defined
// register, returns the number of this register. In the other case, returns 0.
static unsigned isDbgValueDescribedByReg(const MachineInstr &MI) {
assert(MI.isDebugValue() && "expected a DBG_VALUE");
assert(MI.getNumOperands() == 4 && "malformed DBG_VALUE");
// If location of variable is described using a register (directly
// or indirectly), this register is always a first operand.
return MI.getOperand(0).isReg() ? MI.getOperand(0).getReg() : 0;
}
class LiveDebugValues : public MachineFunctionPass {
private:
const TargetRegisterInfo *TRI;
const TargetInstrInfo *TII;
/// Based on std::pair so it can be used as an index into a DenseMap.
typedef std::pair<const DILocalVariable *, const DILocation *>
DebugVariableBase;
/// A potentially inlined instance of a variable.
struct DebugVariable : public DebugVariableBase {
DebugVariable(const DILocalVariable *Var, const DILocation *InlinedAt)
: DebugVariableBase(Var, InlinedAt) {}
const DILocalVariable *getVar() const { return this->first; };
const DILocation *getInlinedAt() const { return this->second; };
bool operator<(const DebugVariable &DV) const {
if (getVar() == DV.getVar())
return getInlinedAt() < DV.getInlinedAt();
return getVar() < DV.getVar();
}
};
/// A pair of debug variable and value location.
struct VarLoc {
const DebugVariable Var;
const MachineInstr &MI; ///< Only used for cloning a new DBG_VALUE.
enum { InvalidKind = 0, RegisterKind } Kind;
/// The value location. Stored separately to avoid repeatedly
/// extracting it from MI.
union {
struct {
uint32_t RegNo;
uint32_t Offset;
} RegisterLoc;
uint64_t Hash;
} Loc;
VarLoc(const MachineInstr &MI)
: Var(MI.getDebugVariable(), MI.getDebugLoc()->getInlinedAt()), MI(MI),
Kind(InvalidKind) {
static_assert((sizeof(Loc) == sizeof(uint64_t)),
"hash does not cover all members of Loc");
assert(MI.isDebugValue() && "not a DBG_VALUE");
assert(MI.getNumOperands() == 4 && "malformed DBG_VALUE");
if (int RegNo = isDbgValueDescribedByReg(MI)) {
Kind = RegisterKind;
Loc.RegisterLoc.RegNo = RegNo;
uint64_t Offset =
MI.isIndirectDebugValue() ? MI.getOperand(1).getImm() : 0;
// We don't support offsets larger than 4GiB here. They are
// slated to be replaced with DIExpressions anyway.
if (Offset >= (1ULL << 32))
Kind = InvalidKind;
else
Loc.RegisterLoc.Offset = Offset;
}
}
/// If this variable is described by a register, return it,
/// otherwise return 0.
unsigned isDescribedByReg() const {
if (Kind == RegisterKind)
return Loc.RegisterLoc.RegNo;
return 0;
}
void dump() const { MI.dump(); }
bool operator==(const VarLoc &Other) const {
return Var == Other.Var && Loc.Hash == Other.Loc.Hash;
}
/// This operator guarantees that VarLocs are sorted by Variable first.
bool operator<(const VarLoc &Other) const {
if (Var == Other.Var)
return Loc.Hash < Other.Loc.Hash;
return Var < Other.Var;
}
};
typedef UniqueVector<VarLoc> VarLocMap;
typedef SparseBitVector<> VarLocSet;
typedef SmallDenseMap<const MachineBasicBlock *, VarLocSet> VarLocInMBB;
/// This holds the working set of currently open ranges. For fast
/// access, this is done both as a set of VarLocIDs, and a map of
/// DebugVariable to recent VarLocID. Note that a DBG_VALUE ends all
/// previous open ranges for the same variable.
class OpenRangesSet {
VarLocSet VarLocs;
SmallDenseMap<DebugVariableBase, unsigned, 8> Vars;
public:
const VarLocSet &getVarLocs() const { return VarLocs; }
/// Terminate all open ranges for Var by removing it from the set.
void erase(DebugVariable Var) {
auto It = Vars.find(Var);
if (It != Vars.end()) {
unsigned ID = It->second;
VarLocs.reset(ID);
Vars.erase(It);
}
}
/// Terminate all open ranges listed in \c KillSet by removing
/// them from the set.
void erase(const VarLocSet &KillSet, const VarLocMap &VarLocIDs) {
VarLocs.intersectWithComplement(KillSet);
for (unsigned ID : KillSet)
Vars.erase(VarLocIDs[ID].Var);
}
/// Insert a new range into the set.
