[DWARF v5] Don't emit multiple DW_AT_rnglists_base attributes. Some r…

…efactoring of

range lists emissions and added test cases.

Reviewer: dblaikie

Differential Revision: https://reviews.llvm.org/D49522

llvm-svn: 337981

llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp

@@ -420,8 +420,6 @@ void DwarfCompileUnit::addScopeRangeList(DIE &ScopeDIE,
   } else {
     addSectionLabel(ScopeDIE, dwarf::DW_AT_ranges, List.getSym(),
                     RangeSectionSym);
-    if (DD->getDwarfVersion() >= 5)
-      addRnglistsBase();
   }
 
   // Add the range list to the set of ranges to be emitted.

llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp

@@ -820,6 +820,10 @@ void DwarfDebug::finalizeModuleInfo() {
       U.attachRangesOrLowHighPC(U.getUnitDie(), TheCU.takeRanges());
     }
 
+    if (getDwarfVersion() >= 5 && !useSplitDwarf() &&
+        !U.getRangeLists().empty())
+      U.addRnglistsBase();
+
     auto *CUNode = cast<DICompileUnit>(P.first);
     // If compile Unit has macros, emit "DW_AT_macro_info" attribute.
     if (CUNode->getMacros())
@@ -2086,23 +2090,10 @@ static void emitRangeList(AsmPrinter *Asm, DwarfCompileUnit *CU,
   }
 }
 
-void DwarfDebug::emitDebugRnglists() {
-
-  // Don't emit a rangelist table if there are no ranges.
-  if (llvm::all_of(CUMap,
-                   [](const decltype(CUMap)::const_iterator::value_type &Pair) {
-                     DwarfCompileUnit *TheCU = Pair.second;
-                     if (auto *Skel = TheCU->getSkeleton())
-                       TheCU = Skel;
-                     return TheCU->getRangeLists().empty();
-                   }))
-    return;
-
-  assert(getDwarfVersion() >= 5 && "Dwarf version must be 5 or greater");
-  // FIXME: As long as we don't support DW_RLE_base_addrx, we cannot generate
-  // any tables in the .debug_rnglists.dwo section.
-  Asm->OutStreamer->SwitchSection(
-      Asm->getObjFileLowering().getDwarfRnglistsSection());
+// Emit the header of a DWARF 5 range list table. Returns the symbol that
+// designates the end of the table for the caller to emit when the table is
+// complete.
+static MCSymbol *emitRnglistsTableHeader(AsmPrinter *Asm, DwarfFile &Holder) {
   // The length is described by a starting label right after the length field
   // and an end label.
   MCSymbol *TableStart = Asm->createTempSymbol("debug_rnglist_table_start");
@@ -2111,56 +2102,52 @@ void DwarfDebug::emitDebugRnglists() {
   Asm->EmitLabelDifference(TableEnd, TableStart, 4);
   Asm->OutStreamer->EmitLabel(TableStart);
   // Version number (DWARF v5 and later).
-  Asm->emitInt16(getDwarfVersion());
+  Asm->emitInt16(Asm->OutStreamer->getContext().getDwarfVersion());
   // Address size.
   Asm->emitInt8(Asm->MAI->getCodePointerSize());
   // Segment selector size.
   Asm->emitInt8(0);
 
-  MCSymbol *RnglistTableBaseSym =
-      (useSplitDwarf() ? SkeletonHolder : InfoHolder).getRnglistsTableBaseSym();
+  MCSymbol *RnglistTableBaseSym = Holder.getRnglistsTableBaseSym();
 
   // FIXME: Generate the offsets table and use DW_FORM_rnglistx with the
   // DW_AT_ranges attribute. Until then set the number of offsets to 0.
   Asm->emitInt32(0);
   Asm->OutStreamer->EmitLabel(RnglistTableBaseSym);
-
-  // Emit the individual range lists.
-  for (const auto &I : CUMap) {
-    DwarfCompileUnit *TheCU = I.second;
-    if (auto *Skel = TheCU->getSkeleton())
-      TheCU = Skel;
-    for (const RangeSpanList &List : TheCU->getRangeLists())
-      emitRangeList(Asm, TheCU, List);
-  }
-
-  Asm->OutStreamer->EmitLabel(TableEnd);
+  return TableEnd;
 }
 
