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

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//===- LiveDebugVariables.cpp - Tracking debug info variables -------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements the LiveDebugVariables analysis.
//
// Remove all DBG_VALUE instructions referencing virtual registers and replace
// them with a data structure tracking where live user variables are kept - in a
// virtual register or in a stack slot.
//
// Allow the data structure to be updated during register allocation when values
// are moved between registers and stack slots. Finally emit new DBG_VALUE
// instructions after register allocation is complete.
//
//===----------------------------------------------------------------------===//
#include "LiveDebugVariables.h"
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/IntervalMap.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SmallSet.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/CodeGen/LexicalScopes.h"
#include "llvm/CodeGen/LiveInterval.h"
#include "llvm/CodeGen/LiveIntervalAnalysis.h"
#include "llvm/CodeGen/MachineBasicBlock.h"
#include "llvm/CodeGen/MachineDominators.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineOperand.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/SlotIndexes.h"
#include "llvm/CodeGen/VirtRegMap.h"
#include "llvm/IR/DebugInfoMetadata.h"
#include "llvm/IR/DebugLoc.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/Metadata.h"
#include "llvm/MC/MCRegisterInfo.h"
#include "llvm/Pass.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Target/TargetOpcodes.h"
#include "llvm/Target/TargetRegisterInfo.h"
#include "llvm/Target/TargetSubtargetInfo.h"
#include <algorithm>
#include <cassert>
#include <iterator>
#include <memory>
#include <utility>
using namespace llvm;
#define DEBUG_TYPE "livedebugvars"
static cl::opt<bool>
EnableLDV("live-debug-variables", cl::init(true),
cl::desc("Enable the live debug variables pass"), cl::Hidden);
STATISTIC(NumInsertedDebugValues, "Number of DBG_VALUEs inserted");
char LiveDebugVariables::ID = 0;
INITIALIZE_PASS_BEGIN(LiveDebugVariables, DEBUG_TYPE,
"Debug Variable Analysis", false, false)
INITIALIZE_PASS_DEPENDENCY(MachineDominatorTree)
INITIALIZE_PASS_DEPENDENCY(LiveIntervals)
INITIALIZE_PASS_END(LiveDebugVariables, DEBUG_TYPE,
"Debug Variable Analysis", false, false)
void LiveDebugVariables::getAnalysisUsage(AnalysisUsage &AU) const {
AU.addRequired<MachineDominatorTree>();
AU.addRequiredTransitive<LiveIntervals>();
AU.setPreservesAll();
MachineFunctionPass::getAnalysisUsage(AU);
}
LiveDebugVariables::LiveDebugVariables() : MachineFunctionPass(ID) {
initializeLiveDebugVariablesPass(*PassRegistry::getPassRegistry());
}
enum : unsigned { UndefLocNo = ~0U };
/// Describes a location by number along with some flags about the original
/// usage of the location.
class DbgValueLocation {
public:
DbgValueLocation(unsigned LocNo, bool WasIndirect)
: LocNo(LocNo), WasIndirect(WasIndirect) {
static_assert(sizeof(*this) == sizeof(unsigned), "bad bitfield packing");
assert(locNo() == LocNo && "location truncation");
}
DbgValueLocation() : LocNo(0), WasIndirect(0) {}
unsigned locNo() const {
// Fix up the undef location number, which gets truncated.
return LocNo == INT_MAX ? UndefLocNo : LocNo;
}
bool wasIndirect() const { return WasIndirect; }
bool isUndef() const { return locNo() == UndefLocNo; }
DbgValueLocation changeLocNo(unsigned NewLocNo) const {
return DbgValueLocation(NewLocNo, WasIndirect);
}
friend inline bool operator==(const DbgValueLocation &LHS,
const DbgValueLocation &RHS) {
return LHS.LocNo == RHS.LocNo && LHS.WasIndirect == RHS.WasIndirect;
}
friend inline bool operator!=(const DbgValueLocation &LHS,
const DbgValueLocation &RHS) {
return !(LHS == RHS);
}
private:
unsigned LocNo : 31;
unsigned WasIndirect : 1;
};
/// LocMap - Map of where a user value is live, and its location.
using LocMap = IntervalMap<SlotIndex, DbgValueLocation, 4>;
namespace {
class LDVImpl;
/// UserValue - A user value is a part of a debug info user variable.
///
/// A DBG_VALUE instruction notes that (a sub-register of) a virtual register
/// holds part of a user variable. The part is identified by a byte offset.
///
/// UserValues are grouped into equivalence classes for easier searching. Two
/// user values are related if they refer to the same variable, or if they are
/// held by the same virtual register. The equivalence class is the transitive
/// closure of that relation.
class UserValue {
const DILocalVariable *Variable; ///< The debug info variable we are part of.
const DIExpression *Expression; ///< Any complex address expression.
DebugLoc dl; ///< The debug location for the variable. This is
///< used by dwarf writer to find lexical scope.
UserValue *leader; ///< Equivalence class leader.
UserValue *next = nullptr; ///< Next value in equivalence class, or null.
/// Numbered locations referenced by locmap.
SmallVector<MachineOperand, 4> locations;
/// Map of slot indices where this value is live.
LocMap locInts;
/// Set of interval start indexes that have been trimmed to the
/// lexical scope.
SmallSet<SlotIndex, 2> trimmedDefs;
/// insertDebugValue - Insert a DBG_VALUE into MBB at Idx for LocNo.
void insertDebugValue(MachineBasicBlock *MBB, SlotIndex StartIdx,
SlotIndex StopIdx,
DbgValueLocation Loc, bool Spilled, LiveIntervals &LIS,
const TargetInstrInfo &TII,
const TargetRegisterInfo &TRI);
/// splitLocation - Replace OldLocNo ranges with NewRegs ranges where NewRegs
/// is live. Returns true if any changes were made.
bool splitLocation(unsigned OldLocNo, ArrayRef<unsigned> NewRegs,
LiveIntervals &LIS);
public:
/// UserValue - Create a new UserValue.
