maxjhandsome
/
llvm-project
forked from OSchip/llvm-project
1
0
Fork 0
Code Issues Pull Requests Packages Releases Wiki Activity
llvm-project/llvm/lib/CodeGen/LiveDebugValues.cpp

1214 lines
47 KiB
C++
Raw Blame History

//===- LiveDebugValues.cpp - Tracking Debug Value MIs ---------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
///
/// 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/DenseMap.h"
#include "llvm/ADT/PostOrderIterator.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/SmallSet.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/SparseBitVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/UniqueVector.h"
#include "llvm/CodeGen/LexicalScopes.h"
#include "llvm/CodeGen/MachineBasicBlock.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineMemOperand.h"
#include "llvm/CodeGen/MachineOperand.h"
#include "llvm/CodeGen/PseudoSourceValue.h"
#include "llvm/CodeGen/RegisterScavenging.h"
#include "llvm/CodeGen/TargetFrameLowering.h"
#include "llvm/CodeGen/TargetInstrInfo.h"
#include "llvm/CodeGen/TargetLowering.h"
#include "llvm/CodeGen/TargetRegisterInfo.h"
#include "llvm/CodeGen/TargetSubtargetInfo.h"
#include "llvm/Config/llvm-config.h"
#include "llvm/IR/DIBuilder.h"
#include "llvm/IR/DebugInfoMetadata.h"
#include "llvm/IR/DebugLoc.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/Module.h"
#include "llvm/MC/MCRegisterInfo.h"
#include "llvm/Pass.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
#include <algorithm>
#include <cassert>
#include <cstdint>
#include <functional>
#include <queue>
#include <tuple>
#include <utility>
#include <vector>
using namespace llvm;
#define DEBUG_TYPE "livedebugvalues"
STATISTIC(NumInserted, "Number of DBG_VALUE instructions inserted");
// 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 Register 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() : Register();
}
namespace {
class LiveDebugValues : public MachineFunctionPass {
private:
const TargetRegisterInfo *TRI;
const TargetInstrInfo *TII;
const TargetFrameLowering *TFI;
BitVector CalleeSavedRegs;
LexicalScopes LS;
enum struct TransferKind { TransferCopy, TransferSpill, TransferRestore };
/// Keeps track of lexical scopes associated with a user value's source
/// location.
class UserValueScopes {
DebugLoc DL;
LexicalScopes &LS;
SmallPtrSet<const MachineBasicBlock *, 4> LBlocks;
public:
UserValueScopes(DebugLoc D, LexicalScopes &L) : DL(std::move(D)), LS(L) {}
/// Return true if current scope dominates at least one machine
/// instruction in a given machine basic block.
bool dominates(MachineBasicBlock *MBB) {
if (LBlocks.empty())
LS.getMachineBasicBlocks(DL, LBlocks);
return LBlocks.count(MBB) != 0 || LS.dominates(DL, MBB);
}
};
using FragmentInfo = DIExpression::FragmentInfo;
using OptFragmentInfo = Optional<DIExpression::FragmentInfo>;
/// Storage for identifying a potentially inlined instance of a variable,
/// or a fragment thereof.
class DebugVariable {
const DILocalVariable *Variable;
OptFragmentInfo Fragment;
const DILocation *InlinedAt;
/// Fragment that will overlap all other fragments. Used as default when
/// caller demands a fragment.
static const FragmentInfo DefaultFragment;
public:
DebugVariable(const DILocalVariable *Var, OptFragmentInfo &&FragmentInfo,
const DILocation *InlinedAt)
: Variable(Var), Fragment(FragmentInfo), InlinedAt(InlinedAt) {}
DebugVariable(const DILocalVariable *Var, OptFragmentInfo &FragmentInfo,
const DILocation *InlinedAt)
: Variable(Var), Fragment(FragmentInfo), InlinedAt(InlinedAt) {}
DebugVariable(const DILocalVariable *Var, const DIExpression *DIExpr,
const DILocation *InlinedAt)
: DebugVariable(Var, DIExpr->getFragmentInfo(), InlinedAt) {}
DebugVariable(const MachineInstr &MI)
: DebugVariable(MI.getDebugVariable(),
MI.getDebugExpression()->getFragmentInfo(),
MI.getDebugLoc()->getInlinedAt()) {}
const DILocalVariable *getVar() const { return Variable; }
const OptFragmentInfo &getFragment() const { return Fragment; }
const DILocation *getInlinedAt() const { return InlinedAt; }
const FragmentInfo getFragmentDefault() const {
return Fragment.getValueOr(DefaultFragment);
}
static bool isFragmentDefault(FragmentInfo &F) {
return F == DefaultFragment;
}
bool operator==(const DebugVariable &Other) const {
return std::tie(Variable, Fragment, InlinedAt) ==
std::tie(Other.Variable, Other.Fragment, Other.InlinedAt);
}
bool operator<(const DebugVariable &Other) const {
return std::tie(Variable, Fragment, InlinedAt) <
std::tie(Other.Variable, Other.Fragment, Other.InlinedAt);
}
};
friend struct llvm::DenseMapInfo<DebugVariable>;
/// A pair of debug variable and value location.
