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//===-- llvm/lib/CodeGen/AsmPrinter/DebugHandlerBase.cpp -------*- C++ -*--===//
//
// 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
//
//===----------------------------------------------------------------------===//
//
// Common functionality for different debug information format backends.
// LLVM currently supports DWARF and CodeView.
//
//===----------------------------------------------------------------------===//
#include "llvm/CodeGen/DebugHandlerBase.h"
#include "llvm/CodeGen/AsmPrinter.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/MachineModuleInfo.h"
#include "llvm/CodeGen/TargetSubtargetInfo.h"
#include "llvm/IR/DebugInfo.h"
#include "llvm/MC/MCStreamer.h"
#include "llvm/Support/CommandLine.h"
using namespace llvm;
#define DEBUG_TYPE "dwarfdebug"
/// If true, we drop variable location ranges which exist entirely outside the
/// variable's lexical scope instruction ranges.
static cl::opt<bool> TrimVarLocs("trim-var-locs", cl::Hidden, cl::init(true));
std::optional<DbgVariableLocation>
DbgVariableLocation::extractFromMachineInstruction(
const MachineInstr &Instruction) {
DbgVariableLocation Location;
// Variables calculated from multiple locations can't be represented here.
if (Instruction.getNumDebugOperands() != 1)
return std::nullopt;
if (!Instruction.getDebugOperand(0).isReg())
return std::nullopt;
Location.Register = Instruction.getDebugOperand(0).getReg();
Location.FragmentInfo.reset();
// We only handle expressions generated by DIExpression::appendOffset,
// which doesn't require a full stack machine.
int64_t Offset = 0;
const DIExpression *DIExpr = Instruction.getDebugExpression();
auto Op = DIExpr->expr_op_begin();
// We can handle a DBG_VALUE_LIST iff it has exactly one location operand that
// appears exactly once at the start of the expression.
if (Instruction.isDebugValueList()) {
if (Instruction.getNumDebugOperands() == 1 &&
Op->getOp() == dwarf::DW_OP_LLVM_arg)
++Op;
else
return std::nullopt;
}
while (Op != DIExpr->expr_op_end()) {
switch (Op->getOp()) {
case dwarf::DW_OP_constu: {
int Value = Op->getArg(0);
++Op;
if (Op != DIExpr->expr_op_end()) {
switch (Op->getOp()) {
case dwarf::DW_OP_minus:
Offset -= Value;
break;
case dwarf::DW_OP_plus:
Offset += Value;
break;
default:
continue;
}
}
} break;
case dwarf::DW_OP_plus_uconst:
Offset += Op->getArg(0);
break;
case dwarf::DW_OP_LLVM_fragment:
Location.FragmentInfo = {Op->getArg(1), Op->getArg(0)};
break;
case dwarf::DW_OP_deref:
Location.LoadChain.push_back(Offset);
Offset = 0;
break;
default:
return std::nullopt;
}
++Op;
}
// Do one final implicit DW_OP_deref if this was an indirect DBG_VALUE
// instruction.
// FIXME: Replace these with DIExpression.
if (Instruction.isIndirectDebugValue())
Location.LoadChain.push_back(Offset);
return Location;
}
DebugHandlerBase::DebugHandlerBase(AsmPrinter *A) : Asm(A), MMI(Asm->MMI) {}
void DebugHandlerBase::beginModule(Module *M) {
if (M->debug_compile_units().empty())
Asm = nullptr;
}
// Each LexicalScope has first instruction and last instruction to mark
// beginning and end of a scope respectively. Create an inverse map that list
// scopes starts (and ends) with an instruction. One instruction may start (or
// end) multiple scopes. Ignore scopes that are not reachable.
void DebugHandlerBase::identifyScopeMarkers() {
SmallVector<LexicalScope *, 4> WorkList;
WorkList.push_back(LScopes.getCurrentFunctionScope());
while (!WorkList.empty()) {
LexicalScope *S = WorkList.pop_back_val();
const SmallVectorImpl<LexicalScope *> &Children = S->getChildren();
if (!Children.empty())
WorkList.append(Children.begin(), Children.end());
if (S->isAbstractScope())
continue;
for (const InsnRange &R : S->getRanges()) {
assert(R.first && "InsnRange does not have first instruction!");
assert(R.second && "InsnRange does not have second instruction!");
requestLabelBeforeInsn(R.first);
requestLabelAfterInsn(R.second);
}
}
}
// Return Label preceding the instruction.