UserValue(const DILocalVariable *var, const DIExpression *expr, DebugLoc L,
LocMap::Allocator &alloc)
: Variable(var), Expression(expr), dl(std::move(L)), leader(this),
locInts(alloc) {}
/// getLeader - Get the leader of this value's equivalence class.
UserValue *getLeader() {
UserValue *l = leader;
while (l != l->leader)
l = l->leader;
return leader = l;
}
/// getNext - Return the next UserValue in the equivalence class.
UserValue *getNext() const { return next; }
/// match - Does this UserValue match the parameters?
bool match(const DILocalVariable *Var, const DIExpression *Expr,
const DILocation *IA) const {
// FIXME: The fragment should be part of the equivalence class, but not
// other things in the expression like stack values.
return Var == Variable && Expr == Expression && dl->getInlinedAt() == IA;
}
/// merge - Merge equivalence classes.
static UserValue *merge(UserValue *L1, UserValue *L2) {
L2 = L2->getLeader();
if (!L1)
return L2;
L1 = L1->getLeader();
if (L1 == L2)
return L1;
// Splice L2 before L1's members.
UserValue *End = L2;
while (End->next) {
End->leader = L1;
End = End->next;
}
End->leader = L1;
End->next = L1->next;
L1->next = L2;
return L1;
}
/// getLocationNo - Return the location number that matches Loc.
unsigned getLocationNo(const MachineOperand &LocMO) {
if (LocMO.isReg()) {
if (LocMO.getReg() == 0)
return UndefLocNo;
// For register locations we dont care about use/def and other flags.
for (unsigned i = 0, e = locations.size(); i != e; ++i)
if (locations[i].isReg() &&
locations[i].getReg() == LocMO.getReg() &&
locations[i].getSubReg() == LocMO.getSubReg())
return i;
} else
for (unsigned i = 0, e = locations.size(); i != e; ++i)
if (LocMO.isIdenticalTo(locations[i]))
return i;
locations.push_back(LocMO);
// We are storing a MachineOperand outside a MachineInstr.
locations.back().clearParent();
// Don't store def operands.
if (locations.back().isReg())
locations.back().setIsUse();
return locations.size() - 1;
}
/// mapVirtRegs - Ensure that all virtual register locations are mapped.
void mapVirtRegs(LDVImpl *LDV);
/// addDef - Add a definition point to this value.
void addDef(SlotIndex Idx, const MachineOperand &LocMO, bool IsIndirect) {
DbgValueLocation Loc(getLocationNo(LocMO), IsIndirect);
// Add a singular (Idx,Idx) -> Loc mapping.
LocMap::iterator I = locInts.find(Idx);
if (!I.valid() || I.start() != Idx)
I.insert(Idx, Idx.getNextSlot(), Loc);
else
// A later DBG_VALUE at the same SlotIndex overrides the old location.
I.setValue(Loc);
}
/// extendDef - Extend the current definition as far as possible down.
/// Stop when meeting an existing def or when leaving the live
/// range of VNI.
/// End points where VNI is no longer live are added to Kills.
/// @param Idx Starting point for the definition.
/// @param Loc Location number to propagate.
/// @param LR Restrict liveness to where LR has the value VNI. May be null.
/// @param VNI When LR is not null, this is the value to restrict to.
/// @param Kills Append end points of VNI's live range to Kills.
/// @param LIS Live intervals analysis.
void extendDef(SlotIndex Idx, DbgValueLocation Loc,
LiveRange *LR, const VNInfo *VNI,
SmallVectorImpl<SlotIndex> *Kills,
LiveIntervals &LIS);
/// addDefsFromCopies - The value in LI/LocNo may be copies to other
/// registers. Determine if any of the copies are available at the kill
/// points, and add defs if possible.
/// @param LI Scan for copies of the value in LI->reg.
/// @param LocNo Location number of LI->reg.
/// @param WasIndirect Indicates if the original use of LI->reg was indirect
/// @param Kills Points where the range of LocNo could be extended.
/// @param NewDefs Append (Idx, LocNo) of inserted defs here.
void addDefsFromCopies(
LiveInterval *LI, unsigned LocNo, bool WasIndirect,
const SmallVectorImpl<SlotIndex> &Kills,
SmallVectorImpl<std::pair<SlotIndex, DbgValueLocation>> &NewDefs,
MachineRegisterInfo &MRI, LiveIntervals &LIS);
/// computeIntervals - Compute the live intervals of all locations after
/// collecting all their def points.
void computeIntervals(MachineRegisterInfo &MRI, const TargetRegisterInfo &TRI,
LiveIntervals &LIS, LexicalScopes &LS);
/// splitRegister - Replace OldReg ranges with NewRegs ranges where NewRegs is
/// live. Returns true if any changes were made.
bool splitRegister(unsigned OldLocNo, ArrayRef<unsigned> NewRegs,
LiveIntervals &LIS);
/// rewriteLocations - Rewrite virtual register locations according to the
/// provided virtual register map. Record which locations were spilled.
void rewriteLocations(VirtRegMap &VRM, const TargetRegisterInfo &TRI,
BitVector &SpilledLocations);
/// emitDebugValues - Recreate DBG_VALUE instruction from data structures.
void emitDebugValues(VirtRegMap *VRM, LiveIntervals &LIS,
const TargetInstrInfo &TII,
const TargetRegisterInfo &TRI,
const BitVector &SpilledLocations);
/// getDebugLoc - Return DebugLoc of this UserValue.