struct VarLoc {
// The location at which a spilled variable resides. It consists of a
// register and an offset.
struct SpillLoc {
unsigned SpillBase;
int SpillOffset;
bool operator==(const SpillLoc &Other) const {
return SpillBase == Other.SpillBase && SpillOffset == Other.SpillOffset;
}
};
const DebugVariable Var;
const MachineInstr &MI; ///< Only used for cloning a new DBG_VALUE.
mutable UserValueScopes UVS;
enum VarLocKind {
InvalidKind = 0,
RegisterKind,
SpillLocKind,
ImmediateKind
} Kind = InvalidKind;
/// The value location. Stored separately to avoid repeatedly
/// extracting it from MI.
union {
uint64_t RegNo;
SpillLoc SpillLocation;
uint64_t Hash;
int64_t Immediate;
const ConstantFP *FPImm;
const ConstantInt *CImm;
} Loc;
VarLoc(const MachineInstr &MI, LexicalScopes &LS)
: Var(MI), MI(MI), UVS(MI.getDebugLoc(), LS) {
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.RegNo = RegNo;
} else if (MI.getOperand(0).isImm()) {
Kind = ImmediateKind;
Loc.Immediate = MI.getOperand(0).getImm();
} else if (MI.getOperand(0).isFPImm()) {
Kind = ImmediateKind;
Loc.FPImm = MI.getOperand(0).getFPImm();
} else if (MI.getOperand(0).isCImm()) {
Kind = ImmediateKind;
Loc.CImm = MI.getOperand(0).getCImm();
}
}
/// The constructor for spill locations.
VarLoc(const MachineInstr &MI, unsigned SpillBase, int SpillOffset,
LexicalScopes &LS)
: Var(MI), MI(MI), UVS(MI.getDebugLoc(), LS) {
assert(MI.isDebugValue() && "not a DBG_VALUE");
assert(MI.getNumOperands() == 4 && "malformed DBG_VALUE");
Kind = SpillLocKind;
Loc.SpillLocation = {SpillBase, SpillOffset};
}
// Is the Loc field a constant or constant object?
bool isConstant() const { return Kind == ImmediateKind; }
/// If this variable is described by a register, return it,
/// otherwise return 0.
unsigned isDescribedByReg() const {
if (Kind == RegisterKind)
return Loc.RegNo;
return 0;
}
/// Determine whether the lexical scope of this value's debug location
/// dominates MBB.
bool dominates(MachineBasicBlock &MBB) const { return UVS.dominates(&MBB); }
#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
LLVM_DUMP_METHOD void dump() const { MI.dump(); }
#endif
bool operator==(const VarLoc &Other) const {
return Kind == Other.Kind && 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;
}
};
using VarLocMap = UniqueVector<VarLoc>;
using VarLocSet = SparseBitVector<>;
using VarLocInMBB = SmallDenseMap<const MachineBasicBlock *, VarLocSet>;
struct TransferDebugPair {
MachineInstr *TransferInst;
MachineInstr *DebugInst;
};
using TransferMap = SmallVector<TransferDebugPair, 4>;
// Types for recording sets of variable fragments that overlap. For a given
// local variable, we record all other fragments of that variable that could
// overlap it, to reduce search time.
using FragmentOfVar =
std::pair<const DILocalVariable *, DIExpression::FragmentInfo>;
using OverlapMap =
DenseMap<FragmentOfVar, SmallVector<DIExpression::FragmentInfo, 1>>;
// Helper while building OverlapMap, a map of all fragments seen for a given
// DILocalVariable.
using VarToFragments =
DenseMap<const DILocalVariable *, SmallSet<FragmentInfo, 4>>;
/// 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<DebugVariable, unsigned, 8> Vars;
OverlapMap &OverlappingFragments;
public:
OpenRangesSet(OverlapMap &_OLapMap) : OverlappingFragments(_OLapMap) {}
const VarLocSet &getVarLocs() const { return VarLocs; }
/// Terminate all open ranges for Var by removing it from the set.
void erase(DebugVariable Var);
/// 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, DebugVariable 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();
}
};
bool isSpillInstruction(const MachineInstr &MI, MachineFunction *MF,
unsigned &Reg);
/// If a given instruction is identified as a spill, return the spill location
/// and set \p Reg to the spilled register.
Optional<VarLoc::SpillLoc> isRestoreInstruction(const MachineInstr &MI,
MachineFunction *MF,
unsigned &Reg);
/// Given a spill instruction, extract the register and offset used to
/// address the spill location in a target independent way.
