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[CodeView] Combine variable def ranges that are continuous.
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It saves about 1.13% size for chrome.dll.pdb on chrome official build.

Reviewed By: rnk

Differential Revision: https://reviews.llvm.org/D125721
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@ZequanWu
ZequanWu committed May 20, 2022
1 parent d497129 commit 9886046
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Showing 3 changed files with 77 additions and 55 deletions.
56 changes: 26 additions & 30 deletions llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp
View file
Expand Up @@ -1242,9 +1242,9 @@ void CodeViewDebug::emitDebugInfoForFunction(const Function *GV,
OS.emitCVLinetableDirective(FI.FuncId, Fn, FI.End);
}

CodeViewDebug::LocalVarDefRange
CodeViewDebug::LocalVarDef
CodeViewDebug::createDefRangeMem(uint16_t CVRegister, int Offset) {
LocalVarDefRange DR;
LocalVarDef DR;
DR.InMemory = -1;
DR.DataOffset = Offset;
assert(DR.DataOffset == Offset && "truncation");
Expand Down Expand Up @@ -1296,19 +1296,19 @@ void CodeViewDebug::collectVariableInfoFromMFTable(
"Frame offsets with a scalable component are not supported");

// Calculate the label ranges.
LocalVarDefRange DefRange =
LocalVarDef DefRange =
createDefRangeMem(CVReg, FrameOffset.getFixed() + ExprOffset);

LocalVariable Var;
Var.DIVar = VI.Var;

for (const InsnRange &Range : Scope->getRanges()) {
const MCSymbol *Begin = getLabelBeforeInsn(Range.first);
const MCSymbol *End = getLabelAfterInsn(Range.second);
End = End ? End : Asm->getFunctionEnd();
DefRange.Ranges.emplace_back(Begin, End);
Var.DefRanges[DefRange].emplace_back(Begin, End);
}

LocalVariable Var;
Var.DIVar = VI.Var;
Var.DefRanges.emplace_back(std::move(DefRange));
if (Deref)
Var.UseReferenceType = true;

Expand Down Expand Up @@ -1367,24 +1367,18 @@ void CodeViewDebug::calculateRanges(
// We can only handle a register or an offseted load of a register.
if (Location->Register == 0 || Location->LoadChain.size() > 1)
continue;
{
LocalVarDefRange DR;
DR.CVRegister = TRI->getCodeViewRegNum(Location->Register);
DR.InMemory = !Location->LoadChain.empty();
DR.DataOffset =
!Location->LoadChain.empty() ? Location->LoadChain.back() : 0;
if (Location->FragmentInfo) {
DR.IsSubfield = true;
DR.StructOffset = Location->FragmentInfo->OffsetInBits / 8;
} else {
DR.IsSubfield = false;
DR.StructOffset = 0;
}

if (Var.DefRanges.empty() ||
Var.DefRanges.back().isDifferentLocation(DR)) {
Var.DefRanges.emplace_back(std::move(DR));
}
LocalVarDef DR;
DR.CVRegister = TRI->getCodeViewRegNum(Location->Register);
DR.InMemory = !Location->LoadChain.empty();
DR.DataOffset =
!Location->LoadChain.empty() ? Location->LoadChain.back() : 0;
if (Location->FragmentInfo) {
DR.IsSubfield = true;
DR.StructOffset = Location->FragmentInfo->OffsetInBits / 8;
} else {
DR.IsSubfield = false;
DR.StructOffset = 0;
}

// Compute the label range.
Expand All @@ -1401,7 +1395,7 @@ void CodeViewDebug::calculateRanges(
// If the last range end is our begin, just extend the last range.
// Otherwise make a new range.
SmallVectorImpl<std::pair<const MCSymbol *, const MCSymbol *>> &R =
Var.DefRanges.back().Ranges;
Var.DefRanges[DR];
if (!R.empty() && R.back().second == Begin)
R.back().second = End;
else
Expand Down Expand Up @@ -2814,7 +2808,9 @@ void CodeViewDebug::emitLocalVariable(const FunctionInfo &FI,
// records and on disk formats are described in SymbolRecords.h. BytePrefix
// should be big enough to hold all forms without memory allocation.
SmallString<20> BytePrefix;
for (const LocalVarDefRange &DefRange : Var.DefRanges) {
for (const auto &Pair : Var.DefRanges) {
LocalVarDef DefRange = Pair.first;
const auto &Ranges = Pair.second;
BytePrefix.clear();
if (DefRange.InMemory) {
int Offset = DefRange.DataOffset;
Expand All @@ -2838,7 +2834,7 @@ void CodeViewDebug::emitLocalVariable(const FunctionInfo &FI,
: (EncFP == FI.EncodedLocalFramePtrReg))) {
DefRangeFramePointerRelHeader DRHdr;
DRHdr.Offset = Offset;
OS.emitCVDefRangeDirective(DefRange.Ranges, DRHdr);
OS.emitCVDefRangeDirective(Ranges, DRHdr);
} else {
uint16_t RegRelFlags = 0;
if (DefRange.IsSubfield) {
Expand All @@ -2850,7 +2846,7 @@ void CodeViewDebug::emitLocalVariable(const FunctionInfo &FI,
DRHdr.Register = Reg;
DRHdr.Flags = RegRelFlags;
DRHdr.BasePointerOffset = Offset;
OS.emitCVDefRangeDirective(DefRange.Ranges, DRHdr);
OS.emitCVDefRangeDirective(Ranges, DRHdr);
}
} else {
assert(DefRange.DataOffset == 0 && "unexpected offset into register");
Expand All @@ -2859,12 +2855,12 @@ void CodeViewDebug::emitLocalVariable(const FunctionInfo &FI,
DRHdr.Register = DefRange.CVRegister;
DRHdr.MayHaveNoName = 0;
DRHdr.OffsetInParent = DefRange.StructOffset;
OS.emitCVDefRangeDirective(DefRange.Ranges, DRHdr);
OS.emitCVDefRangeDirective(Ranges, DRHdr);
} else {
DefRangeRegisterHeader DRHdr;
DRHdr.Register = DefRange.CVRegister;
DRHdr.MayHaveNoName = 0;
OS.emitCVDefRangeDirective(DefRange.Ranges, DRHdr);
OS.emitCVDefRangeDirective(Ranges, DRHdr);
}
}
}
Expand Down
70 changes: 49 additions & 21 deletions llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.h
View file
Expand Up @@ -50,18 +50,8 @@ class MachineFunction;

