[DWARF] Basic support for producing DWARFv5 .debug_addr section

[vleschuk]

Summary

This revision implements support for generating DWARFv5 .debug_addr section. It is dependent on https://reviews.llvm.org/D49676 as we need working consumer to execute test.

The implementation is pretty straight-forward: we just check the dwarf version and emit section header if needed.

[vleschuk]

This revision implements support for generating DWARFv5 .debug_addr section. It is dependent on https://reviews.llvm.org/D49676 as we need working consumer to execute test.

The implementation is pretty straight-forward: we just check the dwarf version and emit section header if needed.

UPD Changed type for AddrSize from uint32_t to uint8_t.

[dblaikie]

lib/CodeGen/AsmPrinter/DwarfDebug.cpp

2299–2307

I'd sink this functionality down into AddressPool::emit instead - it can query the AsmPrinter for DWARF version & decide what format to produce the address pool in internally.

test/DebugInfo/X86/debug_addr.ll

9

These return statements seem unnecessary? (in the text of this comment, and in the IR of the sample - not that it'd make much of a difference)

24

There's no header in debug_addr sections in DWARFv4, is there - what's this then?

Also is this consistent with the way other section contributions are described (I don't recall text like "Addr Section params" in other output - like the way those attributes are printed out like "Compile Unit: ..." rather than "Unit Section params")?

[vleschuk]

test/DebugInfo/X86/debug_addr.ll

9

Removed them from the comment, not sure that I understood what do you suggest to remove from IR (IR code would be the same with or without explicit return statements in C code).

24

Changed it in dependency revision: https://reviews.llvm.org/D49676.

[vleschuk]

• Adopted producer test to match recent changes (got rid of "params" from "Addr Section params" message).
• Removed explicit return from test sample
• Moved header emission to AddressPool class

[vleschuk]

test/DebugInfo/X86/debug_addr.ll

24

There's no header in debug_addr sections in DWARFv4, is there - what's this then?

You are correct, there is no header, these values are taken from CU. In code they still are placed into Header structure and I think it is useful to dump this structure into output.

[dblaikie]

test/DebugInfo/X86/debug_addr.ll

9

I meant update the IR to match the changed text - but really all it's going to do is change the DebugLoc of the ret IR instruction, which isn't a big deal. No worries.

24

As for the name/header - maybe take a look at all the other sections to see about something consistent. For example it looks like other header printing (debug_info/types, pubnames/types, etc) doesn't use a comma between values. But otherwise looks like what you're showing is modeled fairly closely off the printing of compile units? Seems OK if you could unify them a bit more (skip the commas, for example).

I'd still skip the header parameters in the case where they are not present in the binary format - to make the dump more accurately communicate what data is being rendered/where it's coming from.

& I'd probably skip the "Addr: [" wrapper - most of the other dumping dumps the contents without a container/braces/etc, I think? (sometimes with a header for columns if there are multiple columns)

lib/CodeGen/AsmPrinter/AddressPool.h

 
 public:
   AddressPool() = default;
 
   /// Returns the index into the address pool with the given
   /// label/symbol.
   unsigned getIndex(const MCSymbol *Sym, bool TLS = false);
 
+  void emitHeader(AsmPrinter &Asm, MCSection *Section);
+
   void emit(AsmPrinter &Asm, MCSection *AddrSection);
 
   bool isEmpty() { return Pool.empty(); }
 
   bool hasBeenUsed() const { return HasBeenUsed; }
 
   void resetUsedFlag() { HasBeenUsed = false; }
 };
 
 } // end namespace llvm
 
 #endif // LLVM_LIB_CODEGEN_ASMPRINTER_ADDRESSPOOL_H

lib/CodeGen/AsmPrinter/AddressPool.cpp

 
 unsigned AddressPool::getIndex(const MCSymbol *Sym, bool TLS) {
   HasBeenUsed = true;
   auto IterBool =
       Pool.insert(std::make_pair(Sym, AddressPoolEntry(Pool.size(), TLS)));
   return IterBool.first->second.Number;
 }
 