MCSymbol *DebugHandlerBase::getLabelBeforeInsn(const MachineInstr *MI) {
MCSymbol *Label = LabelsBeforeInsn.lookup(MI);
assert(Label && "Didn't insert label before instruction");
return Label;
}
// Return Label immediately following the instruction.
MCSymbol *DebugHandlerBase::getLabelAfterInsn(const MachineInstr *MI) {
return LabelsAfterInsn.lookup(MI);
}
/// If this type is derived from a base type then return base type size.
uint64_t DebugHandlerBase::getBaseTypeSize(const DIType *Ty) {
assert(Ty);
const DIDerivedType *DDTy = dyn_cast<DIDerivedType>(Ty);
if (!DDTy)
return Ty->getSizeInBits();
unsigned Tag = DDTy->getTag();
if (Tag != dwarf::DW_TAG_member && Tag != dwarf::DW_TAG_typedef &&
Tag != dwarf::DW_TAG_const_type && Tag != dwarf::DW_TAG_volatile_type &&
Tag != dwarf::DW_TAG_restrict_type && Tag != dwarf::DW_TAG_atomic_type &&
Tag != dwarf::DW_TAG_immutable_type)
return DDTy->getSizeInBits();
DIType *BaseType = DDTy->getBaseType();
if (!BaseType)
return 0;
// If this is a derived type, go ahead and get the base type, unless it's a
// reference then it's just the size of the field. Pointer types have no need
// of this since they're a different type of qualification on the type.
if (BaseType->getTag() == dwarf::DW_TAG_reference_type ||
BaseType->getTag() == dwarf::DW_TAG_rvalue_reference_type)
return Ty->getSizeInBits();
return getBaseTypeSize(BaseType);
}
bool DebugHandlerBase::isUnsignedDIType(const DIType *Ty) {
if (isa<DIStringType>(Ty)) {
// Some transformations (e.g. instcombine) may decide to turn a Fortran
// character object into an integer, and later ones (e.g. SROA) may
// further inject a constant integer in a llvm.dbg.value call to track
// the object's value. Here we trust the transformations are doing the
// right thing, and treat the constant as unsigned to preserve that value
// (i.e. avoid sign extension).
return true;
}
if (auto *CTy = dyn_cast<DICompositeType>(Ty)) {
if (CTy->getTag() == dwarf::DW_TAG_enumeration_type) {
if (!(Ty = CTy->getBaseType()))
// FIXME: Enums without a fixed underlying type have unknown signedness
// here, leading to incorrectly emitted constants.
return false;
} else
// (Pieces of) aggregate types that get hacked apart by SROA may be
// represented by a constant. Encode them as unsigned bytes.
return true;
}
if (auto *DTy = dyn_cast<DIDerivedType>(Ty)) {
dwarf::Tag T = (dwarf::Tag)Ty->getTag();
// Encode pointer constants as unsigned bytes. This is used at least for
// null pointer constant emission.
