[DebugInfo] Fix reading location tables of v5 units in DWP.

[ikudrin]

Summary

Without the patch, all version 5 compile units in a DWP file read location tables from the beginning of a .debug_loclists.dwo section. The patch fixes that by adjusting the reading offset the same way as for pre-v5 units. The section identifier to find the contribution entry corresponds to the version of the unit.

[jhenderson]

Again, looks good, although I'm not up-to-speed on the .debug_loc/.debug_loclists format, so this should get a second pair of eyes on it.

[labath]

looks good to me too

[dblaikie]

llvm/test/DebugInfo/X86/dwp-v2-loc.s

2–4

Was this not already tested?

[labath]

llvm/test/DebugInfo/X86/dwp-v2-loc.s

2–4

I was thinking the same thing. The v2 version of this patch (https://reviews.llvm.org/D53155) did include a test case, but that one was based on running llc+dwp. I think that this kind of a test is preferable for testing dumping. I was thinking about deleting the other test, but then then I thought, maybe it is still valueable as it also tests llvm-dwp?

[dblaikie]

llvm/test/DebugInfo/X86/dwp-v2-loc.s

2–4

Ah, yep - I'll blame my past lazy self. I've not always been good about doing the Right Thing and adding the llvm-dwarfdump functionality separately (& testing it with object files or assembly tests) then adding the production functionality (& testing that with IR+llvm-dwarfdump). Yep, both testing makes sense.

[ikudrin]

• Rebase to the tip.

llvm/lib/DebugInfo/DWARF/DWARFUnit.cpp

DWARFUnit::DWARFUnit(DWARFContext &DC, const DWARFSection &Section,
     : Context(DC), InfoSection(Section), Header(Header), Abbrev(DA),
       RangeSection(RS), LineSection(LS), StringSection(SS),
       StringOffsetSection(SOS), AddrOffsetSection(AOS), isLittleEndian(LE),
       IsDWO(IsDWO), UnitVector(UnitVector) {
   clear();
   if (IsDWO) {
     // If we are reading a package file, we need to adjust the location list
     // data based on the index entries.
-    StringRef Data = LocSection->Data;
+    StringRef Data = Header.getVersion() >= 5
+                         ? Context.getDWARFObj().getLoclistsDWOSection().Data
+                         : LocSection->Data;
     if (auto *IndexEntry = Header.getIndexEntry())
-      if (const auto *C = IndexEntry->getContribution(DW_SECT_EXT_LOC))
+      if (const auto *C = IndexEntry->getContribution(
+              Header.getVersion() >= 5 ? DW_SECT_LOCLISTS : DW_SECT_EXT_LOC))
         Data = Data.substr(C->Offset, C->Length);
 
-    DWARFDataExtractor DWARFData =
-        Header.getVersion() >= 5
-            ? DWARFDataExtractor(Context.getDWARFObj(),
-                                 Context.getDWARFObj().getLoclistsDWOSection(),
-                                 isLittleEndian, getAddressByteSize())
-            : DWARFDataExtractor(Data, isLittleEndian, getAddressByteSize());
+    DWARFDataExtractor DWARFData(Data, isLittleEndian, getAddressByteSize());
     LocTable =
         std::make_unique<DWARFDebugLoclists>(DWARFData, Header.getVersion());
-
   } else if (Header.getVersion() >= 5) {
     LocTable = std::make_unique<DWARFDebugLoclists>(
         DWARFDataExtractor(Context.getDWARFObj(),
                            Context.getDWARFObj().getLoclistsSection(),
                            isLittleEndian, getAddressByteSize()),
         Header.getVersion());
   } else {
     LocTable = std::make_unique<DWARFDebugLoc>(