DebugLoc getDebugLoc() { return dl;}
void print(raw_ostream &, const TargetRegisterInfo *);
};
/// LDVImpl - Implementation of the LiveDebugVariables pass.
class LDVImpl {
LiveDebugVariables &pass;
LocMap::Allocator allocator;
MachineFunction *MF = nullptr;
LiveIntervals *LIS;
const TargetRegisterInfo *TRI;
/// Whether emitDebugValues is called.
bool EmitDone = false;
/// Whether the machine function is modified during the pass.
bool ModifiedMF = false;
/// userValues - All allocated UserValue instances.
SmallVector<std::unique_ptr<UserValue>, 8> userValues;
/// Map virtual register to eq class leader.
using VRMap = DenseMap<unsigned, UserValue *>;
VRMap virtRegToEqClass;
/// Map user variable to eq class leader.
using UVMap = DenseMap<const DILocalVariable *, UserValue *>;
UVMap userVarMap;
/// getUserValue - Find or create a UserValue.
UserValue *getUserValue(const DILocalVariable *Var, const DIExpression *Expr,
const DebugLoc &DL);
/// lookupVirtReg - Find the EC leader for VirtReg or null.
UserValue *lookupVirtReg(unsigned VirtReg);
/// handleDebugValue - Add DBG_VALUE instruction to our maps.
/// @param MI DBG_VALUE instruction
/// @param Idx Last valid SLotIndex before instruction.
/// @return True if the DBG_VALUE instruction should be deleted.
bool handleDebugValue(MachineInstr &MI, SlotIndex Idx);
/// collectDebugValues - Collect and erase all DBG_VALUE instructions, adding
/// a UserValue def for each instruction.
/// @param mf MachineFunction to be scanned.
/// @return True if any debug values were found.
bool collectDebugValues(MachineFunction &mf);
/// computeIntervals - Compute the live intervals of all user values after
/// collecting all their def points.
void computeIntervals();
public:
LDVImpl(LiveDebugVariables *ps) : pass(*ps) {}
bool runOnMachineFunction(MachineFunction &mf);
/// clear - Release all memory.
void clear() {
MF = nullptr;
userValues.clear();
virtRegToEqClass.clear();
userVarMap.clear();
// Make sure we call emitDebugValues if the machine function was modified.
assert((!ModifiedMF || EmitDone) &&
"Dbg values are not emitted in LDV");
EmitDone = false;
ModifiedMF = false;
}
/// mapVirtReg - Map virtual register to an equivalence class.
void mapVirtReg(unsigned VirtReg, UserValue *EC);
/// splitRegister - Replace all references to OldReg with NewRegs.
void splitRegister(unsigned OldReg, ArrayRef<unsigned> NewRegs);
/// emitDebugValues - Recreate DBG_VALUE instruction from data structures.
void emitDebugValues(VirtRegMap *VRM);
void print(raw_ostream&);
};
} // end anonymous namespace
#ifdef LLVM_ENABLE_DUMP
static void printDebugLoc(const DebugLoc &DL, raw_ostream &CommentOS,
const LLVMContext &Ctx) {
if (!DL)
return;
auto *Scope = cast<DIScope>(DL.getScope());
// Omit the directory, because it's likely to be long and uninteresting.
CommentOS << Scope->getFilename();
CommentOS << ':' << DL.getLine();
if (DL.getCol() != 0)
CommentOS << ':' << DL.getCol();
DebugLoc InlinedAtDL = DL.getInlinedAt();
if (!InlinedAtDL)
return;
CommentOS << " @[ ";
printDebugLoc(InlinedAtDL, CommentOS, Ctx);
CommentOS << " ]";
}
static void printExtendedName(raw_ostream &OS, const DILocalVariable *V,
const DILocation *DL) {
const LLVMContext &Ctx = V->getContext();
StringRef Res = V->getName();
if (!Res.empty())
OS << Res << "," << V->getLine();
if (auto *InlinedAt = DL->getInlinedAt()) {
if (DebugLoc InlinedAtDL = InlinedAt) {
OS << " @[";
printDebugLoc(InlinedAtDL, OS, Ctx);
OS << "]";
}
}
}
void UserValue::print(raw_ostream &OS, const TargetRegisterInfo *TRI) {
auto *DV = cast<DILocalVariable>(Variable);
OS << "!\"";
printExtendedName(OS, DV, dl);
OS << "\"\t";
for (LocMap::const_iterator I = locInts.begin(); I.valid(); ++I) {
OS << " [" << I.start() << ';' << I.stop() << "):";
if (I.value().isUndef())
OS << "undef";
else {
OS << I.value().locNo();
if (I.value().wasIndirect())
OS << " ind";
}
}
for (unsigned i = 0, e = locations.size(); i != e; ++i) {
OS << " Loc" << i << '=';
locations[i].print(OS, TRI);
}
OS << '\n';
}
void LDVImpl::print(raw_ostream &OS) {
OS << "********** DEBUG VARIABLES **********\n";
for (unsigned i = 0, e = userValues.size(); i != e; ++i)
userValues[i]->print(OS, TRI);
}
#endif
void UserValue::mapVirtRegs(LDVImpl *LDV) {
for (unsigned i = 0, e = locations.size(); i != e; ++i)
if (locations[i].isReg() &&
TargetRegisterInfo::isVirtualRegister(locations[i].getReg()))
LDV->mapVirtReg(locations[i].getReg(), this);
}
UserValue *LDVImpl::getUserValue(const DILocalVariable *Var,
const DIExpression *Expr, const DebugLoc &DL) {
UserValue *&Leader = userVarMap[Var];
if (Leader) {
UserValue *UV = Leader->getLeader();
Leader = UV;
for (; UV; UV = UV->getNext())
if (UV->match(Var, Expr, DL->getInlinedAt()))
return UV;
}
userValues.push_back(
llvm::make_unique<UserValue>(Var, Expr, DL, allocator));
UserValue *UV = userValues.back().get();
Leader = UserValue::merge(Leader, UV);
return UV;
}
void LDVImpl::mapVirtReg(unsigned VirtReg, UserValue *EC) {
assert(TargetRegisterInfo::isVirtualRegister(VirtReg) && "Only map VirtRegs");
UserValue *&Leader = virtRegToEqClass[VirtReg];
Leader = UserValue::merge(Leader, EC);
}
UserValue *LDVImpl::lookupVirtReg(unsigned VirtReg) {
if (UserValue *UV = virtRegToEqClass.lookup(VirtReg))
return UV->getLeader();
return nullptr;
}
bool LDVImpl::handleDebugValue(MachineInstr &MI, SlotIndex Idx) {
// DBG_VALUE loc, offset, variable
if (MI.getNumOperands() != 4 ||
!(MI.getOperand(1).isReg() || MI.getOperand(1).isImm()) ||
!MI.getOperand(2).isMetadata()) {
DEBUG(dbgs() << "Can't handle " << MI);
return false;
}
// Get or create the UserValue for (variable,offset) here.