void insert(unsigned VarLocID, DebugVariableBase Var) {
VarLocs.set(VarLocID);
Vars.insert({Var, VarLocID});
}
/// Empty the set.
void clear() {
VarLocs.clear();
Vars.clear();
}
/// Return whether the set is empty or not.
bool empty() const {
assert(Vars.empty() == VarLocs.empty() && "open ranges are inconsistent");
return VarLocs.empty();
}
};
void transferDebugValue(const MachineInstr &MI, OpenRangesSet &OpenRanges,
VarLocMap &VarLocIDs);
void transferRegisterDef(MachineInstr &MI, OpenRangesSet &OpenRanges,
const VarLocMap &VarLocIDs);
bool transferTerminatorInst(MachineInstr &MI, OpenRangesSet &OpenRanges,
VarLocInMBB &OutLocs, const VarLocMap &VarLocIDs);
bool transfer(MachineInstr &MI, OpenRangesSet &OpenRanges,
VarLocInMBB &OutLocs, VarLocMap &VarLocIDs);
bool join(MachineBasicBlock &MBB, VarLocInMBB &OutLocs, VarLocInMBB &InLocs,
const VarLocMap &VarLocIDs);
bool ExtendRanges(MachineFunction &MF);
public:
static char ID;
/// Default construct and initialize the pass.
LiveDebugValues();
/// Tell the pass manager which passes we depend on and what
/// information we preserve.
void getAnalysisUsage(AnalysisUsage &AU) const override;
MachineFunctionProperties getRequiredProperties() const override {
return MachineFunctionProperties().set(
MachineFunctionProperties::Property::AllVRegsAllocated);
}
/// Print to ostream with a message.
void printVarLocInMBB(const MachineFunction &MF, const VarLocInMBB &V,
const VarLocMap &VarLocIDs, const char *msg,
raw_ostream &Out) const;
/// Calculate the liveness information for the given machine function.
bool runOnMachineFunction(MachineFunction &MF) override;
};
} // namespace
//===----------------------------------------------------------------------===//
// Implementation
//===----------------------------------------------------------------------===//
char LiveDebugValues::ID = 0;
char &llvm::LiveDebugValuesID = LiveDebugValues::ID;
INITIALIZE_PASS(LiveDebugValues, "livedebugvalues", "Live DEBUG_VALUE analysis",
false, false)
/// Default construct and initialize the pass.
LiveDebugValues::LiveDebugValues() : MachineFunctionPass(ID) {
initializeLiveDebugValuesPass(*PassRegistry::getPassRegistry());
}
/// Tell the pass manager which passes we depend on and what information we
/// preserve.
void LiveDebugValues::getAnalysisUsage(AnalysisUsage &AU) const {
AU.setPreservesCFG();
MachineFunctionPass::getAnalysisUsage(AU);
}
//===----------------------------------------------------------------------===//
// Debug Range Extension Implementation
//===----------------------------------------------------------------------===//
void LiveDebugValues::printVarLocInMBB(const MachineFunction &MF,
const VarLocInMBB &V,
const VarLocMap &VarLocIDs,
const char *msg,
raw_ostream &Out) const {
for (const MachineBasicBlock &BB : MF) {
const auto &L = V.lookup(&BB);
Out << "MBB: " << BB.getName() << ":\n";
for (unsigned VLL : L) {
const VarLoc &VL = VarLocIDs[VLL];
Out << " Var: " << VL.Var.getVar()->getName();
Out << " MI: ";
VL.dump();
Out << "\n";
}
}
Out << "\n";
}
/// End all previous ranges related to @MI and start a new range from @MI
/// if it is a DBG_VALUE instr.
void LiveDebugValues::transferDebugValue(const MachineInstr &MI,
OpenRangesSet &OpenRanges,
VarLocMap &VarLocIDs) {
if (!MI.isDebugValue())
return;
const DILocalVariable *Var = MI.getDebugVariable();
const DILocation *DebugLoc = MI.getDebugLoc();
const DILocation *InlinedAt = DebugLoc->getInlinedAt();
assert(Var->isValidLocationForIntrinsic(DebugLoc) &&
"Expected inlined-at fields to agree");
// End all previous ranges of Var.
DebugVariable V(Var, InlinedAt);
OpenRanges.erase(V);
// Add the VarLoc to OpenRanges from this DBG_VALUE.