llvm/test/DebugInfo/X86/dwp-v2-loc.s

+## The test checks that pre-v5 compile units in package files read their
+## location tables from .debug_loc.dwo sections.
+## See dwp-v5-loclists.s for v5 units.
+
+# RUN: llvm-mc -triple x86_64-unknown-linux %s -filetype=obj -o - | \
+# RUN:   llvm-dwarfdump -debug-info -debug-loc - | \
+# RUN:   FileCheck %s
+
+# CHECK:      .debug_info.dwo contents:
+# CHECK:      DW_TAG_compile_unit
+# CHECK-NEXT:   DW_AT_GNU_dwo_id (0x1100001122222222)
+# CHECK:      DW_TAG_variable
+# CHECK-NEXT:   DW_AT_name ("a")
+# CHECK-NEXT:   DW_AT_location (0x00000000:
+# CHECK-NEXT:     DW_LLE_startx_length (0x0000000000000001, 0x0000000000000010): DW_OP_reg5 RDI)
+
+# CHECK:      .debug_loc.dwo contents:
+# CHECK:      0x00000013:
+# CHECK-NEXT:   DW_LLE_startx_length (0x00000001, 0x00000010): DW_OP_reg5 RDI
+
+.section .debug_abbrev.dwo, "e", @progbits
+.LAbbrevBegin:
+    .uleb128 1                      # Abbreviation Code
+    .uleb128 17                     # DW_TAG_compile_unit
+    .byte 1                         # DW_CHILDREN_yes
+    .uleb128 0x2131                 # DW_AT_GNU_dwo_id
+    .uleb128 7                      # DW_FORM_data8
+    .byte 0                         # EOM(1)
+    .byte 0                         # EOM(2)
+    .uleb128 2                      # Abbreviation Code
+    .uleb128 52                     # DW_TAG_variable
+    .byte 0                         # DW_CHILDREN_no
+    .uleb128 3                      # DW_AT_name
+    .uleb128 8                      # DW_FORM_string
+    .uleb128 2                      # DW_AT_location
+    .uleb128 23                     # DW_FORM_sec_offset
+    .byte 0                         # EOM(1)
+    .byte 0                         # EOM(2)
+    .byte 0                         # EOM(3)
+.LAbbrevEnd:
+
+    .section .debug_info.dwo, "e", @progbits
+.LCUBegin:
+    .long .LCUEnd-.LCUVersion       # Length of Unit
+.LCUVersion:
+    .short 4                        # Version
+    .long 0                         # Abbrev offset
+    .byte 8                         # Address size
+    .uleb128 1                      # Abbrev [1] DW_TAG_compile_unit
+    .quad 0x1100001122222222        # DW_AT_GNU_dwo_id
+    .uleb128 2                      # Abbrev [2] DW_TAG_variable
+    .asciz "a"                      # DW_AT_name
+    .long 0                         # DW_AT_location
+    .byte 0                         # End Of Children Mark
+.LCUEnd:
+
+.section .debug_loc.dwo, "e", @progbits
+## Start the section with a number of dummy DW_LLE_end_of_list entries to check
+## that the reading offset is correctly adjusted.
+    .zero 0x13
+.LLocBegin:
+    .byte 3                         # DW_LLE_startx_length
+    .uleb128 1                      # Index
+    .long 0x10                      # Length
+    .short 1                        # Loc expr size
+    .byte 85                        # DW_OP_reg5
+    .byte 0                         # DW_LLE_end_of_list
+.LLocEnd:
+
+    .section .debug_cu_index, "", @progbits
+## Header:
+    .long 2                         # Version
+    .long 3                         # Section count
+    .long 1                         # Unit count
+    .long 2                         # Slot count
+## Hash Table of Signatures:
+    .quad 0x1100001122222222
+    .quad 0
+## Parallel Table of Indexes:
+    .long 1
+    .long 0
+## Table of Section Offsets:
+## Row 0:
+    .long 1                         # DW_SECT_INFO
+    .long 3                         # DW_SECT_ABBREV
+    .long 5                         # DW_SECT_LOC
+## Row 1:
+    .long 0                         # Offset in .debug_info.dwo
+    .long 0                         # Offset in .debug_abbrev.dwo
+    .long .LLocBegin-.debug_loc.dwo # Offset in .debug_loc.dwo
+## Table of Section Sizes:
+    .long .LCUEnd-.LCUBegin         # Size in .debug_info.dwo
+    .long .LAbbrevEnd-.LAbbrevBegin # Size in .debug_abbrev.dwo
+    .long .LLocEnd-.LLocBegin       # Size in .debug_loc.dwo