VarLoc::SpillLoc extractSpillBaseRegAndOffset(const MachineInstr &MI);
void insertTransferDebugPair(MachineInstr &MI, OpenRangesSet &OpenRanges,
TransferMap &Transfers, VarLocMap &VarLocIDs,
unsigned OldVarID, TransferKind Kind,
unsigned NewReg = 0);
void transferDebugValue(const MachineInstr &MI, OpenRangesSet &OpenRanges,
VarLocMap &VarLocIDs);
void transferSpillOrRestoreInst(MachineInstr &MI, OpenRangesSet &OpenRanges,
VarLocMap &VarLocIDs, TransferMap &Transfers);
void transferRegisterCopy(MachineInstr &MI, OpenRangesSet &OpenRanges,
VarLocMap &VarLocIDs, TransferMap &Transfers);
void transferRegisterDef(MachineInstr &MI, OpenRangesSet &OpenRanges,
const VarLocMap &VarLocIDs);
bool transferTerminatorInst(MachineInstr &MI, OpenRangesSet &OpenRanges,
VarLocInMBB &OutLocs, const VarLocMap &VarLocIDs);
bool process(MachineInstr &MI, OpenRangesSet &OpenRanges,
VarLocInMBB &OutLocs, VarLocMap &VarLocIDs,
TransferMap &Transfers, bool transferChanges,
OverlapMap &OverlapFragments, VarToFragments &SeenFragments);
void accumulateFragmentMap(MachineInstr &MI, VarToFragments &SeenFragments,
OverlapMap &OLapMap);
bool join(MachineBasicBlock &MBB, VarLocInMBB &OutLocs, VarLocInMBB &InLocs,
const VarLocMap &VarLocIDs,
SmallPtrSet<const MachineBasicBlock *, 16> &Visited,
SmallPtrSetImpl<const MachineBasicBlock *> &ArtificialBlocks);
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::NoVRegs);
}
/// 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;
};
} // end anonymous namespace
namespace llvm {
template <> struct DenseMapInfo<LiveDebugValues::DebugVariable> {
using DV = LiveDebugValues::DebugVariable;
using OptFragmentInfo = LiveDebugValues::OptFragmentInfo;
using FragmentInfo = LiveDebugValues::FragmentInfo;
// Empty key: no key should be generated that has no DILocalVariable.
static inline DV getEmptyKey() {
return DV(nullptr, OptFragmentInfo(), nullptr);
}
// Difference in tombstone is that the Optional is meaningful
static inline DV getTombstoneKey() {
return DV(nullptr, OptFragmentInfo({0, 0}), nullptr);
}
static unsigned getHashValue(const DV &D) {
unsigned HV = 0;
const OptFragmentInfo &Fragment = D.getFragment();
if (Fragment)
HV = DenseMapInfo<FragmentInfo>::getHashValue(*Fragment);
return hash_combine(D.getVar(), HV, D.getInlinedAt());
}
static bool isEqual(const DV &A, const DV &B) { return A == B; }
};
} // namespace llvm
//===----------------------------------------------------------------------===//
// Implementation
//===----------------------------------------------------------------------===//
const DIExpression::FragmentInfo
LiveDebugValues::DebugVariable::DefaultFragment = {
std::numeric_limits<uint64_t>::max(),
std::numeric_limits<uint64_t>::min()};
char LiveDebugValues::ID = 0;
char &llvm::LiveDebugValuesID = LiveDebugValues::ID;
INITIALIZE_PASS(LiveDebugValues, DEBUG_TYPE, "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);
}
/// Erase a variable from the set of open ranges, and additionally erase any
/// fragments that may overlap it.
void LiveDebugValues::OpenRangesSet::erase(DebugVariable Var) {
// Erasure helper.
auto DoErase = [this](DebugVariable VarToErase) {
auto It = Vars.find(VarToErase);
if (It != Vars.end()) {
unsigned ID = It->second;
VarLocs.reset(ID);
Vars.erase(It);
}
};
// Erase the variable/fragment that ends here.
DoErase(Var);
// Extract the fragment. Interpret an empty fragment as one that covers all
// possible bits.
FragmentInfo ThisFragment = Var.getFragmentDefault();
// There may be fragments that overlap the designated fragment. Look them up
// in the pre-computed overlap map, and erase them too.