// TODO: Currently handles DBG_VALUE which has only reg as location.
if (isDbgValueDescribedByReg(MI)) {
VarLoc VL(MI);
unsigned ID = VarLocIDs.insert(VL);
OpenRanges.insert(ID, VL.Var);
}
}
/// A definition of a register may mark the end of a range.
void LiveDebugValues::transferRegisterDef(MachineInstr &MI,
OpenRangesSet &OpenRanges,
const VarLocMap &VarLocIDs) {
MachineFunction *MF = MI.getParent()->getParent();
const TargetLowering *TLI = MF->getSubtarget().getTargetLowering();
unsigned SP = TLI->getStackPointerRegisterToSaveRestore();
SparseBitVector<> KillSet;
for (const MachineOperand &MO : MI.operands()) {
if (MO.isReg() && MO.isDef() && MO.getReg() &&
TRI->isPhysicalRegister(MO.getReg())) {
// Remove ranges of all aliased registers.
for (MCRegAliasIterator RAI(MO.getReg(), TRI, true); RAI.isValid(); ++RAI)
for (unsigned ID : OpenRanges.getVarLocs())
if (VarLocIDs[ID].isDescribedByReg() == *RAI)
KillSet.set(ID);
} else if (MO.isRegMask()) {
// Remove ranges of all clobbered registers. Register masks don't usually
// list SP as preserved. While the debug info may be off for an
// instruction or two around callee-cleanup calls, transferring the
// DEBUG_VALUE across the call is still a better user experience.
for (unsigned ID : OpenRanges.getVarLocs()) {
unsigned Reg = VarLocIDs[ID].isDescribedByReg();
if (Reg && Reg != SP && MO.clobbersPhysReg(Reg))
KillSet.set(ID);
}
}
}
OpenRanges.erase(KillSet, VarLocIDs);
}
/// Terminate all open ranges at the end of the current basic block.
bool LiveDebugValues::transferTerminatorInst(MachineInstr &MI,
OpenRangesSet &OpenRanges,
VarLocInMBB &OutLocs,
const VarLocMap &VarLocIDs) {
bool Changed = false;
const MachineBasicBlock *CurMBB = MI.getParent();
if (!(MI.isTerminator() || (&MI == &CurMBB->instr_back())))
return false;
if (OpenRanges.empty())
return false;
DEBUG(for (unsigned ID : OpenRanges.getVarLocs()) {
// Copy OpenRanges to OutLocs, if not already present.
dbgs() << "Add to OutLocs: "; VarLocIDs[ID].dump();
});
VarLocSet &VLS = OutLocs[CurMBB];
Changed = VLS |= OpenRanges.getVarLocs();
OpenRanges.clear();
return Changed;
}
/// This routine creates OpenRanges and OutLocs.
bool LiveDebugValues::transfer(MachineInstr &MI, OpenRangesSet &OpenRanges,
VarLocInMBB &OutLocs, VarLocMap &VarLocIDs) {
bool Changed = false;
transferDebugValue(MI, OpenRanges, VarLocIDs);
transferRegisterDef(MI, OpenRanges, VarLocIDs);
Changed = transferTerminatorInst(MI, OpenRanges, OutLocs, VarLocIDs);
return Changed;
}
/// This routine joins the analysis results of all incoming edges in @MBB by
/// inserting a new DBG_VALUE instruction at the start of the @MBB - if the same
/// source variable in all the predecessors of @MBB reside in the same location.
bool LiveDebugValues::join(MachineBasicBlock &MBB, VarLocInMBB &OutLocs,
VarLocInMBB &InLocs, const VarLocMap &VarLocIDs) {
DEBUG(dbgs() << "join MBB: " << MBB.getName() << "\n");
bool Changed = false;
VarLocSet InLocsT; // Temporary incoming locations.
// For all predecessors of this MBB, find the set of VarLocs that
// can be joined.
for (auto p : MBB.predecessors()) {
auto OL = OutLocs.find(p);
// Join is null in case of empty OutLocs from any of the pred.
if (OL == OutLocs.end())
return false;
// Just copy over the Out locs to incoming locs for the first predecessor.
if (p == *MBB.pred_begin()) {
InLocsT = OL->second;
continue;
}
// Join with this predecessor.
InLocsT &= OL->second;
}
if (InLocsT.empty())
return false;
VarLocSet &ILS = InLocs[&MBB];
// Insert DBG_VALUE instructions, if not already inserted.
