[llvm] r374600 - DebugInfo: Use base address selection entries for debug_loc

Adrian Prantl via llvm-commits llvm-commits at lists.llvm.org
Mon Nov 4 17:08:56 PST 2019


Jonas, does this assertion reproduce on our bots, too?
Reid, I assume the reproducer is going to be really large?

-- adrian

> On Nov 4, 2019, at 5:00 PM, Reid Kleckner <rnk at google.com> wrote:
> 
> This appears to cause dsymutil to assert: https://crbug.com/1019517 <https://crbug.com/1019517>
> Assertion failed: (Die >= First && Die < First + DieArray.size()), function getDIEIndex, file /b/rr/tmp9JWo9i/w/src/third_party/llvm/include/llvm/DebugInfo/DWARF/DWARFUnit.h, line 236. 
> 
> Should this be conditional on some feature like DWARF 5, gdb tuning, lldb tuning, OS, or something else? 
> 
> On Fri, Oct 11, 2019 at 2:50 PM David Blaikie via llvm-commits <llvm-commits at lists.llvm.org <mailto:llvm-commits at lists.llvm.org>> wrote:
> Author: dblaikie
> Date: Fri Oct 11 14:52:41 2019
> New Revision: 374600
> 
> URL: http://llvm.org/viewvc/llvm-project?rev=374600&view=rev <http://llvm.org/viewvc/llvm-project?rev=374600&view=rev>
> Log:
> DebugInfo: Use base address selection entries for debug_loc
> 
> Unify the range and loc emission (for both DWARFv4 and DWARFv5 style lists) and take advantage of that unification to use strategic base addresses for loclists.
> 
> Differential Revision: https://reviews.llvm.org/D68620 <https://reviews.llvm.org/D68620>
> 
> Modified:
>     llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
>     llvm/trunk/test/CodeGen/X86/debug-loclists.ll
>     llvm/trunk/test/DebugInfo/X86/sret.ll
> 
> Modified: llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp?rev=374600&r1=374599&r2=374600&view=diff <http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp?rev=374600&r1=374599&r2=374600&view=diff>
> ==============================================================================
> --- llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp (original)
> +++ llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp Fri Oct 11 14:52:41 2019
> @@ -2293,14 +2293,121 @@ static MCSymbol *emitLoclistsTableHeader
>    return TableEnd;
>  }
> 
> +template <typename Ranges, typename PayloadEmitter>
> +static void emitRangeList(
> +    DwarfDebug &DD, AsmPrinter *Asm, MCSymbol *Sym, const Ranges &R,
> +    const DwarfCompileUnit &CU, unsigned BaseAddressx, unsigned OffsetPair,
> +    unsigned StartxLength, unsigned EndOfList,
> +    StringRef (*StringifyEnum)(unsigned),
> +    bool ShouldUseBaseAddress,
> +    PayloadEmitter EmitPayload) {
> +
> +  auto Size = Asm->MAI->getCodePointerSize();
> +  bool UseDwarf5 = DD.getDwarfVersion() >= 5;
> +
> +  // Emit our symbol so we can find the beginning of the range.
> +  Asm->OutStreamer->EmitLabel(Sym);
> +
> +  // Gather all the ranges that apply to the same section so they can share
> +  // a base address entry.
> +  MapVector<const MCSection *, std::vector<decltype(&*R.begin())>> SectionRanges;
> +
> +  for (const auto &Range : R)
> +    SectionRanges[&Range.Begin->getSection()].push_back(&Range);
> +
> +  const MCSymbol *CUBase = CU.getBaseAddress();
> +  bool BaseIsSet = false;
> +  for (const auto &P : SectionRanges) {
> +    auto *Base = CUBase;
> +    if (!Base && ShouldUseBaseAddress) {
> +      const MCSymbol *Begin = P.second.front()->Begin;
> +      const MCSymbol *NewBase = DD.getSectionLabel(&Begin->getSection());
> +      if (!UseDwarf5) {
> +        Base = NewBase;
> +        BaseIsSet = true;
> +        Asm->OutStreamer->EmitIntValue(-1, Size);
> +        Asm->OutStreamer->AddComment("  base address");
> +        Asm->OutStreamer->EmitSymbolValue(Base, Size);
> +      } else if (NewBase != Begin || P.second.size() > 1) {
> +        // Only use a base address if
> +        //  * the existing pool address doesn't match (NewBase != Begin)
> +        //  * or, there's more than one entry to share the base address
> +        Base = NewBase;
> +        BaseIsSet = true;
> +        Asm->OutStreamer->AddComment(StringifyEnum(BaseAddressx));
> +        Asm->emitInt8(BaseAddressx);
> +        Asm->OutStreamer->AddComment("  base address index");
> +        Asm->EmitULEB128(DD.getAddressPool().getIndex(Base));
> +      }
> +    } else if (BaseIsSet && !UseDwarf5) {
> +      BaseIsSet = false;
> +      assert(!Base);
> +      Asm->OutStreamer->EmitIntValue(-1, Size);
> +      Asm->OutStreamer->EmitIntValue(0, Size);
> +    }
> +
> +    for (const auto *RS : P.second) {
> +      const MCSymbol *Begin = RS->Begin;
> +      const MCSymbol *End = RS->End;
> +      assert(Begin && "Range without a begin symbol?");
> +      assert(End && "Range without an end symbol?");
> +      if (Base) {
> +        if (UseDwarf5) {
> +          // Emit offset_pair when we have a base.