bool IsIndirect = MI.getOperand(1).isImm();
if (IsIndirect)
assert(MI.getOperand(1).getImm() == 0 && "DBG_VALUE with nonzero offset");
const DILocalVariable *Var = MI.getDebugVariable();
const DIExpression *Expr = MI.getDebugExpression();
UserValue *UV =
getUserValue(Var, Expr, MI.getDebugLoc());
UV->addDef(Idx, MI.getOperand(0), IsIndirect);
return true;
}
bool LDVImpl::collectDebugValues(MachineFunction &mf) {
bool Changed = false;
for (MachineFunction::iterator MFI = mf.begin(), MFE = mf.end(); MFI != MFE;
++MFI) {
MachineBasicBlock *MBB = &*MFI;
for (MachineBasicBlock::iterator MBBI = MBB->begin(), MBBE = MBB->end();
MBBI != MBBE;) {
if (!MBBI->isDebugValue()) {
++MBBI;
continue;
}
// DBG_VALUE has no slot index, use the previous instruction instead.
SlotIndex Idx =
MBBI == MBB->begin()
? LIS->getMBBStartIdx(MBB)
: LIS->getInstructionIndex(*std::prev(MBBI)).getRegSlot();
// Handle consecutive DBG_VALUE instructions with the same slot index.
do {
if (handleDebugValue(*MBBI, Idx)) {
MBBI = MBB->erase(MBBI);
Changed = true;
} else
++MBBI;
} while (MBBI != MBBE && MBBI->isDebugValue());
}
}
return Changed;
}
/// We only propagate DBG_VALUES locally here. LiveDebugValues performs a
/// data-flow analysis to propagate them beyond basic block boundaries.
void UserValue::extendDef(SlotIndex Idx, DbgValueLocation Loc, LiveRange *LR,
const VNInfo *VNI, SmallVectorImpl<SlotIndex> *Kills,
LiveIntervals &LIS) {
SlotIndex Start = Idx;
MachineBasicBlock *MBB = LIS.getMBBFromIndex(Start);
SlotIndex Stop = LIS.getMBBEndIdx(MBB);
LocMap::iterator I = locInts.find(Start);
// Limit to VNI's live range.
bool ToEnd = true;
if (LR && VNI) {
LiveInterval::Segment *Segment = LR->getSegmentContaining(Start);
if (!Segment || Segment->valno != VNI) {
if (Kills)
Kills->push_back(Start);
return;
}
if (Segment->end < Stop) {
Stop = Segment->end;
ToEnd = false;
}
}
// There could already be a short def at Start.
if (I.valid() && I.start() <= Start) {
// Stop when meeting a different location or an already extended interval.
Start = Start.getNextSlot();
if (I.value() != Loc || I.stop() != Start)
return;
// This is a one-slot placeholder. Just skip it.
++I;
}
// Limited by the next def.
if (I.valid() && I.start() < Stop) {
Stop = I.start();
ToEnd = false;
}
// Limited by VNI's live range.
else if (!ToEnd && Kills)
Kills->push_back(Stop);
if (Start < Stop)
I.insert(Start, Stop, Loc);
}
void UserValue::addDefsFromCopies(
LiveInterval *LI, unsigned LocNo, bool WasIndirect,
const SmallVectorImpl<SlotIndex> &Kills,
SmallVectorImpl<std::pair<SlotIndex, DbgValueLocation>> &NewDefs,
MachineRegisterInfo &MRI, LiveIntervals &LIS) {
if (Kills.empty())
return;
// Don't track copies from physregs, there are too many uses.
if (!TargetRegisterInfo::isVirtualRegister(LI->reg))
return;
// Collect all the (vreg, valno) pairs that are copies of LI.
SmallVector<std::pair<LiveInterval*, const VNInfo*>, 8> CopyValues;
for (MachineOperand &MO : MRI.use_nodbg_operands(LI->reg)) {
MachineInstr *MI = MO.getParent();
// Copies of the full value.
if (MO.getSubReg() || !MI->isCopy())
continue;
unsigned DstReg = MI->getOperand(0).getReg();
// Don't follow copies to physregs. These are usually setting up call
// arguments, and the argument registers are always call clobbered. We are
// better off in the source register which could be a callee-saved register,
// or it could be spilled.
if (!TargetRegisterInfo::isVirtualRegister(DstReg))
continue;
// Is LocNo extended to reach this copy? If not, another def may be blocking
// it, or we are looking at a wrong value of LI.