auto MapIt = OverlappingFragments.find({Var.getVar(), ThisFragment});
if (MapIt != OverlappingFragments.end()) {
for (auto Fragment : MapIt->second) {
LiveDebugValues::OptFragmentInfo FragmentHolder;
if (!DebugVariable::isFragmentDefault(Fragment))
FragmentHolder = LiveDebugValues::OptFragmentInfo(Fragment);
DoErase({Var.getVar(), FragmentHolder, Var.getInlinedAt()});
}
}
}
//===----------------------------------------------------------------------===//
// Debug Range Extension Implementation
//===----------------------------------------------------------------------===//
#ifndef NDEBUG
void LiveDebugValues::printVarLocInMBB(const MachineFunction &MF,
const VarLocInMBB &V,
const VarLocMap &VarLocIDs,
const char *msg,
raw_ostream &Out) const {
Out << '\n' << msg << '\n';
for (const MachineBasicBlock &BB : MF) {
const VarLocSet &L = V.lookup(&BB);
if (L.empty())
continue;
Out << "MBB: " << BB.getNumber() << ":\n";
for (unsigned VLL : L) {
const VarLoc &VL = VarLocIDs[VLL];
Out << " Var: " << VL.Var.getVar()->getName();
Out << " MI: ";
VL.dump();
}
}
Out << "\n";
}
#endif
LiveDebugValues::VarLoc::SpillLoc
LiveDebugValues::extractSpillBaseRegAndOffset(const MachineInstr &MI) {
assert(MI.hasOneMemOperand() &&
"Spill instruction does not have exactly one memory operand?");
auto MMOI = MI.memoperands_begin();
const PseudoSourceValue *PVal = (*MMOI)->getPseudoValue();
assert(PVal->kind() == PseudoSourceValue::FixedStack &&
"Inconsistent memory operand in spill instruction");
int FI = cast<FixedStackPseudoSourceValue>(PVal)->getFrameIndex();
const MachineBasicBlock *MBB = MI.getParent();
unsigned Reg;
int Offset = TFI->getFrameIndexReference(*MBB->getParent(), FI, Reg);
return {Reg, Offset};
}
/// 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 DIExpression *Expr = MI.getDebugExpression();
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, Expr, InlinedAt);
OpenRanges.erase(V);
// Add the VarLoc to OpenRanges from this DBG_VALUE.
unsigned ID;
if (isDbgValueDescribedByReg(MI) || MI.getOperand(0).isImm() ||
MI.getOperand(0).isFPImm() || MI.getOperand(0).isCImm()) {
// Use normal VarLoc constructor for registers and immediates.
VarLoc VL(MI, LS);
ID = VarLocIDs.insert(VL);
OpenRanges.insert(ID, VL.Var);
} else if (MI.hasOneMemOperand()) {
// It's a stack spill -- fetch spill base and offset.
VarLoc::SpillLoc SpillLocation = extractSpillBaseRegAndOffset(MI);
VarLoc VL(MI, SpillLocation.SpillBase, SpillLocation.SpillOffset, LS);
ID = VarLocIDs.insert(VL);
OpenRanges.insert(ID, VL.Var);
} else {
// This must be an undefined location. We should leave OpenRanges closed.
assert(MI.getOperand(0).isReg() && MI.getOperand(0).getReg() == 0 &&
"Unexpected non-undef DBG_VALUE encountered");
}
}
/// Create new TransferDebugPair and insert it in \p Transfers. The VarLoc
/// with \p OldVarID should be deleted form \p OpenRanges and replaced with
/// new VarLoc. If \p NewReg is different than default zero value then the
/// new location will be register location created by the copy like instruction,
/// otherwise it is variable's location on the stack.
void LiveDebugValues::insertTransferDebugPair(
MachineInstr &MI, OpenRangesSet &OpenRanges, TransferMap &Transfers,
VarLocMap &VarLocIDs, unsigned OldVarID, TransferKind Kind,
unsigned NewReg) {
const MachineInstr *DebugInstr = &VarLocIDs[OldVarID].MI;
MachineFunction *MF = MI.getParent()->getParent();
MachineInstr *NewDebugInstr;
auto ProcessVarLoc = [&MI, &OpenRanges, &Transfers, &DebugInstr,
&VarLocIDs](VarLoc &VL, MachineInstr *NewDebugInstr) {
unsigned LocId = VarLocIDs.insert(VL);
// Close this variable's previous location range.
DebugVariable V(*DebugInstr);
OpenRanges.erase(V);
OpenRanges.insert(LocId, VL.Var);
// The newly created DBG_VALUE instruction NewDebugInstr must be inserted
// after MI. Keep track of the pairing.
TransferDebugPair MIP = {&MI, NewDebugInstr};
Transfers.push_back(MIP);
};
// End all previous ranges of Var.
OpenRanges.erase(VarLocIDs[OldVarID].Var);
switch (Kind) {
case TransferKind::TransferCopy: {
assert(NewReg &&
"No register supplied when handling a copy of a debug value");
// Create a DBG_VALUE instruction to describe the Var in its new
// register location.
NewDebugInstr = BuildMI(
*MF, DebugInstr->getDebugLoc(), DebugInstr->getDesc(),
DebugInstr->isIndirectDebugValue(), NewReg,
DebugInstr->getDebugVariable(), DebugInstr->getDebugExpression());
if (DebugInstr->isIndirectDebugValue())
NewDebugInstr->getOperand(1).setImm(DebugInstr->getOperand(1).getImm());
VarLoc VL(*NewDebugInstr, LS);
ProcessVarLoc(VL, NewDebugInstr);
LLVM_DEBUG(dbgs() << "Creating DBG_VALUE inst for register copy: ";
NewDebugInstr->print(dbgs(), /*IsStandalone*/false,
/*SkipOpers*/false, /*SkipDebugLoc*/false,
/*AddNewLine*/true, TII));
return;
}
case TransferKind::TransferSpill: {
// Create a DBG_VALUE instruction to describe the Var in its spilled
// location.