VarLocSet Diff = InLocsT;
Diff.intersectWithComplement(ILS);
for (auto ID : Diff) {
// This VarLoc is not found in InLocs i.e. it is not yet inserted. So, a
// new range is started for the var from the mbb's beginning by inserting
// a new DBG_VALUE. transfer() will end this range however appropriate.
const VarLoc &DiffIt = VarLocIDs[ID];
const MachineInstr *DMI = &DiffIt.MI;
MachineInstr *MI =
BuildMI(MBB, MBB.instr_begin(), DMI->getDebugLoc(), DMI->getDesc(),
DMI->isIndirectDebugValue(), DMI->getOperand(0).getReg(), 0,
DMI->getDebugVariable(), DMI->getDebugExpression());
if (DMI->isIndirectDebugValue())
MI->getOperand(1).setImm(DMI->getOperand(1).getImm());
DEBUG(dbgs() << "Inserted: "; MI->dump(););
ILS.set(ID);
++NumInserted;
Changed = true;
}
return Changed;
}
/// Calculate the liveness information for the given machine function and
/// extend ranges across basic blocks.
bool LiveDebugValues::ExtendRanges(MachineFunction &MF) {
DEBUG(dbgs() << "\nDebug Range Extension\n");
bool Changed = false;
bool OLChanged = false;
bool MBBJoined = false;
VarLocMap VarLocIDs; // Map VarLoc<>unique ID for use in bitvectors.
OpenRangesSet OpenRanges; // Ranges that are open until end of bb.
VarLocInMBB OutLocs; // Ranges that exist beyond bb.
VarLocInMBB InLocs; // Ranges that are incoming after joining.
DenseMap<unsigned int, MachineBasicBlock *> OrderToBB;
DenseMap<MachineBasicBlock *, unsigned int> BBToOrder;
std::priority_queue<unsigned int, std::vector<unsigned int>,
std::greater<unsigned int>>
Worklist;
std::priority_queue<unsigned int, std::vector<unsigned int>,
std::greater<unsigned int>>
Pending;
// Initialize every mbb with OutLocs.
for (auto &MBB : MF)
for (auto &MI : MBB)
transfer(MI, OpenRanges, OutLocs, VarLocIDs);
DEBUG(printVarLocInMBB(MF, OutLocs, VarLocIDs, "OutLocs after initialization",
dbgs()));
ReversePostOrderTraversal<MachineFunction *> RPOT(&MF);
unsigned int RPONumber = 0;
for (auto RI = RPOT.begin(), RE = RPOT.end(); RI != RE; ++RI) {
OrderToBB[RPONumber] = *RI;
BBToOrder[*RI] = RPONumber;
Worklist.push(RPONumber);
++RPONumber;
}
// This is a standard "union of predecessor outs" dataflow problem.
// To solve it, we perform join() and transfer() using the two worklist method
// until the ranges converge.
// Ranges have converged when both worklists are empty.
while (!Worklist.empty() || !Pending.empty()) {
// We track what is on the pending worklist to avoid inserting the same
// thing twice. We could avoid this with a custom priority queue, but this
// is probably not worth it.
SmallPtrSet<MachineBasicBlock *, 16> OnPending;
while (!Worklist.empty()) {
MachineBasicBlock *MBB = OrderToBB[Worklist.top()];
Worklist.pop();
MBBJoined = join(*MBB, OutLocs, InLocs, VarLocIDs);
if (MBBJoined) {
MBBJoined = false;
Changed = true;
for (auto &MI : *MBB)
OLChanged |= transfer(MI, OpenRanges, OutLocs, VarLocIDs);
DEBUG(printVarLocInMBB(MF, OutLocs, VarLocIDs,
"OutLocs after propagating", dbgs()));
DEBUG(printVarLocInMBB(MF, InLocs, VarLocIDs,
"InLocs after propagating", dbgs()));
if (OLChanged) {
OLChanged = false;
for (auto s : MBB->successors())
if (OnPending.insert(s).second) {
Pending.push(BBToOrder[s]);
}
}
}
}
Worklist.swap(Pending);
// At this point, pending must be empty, since it was just the empty
// worklist
assert(Pending.empty() && "Pending should be empty");
}
DEBUG(printVarLocInMBB(MF, OutLocs, VarLocIDs, "Final OutLocs", dbgs()));
DEBUG(printVarLocInMBB(MF, InLocs, VarLocIDs, "Final InLocs", dbgs()));
return Changed;
}
bool LiveDebugValues::runOnMachineFunction(MachineFunction &MF) {
TRI = MF.getSubtarget().getRegisterInfo();
TII = MF.getSubtarget().getInstrInfo();
bool Changed = false;
Changed |= ExtendRanges(MF);
return Changed;
}
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