+
+void AddressPool::emitHeader(AsmPrinter &Asm, MCSection *Section) {
+  static const uint8_t AddrSize = Asm.getDataLayout().getPointerSize();
+  Asm.OutStreamer->SwitchSection(Section);
+
+  uint64_t Length = sizeof(uint16_t) // version
+                  + sizeof(uint8_t)  // address_size
+                  + sizeof(uint8_t)  // segment_selector_size
+                  + AddrSize * Pool.size(); // entries
+  Asm.emitInt32(Length); // TODO: Support DWARF64 format.
+  Asm.emitInt16(Asm.getDwarfVersion());
+  Asm.emitInt8(AddrSize);
+  Asm.emitInt8(0); // TODO: Support non-zero segment_selector_size.
+}
+
 // Emit addresses into the section given.
 void AddressPool::emit(AsmPrinter &Asm, MCSection *AddrSection) {
   if (Pool.empty())
     return;
 
   // Start the dwarf addr section.
   Asm.OutStreamer->SwitchSection(AddrSection);
 

lib/CodeGen/AsmPrinter/DwarfDebug.h

class DwarfDebug : public DebugHandlerBase {
   void emitDebugLineDWO();
 
   /// Emit the dwo stringoffsets table header.
   void emitStringOffsetsTableHeaderDWO();
 
   /// Emit the debug str dwo section.
   void emitDebugStrDWO();
 
+  /// Emit DWO addresses.
+  void emitDebugAddr();
+
   /// Flags to let the linker know we have emitted new style pubnames. Only
   /// emit it here if we don't have a skeleton CU for split dwarf.
   void addGnuPubAttributes(DwarfCompileUnit &U, DIE &D) const;
 
   /// Create new DwarfCompileUnit for the given metadata node with tag
   /// DW_TAG_compile_unit.
   DwarfCompileUnit &getOrCreateDwarfCompileUnit(const DICompileUnit *DIUnit);
 

lib/CodeGen/AsmPrinter/DwarfDebug.cpp

void DwarfDebug::endModule() {
   // Emit info into a debug macinfo section.
   emitDebugMacinfo();
 
   if (useSplitDwarf()) {
     emitDebugStrDWO();
     emitDebugInfoDWO();
     emitDebugAbbrevDWO();
     emitDebugLineDWO();
-    // Emit DWO addresses.
-    AddrPool.emit(*Asm, Asm->getObjFileLowering().getDwarfAddrSection());
+    emitDebugAddr();
   }
 
   // Emit info into the dwarf accelerator table sections.
   switch (getAccelTableKind()) {
   case AccelTableKind::Apple:
     emitAccelNames();
     emitAccelObjC();
     emitAccelNamespaces();
void DwarfDebug::emitDebugStrDWO() {
   if (useSegmentedStringOffsetsTable())
     emitStringOffsetsTableHeaderDWO();
   assert(useSplitDwarf() && "No split dwarf?");
   MCSection *OffSec = Asm->getObjFileLowering().getDwarfStrOffDWOSection();
   InfoHolder.emitStrings(Asm->getObjFileLowering().getDwarfStrDWOSection(),
                          OffSec, /* UseRelativeOffsets = */ false);
 }
 
+// Emit DWO addresses.
+void DwarfDebug::emitDebugAddr() {
+  assert(useSplitDwarf() && "No split dwarf?");
+  MCSection *Section = Asm->getObjFileLowering().getDwarfAddrSection();
+  if (Asm->getDwarfVersion() >= 5)
+    AddrPool.emitHeader(*Asm, Section);
+  AddrPool.emit(*Asm, Section);
+}
+
 MCDwarfDwoLineTable *DwarfDebug::getDwoLineTable(const DwarfCompileUnit &CU) {
   if (!useSplitDwarf())
     return nullptr;
   const DICompileUnit *DIUnit = CU.getCUNode();
   SplitTypeUnitFileTable.maybeSetRootFile(
       DIUnit->getDirectory(), DIUnit->getFilename(),
       CU.getMD5AsBytes(DIUnit->getFile()), DIUnit->getSource());
   return &SplitTypeUnitFileTable;