VarLoc::SpillLoc SpillLocation = extractSpillBaseRegAndOffset(MI);
auto *SpillExpr = DIExpression::prepend(DebugInstr->getDebugExpression(),
DIExpression::ApplyOffset,
SpillLocation.SpillOffset);
NewDebugInstr = BuildMI(
*MF, DebugInstr->getDebugLoc(), DebugInstr->getDesc(), true,
SpillLocation.SpillBase, DebugInstr->getDebugVariable(), SpillExpr);
VarLoc VL(*NewDebugInstr, SpillLocation.SpillBase,
SpillLocation.SpillOffset, LS);
ProcessVarLoc(VL, NewDebugInstr);
LLVM_DEBUG(dbgs() << "Creating DBG_VALUE inst for spill: ";
NewDebugInstr->print(dbgs(), /*IsStandalone*/false,
/*SkipOpers*/false, /*SkipDebugLoc*/false,
/*AddNewLine*/true, TII));
return;
}
case TransferKind::TransferRestore: {
assert(NewReg &&
"No register supplied when handling a restore of a debug value");
MachineFunction *MF = MI.getMF();
DIBuilder DIB(*const_cast<Function &>(MF->getFunction()).getParent());
NewDebugInstr =
BuildMI(*MF, DebugInstr->getDebugLoc(), DebugInstr->getDesc(), false,
NewReg, DebugInstr->getDebugVariable(), DIB.createExpression());
VarLoc VL(*NewDebugInstr, LS);
ProcessVarLoc(VL, NewDebugInstr);
LLVM_DEBUG(dbgs() << "Creating DBG_VALUE inst for register restore: ";
NewDebugInstr->print(dbgs(), /*IsStandalone*/false,
/*SkipOpers*/false, /*SkipDebugLoc*/false,
/*AddNewLine*/true, TII));
return;
}
}
llvm_unreachable("Invalid transfer kind");
}
/// 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.getMF();
const TargetLowering *TLI = MF->getSubtarget().getTargetLowering();
unsigned SP = TLI->getStackPointerRegisterToSaveRestore();
SparseBitVector<> KillSet;
for (const MachineOperand &MO : MI.operands()) {
// Determine whether the operand is a register def. Assume that call
// instructions never clobber SP, because some backends (e.g., AArch64)
// never list SP in the regmask.
if (MO.isReg() && MO.isDef() && MO.getReg() &&
TRI->isPhysicalRegister(MO.getReg()) &&
!(MI.isCall() && MO.getReg() == SP)) {
// 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);
}
/// Decide if @MI is a spill instruction and return true if it is. We use 2
/// criteria to make this decision:
/// - Is this instruction a store to a spill slot?
/// - Is there a register operand that is both used and killed?
/// TODO: Store optimization can fold spills into other stores (including
/// other spills). We do not handle this yet (more than one memory operand).
bool LiveDebugValues::isSpillInstruction(const MachineInstr &MI,
MachineFunction *MF, unsigned &Reg) {
SmallVector<const MachineMemOperand*, 1> Accesses;
// TODO: Handle multiple stores folded into one.
if (!MI.hasOneMemOperand())
return false;
if (!MI.getSpillSize(TII) && !MI.getFoldedSpillSize(TII))
return false; // This is not a spill instruction, since no valid size was
// returned from either function.
auto isKilledReg = [&](const MachineOperand MO, unsigned &Reg) {
if (!MO.isReg() || !MO.isUse()) {
Reg = 0;
return false;
}
Reg = MO.getReg();
return MO.isKill();
};
for (const MachineOperand &MO : MI.operands()) {
// In a spill instruction generated by the InlineSpiller the spilled
// register has its kill flag set.
if (isKilledReg(MO, Reg))
return true;
if (Reg != 0) {
// Check whether next instruction kills the spilled register.
// FIXME: Current solution does not cover search for killed register in
// bundles and instructions further down the chain.
auto NextI = std::next(MI.getIterator());
// Skip next instruction that points to basic block end iterator.
if (MI.getParent()->end() == NextI)
continue;
unsigned RegNext;
for (const MachineOperand &MONext : NextI->operands()) {
// Return true if we came across the register from the
// previous spill instruction that is killed in NextI.
if (isKilledReg(MONext, RegNext) && RegNext == Reg)
return true;
}
}
}
// Return false if we didn't find spilled register.
return false;
}
Optional<LiveDebugValues::VarLoc::SpillLoc>
LiveDebugValues::isRestoreInstruction(const MachineInstr &MI,
MachineFunction *MF, unsigned &Reg) {
if (!MI.hasOneMemOperand())
return None;
// FIXME: Handle folded restore instructions with more than one memory
// operand.
if (MI.getRestoreSize(TII)) {
Reg = MI.getOperand(0).getReg();
return extractSpillBaseRegAndOffset(MI);
}
return None;
}
/// A spilled register may indicate that we have to end the current range of
/// a variable and create a new one for the spill location.
/// A restored register may indicate the reverse situation.
/// We don't want to insert any instructions in process(), so we just create
/// the DBG_VALUE without inserting it and keep track of it in \p Transfers.