SlotIndex Idx = LIS.getInstructionIndex(*MI);
LocMap::iterator I = locInts.find(Idx.getRegSlot(true));
if (!I.valid() || I.value().locNo() != LocNo)
continue;
if (!LIS.hasInterval(DstReg))
continue;
LiveInterval *DstLI = &LIS.getInterval(DstReg);
const VNInfo *DstVNI = DstLI->getVNInfoAt(Idx.getRegSlot());
assert(DstVNI && DstVNI->def == Idx.getRegSlot() && "Bad copy value");
CopyValues.push_back(std::make_pair(DstLI, DstVNI));
}
if (CopyValues.empty())
return;
DEBUG(dbgs() << "Got " << CopyValues.size() << " copies of " << *LI << '\n');
// Try to add defs of the copied values for each kill point.
for (unsigned i = 0, e = Kills.size(); i != e; ++i) {
SlotIndex Idx = Kills[i];
for (unsigned j = 0, e = CopyValues.size(); j != e; ++j) {
LiveInterval *DstLI = CopyValues[j].first;
const VNInfo *DstVNI = CopyValues[j].second;
if (DstLI->getVNInfoAt(Idx) != DstVNI)
continue;
// Check that there isn't already a def at Idx
LocMap::iterator I = locInts.find(Idx);
if (I.valid() && I.start() <= Idx)
continue;
DEBUG(dbgs() << "Kill at " << Idx << " covered by valno #"
<< DstVNI->id << " in " << *DstLI << '\n');
MachineInstr *CopyMI = LIS.getInstructionFromIndex(DstVNI->def);
assert(CopyMI && CopyMI->isCopy() && "Bad copy value");
unsigned LocNo = getLocationNo(CopyMI->getOperand(0));
DbgValueLocation NewLoc(LocNo, WasIndirect);
I.insert(Idx, Idx.getNextSlot(), NewLoc);
NewDefs.push_back(std::make_pair(Idx, NewLoc));
break;
}
}
}
void UserValue::computeIntervals(MachineRegisterInfo &MRI,
const TargetRegisterInfo &TRI,
LiveIntervals &LIS, LexicalScopes &LS) {
SmallVector<std::pair<SlotIndex, DbgValueLocation>, 16> Defs;
// Collect all defs to be extended (Skipping undefs).
for (LocMap::const_iterator I = locInts.begin(); I.valid(); ++I)
if (!I.value().isUndef())
Defs.push_back(std::make_pair(I.start(), I.value()));
// Extend all defs, and possibly add new ones along the way.
for (unsigned i = 0; i != Defs.size(); ++i) {
SlotIndex Idx = Defs[i].first;
DbgValueLocation Loc = Defs[i].second;
const MachineOperand &LocMO = locations[Loc.locNo()];
if (!LocMO.isReg()) {
extendDef(Idx, Loc, nullptr, nullptr, nullptr, LIS);
continue;
}
// Register locations are constrained to where the register value is live.
if (TargetRegisterInfo::isVirtualRegister(LocMO.getReg())) {
LiveInterval *LI = nullptr;
const VNInfo *VNI = nullptr;
if (LIS.hasInterval(LocMO.getReg())) {
LI = &LIS.getInterval(LocMO.getReg());
VNI = LI->getVNInfoAt(Idx);
}
SmallVector<SlotIndex, 16> Kills;
extendDef(Idx, Loc, LI, VNI, &Kills, LIS);
if (LI)
addDefsFromCopies(LI, Loc.locNo(), Loc.wasIndirect(), Kills, Defs, MRI,
LIS);
continue;
}
// For physregs, we only mark the start slot idx. DwarfDebug will see it
// as if the DBG_VALUE is valid up until the end of the basic block, or
// the next def of the physical register. So we do not need to extend the
// range. It might actually happen that the DBG_VALUE is the last use of
// the physical register (e.g. if this is an unused input argument to a
// function).
}
// Erase all the undefs.
for (LocMap::iterator I = locInts.begin(); I.valid();)
if (I.value().isUndef())
I.erase();
else
++I;
// The computed intervals may extend beyond the range of the debug
// location's lexical scope. In this case, splitting of an interval
// can result in an interval outside of the scope being created,
// causing extra unnecessary DBG_VALUEs to be emitted. To prevent
// this, trim the intervals to the lexical scope.
LexicalScope *Scope = LS.findLexicalScope(dl);
if (!Scope)
return;
SlotIndex PrevEnd;
LocMap::iterator I = locInts.begin();
// Iterate over the lexical scope ranges. Each time round the loop
// we check the intervals for overlap with the end of the previous
// range and the start of the next. The first range is handled as
// a special case where there is no PrevEnd.
for (const InsnRange &Range : Scope->getRanges()) {
SlotIndex RStart = LIS.getInstructionIndex(*Range.first);
SlotIndex REnd = LIS.getInstructionIndex(*Range.second);
// At the start of each iteration I has been advanced so that
// I.stop() >= PrevEnd. Check for overlap.
if (PrevEnd && I.start() < PrevEnd) {
SlotIndex IStop = I.stop();
DbgValueLocation Loc = I.value();
// Stop overlaps previous end - trim the end of the interval to
// the scope range.
I.setStopUnchecked(PrevEnd);
++I;
// If the interval also overlaps the start of the "next" (i.e.
// current) range create a new interval for the remainder (which
// may be further trimmed).
if (RStart < IStop)
I.insert(RStart, IStop, Loc);
}
// Advance I so that I.stop() >= RStart, and check for overlap.
I.advanceTo(RStart);
if (!I.valid())
return;
if (I.start() < RStart) {
// Interval start overlaps range - trim to the scope range.
I.setStartUnchecked(RStart);
// Remember that this interval was trimmed.
trimmedDefs.insert(RStart);
}
// The end of a lexical scope range is the last instruction in the
// range. To convert to an interval we need the index of the
// instruction after it.