llvm/test/DebugInfo/X86/dwp-v5-loclists.s

+## The test checks that v5 compile units in package files read their
+## location tables from .debug_loclists.dwo sections.
+## See dwp-v2-loc.s for pre-v5 units.
+
+# RUN: llvm-mc -triple x86_64-unknown-linux %s -filetype=obj -o - | \
+# RUN:   llvm-dwarfdump -debug-info -debug-loclists - | \
+# RUN:   FileCheck %s
+
+# CHECK:      .debug_info.dwo contents:
+# CHECK:      DW_TAG_compile_unit
+# CHECK:      DW_TAG_variable
+# CHECK-NEXT:   DW_AT_name ("a")
+# CHECK-NEXT:   DW_AT_location (0x{{[0-9a-f]+}}:
+# CHECK-NEXT:     DW_LLE_startx_length (0x0000000000000001, 0x0000000000000010): DW_OP_reg5 RDI)
+
+# CHECK:      .debug_loclists.dwo contents:
+# CHECK:      locations list header:
+# CHECK:      locations list header:
+# CHECK:      0x{{[0-9a-f]+}}:
+# CHECK-NEXT:   DW_LLE_startx_length (0x0000000000000001, 0x0000000000000010): DW_OP_reg5 RDI
+
+.section .debug_abbrev.dwo, "e", @progbits
+.LAbbrevBegin:
+    .uleb128 1                          # Abbreviation Code
+    .uleb128 17                         # DW_TAG_compile_unit
+    .byte 1                             # DW_CHILDREN_yes
+    .byte 0                             # EOM(1)
+    .byte 0                             # EOM(2)
+    .uleb128 2                          # Abbreviation Code
+    .uleb128 52                         # DW_TAG_variable
+    .byte 0                             # DW_CHILDREN_no
+    .uleb128 3                          # DW_AT_name
+    .uleb128 8                          # DW_FORM_string
+    .uleb128 2                          # DW_AT_location
+    .uleb128 23                         # DW_FORM_sec_offset
+    .byte 0                             # EOM(1)
+    .byte 0                             # EOM(2)
+    .byte 0                             # EOM(3)
+.LAbbrevEnd:
+
+    .section .debug_info.dwo, "e", @progbits
+.LCUBegin:
+    .long .LCUEnd-.LCUVersion           # Length of Unit
+.LCUVersion:
+    .short 5                            # Version
+    .byte 5                             # DW_UT_split_compile
+    .byte 8                             # Address size
+    .long 0                             # Abbrev offset
+    .quad 0x1100001122222222            # DWO id
+    .uleb128 1                          # Abbrev [1] DW_TAG_compile_unit
+    .uleb128 2                          # Abbrev [2] DW_TAG_variable
+    .asciz "a"                          # DW_AT_name
+    .long .LLL0-.LLLBegin               # DW_AT_location
+    .byte 0                             # End Of Children Mark
+.LCUEnd:
+
+.section .debug_loclists.dwo, "e", @progbits
+## Start the section with an unused table to check that the reading offset
+## of the real table is correctly adjusted.
+    .long .LLLDummyEnd-.LLLDummyVersion # Length of Unit
+.LLLDummyVersion:
+    .short 5                            # Version
+    .byte 8                             # Address size
+    .byte 0                             # Segment selector size
+    .long 0                             # Offset entry count
+    .byte 0                             # DW_LLE_end_of_list
+.LLLDummyEnd:
+
+.LLLBegin:
+    .long .LLLEnd-.LLLVersion           # Length of Unit
+.LLLVersion:
+    .short 5                            # Version
+    .byte 8                             # Address size
+    .byte 0                             # Segment selector size
+    .long 0                             # Offset entry count
+.LLL0:
+    .byte 3                             # DW_LLE_startx_length
+    .uleb128 1                          # Index
+    .uleb128 0x10                       # Length
+    .uleb128 1                          # Loc expr size
+    .byte 85                            # DW_OP_reg5
+    .byte 0                             # DW_LLE_end_of_list
+.LLLEnd:
+
+    .section .debug_cu_index, "", @progbits
+## Header:
+    .short 5                            # Version
+    .space 2                            # Padding
+    .long 3                             # Section count
+    .long 1                             # Unit count
+    .long 2                             # Slot count
+## Hash Table of Signatures:
+    .quad 0x1100001122222222
+    .quad 0
+## Parallel Table of Indexes:
+    .long 1
+    .long 0
+## Table of Section Offsets:
+## Row 0:
+    .long 1                             # DW_SECT_INFO
+    .long 3                             # DW_SECT_ABBREV
+    .long 5                             # DW_SECT_LOCLISTS
+## Row 1:
+    .long 0                             # Offset in .debug_info.dwo
+    .long 0                             # Offset in .debug_abbrev.dwo
+    .long .LLLBegin-.debug_loclists.dwo # Offset in .debug_loclists.dwo
+## Table of Section Sizes:
+    .long .LCUEnd-.LCUBegin             # Size in .debug_info.dwo
+    .long .LAbbrevEnd-.LAbbrevBegin     # Size in .debug_abbrev.dwo
+    .long .LLLEnd-.LLLBegin             # Size in .debug_loclists.dwo