/// It will be inserted into the BB when we're done iterating over the
/// instructions.
void LiveDebugValues::transferSpillOrRestoreInst(MachineInstr &MI,
OpenRangesSet &OpenRanges,
VarLocMap &VarLocIDs,
TransferMap &Transfers) {
MachineFunction *MF = MI.getMF();
TransferKind TKind;
unsigned Reg;
Optional<VarLoc::SpillLoc> Loc;
LLVM_DEBUG(dbgs() << "Examining instruction: "; MI.dump(););
if (isSpillInstruction(MI, MF, Reg)) {
TKind = TransferKind::TransferSpill;
LLVM_DEBUG(dbgs() << "Recognized as spill: "; MI.dump(););
LLVM_DEBUG(dbgs() << "Register: " << Reg << " " << printReg(Reg, TRI)
<< "\n");
} else {
if (!(Loc = isRestoreInstruction(MI, MF, Reg)))
return;
TKind = TransferKind::TransferRestore;
LLVM_DEBUG(dbgs() << "Recognized as restore: "; MI.dump(););
LLVM_DEBUG(dbgs() << "Register: " << Reg << " " << printReg(Reg, TRI)
<< "\n");
}
// Check if the register or spill location is the location of a debug value.
for (unsigned ID : OpenRanges.getVarLocs()) {
if (TKind == TransferKind::TransferSpill &&
VarLocIDs[ID].isDescribedByReg() == Reg) {
LLVM_DEBUG(dbgs() << "Spilling Register " << printReg(Reg, TRI) << '('
<< VarLocIDs[ID].Var.getVar()->getName() << ")\n");
} else if (TKind == TransferKind::TransferRestore &&
VarLocIDs[ID].Loc.SpillLocation == *Loc) {
LLVM_DEBUG(dbgs() << "Restoring Register " << printReg(Reg, TRI) << '('
<< VarLocIDs[ID].Var.getVar()->getName() << ")\n");
} else
continue;
insertTransferDebugPair(MI, OpenRanges, Transfers, VarLocIDs, ID, TKind,
Reg);
return;
}
}
/// If \p MI is a register copy instruction, that copies a previously tracked
/// value from one register to another register that is callee saved, we
/// create new DBG_VALUE instruction described with copy destination register.
void LiveDebugValues::transferRegisterCopy(MachineInstr &MI,
OpenRangesSet &OpenRanges,
VarLocMap &VarLocIDs,
TransferMap &Transfers) {
const MachineOperand *SrcRegOp, *DestRegOp;
if (!TII->isCopyInstr(MI, SrcRegOp, DestRegOp) || !SrcRegOp->isKill() ||
!DestRegOp->isDef())
return;
auto isCalleSavedReg = [&](unsigned Reg) {
for (MCRegAliasIterator RAI(Reg, TRI, true); RAI.isValid(); ++RAI)
if (CalleeSavedRegs.test(*RAI))
return true;
return false;
};
unsigned SrcReg = SrcRegOp->getReg();
unsigned DestReg = DestRegOp->getReg();
// We want to recognize instructions where destination register is callee
// saved register. If register that could be clobbered by the call is
// included, there would be a great chance that it is going to be clobbered
// soon. It is more likely that previous register location, which is callee
// saved, is going to stay unclobbered longer, even if it is killed.
if (!isCalleSavedReg(DestReg))
return;
for (unsigned ID : OpenRanges.getVarLocs()) {
if (VarLocIDs[ID].isDescribedByReg() == SrcReg) {
insertTransferDebugPair(MI, OpenRanges, Transfers, VarLocIDs, ID,
TransferKind::TransferCopy, DestReg);
return;
}
}
}
/// 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->back())))
return false;
if (OpenRanges.empty())
return false;
LLVM_DEBUG(for (unsigned ID
: OpenRanges.getVarLocs()) {
// Copy OpenRanges to OutLocs, if not already present.
dbgs() << "Add to OutLocs in MBB #" << CurMBB->getNumber() << ": ";
VarLocIDs[ID].dump();
});
VarLocSet &VLS = OutLocs[CurMBB];
Changed = VLS |= OpenRanges.getVarLocs();
// New OutLocs set may be different due to spill, restore or register
// copy instruction processing.
if (Changed)
VLS = OpenRanges.getVarLocs();
OpenRanges.clear();
return Changed;
}
/// Accumulate a mapping between each DILocalVariable fragment and other
/// fragments of that DILocalVariable which overlap. This reduces work during
/// the data-flow stage from "Find any overlapping fragments" to "Check if the
/// known-to-overlap fragments are present".
/// \param MI A previously unprocessed DEBUG_VALUE instruction to analyze for
/// fragment usage.
/// \param SeenFragments Map from DILocalVariable to all fragments of that
/// Variable which are known to exist.