-/// Emit address ranges into the .debug_ranges section or DWARF v5 rangelists
-/// into the .debug_rnglists section.
+/// Emit address ranges into the .debug_ranges section or into the DWARF v5
+/// .debug_rnglists section.
 void DwarfDebug::emitDebugRanges() {
   if (CUMap.empty())
     return;
 
+  auto NoRangesPresent = [this]() {
+    return llvm::all_of(
+        CUMap, [](const decltype(CUMap)::const_iterator::value_type &Pair) {
+          return Pair.second->getRangeLists().empty();
+        });
+  };
+
   if (!useRangesSection()) {
-    assert(llvm::all_of(
-               CUMap,
-               [](const decltype(CUMap)::const_iterator::value_type &Pair) {
-                 return Pair.second->getRangeLists().empty();
-               }) &&
-           "No debug ranges expected.");
+    assert(NoRangesPresent() && "No debug ranges expected.");
     return;
   }
 
-  if (getDwarfVersion() >= 5) {
-    emitDebugRnglists();
+  if (NoRangesPresent())
     return;
-  }
 
   // Start the dwarf ranges section.
-  Asm->OutStreamer->SwitchSection(
-      Asm->getObjFileLowering().getDwarfRangesSection());
+  MCSymbol *TableEnd = nullptr;
+  if (getDwarfVersion() >= 5) {
+    Asm->OutStreamer->SwitchSection(
+        Asm->getObjFileLowering().getDwarfRnglistsSection());
+    TableEnd = emitRnglistsTableHeader(Asm, useSplitDwarf() ? SkeletonHolder
+                                                            : InfoHolder);
+  } else
+    Asm->OutStreamer->SwitchSection(
+        Asm->getObjFileLowering().getDwarfRangesSection());
 
   // Grab the specific ranges for the compile units in the module.
   for (const auto &I : CUMap) {
@@ -2173,6 +2160,9 @@ void DwarfDebug::emitDebugRanges() {
     for (const RangeSpanList &List : TheCU->getRangeLists())
       emitRangeList(Asm, TheCU, List);
   }
+
+  if (TableEnd)
+    Asm->OutStreamer->EmitLabel(TableEnd);
 }
 
 void DwarfDebug::handleMacroNodes(DIMacroNodeArray Nodes, DwarfCompileUnit &U) {
@@ -2248,9 +2238,6 @@ void DwarfDebug::initSkeletonUnit(const DwarfUnit &U, DIE &Die,
   SkeletonHolder.addUnit(std::move(NewU));
 }
 
-// This DIE has the following attributes: DW_AT_comp_dir, DW_AT_stmt_list,
-// DW_AT_low_pc, DW_AT_high_pc, DW_AT_ranges, DW_AT_dwo_name, DW_AT_dwo_id,
-// DW_AT_addr_base, DW_AT_ranges_base or DW_AT_rnglists_base.
 DwarfCompileUnit &DwarfDebug::constructSkeletonCU(const DwarfCompileUnit &CU) {
 
   auto OwnedUnit = llvm::make_unique<DwarfCompileUnit>(

llvm/lib/CodeGen/AsmPrinter/DwarfDebug.h

@@ -423,8 +423,13 @@ class DwarfDebug : public DebugHandlerBase {
   void initSkeletonUnit(const DwarfUnit &U, DIE &Die,
                         std::unique_ptr<DwarfCompileUnit> NewU);
 
-  /// Construct the split debug info compile unit for the debug info
-  /// section.
+  /// Construct the split debug info compile unit for the debug info section.
+  /// In DWARF v5, the skeleton unit DIE may have the following attributes:
+  /// DW_AT_addr_base, DW_AT_comp_dir, DW_AT_dwo_name, DW_AT_high_pc,
+  /// DW_AT_low_pc, DW_AT_ranges, DW_AT_stmt_list, and DW_AT_str_offsets_base.
+  /// Prior to DWARF v5 it may also have DW_AT_GNU_dwo_id. DW_AT_GNU_dwo_name
+  /// is used instead of DW_AT_dwo_name, Dw_AT_GNU_addr_base instead of
+  /// DW_AT_addr_base, and DW_AT_GNU_ranges_base instead of DW_AT_rnglists_base.
   DwarfCompileUnit &constructSkeletonCU(const DwarfCompileUnit &CU);
 
   /// Emit the debug info dwo section.

