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Differential D43943

[DEBUGINFO] Add flag for DWARF2 to use sections as references.
ClosedPublic

Authored by ABataev on Mar 1 2018, 7:28 AM.

Details

Reviewers
echristo
probinson
jlebar
aprantl
Commits
rGbff360865b53: [DEBUGINFO] Add flag for DWARF2 to use sections as references.
rL328314: [DEBUGINFO] Add flag for DWARF2 to use sections as references.
Summary

Some targets does not support labels inside debug sections, but support
references in form section+offset. Patch adds initial support
for this. Also, this patch disables emission of all additional debug
sections that may have labels inside of it (like pub sections and
string tables).

Diff Detail

Repository
rL LLVM

Event Timeline

ABataev created this revision.Mar 1 2018, 7:28 AM
Herald added a subscriber: JDevlieghere. · View Herald TranscriptMar 1 2018, 7:28 AM
Harbormaster completed remote builds in B15571: Diff 136521.Mar 1 2018, 7:29 AM
echristo added a comment.Mar 8 2018, 5:43 PM

Some inline comments.

lib/CodeGen/AsmPrinter/DwarfDebug.cpp
320 ↗(On Diff #136521)

Why?

751 ↗(On Diff #136521)

Can you explain why this one is necessary?

1579–1583 ↗(On Diff #136521)

Let's refactor this into a "DwarfEmitOffset" function and use it in all of the places we want to emit a label plus an offset, then this becomes a two line patch.

ABataev added inline comments.Mar 21 2018, 6:33 AM
lib/CodeGen/AsmPrinter/DwarfDebug.cpp
320 ↗(On Diff #136521)

Removed

751 ↗(On Diff #136521)

It was fixed already in another patch

1579–1583 ↗(On Diff #136521)

Ok, will do

ABataev updated this revision to Diff 139288.Mar 21 2018, 7:16 AM

Updated to the latest version + fixes.

Harbormaster completed remote builds in B16301: Diff 139288.Mar 21 2018, 7:16 AM
JDevlieghere added a reviewer: aprantl.Mar 22 2018, 7:03 AM
echristo added inline comments.Mar 22 2018, 8:23 AM
lib/CodeGen/AsmPrinter/DwarfDebug.cpp
1579–1583 ↗(On Diff #136521)

Feels like you should be able to refactor the if conditional into the function as well and generally just use it everywhere?

Also means you can probably split it into two patches:

  1. Add EmitDwarfOffset
  2. Add support for useSectionsAsReferences

Thoughts?

ABataev updated this revision to Diff 139479.Mar 22 2018, 11:09 AM

Update after review

Harbormaster completed remote builds in B16354: Diff 139479.Mar 22 2018, 11:10 AM
echristo accepted this revision.Mar 22 2018, 11:42 AM

Works for me. Might want to make sure that any other uses are updated as well.

This revision is now accepted and ready to land.Mar 22 2018, 11:42 AM
Closed by commit rL328314: [DEBUGINFO] Add flag for DWARF2 to use sections as references. (authored by ABataev). · Explain WhyMar 23 2018, 6:38 AM
This revision was automatically updated to reflect the committed changes.
ikudrin mentioned this in D82311: [DebugInfo] Fix emitting offsets to CUs with -dwarf-sections-as-references=Enable..Jun 23 2020, 1:00 AM

Revision Contents

PathSize
llvm/
trunk/
lib/
CodeGen/
AsmPrinter/
13 lines
12 lines
22 lines
test/
DebugInfo/
X86/
54 lines