REnd = REnd.getNextIndex();
// Advance I to first interval outside current range.
I.advanceTo(REnd);
if (!I.valid())
return;
PrevEnd = REnd;
}
// Check for overlap with end of final range.
if (PrevEnd && I.start() < PrevEnd)
I.setStopUnchecked(PrevEnd);
}
void LDVImpl::computeIntervals() {
LexicalScopes LS;
LS.initialize(*MF);
for (unsigned i = 0, e = userValues.size(); i != e; ++i) {
userValues[i]->computeIntervals(MF->getRegInfo(), *TRI, *LIS, LS);
userValues[i]->mapVirtRegs(this);
}
}
bool LDVImpl::runOnMachineFunction(MachineFunction &mf) {
clear();
MF = &mf;
LIS = &pass.getAnalysis<LiveIntervals>();
TRI = mf.getSubtarget().getRegisterInfo();
DEBUG(dbgs() << "********** COMPUTING LIVE DEBUG VARIABLES: "
<< mf.getName() << " **********\n");
bool Changed = collectDebugValues(mf);
computeIntervals();
DEBUG(print(dbgs()));
ModifiedMF = Changed;
return Changed;
}
static void removeDebugValues(MachineFunction &mf) {
for (MachineBasicBlock &MBB : mf) {
for (auto MBBI = MBB.begin(), MBBE = MBB.end(); MBBI != MBBE; ) {
if (!MBBI->isDebugValue()) {
++MBBI;
continue;
}
MBBI = MBB.erase(MBBI);
}
}
}
bool LiveDebugVariables::runOnMachineFunction(MachineFunction &mf) {
if (!EnableLDV)
return false;
if (!mf.getFunction()->getSubprogram()) {
removeDebugValues(mf);
return false;
}
if (!pImpl)
pImpl = new LDVImpl(this);
return static_cast<LDVImpl*>(pImpl)->runOnMachineFunction(mf);
}
void LiveDebugVariables::releaseMemory() {
if (pImpl)
static_cast<LDVImpl*>(pImpl)->clear();
}
LiveDebugVariables::~LiveDebugVariables() {
if (pImpl)
delete static_cast<LDVImpl*>(pImpl);
}
//===----------------------------------------------------------------------===//
// Live Range Splitting
//===----------------------------------------------------------------------===//
bool
UserValue::splitLocation(unsigned OldLocNo, ArrayRef<unsigned> NewRegs,
LiveIntervals& LIS) {
DEBUG({
dbgs() << "Splitting Loc" << OldLocNo << '\t';
print(dbgs(), nullptr);
});
bool DidChange = false;
LocMap::iterator LocMapI;
LocMapI.setMap(locInts);
for (unsigned i = 0; i != NewRegs.size(); ++i) {
LiveInterval *LI = &LIS.getInterval(NewRegs[i]);
if (LI->empty())
continue;
// Don't allocate the new LocNo until it is needed.
unsigned NewLocNo = UndefLocNo;
// Iterate over the overlaps between locInts and LI.
LocMapI.find(LI->beginIndex());
if (!LocMapI.valid())
continue;
LiveInterval::iterator LII = LI->advanceTo(LI->begin(), LocMapI.start());
LiveInterval::iterator LIE = LI->end();
while (LocMapI.valid() && LII != LIE) {
// At this point, we know that LocMapI.stop() > LII->start.
LII = LI->advanceTo(LII, LocMapI.start());
if (LII == LIE)
break;
// Now LII->end > LocMapI.start(). Do we have an overlap?
if (LocMapI.value().locNo() == OldLocNo && LII->start < LocMapI.stop()) {
// Overlapping correct location. Allocate NewLocNo now.
if (NewLocNo == UndefLocNo) {
MachineOperand MO = MachineOperand::CreateReg(LI->reg, false);
MO.setSubReg(locations[OldLocNo].getSubReg());
NewLocNo = getLocationNo(MO);
DidChange = true;
}
SlotIndex LStart = LocMapI.start();
SlotIndex LStop = LocMapI.stop();
DbgValueLocation OldLoc = LocMapI.value();
// Trim LocMapI down to the LII overlap.
if (LStart < LII->start)
LocMapI.setStartUnchecked(LII->start);
if (LStop > LII->end)
LocMapI.setStopUnchecked(LII->end);
// Change the value in the overlap. This may trigger coalescing.
LocMapI.setValue(OldLoc.changeLocNo(NewLocNo));
// Re-insert any removed OldLocNo ranges.
if (LStart < LocMapI.start()) {
LocMapI.insert(LStart, LocMapI.start(), OldLoc);
++LocMapI;
assert(LocMapI.valid() && "Unexpected coalescing");
}
if (LStop > LocMapI.stop()) {
++LocMapI;
LocMapI.insert(LII->end, LStop, OldLoc);
--LocMapI;
}
}
// Advance to the next overlap.
if (LII->end < LocMapI.stop()) {
if (++LII == LIE)
break;
LocMapI.advanceTo(LII->start);
} else {
++LocMapI;
if (!LocMapI.valid())
break;
LII = LI->advanceTo(LII, LocMapI.start());
}
}
}
// Finally, remove any remaining OldLocNo intervals and OldLocNo itself.