> +          Asm->OutStreamer->AddComment(StringifyEnum(OffsetPair));
> +          Asm->emitInt8(OffsetPair);
> +          Asm->OutStreamer->AddComment("  starting offset");
> +          Asm->EmitLabelDifferenceAsULEB128(Begin, Base);
> +          Asm->OutStreamer->AddComment("  ending offset");
> +          Asm->EmitLabelDifferenceAsULEB128(End, Base);
> +        } else {
> +          Asm->EmitLabelDifference(Begin, Base, Size);
> +          Asm->EmitLabelDifference(End, Base, Size);
> +        }
> +      } else if (UseDwarf5) {
> +        Asm->OutStreamer->AddComment(StringifyEnum(StartxLength));
> +        Asm->emitInt8(StartxLength);
> +        Asm->OutStreamer->AddComment("  start index");
> +        Asm->EmitULEB128(DD.getAddressPool().getIndex(Begin));
> +        Asm->OutStreamer->AddComment("  length");
> +        Asm->EmitLabelDifferenceAsULEB128(End, Begin);
> +      } else {
> +        Asm->OutStreamer->EmitSymbolValue(Begin, Size);
> +        Asm->OutStreamer->EmitSymbolValue(End, Size);
> +      }
> +      EmitPayload(*RS);
> +    }
> +  }
> +
> +  if (UseDwarf5) {
> +    Asm->OutStreamer->AddComment(StringifyEnum(EndOfList));
> +    Asm->emitInt8(EndOfList);
> +  } else {
> +    // Terminate the list with two 0 values.
> +    Asm->OutStreamer->EmitIntValue(0, Size);
> +    Asm->OutStreamer->EmitIntValue(0, Size);
> +  }
> +}
> +
> +static void emitLocList(DwarfDebug &DD, AsmPrinter *Asm, const DebugLocStream::List &List) {
> +  emitRangeList(
> +      DD, Asm, List.Label, DD.getDebugLocs().getEntries(List), *List.CU,
> +      dwarf::DW_LLE_base_addressx, dwarf::DW_LLE_offset_pair,
> +      dwarf::DW_LLE_startx_length, dwarf::DW_LLE_end_of_list,
> +      llvm::dwarf::LocListEncodingString,
> +      /* ShouldUseBaseAddress */ true,
> +      [&](const DebugLocStream::Entry &E) {
> +        DD.emitDebugLocEntryLocation(E, List.CU);
> +      });
> +}
> +
>  // Emit locations into the .debug_loc/.debug_rnglists section.
>  void DwarfDebug::emitDebugLoc() {
>    if (DebugLocs.getLists().empty())
>      return;
> 
> -  bool IsLocLists = getDwarfVersion() >= 5;
>    MCSymbol *TableEnd = nullptr;
> -  if (IsLocLists) {
> +  if (getDwarfVersion() >= 5) {
>      Asm->OutStreamer->SwitchSection(
>          Asm->getObjFileLowering().getDwarfLoclistsSection());
>      TableEnd = emitLoclistsTableHeader(Asm, useSplitDwarf() ? SkeletonHolder
> @@ -2310,63 +2417,8 @@ void DwarfDebug::emitDebugLoc() {
>          Asm->getObjFileLowering().getDwarfLocSection());
>    }
> 
> -  unsigned char Size = Asm->MAI->getCodePointerSize();
> -  for (const auto &List : DebugLocs.getLists()) {
> -    Asm->OutStreamer->EmitLabel(List.Label);
> -
> -    const DwarfCompileUnit *CU = List.CU;
> -    const MCSymbol *Base = CU->getBaseAddress();
> -    for (const auto &Entry : DebugLocs.getEntries(List)) {
> -      if (Base) {
> -        // Set up the range. This range is relative to the entry point of the
> -        // compile unit. This is a hard coded 0 for low_pc when we're emitting
> -        // ranges, or the DW_AT_low_pc on the compile unit otherwise.
> -        if (IsLocLists) {
> -          Asm->OutStreamer->AddComment("DW_LLE_offset_pair");
> -          Asm->OutStreamer->EmitIntValue(dwarf::DW_LLE_offset_pair, 1);
> -          Asm->OutStreamer->AddComment("  starting offset");
> -          Asm->EmitLabelDifferenceAsULEB128(Entry.Begin, Base);
> -          Asm->OutStreamer->AddComment("  ending offset");
> -          Asm->EmitLabelDifferenceAsULEB128(Entry.End, Base);
> -        } else {
> -          Asm->EmitLabelDifference(Entry.Begin, Base, Size);
> -          Asm->EmitLabelDifference(Entry.End, Base, Size);
> -        }
> -
> -        emitDebugLocEntryLocation(Entry, CU);
> -        continue;
> -      }
> -
> -      // We have no base address.