/// \param OverlappingFragments The overlap map being constructed, from one
/// Var/Fragment pair to a vector of fragments known to overlap.
void LiveDebugValues::accumulateFragmentMap(MachineInstr &MI,
VarToFragments &SeenFragments,
OverlapMap &OverlappingFragments) {
DebugVariable MIVar(MI);
FragmentInfo ThisFragment = MIVar.getFragmentDefault();
// If this is the first sighting of this variable, then we are guaranteed
// there are currently no overlapping fragments either. Initialize the set
// of seen fragments, record no overlaps for the current one, and return.
auto SeenIt = SeenFragments.find(MIVar.getVar());
if (SeenIt == SeenFragments.end()) {
SmallSet<FragmentInfo, 4> OneFragment;
OneFragment.insert(ThisFragment);
SeenFragments.insert({MIVar.getVar(), OneFragment});
OverlappingFragments.insert({{MIVar.getVar(), ThisFragment}, {}});
return;
}
// If this particular Variable/Fragment pair already exists in the overlap
// map, it has already been accounted for.
auto IsInOLapMap =
OverlappingFragments.insert({{MIVar.getVar(), ThisFragment}, {}});
if (!IsInOLapMap.second)
return;
auto &ThisFragmentsOverlaps = IsInOLapMap.first->second;
auto &AllSeenFragments = SeenIt->second;
// Otherwise, examine all other seen fragments for this variable, with "this"
// fragment being a previously unseen fragment. Record any pair of
// overlapping fragments.
for (auto &ASeenFragment : AllSeenFragments) {
// Does this previously seen fragment overlap?
if (DIExpression::fragmentsOverlap(ThisFragment, ASeenFragment)) {
// Yes: Mark the current fragment as being overlapped.
ThisFragmentsOverlaps.push_back(ASeenFragment);
// Mark the previously seen fragment as being overlapped by the current
// one.
auto ASeenFragmentsOverlaps =
OverlappingFragments.find({MIVar.getVar(), ASeenFragment});
assert(ASeenFragmentsOverlaps != OverlappingFragments.end() &&
"Previously seen var fragment has no vector of overlaps");
ASeenFragmentsOverlaps->second.push_back(ThisFragment);
}
}
AllSeenFragments.insert(ThisFragment);
}
/// This routine creates OpenRanges and OutLocs.
bool LiveDebugValues::process(MachineInstr &MI, OpenRangesSet &OpenRanges,
VarLocInMBB &OutLocs, VarLocMap &VarLocIDs,
TransferMap &Transfers, bool transferChanges,
OverlapMap &OverlapFragments,
VarToFragments &SeenFragments) {
bool Changed = false;
transferDebugValue(MI, OpenRanges, VarLocIDs);
transferRegisterDef(MI, OpenRanges, VarLocIDs);
if (transferChanges) {
transferRegisterCopy(MI, OpenRanges, VarLocIDs, Transfers);
transferSpillOrRestoreInst(MI, OpenRanges, VarLocIDs, Transfers);
} else {
// Build up a map of overlapping fragments on the first run through.
if (MI.isDebugValue())
accumulateFragmentMap(MI, SeenFragments, OverlapFragments);
}
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,
SmallPtrSet<const MachineBasicBlock *, 16> &Visited,
SmallPtrSetImpl<const MachineBasicBlock *> &ArtificialBlocks) {
LLVM_DEBUG(dbgs() << "join MBB: " << MBB.getNumber() << "\n");
bool Changed = false;
VarLocSet InLocsT; // Temporary incoming locations.
// For all predecessors of this MBB, find the set of VarLocs that
// can be joined.
int NumVisited = 0;
for (auto p : MBB.predecessors()) {
// Ignore unvisited predecessor blocks. As we are processing
// the blocks in reverse post-order any unvisited block can
// be considered to not remove any incoming values.
if (!Visited.count(p)) {
LLVM_DEBUG(dbgs() << " ignoring unvisited pred MBB: " << p->getNumber()
<< "\n");
continue;
}
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 visited
// predecessor, and for all other predecessors join the Out locs.
if (!NumVisited)
InLocsT = OL->second;
else
InLocsT &= OL->second;
LLVM_DEBUG({
if (!InLocsT.empty()) {
for (auto ID : InLocsT)
dbgs() << " gathered candidate incoming var: "
<< VarLocIDs[ID].Var.getVar()->getName() << "\n";
}
});
NumVisited++;
}
// Filter out DBG_VALUES that are out of scope.