locations.erase(locations.begin() + OldLocNo);
LocMapI.goToBegin();
while (LocMapI.valid()) {
DbgValueLocation v = LocMapI.value();
if (v.locNo() == OldLocNo) {
DEBUG(dbgs() << "Erasing [" << LocMapI.start() << ';'
<< LocMapI.stop() << ")\n");
LocMapI.erase();
} else {
if (v.locNo() > OldLocNo)
LocMapI.setValueUnchecked(v.changeLocNo(v.locNo() - 1));
++LocMapI;
}
}
DEBUG({dbgs() << "Split result: \t"; print(dbgs(), nullptr);});
return DidChange;
}
bool
UserValue::splitRegister(unsigned OldReg, ArrayRef<unsigned> NewRegs,
LiveIntervals &LIS) {
bool DidChange = false;
// Split locations referring to OldReg. Iterate backwards so splitLocation can
// safely erase unused locations.
for (unsigned i = locations.size(); i ; --i) {
unsigned LocNo = i-1;
const MachineOperand *Loc = &locations[LocNo];
if (!Loc->isReg() || Loc->getReg() != OldReg)
continue;
DidChange |= splitLocation(LocNo, NewRegs, LIS);
}
return DidChange;
}
void LDVImpl::splitRegister(unsigned OldReg, ArrayRef<unsigned> NewRegs) {
bool DidChange = false;
for (UserValue *UV = lookupVirtReg(OldReg); UV; UV = UV->getNext())
DidChange |= UV->splitRegister(OldReg, NewRegs, *LIS);
if (!DidChange)
return;
// Map all of the new virtual registers.
UserValue *UV = lookupVirtReg(OldReg);
for (unsigned i = 0; i != NewRegs.size(); ++i)
mapVirtReg(NewRegs[i], UV);
}
void LiveDebugVariables::
splitRegister(unsigned OldReg, ArrayRef<unsigned> NewRegs, LiveIntervals &LIS) {
if (pImpl)
static_cast<LDVImpl*>(pImpl)->splitRegister(OldReg, NewRegs);
}
void UserValue::rewriteLocations(VirtRegMap &VRM, const TargetRegisterInfo &TRI,
BitVector &SpilledLocations) {
// Build a set of new locations with new numbers so we can coalesce our
// IntervalMap if two vreg intervals collapse to the same physical location.
// Use MapVector instead of SetVector because MapVector::insert returns the
// position of the previously or newly inserted element. The boolean value
// tracks if the location was produced by a spill.
// FIXME: This will be problematic if we ever support direct and indirect
// frame index locations, i.e. expressing both variables in memory and
// 'int x, *px = &x'. The "spilled" bit must become part of the location.
MapVector<MachineOperand, bool> NewLocations;
SmallVector<unsigned, 4> LocNoMap(locations.size());
for (unsigned I = 0, E = locations.size(); I != E; ++I) {
bool Spilled = false;
MachineOperand Loc = locations[I];
// Only virtual registers are rewritten.
if (Loc.isReg() && Loc.getReg() &&
TargetRegisterInfo::isVirtualRegister(Loc.getReg())) {
unsigned VirtReg = Loc.getReg();
if (VRM.isAssignedReg(VirtReg) &&
TargetRegisterInfo::isPhysicalRegister(VRM.getPhys(VirtReg))) {
// This can create a %noreg operand in rare cases when the sub-register
// index is no longer available. That means the user value is in a
// non-existent sub-register, and %noreg is exactly what we want.
Loc.substPhysReg(VRM.getPhys(VirtReg), TRI);
} else if (VRM.getStackSlot(VirtReg) != VirtRegMap::NO_STACK_SLOT) {
// FIXME: Translate SubIdx to a stackslot offset.
Loc = MachineOperand::CreateFI(VRM.getStackSlot(VirtReg));
Spilled = true;
} else {
Loc.setReg(0);
Loc.setSubReg(0);
}
}
// Insert this location if it doesn't already exist and record a mapping
// from the old number to the new number.
auto InsertResult = NewLocations.insert({Loc, Spilled});
unsigned NewLocNo = std::distance(NewLocations.begin(), InsertResult.first);
LocNoMap[I] = NewLocNo;
}
// Rewrite the locations and record which ones were spill slots.
locations.clear();
SpilledLocations.clear();
SpilledLocations.resize(NewLocations.size());
for (auto &Pair : NewLocations) {
locations.push_back(Pair.first);
if (Pair.second) {
unsigned NewLocNo = std::distance(&*NewLocations.begin(), &Pair);
SpilledLocations.set(NewLocNo);
}
}
// Update the interval map, but only coalesce left, since intervals to the
// right use the old location numbers. This should merge two contiguous
// DBG_VALUE intervals with different vregs that were allocated to the same
// physical register.
for (LocMap::iterator I = locInts.begin(); I.valid(); ++I) {
DbgValueLocation Loc = I.value();
unsigned NewLocNo = LocNoMap[Loc.locNo()];
I.setValueUnchecked(Loc.changeLocNo(NewLocNo));
I.setStart(I.start());
}
}
/// Find an iterator for inserting a DBG_VALUE instruction.
static MachineBasicBlock::iterator
findInsertLocation(MachineBasicBlock *MBB, SlotIndex Idx,
LiveIntervals &LIS) {
SlotIndex Start = LIS.getMBBStartIdx(MBB);
Idx = Idx.getBaseIndex();
// Try to find an insert location by going backwards from Idx.