> -      if (IsLocLists) {
> -        // TODO: Use DW_LLE_base_addressx + DW_LLE_offset_pair, or
> -        // DW_LLE_startx_length in case if there is only a single range.
> -        // That should reduce the size of the debug data emited.
> -        // For now just use the DW_LLE_startx_length for all cases.
> -        Asm->OutStreamer->AddComment("DW_LLE_startx_length");
> -        Asm->emitInt8(dwarf::DW_LLE_startx_length);
> -        Asm->OutStreamer->AddComment("  start idx");
> -        Asm->EmitULEB128(AddrPool.getIndex(Entry.Begin));
> -        Asm->OutStreamer->AddComment("  length");
> -        Asm->EmitLabelDifferenceAsULEB128(Entry.End, Entry.Begin);
> -      } else {
> -        Asm->OutStreamer->EmitSymbolValue(Entry.Begin, Size);
> -        Asm->OutStreamer->EmitSymbolValue(Entry.End, Size);
> -      }
> -
> -      emitDebugLocEntryLocation(Entry, CU);
> -    }
> -
> -    if (IsLocLists) {
> -      // .debug_loclists section ends with DW_LLE_end_of_list.
> -      Asm->OutStreamer->AddComment("DW_LLE_end_of_list");
> -      Asm->OutStreamer->EmitIntValue(dwarf::DW_LLE_end_of_list, 1);
> -    } else {
> -      // Terminate the .debug_loc list with two 0 values.
> -      Asm->OutStreamer->EmitIntValue(0, Size);
> -      Asm->OutStreamer->EmitIntValue(0, Size);
> -    }
> -  }
> +  for (const auto &List : DebugLocs.getLists())
> +    emitLocList(*this, Asm, List);
> 
>    if (TableEnd)
>      Asm->OutStreamer->EmitLabel(TableEnd);
> @@ -2556,103 +2608,16 @@ void DwarfDebug::emitDebugARanges() {
>    }
>  }
> 
> -template <typename Ranges>
> -static void emitRangeList(DwarfDebug &DD, AsmPrinter *Asm, MCSymbol *Sym,
> -                          const Ranges &R, const DwarfCompileUnit &CU,
> -                          unsigned BaseAddressx, unsigned OffsetPair,
> -                          unsigned StartxLength, unsigned EndOfList,
> -                          StringRef (*StringifyEnum)(unsigned)) {
> -  auto DwarfVersion = DD.getDwarfVersion();
> -  // Emit our symbol so we can find the beginning of the range.
> -  Asm->OutStreamer->EmitLabel(Sym);
> -  // Gather all the ranges that apply to the same section so they can share
> -  // a base address entry.
> -  MapVector<const MCSection *, std::vector<const RangeSpan *>> SectionRanges;
> -  // Size for our labels.
> -  auto Size = Asm->MAI->getCodePointerSize();
> -
> -  for (const RangeSpan &Range : R)
> -    SectionRanges[&Range.Begin->getSection()].push_back(&Range);
> -
> -  const MCSymbol *CUBase = CU.getBaseAddress();
> -  bool BaseIsSet = false;
> -  for (const auto &P : SectionRanges) {
> -    // Don't bother with a base address entry if there's only one range in
> -    // this section in this range list - for example ranges for a CU will
> -    // usually consist of single regions from each of many sections
> -    // (-ffunction-sections, or just C++ inline functions) except under LTO
> -    // or optnone where there may be holes in a single CU's section
> -    // contributions.
> -    auto *Base = CUBase;
> -    if (!Base && (P.second.size() > 1 || DwarfVersion < 5) &&
> -        (CU.getCUNode()->getRangesBaseAddress() || DwarfVersion >= 5)) {
> -      BaseIsSet = true;
> -      Base = DD.getSectionLabel(&P.second.front()->Begin->getSection());
> -      if (DwarfVersion >= 5) {
> -        Asm->OutStreamer->AddComment(StringifyEnum(BaseAddressx));
> -        Asm->OutStreamer->EmitIntValue(BaseAddressx, 1);
> -        Asm->OutStreamer->AddComment("  base address index");
> -        Asm->EmitULEB128(DD.getAddressPool().getIndex(Base));
> -      } else {
> -        Asm->OutStreamer->EmitIntValue(-1, Size);
> -        Asm->OutStreamer->AddComment("  base address");
> -        Asm->OutStreamer->EmitSymbolValue(Base, Size);
> -      }
> -    } else if (BaseIsSet && DwarfVersion < 5) {
> -      BaseIsSet = false;
> -      assert(!Base);
> -      Asm->OutStreamer->EmitIntValue(-1, Size);
> -      Asm->OutStreamer->EmitIntValue(0, Size);
> -    }
> -
> -    for (const auto *RS : P.second) {
> -      const MCSymbol *Begin = RS->Begin;
> -      const MCSymbol *End = RS->End;
> -      assert(Begin && "Range without a begin symbol?");
> -      assert(End && "Range without an end symbol?");
> -      if (Base) {
> -        if (DwarfVersion >= 5) {
> -          // Emit DW_RLE_offset_pair when we have a base.