Diff 139585

llvm/trunk/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp

Show First 20 Lines • Show All 264 Lines • ▼ Show 20 Lines if (CURanges.empty() || !SameAsPrevCU ||
return; return;
} }
CURanges.back().setEnd(Range.getEnd()); CURanges.back().setEnd(Range.getEnd());
} }
void DwarfCompileUnit::initStmtList() { void DwarfCompileUnit::initStmtList() {
// Define start line table label for each Compile Unit. // Define start line table label for each Compile Unit.
MCSymbol *LineTableStartSym = MCSymbol *LineTableStartSym;
const TargetLoweringObjectFile &TLOF = Asm->getObjFileLowering();
if (DD->useSectionsAsReferences()) {
LineTableStartSym = TLOF.getDwarfLineSection()->getBeginSymbol();
} else {
LineTableStartSym =
Asm->OutStreamer->getDwarfLineTableSymbol(getUniqueID()); Asm->OutStreamer->getDwarfLineTableSymbol(getUniqueID());
}
// DW_AT_stmt_list is a offset of line number information for this // DW_AT_stmt_list is a offset of line number information for this
// compile unit in debug_line section. For split dwarf this is // compile unit in debug_line section. For split dwarf this is
// left in the skeleton CU and so not included. // left in the skeleton CU and so not included.
// The line table entries are not always emitted in assembly, so it // The line table entries are not always emitted in assembly, so it
// is not okay to use line_table_start here. // is not okay to use line_table_start here.
const TargetLoweringObjectFile &TLOF = Asm->getObjFileLowering();
StmtListValue = StmtListValue =
addSectionLabel(getUnitDie(), dwarf::DW_AT_stmt_list, LineTableStartSym, addSectionLabel(getUnitDie(), dwarf::DW_AT_stmt_list, LineTableStartSym,
TLOF.getDwarfLineSection()->getBeginSymbol()); TLOF.getDwarfLineSection()->getBeginSymbol());
} }
void DwarfCompileUnit::applyStmtList(DIE &D) { void DwarfCompileUnit::applyStmtList(DIE &D) {
D.addValue(DIEValueAllocator, *StmtListValue); D.addValue(DIEValueAllocator, *StmtListValue);
} }
▲ Show 20 Lines • Show All 540 Lines • ▼ Show 20 Linesvoid DwarfCompileUnit::createAbstractVariable(const DILocalVariable *Var,
assert(Scope && Scope->isAbstractScope()); assert(Scope && Scope->isAbstractScope());
auto AbsDbgVariable = llvm::make_unique<DbgVariable>(Var, /* IA */ nullptr); auto AbsDbgVariable = llvm::make_unique<DbgVariable>(Var, /* IA */ nullptr);
DU->addScopeVariable(Scope, AbsDbgVariable.get()); DU->addScopeVariable(Scope, AbsDbgVariable.get());
getAbstractVariables()[Var] = std::move(AbsDbgVariable); getAbstractVariables()[Var] = std::move(AbsDbgVariable);
} }
void DwarfCompileUnit::emitHeader(bool UseOffsets) { void DwarfCompileUnit::emitHeader(bool UseOffsets) {
// Don't bother labeling the .dwo unit, as its offset isn't used. // Don't bother labeling the .dwo unit, as its offset isn't used.
if (!Skeleton) { if (!Skeleton && !DD->useSectionsAsReferences()) {
LabelBegin = Asm->createTempSymbol("cu_begin"); LabelBegin = Asm->createTempSymbol("cu_begin");
Asm->OutStreamer->EmitLabel(LabelBegin); Asm->OutStreamer->EmitLabel(LabelBegin);
} }
dwarf::UnitType UT = Skeleton ? dwarf::DW_UT_split_compile dwarf::UnitType UT = Skeleton ? dwarf::DW_UT_split_compile
: DD->useSplitDwarf() ? dwarf::DW_UT_skeleton : DD->useSplitDwarf() ? dwarf::DW_UT_skeleton
: dwarf::DW_UT_compile; : dwarf::DW_UT_compile;
DwarfUnit::emitCommonHeader(UseOffsets, UT); DwarfUnit::emitCommonHeader(UseOffsets, UT);
▲ Show 20 Lines • Show All 161 Lines • Show Last 20 Lines

llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.h

Show First 20 Lines • Show All 258 Lines • ▼ Show 20 Linesclass DwarfDebug : public DebugHandlerBase {
bool UseInlineStrings = false; bool UseInlineStrings = false;
/// Whether to emit DWARF pub sections or not. /// Whether to emit DWARF pub sections or not.
bool UsePubSections = true; bool UsePubSections = true;
/// Allow emission of .debug_ranges section. /// Allow emission of .debug_ranges section.
bool UseRangesSection = true; bool UseRangesSection = true;
/// True if the sections itself must be used as references and don't create
/// temp symbols inside DWARF sections.
bool UseSectionsAsReferences = false;
/// DWARF5 Experimental Options /// DWARF5 Experimental Options
/// @{ /// @{
bool HasDwarfAccelTables; bool HasDwarfAccelTables;
bool HasAppleExtensionAttributes; bool HasAppleExtensionAttributes;
bool HasSplitDwarf; bool HasSplitDwarf;
/// Whether to generate the DWARF v5 string offsets table. /// Whether to generate the DWARF v5 string offsets table.
/// It consists of a series of contributions, each preceded by a header. /// It consists of a series of contributions, each preceded by a header.
▲ Show 20 Lines • Show All 168 Lines • ▼ Show 20 Linesclass DwarfDebug : public DebugHandlerBase {
/// function that describe the same variable. /// function that describe the same variable.
void buildLocationList(SmallVectorImpl<DebugLocEntry> &DebugLoc, void buildLocationList(SmallVectorImpl<DebugLocEntry> &DebugLoc,
const DbgValueHistoryMap::InstrRanges &Ranges); const DbgValueHistoryMap::InstrRanges &Ranges);
/// Collect variable information from the side table maintained by MF. /// Collect variable information from the side table maintained by MF.
void collectVariableInfoFromMFTable(DwarfCompileUnit &TheCU, void collectVariableInfoFromMFTable(DwarfCompileUnit &TheCU,
DenseSet<InlinedVariable> &P); DenseSet<InlinedVariable> &P);
/// Emit the reference to the section.
void emitSectionReference(const DwarfCompileUnit &CU);
protected: protected:
/// Gather pre-function debug information. /// Gather pre-function debug information.
void beginFunctionImpl(const MachineFunction *MF) override; void beginFunctionImpl(const MachineFunction *MF) override;
/// Gather and emit post-function debug information. /// Gather and emit post-function debug information.
void endFunctionImpl(const MachineFunction *MF) override; void endFunctionImpl(const MachineFunction *MF) override;
void skippedNonDebugFunction() override; void skippedNonDebugFunction() override;
▲ Show 20 Lines • Show All 49 Lines • ▼ Show 20 Linespublic:
bool useInlineStrings() const { return UseInlineStrings; } bool useInlineStrings() const { return UseInlineStrings; }
/// Returns whether GNU oub sections should be emitted. /// Returns whether GNU oub sections should be emitted.
bool usePubSections() const { return UsePubSections; } bool usePubSections() const { return UsePubSections; }
/// Returns whether ranges section should be emitted. /// Returns whether ranges section should be emitted.
bool useRangesSection() const { return UseRangesSection; } bool useRangesSection() const { return UseRangesSection; }
/// Returns whether to use sections as labels rather than temp symbols.
bool useSectionsAsReferences() const {
return UseSectionsAsReferences;
}
// Experimental DWARF5 features. // Experimental DWARF5 features.
/// Returns whether or not to emit tables that dwarf consumers can /// Returns whether or not to emit tables that dwarf consumers can
/// use to accelerate lookup. /// use to accelerate lookup.
bool useDwarfAccelTables() const { return HasDwarfAccelTables; } bool useDwarfAccelTables() const { return HasDwarfAccelTables; }
bool useAppleExtensionAttributes() const { bool useAppleExtensionAttributes() const {
return HasAppleExtensionAttributes; return HasAppleExtensionAttributes;
▲ Show 20 Lines • Show All 75 Lines • Show Last 20 Lines

llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp

Show First 20 Lines • Show All 127 Lines • ▼ Show 20 Lines NoDwarfPubSections("no-dwarf-pub-sections", cl::Hidden,
cl::desc("Disable emission of DWARF pub sections."), cl::desc("Disable emission of DWARF pub sections."),
cl::init(false)); cl::init(false));
static cl::opt<bool> static cl::opt<bool>
NoDwarfRangesSection("no-dwarf-ranges-section", cl::Hidden, NoDwarfRangesSection("no-dwarf-ranges-section", cl::Hidden,
cl::desc("Disable emission .debug_ranges section."), cl::desc("Disable emission .debug_ranges section."),
cl::init(false)); cl::init(false));
static cl::opt<DefaultOnOff> DwarfSectionsAsReferences(
"dwarf-sections-as-references", cl::Hidden,
cl::desc("Use sections+offset as references rather than labels."),
cl::values(clEnumVal(Default, "Default for platform"),
clEnumVal(Enable, "Enabled"), clEnumVal(Disable, "Disabled")),
cl::init(Default));
enum LinkageNameOption { enum LinkageNameOption {
DefaultLinkageNames, DefaultLinkageNames,
AllLinkageNames, AllLinkageNames,
AbstractLinkageNames AbstractLinkageNames
}; };
static cl::opt<LinkageNameOption> static cl::opt<LinkageNameOption>
DwarfLinkageNames("dwarf-linkage-names", cl::Hidden, DwarfLinkageNames("dwarf-linkage-names", cl::Hidden,
▲ Show 20 Lines • Show All 174 Lines • ▼ Show 20 LinesDwarfDebug::DwarfDebug(AsmPrinter *A, Module *M)
unsigned DwarfVersion = DwarfVersionNumber ? DwarfVersionNumber unsigned DwarfVersion = DwarfVersionNumber ? DwarfVersionNumber
: MMI->getModule()->getDwarfVersion(); : MMI->getModule()->getDwarfVersion();
// Use dwarf 4 by default if nothing is requested. // Use dwarf 4 by default if nothing is requested.
DwarfVersion = DwarfVersion ? DwarfVersion : dwarf::DWARF_VERSION; DwarfVersion = DwarfVersion ? DwarfVersion : dwarf::DWARF_VERSION;
UsePubSections = !NoDwarfPubSections; UsePubSections = !NoDwarfPubSections;
UseRangesSection = !NoDwarfRangesSection; UseRangesSection = !NoDwarfRangesSection;
// Use sections as references.
UseSectionsAsReferences = DwarfSectionsAsReferences == Enable;
// Work around a GDB bug. GDB doesn't support the standard opcode; // Work around a GDB bug. GDB doesn't support the standard opcode;
// SCE doesn't support GNU's; LLDB prefers the standard opcode, which // SCE doesn't support GNU's; LLDB prefers the standard opcode, which
// is defined as of DWARF 3. // is defined as of DWARF 3.
// See GDB bug 11616 - DW_OP_form_tls_address is unimplemented // See GDB bug 11616 - DW_OP_form_tls_address is unimplemented
// https://sourceware.org/bugzilla/show_bug.cgi?id=11616 // https://sourceware.org/bugzilla/show_bug.cgi?id=11616
UseGNUTLSOpcode = tuneForGDB() || DwarfVersion < 3; UseGNUTLSOpcode = tuneForGDB() || DwarfVersion < 3;
// GDB does not fully support the DWARF 4 representation for bitfields. // GDB does not fully support the DWARF 4 representation for bitfields.
▲ Show 20 Lines • Show All 1,220 Lines • ▼ Show 20 Lines for (const auto &NU : CUMap) {
Asm->OutStreamer->SwitchSection( Asm->OutStreamer->SwitchSection(
GnuStyle ? Asm->getObjFileLowering().getDwarfGnuPubTypesSection() GnuStyle ? Asm->getObjFileLowering().getDwarfGnuPubTypesSection()
: Asm->getObjFileLowering().getDwarfPubTypesSection()); : Asm->getObjFileLowering().getDwarfPubTypesSection());
emitDebugPubSection(GnuStyle, "Types", TheU, TheU->getGlobalTypes()); emitDebugPubSection(GnuStyle, "Types", TheU, TheU->getGlobalTypes());
} }
} }
void DwarfDebug::emitSectionReference(const DwarfCompileUnit &CU) {