MachineInstr *MI;
while (!(MI = LIS.getInstructionFromIndex(Idx))) {
// We've reached the beginning of MBB.
if (Idx == Start) {
MachineBasicBlock::iterator I = MBB->SkipPHIsLabelsAndDebug(MBB->begin());
return I;
}
Idx = Idx.getPrevIndex();
}
// Don't insert anything after the first terminator, though.
return MI->isTerminator() ? MBB->getFirstTerminator() :
std::next(MachineBasicBlock::iterator(MI));
}
/// Find an iterator for inserting the next DBG_VALUE instruction
/// (or end if no more insert locations found).
static MachineBasicBlock::iterator
findNextInsertLocation(MachineBasicBlock *MBB,
MachineBasicBlock::iterator I,
SlotIndex StopIdx, MachineOperand &LocMO,
LiveIntervals &LIS,
const TargetRegisterInfo &TRI) {
if (!LocMO.isReg())
return MBB->instr_end();
unsigned Reg = LocMO.getReg();
// Find the next instruction in the MBB that define the register Reg.
while (I != MBB->end()) {
if (!LIS.isNotInMIMap(*I) &&
SlotIndex::isEarlierEqualInstr(StopIdx, LIS.getInstructionIndex(*I)))
break;
if (I->definesRegister(Reg, &TRI))
// The insert location is directly after the instruction/bundle.
return std::next(I);
++I;
}
return MBB->end();
}
void UserValue::insertDebugValue(MachineBasicBlock *MBB, SlotIndex StartIdx,
SlotIndex StopIdx,
DbgValueLocation Loc, bool Spilled,
LiveIntervals &LIS,
const TargetInstrInfo &TII,
const TargetRegisterInfo &TRI) {
SlotIndex MBBEndIdx = LIS.getMBBEndIdx(&*MBB);
// Only search within the current MBB.
StopIdx = (MBBEndIdx < StopIdx) ? MBBEndIdx : StopIdx;
MachineBasicBlock::iterator I = findInsertLocation(MBB, StartIdx, LIS);
MachineOperand &MO = locations[Loc.locNo()];
++NumInsertedDebugValues;
assert(cast<DILocalVariable>(Variable)
->isValidLocationForIntrinsic(getDebugLoc()) &&
"Expected inlined-at fields to agree");
// If the location was spilled, the new DBG_VALUE will be indirect. If the
// original DBG_VALUE was indirect, we need to add DW_OP_deref to indicate
// that the original virtual register was a pointer.
const DIExpression *Expr = Expression;
bool IsIndirect = Loc.wasIndirect();
if (Spilled) {
if (IsIndirect)
Expr = DIExpression::prepend(Expr, DIExpression::WithDeref);
IsIndirect = true;
}
assert((!Spilled || MO.isFI()) && "a spilled location must be a frame index");
do {
MachineInstrBuilder MIB =
BuildMI(*MBB, I, getDebugLoc(), TII.get(TargetOpcode::DBG_VALUE))
.add(MO);
if (IsIndirect)
MIB.addImm(0U);
else
MIB.addReg(0U, RegState::Debug);
MIB.addMetadata(Variable).addMetadata(Expr);
// Continue and insert DBG_VALUES after every redefinition of register
// associated with the debug value within the range
I = findNextInsertLocation(MBB, I, StopIdx, MO, LIS, TRI);
} while (I != MBB->end());
}
void UserValue::emitDebugValues(VirtRegMap *VRM, LiveIntervals &LIS,
const TargetInstrInfo &TII,
const TargetRegisterInfo &TRI,
const BitVector &SpilledLocations) {
MachineFunction::iterator MFEnd = VRM->getMachineFunction().end();
for (LocMap::const_iterator I = locInts.begin(); I.valid();) {
SlotIndex Start = I.start();
SlotIndex Stop = I.stop();
DbgValueLocation Loc = I.value();
bool Spilled = !Loc.isUndef() ? SpilledLocations.test(Loc.locNo()) : false;
// If the interval start was trimmed to the lexical scope insert the
// DBG_VALUE at the previous index (otherwise it appears after the
// first instruction in the range).
if (trimmedDefs.count(Start))
Start = Start.getPrevIndex();
DEBUG(dbgs() << "\t[" << Start << ';' << Stop << "):" << Loc.locNo());
MachineFunction::iterator MBB = LIS.getMBBFromIndex(Start)->getIterator();
SlotIndex MBBEnd = LIS.getMBBEndIdx(&*MBB);
DEBUG(dbgs() << " BB#" << MBB->getNumber() << '-' << MBBEnd);
insertDebugValue(&*MBB, Start, Stop, Loc, Spilled, LIS, TII, TRI);
// This interval may span multiple basic blocks.
// Insert a DBG_VALUE into each one.
while (Stop > MBBEnd) {
// Move to the next block.
Start = MBBEnd;
if (++MBB == MFEnd)
break;
MBBEnd = LIS.getMBBEndIdx(&*MBB);
DEBUG(dbgs() << " BB#" << MBB->getNumber() << '-' << MBBEnd);
insertDebugValue(&*MBB, Start, Stop, Loc, Spilled, LIS, TII, TRI);
}
DEBUG(dbgs() << '\n');
if (MBB == MFEnd)
break;
++I;
}
}
void LDVImpl::emitDebugValues(VirtRegMap *VRM) {
DEBUG(dbgs() << "********** EMITTING LIVE DEBUG VARIABLES **********\n");
if (!MF)
return;
const TargetInstrInfo *TII = MF->getSubtarget().getInstrInfo();
BitVector SpilledLocations;
for (unsigned i = 0, e = userValues.size(); i != e; ++i) {
DEBUG(userValues[i]->print(dbgs(), TRI));
userValues[i]->rewriteLocations(*VRM, *TRI, SpilledLocations);
userValues[i]->emitDebugValues(VRM, *LIS, *TII, *TRI, SpilledLocations);
}
EmitDone = true;
}
void LiveDebugVariables::emitDebugValues(VirtRegMap *VRM) {
if (pImpl)
static_cast<LDVImpl*>(pImpl)->emitDebugValues(VRM);
}
bool LiveDebugVariables::doInitialization(Module &M) {
return Pass::doInitialization(M);
}
#ifdef LLVM_ENABLE_DUMP
LLVM_DUMP_METHOD void LiveDebugVariables::dump() const {
if (pImpl)
static_cast<LDVImpl*>(pImpl)->print(dbgs());
}
#endif
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