llvm/test/DebugInfo/X86/cu-ranges.ll

@@ -5,6 +5,9 @@
 ; RUN: llc -split-dwarf-file=foo.dwo -O0 %s -mtriple=x86_64-unknown-linux-gnu -filetype=obj -o %t
 ; RUN: llvm-dwarfdump -debug-abbrev %t | FileCheck --check-prefix=NO-FUNCTION-SECTIONS %s
 
+; RUN: llc -dwarf-version=5 -O0 %s -mtriple=x86_64-unknown-linux-gnu -filetype=obj -o %t
+; RUN: llvm-dwarfdump -v %t | FileCheck --check-prefix=DWARF5 %s
+
 ; From:
 ; int foo (int a) {
 ;   return a+1;
@@ -24,6 +27,14 @@
 ; NO-FUNCTION-SECTIONS: DW_AT_low_pc DW_FORM_addr
 ; NO-FUNCTION-SECTIONS-NOT: DW_AT_ranges
 
+; For Dwarf 5 check that we neither generate DW_AT_rnglists_base for the CU DIE nor 
+; a .debug_rnglists section. There is only 1 CU range with no scope ranges.
+;
+; DWARF5:     .debug_info contents:
+; DWARF5:     DW_TAG_compile_unit
+; DWARF5-NOT: DW_AT_rnglists_base [DW_FORM_sec_offset]   
+; DWARF5-NOT: .debug_rnglists contents:
+
 ; Function Attrs: nounwind uwtable
 define i32 @foo(i32 %a) #0 !dbg !4 {
 entry:

llvm/test/DebugInfo/X86/rnglists_base_attr.ll

@@ -0,0 +1,89 @@
+; RUN: llc -dwarf-version=5 -O0 %s -mtriple=x86_64-unknown-linux-gnu -filetype=obj -o %t
+; RUN: llvm-dwarfdump -v %t | FileCheck %s
+
+; Make sure we don't generate a duplicate DW_AT_rnglists_base attribute in the CU DIE
+; when more than one range list is emitted.
+; From the source:
+;
+; void f1();
+; void f2() {
+;   f1();
+;   {
+;     bool b;
+;     f1();
+;     f1();
+;   }
+; }
+; __attribute__((section(".text.foo"))) void f3() { }
+
+; Compile with clang -gwarf5 -S -emit-llvm
+; and change the resulting IR to move the first call to f1() to between
+; the second and the third call. This, along with the dbg.declare instruction
+; for the variable b, creates a gap in the code range for the nested lexical
+; scope that is b's immediate parent scope. A range list is emitted for that scope.
+;
+; In addition, the placement of f3() in a different section forces a 
+; rangelist to be emitted for the CU instead of simply using low/high pc 
+; attributes.
+
+; CHECK:      .debug_info contents:
+; CHECK:      DW_TAG_compile_unit
+; Make sure we have 2 CU ranges.
+; CHECK:      DW_AT_ranges
+; CHECK-NEXT: [0x{{[0-9a-f]+, 0x[0-9a-f]+}}) ".text"
+; CHECK-NEXT: [0x{{[0-9a-f]+, 0x[0-9a-f]+}}) ".text.foo"
+; We should not see any duplicate DW_AT_rnglists_base attributes.
+; CHECK:      DW_AT_rnglists_base [DW_FORM_sec_offset]                   (0x0000000c)
+; CHECK-NOT:  DW_AT_rnglists_base
+;
+; Make sure we see 2 ranges in the lexical block DIE.
+; CHECK:      DW_TAG_lexical_block
+; CHECK-NOT:  DW_TAG
+; CHECK:      DW_AT_ranges
+; CHECK-NEXT: [0x{{[0-9a-f]+, 0x[0-9a-f]+}}) ".text"
+; CHECK-NEXT: [0x{{[0-9a-f]+, 0x[0-9a-f]+}}) ".text"
+
+define dso_local void @_Z2f2v() !dbg !7 {
+entry:
+  %b = alloca i8, align 1
+  call void @llvm.dbg.declare(metadata i8* %b, metadata !11, metadata !DIExpression()), !dbg !14
+  call void @_Z2f1v(), !dbg !15
+  ; The following call has been moved here from right after the alloca
+  call void @_Z2f1v(), !dbg !10  
+  call void @_Z2f1v(), !dbg !16
+  ret void, !dbg !17
+}
+
+declare dso_local void @_Z2f1v()
+
+declare void @llvm.dbg.declare(metadata, metadata, metadata)
+
+define dso_local void @_Z2f3v() section ".text.foo" !dbg !18 {
+entry:
+  ret void, !dbg !19
+}
+
+!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 7.0.0 (trunk 337837)", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !2)
+!1 = !DIFile(filename: "t3.cpp", directory: "/home/test/rangelists", checksumkind: CSK_MD5, checksum: "1ba81b564a832caa8114cd008c199048")
+!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 7.0.0 (trunk 337837)"}
+!7 = distinct !DISubprogram(name: "f2", linkageName: "_Z2f2v", scope: !1, file: !1, line: 2, type: !8, isLocal: false, isDefinition: true, scopeLine: 2, flags: DIFlagPrototyped, isOptimized: false, unit: !0, retainedNodes: !2)
+!8 = !DISubroutineType(types: !9)
+!9 = !{null}
+!10 = !DILocation(line: 3, column: 3, scope: !7)
+!11 = !DILocalVariable(name: "b", scope: !12, file: !1, line: 5, type: !13)
+!12 = distinct !DILexicalBlock(scope: !7, file: !1, line: 4, column: 3)
+!13 = !DIBasicType(name: "bool", size: 8, encoding: DW_ATE_boolean)
+!14 = !DILocation(line: 5, column: 10, scope: !12)
+!15 = !DILocation(line: 6, column: 5, scope: !12)
+!16 = !DILocation(line: 7, column: 5, scope: !12)
+!17 = !DILocation(line: 9, column: 1, scope: !7)
+!18 = distinct !DISubprogram(name: "f3", linkageName: "_Z2f3v", scope: !1, file: !1, line: 10, type: !8, isLocal: false, isDefinition: true, scopeLine: 10, flags: DIFlagPrototyped, isOptimized: false, unit: !0, retainedNodes: !2)
+!19 = !DILocation(line: 10, column: 51, scope: !18)