if (useSectionsAsReferences())
Asm->EmitDwarfOffset(CU.getSection()->getBeginSymbol(),
CU.getDebugSectionOffset());
else
Asm->emitDwarfSymbolReference(CU.getLabelBegin());
}
void DwarfDebug::emitDebugPubSection(bool GnuStyle, StringRef Name, void DwarfDebug::emitDebugPubSection(bool GnuStyle, StringRef Name,
DwarfCompileUnit *TheU, DwarfCompileUnit *TheU,
const StringMap<const DIE *> &Globals) { const StringMap<const DIE *> &Globals) {
if (auto *Skeleton = TheU->getSkeleton()) if (auto *Skeleton = TheU->getSkeleton())
TheU = Skeleton; TheU = Skeleton;
// Emit the header. // Emit the header.
Asm->OutStreamer->AddComment("Length of Public " + Name + " Info"); Asm->OutStreamer->AddComment("Length of Public " + Name + " Info");
MCSymbol *BeginLabel = Asm->createTempSymbol("pub" + Name + "_begin"); MCSymbol *BeginLabel = Asm->createTempSymbol("pub" + Name + "_begin");
MCSymbol *EndLabel = Asm->createTempSymbol("pub" + Name + "_end"); MCSymbol *EndLabel = Asm->createTempSymbol("pub" + Name + "_end");
Asm->EmitLabelDifference(EndLabel, BeginLabel, 4); Asm->EmitLabelDifference(EndLabel, BeginLabel, 4);
Asm->OutStreamer->EmitLabel(BeginLabel); Asm->OutStreamer->EmitLabel(BeginLabel);
Asm->OutStreamer->AddComment("DWARF Version"); Asm->OutStreamer->AddComment("DWARF Version");
Asm->EmitInt16(dwarf::DW_PUBNAMES_VERSION); Asm->EmitInt16(dwarf::DW_PUBNAMES_VERSION);
Asm->OutStreamer->AddComment("Offset of Compilation Unit Info"); Asm->OutStreamer->AddComment("Offset of Compilation Unit Info");
Asm->emitDwarfSymbolReference(TheU->getLabelBegin()); emitSectionReference(*TheU);
Asm->OutStreamer->AddComment("Compilation Unit Length"); Asm->OutStreamer->AddComment("Compilation Unit Length");
Asm->EmitInt32(TheU->getLength()); Asm->EmitInt32(TheU->getLength());
// Emit the pubnames for this compilation unit. // Emit the pubnames for this compilation unit.
for (const auto &GI : Globals) { for (const auto &GI : Globals) {
const char *Name = GI.getKeyData(); const char *Name = GI.getKeyData();
const DIE *Entity = GI.second; const DIE *Entity = GI.second;
▲ Show 20 Lines • Show All 282 Lines • ▼ Show 20 Lines for (DwarfCompileUnit *CU : CUs) {
ContentSize += (List.size() + 1) * TupleSize; ContentSize += (List.size() + 1) * TupleSize;
// For each compile unit, write the list of spans it covers. // For each compile unit, write the list of spans it covers.
Asm->OutStreamer->AddComment("Length of ARange Set"); Asm->OutStreamer->AddComment("Length of ARange Set");
Asm->EmitInt32(ContentSize); Asm->EmitInt32(ContentSize);
Asm->OutStreamer->AddComment("DWARF Arange version number"); Asm->OutStreamer->AddComment("DWARF Arange version number");
Asm->EmitInt16(dwarf::DW_ARANGES_VERSION); Asm->EmitInt16(dwarf::DW_ARANGES_VERSION);
Asm->OutStreamer->AddComment("Offset Into Debug Info Section"); Asm->OutStreamer->AddComment("Offset Into Debug Info Section");
Asm->emitDwarfSymbolReference(CU->getLabelBegin()); emitSectionReference(*CU);
Asm->OutStreamer->AddComment("Address Size (in bytes)"); Asm->OutStreamer->AddComment("Address Size (in bytes)");
Asm->EmitInt8(PtrSize); Asm->EmitInt8(PtrSize);
Asm->OutStreamer->AddComment("Segment Size (in bytes)"); Asm->OutStreamer->AddComment("Segment Size (in bytes)");
Asm->EmitInt8(0); Asm->EmitInt8(0);
Asm->OutStreamer->emitFill(Padding, 0xff); Asm->OutStreamer->emitFill(Padding, 0xff);
for (const ArangeSpan &Span : List) { for (const ArangeSpan &Span : List) {
▲ Show 20 Lines • Show All 372 Lines • Show Last 20 Lines