test/DebugInfo/X86/debug_addr.ll

+; RUN: llc -split-dwarf-file=test.dwo -dwarf-version=4 %s -mtriple=i386-unknown-linux-gnu -filetype=obj -o - | \
+; RUN: llvm-dwarfdump -v - | FileCheck %s -check-prefix=DWARF4
+
+; RUN: llc -split-dwarf-file=test.dwo -dwarf-version=5 %s -mtriple=i386-unknown-linux-gnu -filetype=obj -o - | \
+; RUN: llvm-dwarfdump -v - | FileCheck %s -check-prefix=DWARF5
+
+; Source:
+; void foo() {
+;   return;
+; }
+;
+; void bar() {
+;   return;
+; }
+
+; DWARF4: .debug_info contents:
+; DWARF4: Compile Unit:{{.*}}version = 0x0004
+; DWARF4-NOT: Compile Unit
+; DWARF4: DW_TAG_compile_unit
+; DWARF4-NOT: DW_TAG_{{.*}}
+; DWARF4: DW_AT_GNU_dwo_name{{.*}}test.dwo
+; DWARF4: DW_AT_GNU_addr_base{{.*}}0x00000000
+; DWARF4: .debug_addr contents:
+; DWARF4-NEXT: 0x00000000: Addr Section params: length = 0x00000000, version = 0x0004, addr_size = 0x04, seg_size = 0x00
+; DWARF4-NEXT: Addrs: [
+; DWARF4-NEXT: 0x00000000
+; DWARF4-NEXT: 0x00000010
+; DWARF4-NEXT: ]
+
+; DWARF5: .debug_info contents:
+; DWARF5: Compile Unit:{{.*}}version = 0x0005
+; DWARF5-NOT: Compile Unit
+; DWARF5: DW_TAG_compile_unit
+; DWARF5-NOT: DW_TAG_{{.*}}
+; DWARF5: DW_AT_GNU_dwo_name{{.*}}test.dwo
+; DWARF5: DW_AT_GNU_addr_base{{.*}}0x00000000
+; DWARF5: .debug_addr contents:
+; DWARF5-NEXT: 0x00000000: Addr Section params: length = 0x0000000c, version = 0x0005, addr_size = 0x04, seg_size = 0x00
+; DWARF5-NEXT: Addrs: [
+; DWARF5-NEXT: 0x00000000
+; DWARF5-NEXT: 0x00000010
+; DWARF5-NEXT: ]
+
+; ModuleID = './test.c'
+source_filename = "./test.c"
+target datalayout = "e-m:e-p:32:32-f64:32:64-f80:32-n8:16:32-S128"
+target triple = "i386-unknown-linux-gnu"
+
+; Function Attrs: noinline nounwind optnone
+define void @foo() #0 !dbg !8 {
+entry:
+  ret void, !dbg !12
+}
+
+; Function Attrs: noinline nounwind optnone
+define void @bar() #0 !dbg !13 {
+entry:
+  ret void, !dbg !14
+}
+
+attributes #0 = { noinline nounwind optnone }
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!3, !4, !5, !6}
+!llvm.ident = !{!7}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "clang version 6.0.1", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !2)
+!1 = !DIFile(filename: "test.c", directory: "/tmp")
+!2 = !{}
+!3 = !{i32 1, !"NumRegisterParameters", i32 0}
+!4 = !{i32 2, !"Dwarf Version", i32 5}
+!5 = !{i32 2, !"Debug Info Version", i32 3}
+!6 = !{i32 1, !"wchar_size", i32 4}
+!7 = !{!"clang version 6.0.1"}
+!8 = distinct !DISubprogram(name: "foo", scope: !9, file: !9, line: 1, type: !10, isLocal: false, isDefinition: true, scopeLine: 1, isOptimized: false, unit: !0)
+!9 = !DIFile(filename: "./test.c", directory: "/tmp")
+!10 = !DISubroutineType(types: !11)
+!11 = !{null}
+!12 = !DILocation(line: 2, column: 3, scope: !8)
+!13 = distinct !DISubprogram(name: "bar", scope: !9, file: !9, line: 5, type: !10, isLocal: false, isDefinition: true, scopeLine: 5, isOptimized: false, unit: !0)
+!14 = !DILocation(line: 6, column: 3, scope: !13)