> -          Asm->OutStreamer->AddComment(StringifyEnum(OffsetPair));
> -          Asm->emitInt8(OffsetPair);
> -          Asm->OutStreamer->AddComment("  starting offset");
> -          Asm->EmitLabelDifferenceAsULEB128(Begin, Base);
> -          Asm->OutStreamer->AddComment("  ending offset");
> -          Asm->EmitLabelDifferenceAsULEB128(End, Base);
> -        } else {
> -          Asm->EmitLabelDifference(Begin, Base, Size);
> -          Asm->EmitLabelDifference(End, Base, Size);
> -        }
> -      } else if (DwarfVersion >= 5) {
> -        Asm->OutStreamer->AddComment(StringifyEnum(StartxLength));
> -        Asm->emitInt8(StartxLength);
> -        Asm->OutStreamer->AddComment("  start index");
> -        Asm->EmitULEB128(DD.getAddressPool().getIndex(Begin));
> -        Asm->OutStreamer->AddComment("  length");
> -        Asm->EmitLabelDifferenceAsULEB128(End, Begin);
> -      } else {
> -        Asm->OutStreamer->EmitSymbolValue(Begin, Size);
> -        Asm->OutStreamer->EmitSymbolValue(End, Size);
> -      }
> -    }
> -  }
> -  if (DwarfVersion >= 5) {
> -    Asm->OutStreamer->AddComment(StringifyEnum(EndOfList));
> -    Asm->emitInt8(EndOfList);
> -  } else {
> -    // Terminate the list with two 0 values.
> -    Asm->OutStreamer->EmitIntValue(0, Size);
> -    Asm->OutStreamer->EmitIntValue(0, Size);
> -  }
> -}
> -
>  /// Emit a single range list. We handle both DWARF v5 and earlier.
>  static void emitRangeList(DwarfDebug &DD, AsmPrinter *Asm,
>                            const RangeSpanList &List) {
>    emitRangeList(DD, Asm, List.getSym(), List.getRanges(), List.getCU(),
>                  dwarf::DW_RLE_base_addressx, dwarf::DW_RLE_offset_pair,
>                  dwarf::DW_RLE_startx_length, dwarf::DW_RLE_end_of_list,
> -                llvm::dwarf::RangeListEncodingString);
> +                llvm::dwarf::RangeListEncodingString,
> +                List.getCU().getCUNode()->getRangesBaseAddress() ||
> +                    DD.getDwarfVersion() >= 5,
> +                [](auto) {});
>  }
> 
>  static void emitDebugRangesImpl(DwarfDebug &DD, AsmPrinter *Asm,
> 
> Modified: llvm/trunk/test/CodeGen/X86/debug-loclists.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/debug-loclists.ll?rev=374600&r1=374599&r2=374600&view=diff <http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/debug-loclists.ll?rev=374600&r1=374599&r2=374600&view=diff>
> ==============================================================================
> --- llvm/trunk/test/CodeGen/X86/debug-loclists.ll (original)
> +++ llvm/trunk/test/CodeGen/X86/debug-loclists.ll Fri Oct 11 14:52:41 2019
> @@ -1,144 +1,119 @@
> -; RUN: llc -mtriple=x86_64-pc-linux -filetype=obj -o %t < %s
> -; RUN: llvm-dwarfdump -v %t | FileCheck %s
> +; RUN: llc -mtriple=x86_64-pc-linux -filetype=obj -function-sections -o %t < %s
> +; RUN: llvm-dwarfdump -v -debug-info -debug-loclists %t | FileCheck %s
> 
> -; CHECK:      0x00000033: DW_TAG_formal_parameter [3]
> -; CHECK-NEXT:               DW_AT_location [DW_FORM_sec_offset]   (0x0000000c
> -; CHECK-NEXT:                  [0x0000000000000000, 0x0000000000000004): DW_OP_breg5 RDI+0
> -; CHECK-NEXT:                  [0x0000000000000004, 0x0000000000000012): DW_OP_breg3 RBX+0)
> -; CHECK-NEXT:               DW_AT_name [DW_FORM_strx1]    (indexed (0000000e) string = "a")
> -; CHECK-NEXT:               DW_AT_decl_file [DW_FORM_data1]       ("/home/folder{{\\|\/}}test.cc")