VarLocSet KillSet;
bool IsArtificial = ArtificialBlocks.count(&MBB);
if (!IsArtificial) {
for (auto ID : InLocsT) {
if (!VarLocIDs[ID].dominates(MBB)) {
KillSet.set(ID);
LLVM_DEBUG({
auto Name = VarLocIDs[ID].Var.getVar()->getName();
dbgs() << " killing " << Name << ", it doesn't dominate MBB\n";
});
}
}
}
InLocsT.intersectWithComplement(KillSet);
// As we are processing blocks in reverse post-order we
// should have processed at least one predecessor, unless it
// is the entry block which has no predecessor.
assert((NumVisited || MBB.pred_empty()) &&
"Should have processed at least one predecessor");
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. process() will end this range however appropriate.
const VarLoc &DiffIt = VarLocIDs[ID];
const MachineInstr *DebugInstr = &DiffIt.MI;
MachineInstr *MI = nullptr;
if (DiffIt.isConstant()) {
MachineOperand MO(DebugInstr->getOperand(0));
MI = BuildMI(MBB, MBB.instr_begin(), DebugInstr->getDebugLoc(),
DebugInstr->getDesc(), false, MO,
DebugInstr->getDebugVariable(),
DebugInstr->getDebugExpression());
} else {
MI = BuildMI(MBB, MBB.instr_begin(), DebugInstr->getDebugLoc(),
DebugInstr->getDesc(), DebugInstr->isIndirectDebugValue(),
DebugInstr->getOperand(0).getReg(),
DebugInstr->getDebugVariable(),
DebugInstr->getDebugExpression());
if (DebugInstr->isIndirectDebugValue())
MI->getOperand(1).setImm(DebugInstr->getOperand(1).getImm());
}
LLVM_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) {
LLVM_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.
OverlapMap OverlapFragments; // Map of overlapping variable fragments
OpenRangesSet OpenRanges(OverlapFragments);
// Ranges that are open until end of bb.
VarLocInMBB OutLocs; // Ranges that exist beyond bb.
VarLocInMBB InLocs; // Ranges that are incoming after joining.
TransferMap Transfers; // DBG_VALUEs associated with spills.
VarToFragments SeenFragments;
// Blocks which are artificial, i.e. blocks which exclusively contain
// instructions without locations, or with line 0 locations.
SmallPtrSet<const MachineBasicBlock *, 16> ArtificialBlocks;
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;
enum : bool { dontTransferChanges = false, transferChanges = true };
// Initialize every mbb with OutLocs.
// We are not looking at any spill instructions during the initial pass
// over the BBs. The LiveDebugVariables pass has already created DBG_VALUE
// instructions for spills of registers that are known to be user variables
// within the BB in which the spill occurs.
for (auto &MBB : MF) {
for (auto &MI : MBB) {
process(MI, OpenRanges, OutLocs, VarLocIDs, Transfers,
dontTransferChanges, OverlapFragments, SeenFragments);
}
}
auto hasNonArtificialLocation = [](const MachineInstr &MI) -> bool {
if (const DebugLoc &DL = MI.getDebugLoc())
return DL.getLine() != 0;
return false;
};
for (auto &MBB : MF)
if (none_of(MBB.instrs(), hasNonArtificialLocation))
ArtificialBlocks.insert(&MBB);
LLVM_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 process() using the two worklist method
// until the ranges converge.
// Ranges have converged when both worklists are empty.
SmallPtrSet<const MachineBasicBlock *, 16> Visited;
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;
LLVM_DEBUG(dbgs() << "Processing Worklist\n");
while (!Worklist.empty()) {
MachineBasicBlock *MBB = OrderToBB[Worklist.top()];
Worklist.pop();
MBBJoined =
join(*MBB, OutLocs, InLocs, VarLocIDs, Visited, ArtificialBlocks);
Visited.insert(MBB);
if (MBBJoined) {
MBBJoined = false;
Changed = true;
// Now that we have started to extend ranges across BBs we need to
// examine spill instructions to see whether they spill registers that
// correspond to user variables.
for (auto &MI : *MBB)
OLChanged |=
process(MI, OpenRanges, OutLocs, VarLocIDs, Transfers,
transferChanges, OverlapFragments, SeenFragments);
// Add any DBG_VALUE instructions necessitated by spills.
for (auto &TR : Transfers)
MBB->insertAfter(MachineBasicBlock::iterator(*TR.TransferInst),
TR.DebugInst);
Transfers.clear();
LLVM_DEBUG(printVarLocInMBB(MF, OutLocs, VarLocIDs,
"OutLocs after propagating", dbgs()));
LLVM_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");
}
LLVM_DEBUG(printVarLocInMBB(MF, OutLocs, VarLocIDs, "Final OutLocs", dbgs()));
LLVM_DEBUG(printVarLocInMBB(MF, InLocs, VarLocIDs, "Final InLocs", dbgs()));
return Changed;
}
bool LiveDebugValues::runOnMachineFunction(MachineFunction &MF) {
if (!MF.getFunction().getSubprogram())
// LiveDebugValues will already have removed all DBG_VALUEs.
return false;
// Skip functions from NoDebug compilation units.
if (MF.getFunction().getSubprogram()->getUnit()->getEmissionKind() ==
DICompileUnit::NoDebug)
return false;
TRI = MF.getSubtarget().getRegisterInfo();
TII = MF.getSubtarget().getInstrInfo();
TFI = MF.getSubtarget().getFrameLowering();
TFI->determineCalleeSaves(MF, CalleeSavedRegs,
make_unique<RegScavenger>().get());
LS.initialize(MF);
bool Changed = ExtendRanges(MF);
return Changed;
}
Reference in New Issue View Git Blame Copy Permalink