// FIXME: reference and rvalue_reference /probably/ shouldn't be allowed
// here, but accept them for now due to a bug in SROA producing bogus
// dbg.values.
if (T == dwarf::DW_TAG_pointer_type ||
T == dwarf::DW_TAG_ptr_to_member_type ||
T == dwarf::DW_TAG_reference_type ||
T == dwarf::DW_TAG_rvalue_reference_type)
return true;
assert(T == dwarf::DW_TAG_typedef || T == dwarf::DW_TAG_const_type ||
T == dwarf::DW_TAG_volatile_type ||
T == dwarf::DW_TAG_restrict_type || T == dwarf::DW_TAG_atomic_type ||
T == dwarf::DW_TAG_immutable_type);
assert(DTy->getBaseType() && "Expected valid base type");
return isUnsignedDIType(DTy->getBaseType());
}
auto *BTy = cast<DIBasicType>(Ty);
unsigned Encoding = BTy->getEncoding();
assert((Encoding == dwarf::DW_ATE_unsigned ||
Encoding == dwarf::DW_ATE_unsigned_char ||
Encoding == dwarf::DW_ATE_signed ||
Encoding == dwarf::DW_ATE_signed_char ||
Encoding == dwarf::DW_ATE_float || Encoding == dwarf::DW_ATE_UTF ||
Encoding == dwarf::DW_ATE_boolean ||
(Ty->getTag() == dwarf::DW_TAG_unspecified_type &&
Ty->getName() == "decltype(nullptr)")) &&
"Unsupported encoding");
return Encoding == dwarf::DW_ATE_unsigned ||
Encoding == dwarf::DW_ATE_unsigned_char ||
Encoding == dwarf::DW_ATE_UTF || Encoding == dwarf::DW_ATE_boolean ||
Ty->getTag() == dwarf::DW_TAG_unspecified_type;
}
static bool hasDebugInfo(const MachineModuleInfo *MMI,
const MachineFunction *MF) {
if (!MMI->hasDebugInfo())
return false;
auto *SP = MF->getFunction().getSubprogram();
if (!SP)
return false;
assert(SP->getUnit());
auto EK = SP->getUnit()->getEmissionKind();
if (EK == DICompileUnit::NoDebug)
return false;
return true;
}
void DebugHandlerBase::beginFunction(const MachineFunction *MF) {
PrevInstBB = nullptr;
if (!Asm || !hasDebugInfo(MMI, MF)) {
skippedNonDebugFunction();
return;
}
// Grab the lexical scopes for the function, if we don't have any of those
// then we're not going to be able to do anything.
LScopes.initialize(*MF);
if (LScopes.empty()) {
beginFunctionImpl(MF);
return;
}
// Make sure that each lexical scope will have a begin/end label.
identifyScopeMarkers();
// Calculate history for local variables.
assert(DbgValues.empty() && "DbgValues map wasn't cleaned!");
assert(DbgLabels.empty() && "DbgLabels map wasn't cleaned!");
calculateDbgEntityHistory(MF, Asm->MF->getSubtarget().getRegisterInfo(),
DbgValues, DbgLabels);
InstOrdering.initialize(*MF);
if (TrimVarLocs)
DbgValues.trimLocationRanges(*MF, LScopes, InstOrdering);
LLVM_DEBUG(DbgValues.dump());
// Request labels for the full history.
for (const auto &I : DbgValues) {
const auto &Entries = I.second;
if (Entries.empty())
continue;
auto IsDescribedByReg = [](const MachineInstr *MI) {
return any_of(MI->debug_operands(),
[](auto &MO) { return MO.isReg() && MO.getReg(); });
};
// The first mention of a function argument gets the CurrentFnBegin label,
// so arguments are visible when breaking at function entry.
//
// We do not change the label for values that are described by registers,
// as that could place them above their defining instructions. We should
// ideally not change the labels for constant debug values either, since
// doing that violates the ranges that are calculated in the history map.
