[PATCH] D43943: [DEBUGINFO] Add flag for DWARF2 to use sections as references.
Alexey Bataev via llvm-commits
llvm-commits at lists.llvm.org
Thu Mar 1 07:56:41 PST 2018
1. This is NVPTX.
2. No hope. :) At least, at the moment. llvm emits ptx file that then
compiled by ptxas tool from NVIDIA. This tool has very strict
requirements for the format of the ptx file and does not allow labels in
debug sections, only references to the sections+-offset.
-------------
Best regards,
Alexey Bataev
01.03.2018 10:53, Rafael Avila de Espindola пишет:
> Which targets?
>
> Any hope they could use MC to get a better assembler?
>
> Cheers,
> Rafael
>
> Alexey Bataev via Phabricator via llvm-commits
> <llvm-commits at lists.llvm.org> writes:
>
>> ABataev created this revision.
>> ABataev added reviewers: echristo, probinson, jlebar.
>> Herald added a subscriber: JDevlieghere.
>>
>> 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).
>>
>>
>> Repository:
>> rL LLVM
>>
>> https://nam02.safelinks.protection.outlook.com/?url=https%3A%2F%2Freviews.llvm.org%2FD43943&data=02%7C01%7C%7C58637fc6173b46715d2c08d57f8c9bbc%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C636555164233025117&sdata=ObS%2FHQD3GZ35eXUopqokVHsxrA6ZEegnhfBr0EtxLhk%3D&reserved=0
>>
>> Files:
>> lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
>> lib/CodeGen/AsmPrinter/DwarfDebug.cpp
>> lib/CodeGen/AsmPrinter/DwarfDebug.h
>> test/DebugInfo/X86/sections_as_references.ll
>>
>> Index: test/DebugInfo/X86/sections_as_references.ll
>> ===================================================================
>> --- /dev/null
>> +++ test/DebugInfo/X86/sections_as_references.ll
>> @@ -0,0 +1,54 @@
>> +; RUN: llc -filetype=asm -O0 -mtriple=x86_64-linux-gnu < %s -dwarf-sections-as-references=Enable -dwarf-inlined-strings=Enable -dwarf-version 2 -debugger-tune=lldb | 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 }
>> +
>> + at f = global %struct.foo zeroinitializer, align 1, !dbg !0
>> + at 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}
>> +
>> Index: lib/CodeGen/AsmPrinter/DwarfDebug.h
>> ===================================================================
>> --- lib/CodeGen/AsmPrinter/DwarfDebug.h
>> +++ lib/CodeGen/AsmPrinter/DwarfDebug.h
>> @@ -258,6 +258,10 @@
>> /// Use inlined strings.
>> bool UseInlineStrings = false;
>>
>> + /// 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
>> /// @{
>> bool HasDwarfAccelTables;
>> @@ -501,6 +505,11 @@
>> /// Returns whether to use inline strings.
>> bool useInlineStrings() const { return UseInlineStrings; }
>>
>> + /// Returns whether to use sections as labels rather than temp symbols.
>> + bool useSectionsAsReferences() const {
>> + return UseSectionsAsReferences;
>> + }
>> +
>> // Experimental DWARF5 features.
>>
>> /// Returns whether or not to emit tables that dwarf consumers can
>> Index: lib/CodeGen/AsmPrinter/DwarfDebug.cpp
>> ===================================================================
>> --- lib/CodeGen/AsmPrinter/DwarfDebug.cpp
>> +++ lib/CodeGen/AsmPrinter/DwarfDebug.cpp
>> @@ -123,6 +123,13 @@
>> clEnumVal(Disable, "Disabled")),
>> cl::init(Default));
>>
>> +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 {
>> DefaultLinkageNames,
>> AllLinkageNames,
>> @@ -310,6 +317,10 @@
>> // Use dwarf 4 by default if nothing is requested.
>> DwarfVersion = DwarfVersion ? DwarfVersion : dwarf::DWARF_VERSION;
>>
>> + // Use sections as references in DWARF v2.
>> + UseSectionsAsReferences =
>> + DwarfVersion == 2 && DwarfSectionsAsReferences == Enable;
>> +
>> // Work around a GDB bug. GDB doesn't support the standard opcode;
>> // SCE doesn't support GNU's; LLDB prefers the standard opcode, which
>> // is defined as of DWARF 3.
>> @@ -737,7 +748,7 @@
>> // ranges for all subprogram DIEs for mach-o.