llvm/trunk/test/DebugInfo/X86/sections_as_references.ll

; RUN: llc -filetype=asm -O0 -mtriple=x86_64-linux-gnu < %s -dwarf-sections-as-references=Enable -dwarf-inlined-strings=Enable -no-dwarf-pub-sections -no-dwarf-ranges-section -dwarf-version 2 -debugger-tune=gdb | FileCheck %s
; CHECK: .file
; CHECK-NOT: .L
; CHECK: .section .debug_abbrev
; CHECK-NOT: DW_FORM_str{{p|x}}
; CHECK-NOT: .L
; CHECK: .section .debug_info
; CHECK-NOT: .L
; CHECK: .short 2 # DWARF version number
; CHECK-NOT: .L
; CHECK: .long .debug_abbrev # Offset Into Abbrev. Section
; CHECK-NOT: .L
; CHECK: .long .debug_line # DW_AT_stmt_list
; CHECK-NOT: .L
; CHECK: .long .debug_abbrev # Offset Into Abbrev. Section
; CHECK-NOT: .L
; CHECK: .long .debug_line # DW_AT_stmt_list
; CHECK-NOT: .L
; CHECK: .quad .debug_info+{{[0-9]+}} # DW_AT_type
; CHECK-NOT: .L
; CHECK: .byte 0 # End Of Children Mark
; CHECK-NOT: .L
source_filename = "test/DebugInfo/X86/sections_as_references.ll"
%struct.foo = type { i8 }
@f = global %struct.foo zeroinitializer, align 1, !dbg !0
@g = global %struct.foo zeroinitializer, align 1, !dbg !6
!llvm.dbg.cu = !{!9, !12}
!llvm.module.flags = !{!14, !15}
!0 = !DIGlobalVariableExpression(var: !1, expr: !DIExpression())
!1 = !DIGlobalVariable(name: "f", scope: null, file: !2, line: 2, type: !3, isLocal: false, isDefinition: true)
!2 = !DIFile(filename: "tu1.cpp", directory: "/dir")
!3 = !DICompositeType(tag: DW_TAG_structure_type, name: "foo", file: !4, line: 1, size: 8, align: 8, elements: !5, identifier: "_ZTS3foo")
!4 = !DIFile(filename: "./hdr.h", directory: "/dir")
!5 = !{}
!6 = !DIGlobalVariableExpression(var: !7, expr: !DIExpression())
!7 = !DIGlobalVariable(name: "g", scope: null, file: !8, line: 2, type: !3, isLocal: false, isDefinition: true)
!8 = !DIFile(filename: "tu2.cpp", directory: "/dir")
!9 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !2, producer: "clang", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !5, retainedTypes: !10, globals: !11, imports: !5)
!10 = !{!3}
!11 = !{!0}
!12 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !8, producer: "clang", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !5, retainedTypes: !10, globals: !13, imports: !5)
!13 = !{!6}
!14 = !{i32 2, !"Dwarf Version", i32 2}
!15 = !{i32 1, !"Debug Info Version", i32 3}