[DebugInfo] Fix emitting DWARF64 .debug_str_offsets sections (8/19).

[ikudrin]

Summary

The patch fixes calculating the size of the table and emitting the unit length field.

[dblaikie]

llvm/lib/CodeGen/AsmPrinter/DwarfStringPool.cpp

128

Hmm - this is the line used to emit the offsets in the string offsets table, right? So how is this working/passing the test? Wouldn't it be str_offsets table be messed/too small?

[ikudrin]

llvm/lib/CodeGen/AsmPrinter/DwarfStringPool.cpp

128

This line works for .debug_str_offsets.dwo, emitting which is fixed in D87018.

llvm/lib/CodeGen/AsmPrinter/DwarfStringPool.cpp

 }
 
 void DwarfStringPool::emitStringOffsetsTableHeader(AsmPrinter &Asm,
                                                    MCSection *Section,
                                                    MCSymbol *StartSym) {
   if (getNumIndexedStrings() == 0)
     return;
   Asm.OutStreamer->SwitchSection(Section);
-  unsigned EntrySize = 4;
-  // FIXME: DWARF64
+  unsigned EntrySize = Asm.getDwarfOffsetByteSize();
   // We are emitting the header for a contribution to the string offsets
   // table. The header consists of an entry with the contribution's
   // size (not including the size of the length field), the DWARF version and
   // 2 bytes of padding.
-  Asm.emitInt32(getNumIndexedStrings() * EntrySize + 4);
+  Asm.emitDwarfUnitLength(getNumIndexedStrings() * EntrySize + 4,
+                          "Length of String Offsets Set");
   Asm.emitInt16(Asm.getDwarfVersion());
   Asm.emitInt16(0);
   // Define the symbol that marks the start of the contribution. It is
   // referenced by most unit headers via DW_AT_str_offsets_base.
   // Split units do not use the attribute.
   if (StartSym)
     Asm.OutStreamer->emitLabel(StartSym);
 }
if (OffsetSection) {
     }
 
     Asm.OutStreamer->SwitchSection(OffsetSection);
     unsigned size = 4; // FIXME: DWARF64 is 8.
     for (const auto &Entry : Entries)
       if (UseRelativeOffsets)
         Asm.emitDwarfStringOffset(Entry->getValue());
       else
         Asm.OutStreamer->emitIntValue(Entry->getValue().Offset, size);
   }
 }

llvm/test/DebugInfo/X86/debug-str-offsets-dwarf64.ll

+; This checks that .debug_str_offsets can be generated in the DWARF64 format.
+
+; RUN: llc -mtriple=x86_64 -dwarf-version=5 -dwarf64 -filetype=obj %s -o %t
+; RUN: llvm-dwarfdump -debug-info -debug-str -debug-str-offsets -v %t | \
+; RUN:   FileCheck %s
+
+; CHECK:      .debug_info contents:
+; CHECK-NEXT: Compile Unit: {{.*}}, format = DWARF64,
+; CHECK:      DW_TAG_compile_unit [1] *
+; CHECK:        DW_AT_producer [DW_FORM_strx1] (indexed (00000000) string = "Manual")
+; CHECK:        DW_AT_name [DW_FORM_strx1] (indexed (00000001) string = "foo.c")
+; CHECK:        DW_AT_str_offsets_base [DW_FORM_sec_offset] (0x0000000000000010)
+; CHECK:        DW_AT_comp_dir [DW_FORM_strx1] (indexed (00000002) string = "/tmp")
+; CHECK:      DW_TAG_variable [2]  
+; CHECK:        DW_AT_name [DW_FORM_strx1] (indexed (00000003) string = "foo")
+; CHECK:      DW_TAG_base_type [3]  
+; CHECK:        DW_AT_name [DW_FORM_strx1] (indexed (00000004) string = "int")
+
+; CHECK:      .debug_str contents:
+; CHECK-NEXT: 0x00000000: "Manual"
+; CHECK-NEXT: 0x00000007: "foo.c"
+; CHECK-NEXT: 0x0000000d: "/tmp"
+; CHECK-NEXT: 0x00000012: "foo"
+; CHECK-NEXT: 0x00000016: "int"
+
+; CHECK:      .debug_str_offsets contents:
+; CHECK-NEXT: 0x00000000: Contribution size = 44, Format = DWARF64, Version = 5
+; CHECK-NEXT: 0x00000010: 0000000000000000 "Manual"
+; CHECK-NEXT: 0x00000018: 0000000000000007 "foo.c"
+; CHECK-NEXT: 0x00000020: 000000000000000d "/tmp"
+; CHECK-NEXT: 0x00000028: 0000000000000012 "foo"
+; CHECK-NEXT: 0x00000030: 0000000000000016 "int"
+
+@foo = common dso_local global i32 0, align 4, !dbg !5
+
+!llvm.dbg.cu = !{!2}
+!llvm.module.flags = !{!0}
+
+!0 = !{i32 2, !"Debug Info Version", i32 3}
+!1 = !DIFile(filename: "foo.c", directory: "/tmp")
+!2 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "Manual", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !3, globals: !4, splitDebugInlining: false, nameTableKind: None)
+!3 = !{}
+!4 = !{!5}
+!5 = !DIGlobalVariableExpression(var: !6, expr: !DIExpression())
+!6 = distinct !DIGlobalVariable(name: "foo", scope: !2, file: !1, line: 1, type: !7, isLocal: false, isDefinition: true)
+!7 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)