>> DwarfCompileUnit &U = SkCU ? *SkCU : TheCU;
>> if (unsigned NumRanges = TheCU.getRanges().size()) {
>> - if (NumRanges > 1)
>> + if (NumRanges > 1 && !useSectionsAsReferences())
>> // A DW_AT_low_pc attribute may also be specified in combination with
>> // DW_AT_ranges to specify the default base address for use in
>> // location lists (see Section 2.6.2) and range lists (see Section
>> @@ -1565,7 +1576,13 @@
>> Asm->EmitInt16(dwarf::DW_PUBNAMES_VERSION);
>>
>> Asm->OutStreamer->AddComment("Offset of Compilation Unit Info");
>> - Asm->emitDwarfSymbolReference(TheU->getLabelBegin());
>> + if (useSectionsAsReferences()) {
>> + Asm->EmitLabelPlusOffset(TheU->getSection()->getBeginSymbol(),
>> + TheU->getDebugSectionOffset(),
>> + Asm->MAI->getCodePointerSize());
>> + } else {
>> + Asm->emitDwarfSymbolReference(TheU->getLabelBegin());
>> + }
>>
>> Asm->OutStreamer->AddComment("Compilation Unit Length");
>> Asm->EmitInt32(TheU->getLength());
>> @@ -1864,7 +1881,13 @@
>> Asm->OutStreamer->AddComment("DWARF Arange version number");
>> Asm->EmitInt16(dwarf::DW_ARANGES_VERSION);
>> Asm->OutStreamer->AddComment("Offset Into Debug Info Section");
>> - Asm->emitDwarfSymbolReference(CU->getLabelBegin());
>> + if (useSectionsAsReferences()) {
>> + Asm->EmitLabelPlusOffset(CU->getSection()->getBeginSymbol(),
>> + CU->getDebugSectionOffset(),
>> + Asm->MAI->getCodePointerSize());
>> + } else {
>> + Asm->emitDwarfSymbolReference(CU->getLabelBegin());
>> + }
>> Asm->OutStreamer->AddComment("Address Size (in bytes)");
>> Asm->EmitInt8(PtrSize);
>> Asm->OutStreamer->AddComment("Segment Size (in bytes)");
>> Index: lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
>> ===================================================================
>> --- lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
>> +++ lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
>> @@ -270,15 +270,20 @@
>>
>> void DwarfCompileUnit::initStmtList() {
>> // Define start line table label for each Compile Unit.
>> - MCSymbol *LineTableStartSym =
>> - Asm->OutStreamer->getDwarfLineTableSymbol(getUniqueID());
>> + MCSymbol *LineTableStartSym;
>> + const TargetLoweringObjectFile &TLOF = Asm->getObjFileLowering();
>> + if (DD->useSectionsAsReferences()) {
>> + LineTableStartSym = TLOF.getDwarfLineSection()->getBeginSymbol();
>> + } else {
>> + LineTableStartSym =
>> + Asm->OutStreamer->getDwarfLineTableSymbol(getUniqueID());
>> + }
>>
>> // DW_AT_stmt_list is a offset of line number information for this
>> // compile unit in debug_line section. For split dwarf this is
>> // left in the skeleton CU and so not included.
>> // The line table entries are not always emitted in assembly, so it
>> // is not okay to use line_table_start here.
>> - const TargetLoweringObjectFile &TLOF = Asm->getObjFileLowering();
>> StmtListValue =
>> addSectionLabel(getUnitDie(), dwarf::DW_AT_stmt_list, LineTableStartSym,
>> TLOF.getDwarfLineSection()->getBeginSymbol());
>> @@ -410,9 +415,10 @@
>>
>> void DwarfCompileUnit::attachRangesOrLowHighPC(
>> DIE &Die, SmallVector<RangeSpan, 2> Ranges) {
>> - if (Ranges.size() == 1) {
>> - const auto &single = Ranges.front();
>> - attachLowHighPC(Die, single.getStart(), single.getEnd());
>> + if (Ranges.size() == 1 || DD->useSectionsAsReferences()) {
>> + const RangeSpan &Front = Ranges.front();
>> + const RangeSpan &Back = Ranges.back();
>> + attachLowHighPC(Die, Front.getStart(), Back.getEnd());
>> } else
>> addScopeRangeList(Die, std::move(Ranges));
>> }
>> @@ -834,7 +840,7 @@
>>
>> void DwarfCompileUnit::emitHeader(bool UseOffsets) {
>> // Don't bother labeling the .dwo unit, as its offset isn't used.
>> - if (!Skeleton) {
>> + if (!Skeleton && !DD->useSectionsAsReferences()) {
>> LabelBegin = Asm->createTempSymbol("cu_begin");
>> Asm->OutStreamer->EmitLabel(LabelBegin);
>> }
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