> -; CHECK-NEXT:               DW_AT_decl_line [DW_FORM_data1]       (6)
> -; CHECK-NEXT:               DW_AT_type [DW_FORM_ref4]     (cu + 0x0040 => {0x00000040} "A")
> +; CHECK:      DW_TAG_variable
> +; FIXME: Use DW_FORM_loclistx to reduce relocations
> +; CHECK-NEXT:   DW_AT_location [DW_FORM_sec_offset]   (0x0000000c
> +; CHECK-NEXT:     [0x0000000000000000, 0x0000000000000003): DW_OP_consts +3, DW_OP_stack_value
> +; CHECK-NEXT:     [0x0000000000000003, 0x0000000000000004): DW_OP_consts +4, DW_OP_stack_value)
> +; CHECK-NEXT:   DW_AT_name {{.*}} "y"
> +
> +; CHECK:      DW_TAG_variable
> +; FIXME: Use DW_FORM_loclistx to reduce relocations
> +; CHECK-NEXT:   DW_AT_location [DW_FORM_sec_offset]   (0x0000001d
> +; CHECK-NEXT:     Addr idx 0 (w/ length 3): DW_OP_consts +5, DW_OP_stack_value)
> +; CHECK-NEXT:   DW_AT_name {{.*}} "x"
> +
> +; CHECK:      DW_TAG_variable
> +; FIXME: Use DW_FORM_loclistx to reduce relocations
> +; CHECK-NEXT:   DW_AT_location [DW_FORM_sec_offset]   (0x00000025
> +; CHECK-NEXT:     [0x0000000000000003, 0x0000000000000004): DW_OP_reg0 RAX)
> +; CHECK-NEXT:   DW_AT_name {{.*}} "r"
> 
>  ; CHECK:      .debug_loclists contents:
> -; CHECK-NEXT: 0x00000000: locations list header: length = 0x00000015, version = 0x0005, addr_size = 0x08, seg_size = 0x00, offset_entry_count = 0x00000000
> -; CHECK-NEXT: 0x0000000c:
> -; CHECK-NEXT: DW_LLE_offset_pair(0x0000000000000000, 0x0000000000000004)
> -; CHECK-NEXT:                => [0x0000000000000000, 0x0000000000000004): DW_OP_breg5 RDI+0
> -; CHECK-NEXT: DW_LLE_offset_pair(0x0000000000000004, 0x0000000000000012)
> -; CHECK-NEXT:                => [0x0000000000000004, 0x0000000000000012): DW_OP_breg3 RBX+0
> -
> -; There is no way to use llvm-dwarfdump atm (2018, october) to verify the DW_LLE_* codes emited,
> -; because dumper is not yet implements that. Use asm code to do this check instead.
> -;
> -; RUN: llc -mtriple=x86_64-pc-linux -filetype=asm < %s -o - | FileCheck %s --check-prefix=ASM
> -; ASM:      .section .debug_loclists,"", at progbits
> -; ASM-NEXT: .long .Ldebug_loclist_table_end0-.Ldebug_loclist_table_start0 # Length
> -; ASM-NEXT: .Ldebug_loclist_table_start0:
> -; ASM-NEXT:  .short 5                              # Version
> -; ASM-NEXT:  .byte 8                               # Address size
> -; ASM-NEXT:  .byte 0                               # Segment selector size
> -; ASM-NEXT:  .long 0                               # Offset entry count
> -; ASM-NEXT: .Lloclists_table_base0:                
> -; ASM-NEXT: .Ldebug_loc0:
> -; ASM-NEXT:  .byte 4                               # DW_LLE_offset_pair
> -; ASM-NEXT:  .uleb128 .Lfunc_begin0-.Lfunc_begin0  # starting offset
> -; ASM-NEXT:  .uleb128 .Ltmp0-.Lfunc_begin0         # ending offset
> -; ASM-NEXT:  .byte 2                               # Loc expr size
> -; ASM-NEXT:  .byte 117                             # DW_OP_breg5
> -; ASM-NEXT:  .byte 0                               # 0
> -; ASM-NEXT:  .byte 4                               # DW_LLE_offset_pair
> -; ASM-NEXT:  .uleb128 .Ltmp0-.Lfunc_begin0         # starting offset
> -; ASM-NEXT:  .uleb128 .Ltmp1-.Lfunc_begin0         # ending offset
> -; ASM-NEXT:  .byte 2                               # Loc expr size
> -; ASM-NEXT:  .byte 115                             # DW_OP_breg3
> -; ASM-NEXT:  .byte 0                               # 0