llvm/test/DebugInfo/X86/rnglists_curanges.ll

@@ -0,0 +1,50 @@
+; RUN: llc -dwarf-version=5 -O0 %s -mtriple=x86_64-unknown-linux-gnu -filetype=obj -o %t
+; RUN: llvm-dwarfdump -v %t | FileCheck %s
+;
+; Check that we generate DW_AT_rnglists_base in the CU die, as well as a range 
+; list table when we have more than 1 CU range and no scope range.
+;
+; Generated from:
+; 
+; __attribute__((section("text.foo"))) void f1() {}
+; __attribute__((section("text.bar"))) void f2() {}
+;
+; Compile with clangc -gdwarf-5 -O0 -S -emit-llvm
+;
+; CHECK:      .debug_info contents:
+; CHECK:      DW_TAG_compile_unit
+; CHECK-NOT:  DW_TAG
+; CHECK:      DW_AT_rnglists_base [DW_FORM_sec_offset]                   (0x0000000c)
+; CHECK:      .debug_rnglists contents:
+; CHECK:      0x00000000: range list header: length = 0x0000001d, version = 0x0005,
+; CHECK-SAME: addr_size = 0x08, seg_size = 0x00, offset_entry_count = 0x00000000
+
+; Function Attrs: noinline nounwind optnone uwtable
+define dso_local void @f1() section "text.foo" !dbg !7 {
+entry:
+  ret void, !dbg !10
+}
+
+; Function Attrs: noinline nounwind optnone uwtable
+define dso_local void @f2() section "text.bar" !dbg !11 {
+entry:
+  ret void, !dbg !12
+}
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!3, !4, !5}
+!llvm.ident = !{!6}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "clang version 7.0.0 (trunk 337470)", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !2)
+!1 = !DIFile(filename: "test3.c", directory: "/home/test/rangelists", checksumkind: CSK_MD5, checksum: "f3b46bc2e5bc55bdd511ae4ec29577b6")
+!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 7.0.0 (trunk 337470)"}
+!7 = distinct !DISubprogram(name: "f1", scope: !1, file: !1, line: 1, type: !8, isLocal: false, isDefinition: true, scopeLine: 1, isOptimized: false, unit: !0, retainedNodes: !2)
+!8 = !DISubroutineType(types: !9)
+!9 = !{null}
+!10 = !DILocation(line: 1, column: 49, scope: !7)
+!11 = distinct !DISubprogram(name: "f2", scope: !1, file: !1, line: 2, type: !8, isLocal: false, isDefinition: true, scopeLine: 2, isOptimized: false, unit: !0, retainedNodes: !2)
+!12 = !DILocation(line: 2, column: 49, scope: !11)