/// Collects and handles line tables information in a CodeView format.
class LLVM_LIBRARY_VISIBILITY CodeViewDebug : public DebugHandlerBase {
MCStreamer &OS;
BumpPtrAllocator Allocator;
codeview::GlobalTypeTableBuilder TypeTable;

/// Whether to emit type record hashes into .debug$H.
bool EmitDebugGlobalHashes = false;

/// The codeview CPU type used by the translation unit.
codeview::CPUType TheCPU;

/// Represents the most general definition range.
struct LocalVarDefRange {
public:
struct LocalVarDef {
/// Indicates that variable data is stored in memory relative to the
/// specified register.
int InMemory : 1;
Expand All @@ -79,23 +69,40 @@ class LLVM_LIBRARY_VISIBILITY CodeViewDebug : public DebugHandlerBase {
/// location containing the data.
uint16_t CVRegister;

/// Compares all location fields. This includes all fields except the label
/// ranges.
bool isDifferentLocation(LocalVarDefRange &O) {
return InMemory != O.InMemory || DataOffset != O.DataOffset ||
IsSubfield != O.IsSubfield || StructOffset != O.StructOffset ||
CVRegister != O.CVRegister;
uint64_t static toOpaqueValue(const LocalVarDef DR) {
uint64_t Val = 0;
std::memcpy(&Val, &DR, sizeof(Val));
return Val;
}

SmallVector<std::pair<const MCSymbol *, const MCSymbol *>, 1> Ranges;
LocalVarDef static createFromOpaqueValue(uint64_t Val) {
LocalVarDef DR;
std::memcpy(&DR, &Val, sizeof(Val));
return DR;
}
};

static LocalVarDefRange createDefRangeMem(uint16_t CVRegister, int Offset);
static_assert(sizeof(uint64_t) == sizeof(LocalVarDef), "");

private:
MCStreamer &OS;
BumpPtrAllocator Allocator;
codeview::GlobalTypeTableBuilder TypeTable;

/// Whether to emit type record hashes into .debug$H.
bool EmitDebugGlobalHashes = false;

/// The codeview CPU type used by the translation unit.
codeview::CPUType TheCPU;

static LocalVarDef createDefRangeMem(uint16_t CVRegister, int Offset);

/// Similar to DbgVariable in DwarfDebug, but not dwarf-specific.
struct LocalVariable {
const DILocalVariable *DIVar = nullptr;
SmallVector<LocalVarDefRange, 1> DefRanges;
MapVector<LocalVarDef,
SmallVector<std::pair<const MCSymbol *, const MCSymbol *>, 1>>
DefRanges;
bool UseReferenceType = false;
};

Expand Down Expand Up @@ -493,6 +500,27 @@ class LLVM_LIBRARY_VISIBILITY CodeViewDebug : public DebugHandlerBase {
void beginInstruction(const MachineInstr *MI) override;
};

template <> struct DenseMapInfo<CodeViewDebug::LocalVarDef> {

static inline CodeViewDebug::LocalVarDef getEmptyKey() {
return CodeViewDebug::LocalVarDef::createFromOpaqueValue(~0ULL);
}

static inline CodeViewDebug::LocalVarDef getTombstoneKey() {
return CodeViewDebug::LocalVarDef::createFromOpaqueValue(~0ULL - 1ULL);
}

static unsigned getHashValue(const CodeViewDebug::LocalVarDef &DR) {
return CodeViewDebug::LocalVarDef::toOpaqueValue(DR) * 37ULL;
}

static bool isEqual(const CodeViewDebug::LocalVarDef &LHS,
const CodeViewDebug::LocalVarDef &RHS) {
return CodeViewDebug::LocalVarDef::toOpaqueValue(LHS) ==
CodeViewDebug::LocalVarDef::toOpaqueValue(RHS);
}
};

} // end namespace llvm

#endif // LLVM_LIB_CODEGEN_ASMPRINTER_CODEVIEWDEBUG_H
6 changes: 2 additions & 4 deletions llvm/test/DebugInfo/COFF/pieces.ll
View file
Expand Up @@ -114,10 +114,8 @@
; ASM: .asciz "loop_csr" # Function name
; ASM: .short 4414 # Record kind: S_LOCAL
; ASM: .asciz "o"
; ASM: .cv_def_range [[oy_ox_start]] [[ox_start]], subfield_reg, 24, 0
; ASM: .cv_def_range [[oy_ox_start]] [[oy_start]], subfield_reg, 23, 4
; ASM: .cv_def_range [[ox_start]] [[loopskip_start]], subfield_reg, 24, 0
; ASM: .cv_def_range [[oy_start]] [[loopskip_start]], subfield_reg, 23, 4
; ASM: .cv_def_range [[oy_ox_start]] [[loopskip_start]], subfield_reg, 24, 0
; ASM: .cv_def_range [[oy_ox_start]] [[loopskip_start]], subfield_reg, 23, 4


; OBJ-LABEL: GlobalProcIdSym {
Expand Down

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