> -; ASM-NEXT:  .byte 0                               # DW_LLE_end_of_list
> -; ASM-NEXT: .Ldebug_loclist_table_end0:
> -
> -; ModuleID = 'test.cc'
> -source_filename = "test.cc"
> -target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
> -target triple = "x86_64-unknown-linux-gnu"
> -
> -%struct.A = type { i32 (...)** }
> -
> - at _ZTV1A = dso_local unnamed_addr constant { [4 x i8*] } { [4 x i8*] [i8* null, i8* bitcast ({ i8*, i8* }* @_ZTI1A to i8*), i8* bitcast (void (%struct.A*)* @_ZN1A3fooEv to i8*), i8* bitcast (void (%struct.A*)* @_ZN1A3barEv to i8*)] }, align 8
> - at _ZTVN10__cxxabiv117__class_type_infoE = external dso_local global i8*
> - at _ZTS1A = dso_local constant [3 x i8] c"1A\00", align 1
> - at _ZTI1A = dso_local constant { i8*, i8* } { i8* bitcast (i8** getelementptr inbounds (i8*, i8** @_ZTVN10__cxxabiv117__class_type_infoE, i64 2) to i8*), i8* getelementptr inbounds ([3 x i8], [3 x i8]* @_ZTS1A, i32 0, i32 0) }, align 8
> -
> -; Function Attrs: noinline optnone uwtable
> -define dso_local void @_Z3baz1A(%struct.A* %a) #0 !dbg !7 {
> -entry:
> -  call void @llvm.dbg.declare(metadata %struct.A* %a, metadata !23, metadata !DIExpression()), !dbg !24
> -  call void @_ZN1A3fooEv(%struct.A* %a), !dbg !25
> -  call void @_ZN1A3barEv(%struct.A* %a), !dbg !26
> -  ret void, !dbg !27
> -}
> +; CHECK-NEXT: 0x00000000: locations list header: length = 0x00000029, version = 0x0005, addr_size = 0x08, seg_size = 0x00, offset_entry_count = 0x00000000
> 
> -; Function Attrs: nounwind readnone speculatable
> -declare void @llvm.dbg.declare(metadata, metadata, metadata) #1
> +; Don't use startx_length if there's more than one entry, because the shared
> +; base address will be useful for both the range that does start at the start of
> +; the function, and the one that doesn't.
> 
> -; Function Attrs: noinline nounwind optnone uwtable
> -define dso_local void @_ZN1A3fooEv(%struct.A* %this) unnamed_addr #2 align 2 !dbg !28 {
> -entry:
> -  %this.addr = alloca %struct.A*, align 8
> -  store %struct.A* %this, %struct.A** %this.addr, align 8
> -  call void @llvm.dbg.declare(metadata %struct.A** %this.addr, metadata !29, metadata !DIExpression()), !dbg !31
> -  %this1 = load %struct.A*, %struct.A** %this.addr, align 8
> -  ret void, !dbg !32
> -}
> +; CHECK-NEXT: 0x0000000c:
> +; CHECK-NEXT:             DW_LLE_base_addressx(0x0000000000000000)
> +; CHECK-NEXT:             DW_LLE_offset_pair  (0x0000000000000000, 0x0000000000000003)
> +; CHECK-NEXT:                              => [0x0000000000000000, 0x0000000000000003): DW_OP_consts +3, DW_OP_stack_value
> +; CHECK-NEXT:             DW_LLE_offset_pair  (0x0000000000000003, 0x0000000000000004)
> +; CHECK-NEXT:                              => [0x0000000000000003, 0x0000000000000004): DW_OP_consts +4, DW_OP_stack_value
> +; CHECK-NEXT:             DW_LLE_end_of_list  ()
> +
> +; Show that startx_length can be used when the address range starts at the start of the function.
> +
> +; CHECK:      0x0000001d:
> +; CHECK-NEXT:             DW_LLE_startx_length(0x0000000000000000, 0x0000000000000003)
> +; CHECK-NEXT:                              => Addr idx 0 (w/ length 3): DW_OP_consts +5, DW_OP_stack_value
> +; CHECK-NEXT:             DW_LLE_end_of_list  ()
> +
> +; And use a base address when the range doesn't start at an existing/useful
> +; address in the pool.