// However, we currently do not emit debug values for constant arguments
// directly at the start of the function, so this code is still useful.
const DILocalVariable *DIVar =
Entries.front().getInstr()->getDebugVariable();
if (DIVar->isParameter() &&
getDISubprogram(DIVar->getScope())->describes(&MF->getFunction())) {
if (!IsDescribedByReg(Entries.front().getInstr()))
LabelsBeforeInsn[Entries.front().getInstr()] = Asm->getFunctionBegin();
if (Entries.front().getInstr()->getDebugExpression()->isFragment()) {
// Mark all non-overlapping initial fragments.
for (const auto *I = Entries.begin(); I != Entries.end(); ++I) {
if (!I->isDbgValue())
continue;
const DIExpression *Fragment = I->getInstr()->getDebugExpression();
if (std::any_of(Entries.begin(), I,
[&](DbgValueHistoryMap::Entry Pred) {
return Pred.isDbgValue() &&
Fragment->fragmentsOverlap(
Pred.getInstr()->getDebugExpression());
}))
break;
// The code that generates location lists for DWARF assumes that the
// entries' start labels are monotonically increasing, and since we
// don't change the label for fragments that are described by
// registers, we must bail out when encountering such a fragment.
if (IsDescribedByReg(I->getInstr()))
break;
LabelsBeforeInsn[I->getInstr()] = Asm->getFunctionBegin();
}
}
}
for (const auto &Entry : Entries) {
if (Entry.isDbgValue())
requestLabelBeforeInsn(Entry.getInstr());
else
requestLabelAfterInsn(Entry.getInstr());
}
}
// Ensure there is a symbol before DBG_LABEL.
for (const auto &I : DbgLabels) {
const MachineInstr *MI = I.second;
requestLabelBeforeInsn(MI);
}
PrevInstLoc = DebugLoc();
PrevLabel = Asm->getFunctionBegin();
beginFunctionImpl(MF);
}
void DebugHandlerBase::beginInstruction(const MachineInstr *MI) {
if (!Asm || !MMI->hasDebugInfo())
return;
assert(CurMI == nullptr);
CurMI = MI;
// Insert labels where requested.
DenseMap<const MachineInstr *, MCSymbol *>::iterator I =
LabelsBeforeInsn.find(MI);
// No label needed.
if (I == LabelsBeforeInsn.end())
return;
// Label already assigned.
if (I->second)
return;
if (!PrevLabel) {
PrevLabel = MMI->getContext().createTempSymbol();
Asm->OutStreamer->emitLabel(PrevLabel);
}
I->second = PrevLabel;
}
void DebugHandlerBase::endInstruction() {
if (!Asm || !MMI->hasDebugInfo())
return;
assert(CurMI != nullptr);
// Don't create a new label after DBG_VALUE and other instructions that don't
// generate code.
if (!CurMI->isMetaInstruction()) {
PrevLabel = nullptr;
PrevInstBB = CurMI->getParent();
}
DenseMap<const MachineInstr *, MCSymbol *>::iterator I =
LabelsAfterInsn.find(CurMI);
// No label needed or label already assigned.
if (I == LabelsAfterInsn.end() || I->second) {
CurMI = nullptr;
return;
}
// We need a label after this instruction. With basic block sections, just
// use the end symbol of the section if this is the last instruction of the
// section. This reduces the need for an additional label and also helps
// merging ranges.
if (CurMI->getParent()->isEndSection() && CurMI->getNextNode() == nullptr) {
PrevLabel = CurMI->getParent()->getEndSymbol();
} else if (!PrevLabel) {
PrevLabel = MMI->getContext().createTempSymbol();
Asm->OutStreamer->emitLabel(PrevLabel);
}
I->second = PrevLabel;
CurMI = nullptr;
}
void DebugHandlerBase::endFunction(const MachineFunction *MF) {
if (Asm && hasDebugInfo(MMI, MF))
endFunctionImpl(MF);
DbgValues.clear();
DbgLabels.clear();
LabelsBeforeInsn.clear();
LabelsAfterInsn.clear();
InstOrdering.clear();
}
void DebugHandlerBase::beginBasicBlockSection(const MachineBasicBlock &MBB) {
EpilogBeginBlock = nullptr;
if (!MBB.isEntryBlock())
PrevLabel = MBB.getSymbol();
}
void DebugHandlerBase::endBasicBlockSection(const MachineBasicBlock &MBB) {
PrevLabel = nullptr;
}