> +
> +; CHECK:      0x00000025:
> +; CHECK-NEXT:             DW_LLE_base_addressx(0x0000000000000000)
> +; CHECK-NEXT:             DW_LLE_offset_pair  (0x0000000000000003, 0x0000000000000004)
> +; CHECK-NEXT:                              => [0x0000000000000003, 0x0000000000000004): DW_OP_reg0 RAX
> +; CHECK-NEXT:             DW_LLE_end_of_list  ()
> +
> +; Built with clang -O3 -ffunction-sections from source:
> +; 
> +; int f1(int i, int j) {
> +;   int x = 5;
> +;   int y = 3;
> +;   int r = i + j;
> +;   int undef;
> +;   x = undef;
> +;   y = 4;
> +;   return r;
> +; }
> +; void f2() {
> +; }
> 
> -; Function Attrs: noinline nounwind optnone uwtable
> -define dso_local void @_ZN1A3barEv(%struct.A* %this) unnamed_addr #2 align 2 !dbg !33 {
> +; Function Attrs: norecurse nounwind readnone uwtable
> +define dso_local i32 @_Z2f1ii(i32 %i, i32 %j) local_unnamed_addr !dbg !7 {
>  entry:
> -  %this.addr = alloca %struct.A*, align 8
> -  store %struct.A* %this, %struct.A** %this.addr, align 8
> -  call void @llvm.dbg.declare(metadata %struct.A** %this.addr, metadata !34, metadata !DIExpression()), !dbg !35
> -  %this1 = load %struct.A*, %struct.A** %this.addr, align 8
> -  ret void, !dbg !36
> +  call void @llvm.dbg.value(metadata i32 %i, metadata !12, metadata !DIExpression()), !dbg !18
> +  call void @llvm.dbg.value(metadata i32 %j, metadata !13, metadata !DIExpression()), !dbg !18
> +  call void @llvm.dbg.value(metadata i32 5, metadata !14, metadata !DIExpression()), !dbg !18
> +  call void @llvm.dbg.value(metadata i32 3, metadata !15, metadata !DIExpression()), !dbg !18
> +  %add = add nsw i32 %j, %i, !dbg !19
> +  call void @llvm.dbg.value(metadata i32 %add, metadata !16, metadata !DIExpression()), !dbg !18
> +  call void @llvm.dbg.value(metadata i32 undef, metadata !14, metadata !DIExpression()), !dbg !18
> +  call void @llvm.dbg.value(metadata i32 4, metadata !15, metadata !DIExpression()), !dbg !18
> +  ret i32 %add, !dbg !20
>  }
> 
> -; Function Attrs: noinline norecurse nounwind optnone uwtable
> -define dso_local i32 @main() #3 !dbg !37 {
> +; Function Attrs: norecurse nounwind readnone uwtable
> +define dso_local void @_Z2f2v() local_unnamed_addr !dbg !21 {
>  entry:
> -  %retval = alloca i32, align 4
> -  store i32 0, i32* %retval, align 4
> -  ret i32 0, !dbg !38
> +  ret void, !dbg !24
>  }
> 
> +; Function Attrs: nounwind readnone speculatable willreturn
> +declare void @llvm.dbg.value(metadata, metadata, metadata)
> 
>  !llvm.dbg.cu <http://llvm.dbg.cu/> = !{!0}
>  !llvm.module.flags = !{!3, !4, !5}
>  !llvm.ident = !{!6}
> 
> -!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !1, producer: "clang version 8.0.0 (trunk 344035)", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, nameTableKind: None)
> -!1 = !DIFile(filename: "test.cc", directory: "/home/folder", checksumkind: CSK_MD5, checksum: "e0f357ad6dcb791a774a0dae55baf5e7")
> +!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus_14, file: !1, producer: "clang version 10.0.0 (trunk 374581) (llvm/trunk 374579)", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, nameTableKind: None)
> +!1 = !DIFile(filename: "loc2.cpp", directory: "/usr/local/google/home/blaikie/dev/scratch", checksumkind: CSK_MD5, checksum: "91e0069c680e2a63f4f885ec93f5d07e")
>  !2 = !{}
>  !3 = !{i32 2, !"Dwarf Version", i32 5}
>  !4 = !{i32 2, !"Debug Info Version", i32 3}
>  !5 = !{i32 1, !"wchar_size", i32 4}
> -!6 = !{!"clang version 8.0.0 (trunk 344035)"}
> -!7 = distinct !DISubprogram(name: "baz", linkageName: "_Z3baz1A", scope: !1, file: !1, line: 6, type: !8, isLocal: false, isDefinition: true, scopeLine: 6, flags: DIFlagPrototyped, isOptimized: false, unit: !0, retainedNodes: !2)
> +!6 = !{!"clang version 10.0.0 (trunk 374581) (llvm/trunk 374579)"}
> +!7 = distinct !DISubprogram(name: "f1", linkageName: "_Z2f1ii", scope: !1, file: !1, line: 1, type: !8, scopeLine: 1, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !11)
>  !8 = !DISubroutineType(types: !9)
> -!9 = !{null, !10}
> -!10 = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "A", file: !1, line: 1, size: 64, flags: DIFlagTypePassByReference, elements: !11, vtableHolder: !10, identifier: "_ZTS1A")
> -!11 = !{!12, !18, !22}
> -!12 = !DIDerivedType(tag: DW_TAG_member, name: "_vptr$A", scope: !1, file: !1, baseType: !13, size: 64, flags: DIFlagArtificial)
> -!13 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !14, size: 64)
> -!14 = !DIDerivedType(tag: DW_TAG_pointer_type, name: "__vtbl_ptr_type", baseType: !15, size: 64)
> -!15 = !DISubroutineType(types: !16)
> -!16 = !{!17}
> -!17 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
> -!18 = !DISubprogram(name: "foo", linkageName: "_ZN1A3fooEv", scope: !10, file: !1, line: 2, type: !19, isLocal: false, isDefinition: false, scopeLine: 2, containingType: !10, virtuality: DW_VIRTUALITY_virtual, virtualIndex: 0, flags: DIFlagPrototyped, isOptimized: false)
> -!19 = !DISubroutineType(types: !20)
> -!20 = !{null, !21}
> -!21 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !10, size: 64, flags: DIFlagArtificial | DIFlagObjectPointer)
> -!22 = !DISubprogram(name: "bar", linkageName: "_ZN1A3barEv", scope: !10, file: !1, line: 3, type: !19, isLocal: false, isDefinition: false, scopeLine: 3, containingType: !10, virtuality: DW_VIRTUALITY_virtual, virtualIndex: 1, flags: DIFlagPrototyped, isOptimized: false)
> -!23 = !DILocalVariable(name: "a", arg: 1, scope: !7, file: !1, line: 6, type: !10)
> -!24 = !DILocation(line: 6, column: 19, scope: !7)
> -!25 = !DILocation(line: 7, column: 6, scope: !7)
> -!26 = !DILocation(line: 8, column: 6, scope: !7)
> -!27 = !DILocation(line: 9, column: 1, scope: !7)
> -!28 = distinct !DISubprogram(name: "foo", linkageName: "_ZN1A3fooEv", scope: !10, file: !1, line: 12, type: !19, isLocal: false, isDefinition: true, scopeLine: 12, flags: DIFlagPrototyped, isOptimized: false, unit: !0, declaration: !18, retainedNodes: !2)
> -!29 = !DILocalVariable(name: "this", arg: 1, scope: !28, type: !30, flags: DIFlagArtificial | DIFlagObjectPointer)
> -!30 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !10, size: 64)
> -!31 = !DILocation(line: 0, scope: !28)
> -!32 = !DILocation(line: 12, column: 16, scope: !28)
> -!33 = distinct !DISubprogram(name: "bar", linkageName: "_ZN1A3barEv", scope: !10, file: !1, line: 13, type: !19, isLocal: false, isDefinition: true, scopeLine: 13, flags: DIFlagPrototyped, isOptimized: false, unit: !0, declaration: !22, retainedNodes: !2)
> -!34 = !DILocalVariable(name: "this", arg: 1, scope: !33, type: !30, flags: DIFlagArtificial | DIFlagObjectPointer)
> -!35 = !DILocation(line: 0, scope: !33)
> -!36 = !DILocation(line: 13, column: 16, scope: !33)
> -!37 = distinct !DISubprogram(name: "main", scope: !1, file: !1, line: 15, type: !15, isLocal: false, isDefinition: true, scopeLine: 15, flags: DIFlagPrototyped, isOptimized: false, unit: !0, retainedNodes: !2)
> -!38 = !DILocation(line: 16, column: 3, scope: !37)
> +!9 = !{!10, !10, !10}
> +!10 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
> +!11 = !{!12, !13, !14, !15, !16, !17}
> +!12 = !DILocalVariable(name: "i", arg: 1, scope: !7, file: !1, line: 1, type: !10)
> +!13 = !DILocalVariable(name: "j", arg: 2, scope: !7, file: !1, line: 1, type: !10)
> +!14 = !DILocalVariable(name: "x", scope: !7, file: !1, line: 2, type: !10)
> +!15 = !DILocalVariable(name: "y", scope: !7, file: !1, line: 3, type: !10)
> +!16 = !DILocalVariable(name: "r", scope: !7, file: !1, line: 4, type: !10)
> +!17 = !DILocalVariable(name: "undef", scope: !7, file: !1, line: 5, type: !10)
> +!18 = !DILocation(line: 0, scope: !7)
> +!19 = !DILocation(line: 4, column: 13, scope: !7)
> +!20 = !DILocation(line: 8, column: 3, scope: !7)
> +!21 = distinct !DISubprogram(name: "f2", linkageName: "_Z2f2v", scope: !1, file: !1, line: 10, type: !22, scopeLine: 10, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !2)
> +!22 = !DISubroutineType(types: !23)
> +!23 = !{null}
> +!24 = !DILocation(line: 11, column: 1, scope: !21)
> 
> Modified: llvm/trunk/test/DebugInfo/X86/sret.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/DebugInfo/X86/sret.ll?rev=374600&r1=374599&r2=374600&view=diff <http://llvm.org/viewvc/llvm-project/llvm/trunk/test/DebugInfo/X86/sret.ll?rev=374600&r1=374599&r2=374600&view=diff>
> ==============================================================================
> --- llvm/trunk/test/DebugInfo/X86/sret.ll (original)
> +++ llvm/trunk/test/DebugInfo/X86/sret.ll Fri Oct 11 14:52:41 2019
> @@ -11,6 +11,7 @@
>  ; CHECK: _ZN1B9AInstanceEv
>  ; CHECK: DW_TAG_variable
>  ; CHECK-NEXT:   DW_AT_location [DW_FORM_sec_offset] (0x00000000
> +; CHECK-NEXT:     [0xffffffffffffffff, {{.*}}): {{$}}
>  ; CHECK-NEXT:     [{{.*}}, {{.*}}): DW_OP_breg5 RDI+0
>  ; CHECK-NEXT:     [{{.*}}, {{.*}}): DW_OP_breg6 RBP-24, DW_OP_deref)
>  ; CHECK-NEXT:   DW_AT_name {{.*}}"a"
> 
> 
> _______________________________________________
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> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-commits <https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-commits>

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