[DEBUGINFO] Add -no-dwarf-debug-ranges option.

Summary:
Added option -no-dwarf-debug-ranges option to disable emission of
.debug_ranges section.

Reviewers: probinson, echristo

Subscribers: aprantl, JDevlieghere, llvm-commits

Differential Revision: https://reviews.llvm.org/D44384

llvm-svn: 328030

diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
index 0ff1b50..2cee47c 100644 (file)
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
@@ -410,9 +410,10 @@ void DwarfCompileUnit::addScopeRangeList(DIE &ScopeDIE,
 
 void DwarfCompileUnit::attachRangesOrLowHighPC(
     DIE &Die, SmallVector<RangeSpan, 2> Ranges) {
-  if (Ranges.size() == 1) {
-    const auto &single = Ranges.front();
-    attachLowHighPC(Die, single.getStart(), single.getEnd());
+  if (Ranges.size() == 1 || !DD->useRangesSection()) {
+    const RangeSpan &Front = Ranges.front();
+    const RangeSpan &Back = Ranges.back();
+    attachLowHighPC(Die, Front.getStart(), Back.getEnd());
   } else
     addScopeRangeList(Die, std::move(Ranges));
 }

diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
index b9a17d5..58ef279 100644 (file)
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
@@ -128,6 +128,11 @@ static cl::opt<bool>
                        cl::desc("Disable emission of DWARF pub sections."),
                        cl::init(false));
 
+static cl::opt<bool>
+    NoDwarfRangesSection("no-dwarf-ranges-section", cl::Hidden,
+                         cl::desc("Disable emission .debug_ranges section."),
+                         cl::init(false));
+
 enum LinkageNameOption {
   DefaultLinkageNames,
   AllLinkageNames,
@@ -316,6 +321,7 @@ DwarfDebug::DwarfDebug(AsmPrinter *A, Module *M)
   DwarfVersion = DwarfVersion ? DwarfVersion : dwarf::DWARF_VERSION;
 
   UsePubSections = !NoDwarfPubSections;
+  UseRangesSection = !NoDwarfRangesSection;
 
   // Work around a GDB bug. GDB doesn't support the standard opcode;
   // SCE doesn't support GNU's; LLDB prefers the standard opcode, which
@@ -744,7 +750,7 @@ void DwarfDebug::finalizeModuleInfo() {
     // ranges for all subprogram DIEs for mach-o.
     DwarfCompileUnit &U = SkCU ? *SkCU : TheCU;
     if (unsigned NumRanges = TheCU.getRanges().size()) {
-      if (NumRanges > 1)
+      if (NumRanges > 1 && useRangesSection())
         // A DW_AT_low_pc attribute may also be specified in combination with
         // DW_AT_ranges to specify the default base address for use in
         // location lists (see Section 2.6.2) and range lists (see Section
@@ -1906,6 +1912,16 @@ void DwarfDebug::emitDebugRanges() {
   if (CUMap.empty())
     return;
 
+  if (!useRangesSection()) {
+    assert(llvm::all_of(
+               CUMap,
+               [](const decltype(CUMap)::const_iterator::value_type &Pair) {
+                 return Pair.second->getRangeLists().empty();
+               }) &&
+           "No debug ranges expected.");
+    return;
+  }
+
   // Start the dwarf ranges section.
   Asm->OutStreamer->SwitchSection(
       Asm->getObjFileLowering().getDwarfRangesSection());

diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.h b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.h
index 56a1d63..4459a50 100644 (file)
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.h
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.h
@@ -261,6 +261,9 @@ class DwarfDebug : public DebugHandlerBase {
   /// Whether to emit DWARF pub sections or not.
   bool UsePubSections = true;
 
+  /// Allow emission of .debug_ranges section.
+  bool UseRangesSection = true;
+
   /// DWARF5 Experimental Options
   /// @{
   bool HasDwarfAccelTables;
@@ -507,6 +510,9 @@ public:
   /// Returns whether GNU oub sections should be emitted.
   bool usePubSections() const { return UsePubSections; }
 
+  /// Returns whether ranges section should be emitted.
+  bool useRangesSection() const { return UseRangesSection; }
+
   // Experimental DWARF5 features.
 
   /// Returns whether or not to emit tables that dwarf consumers can

diff --git a/llvm/test/DebugInfo/X86/no_debug_ranges.ll b/llvm/test/DebugInfo/X86/no_debug_ranges.ll
new file mode 100644 (file)
index 0000000..3823c88
--- /dev/null
+++ b/llvm/test/DebugInfo/X86/no_debug_ranges.ll
@@ -0,0 +1,54 @@
+; RUN: llc -filetype=asm -mtriple=x86_64-pc-linux-gnu < %s -o - -dwarf-version=2 -no-dwarf-ranges-section | FileCheck %s --check-prefix=DISABLED
+; RUN: llc -filetype=asm -mtriple=x86_64-pc-linux-gnu < %s -o - -dwarf-version=2 | FileCheck %s
+
+; DISABLED-NOT:  {{DW_AT_ranges|.debug_ranges}}
+; DISABLED:      .section .debug_info
+; DISABLED-NOT:  {{DW_AT_ranges|.section}}
+; DISABLED:      .quad .Lfunc_begin0 # DW_AT_low_pc
+; DISABLED-NEXT: .quad .Lfunc_end1   # DW_AT_high_pc
+; DISABLED-NOT:  {{DW_AT_ranges|.debug_ranges}}
+
+; .debug_ranges section must be emitted by default
+; CHECK: .section .debug_info
+; CHECK: quad 0 # DW_AT_low_pc
+; CHECK-NEXT: long [[RANGE0:[.]Ldebug_ranges[0-9]+]] # DW_AT_ranges
+; CHECK: .debug_ranges
+; CHECK-NEXT: [[RANGE0]]:
+; CHECK-NEXT: .quad .Lfunc_begin0
+; CHECK-NEXT: .quad .Lfunc_end0
+; CHECK-NEXT: .quad .Lfunc_begin1
+; CHECK-NEXT: .quad .Lfunc_end1
+; CHECK-NEXT: .quad 0
+; CHECK-NEXT: .quad 0
+
+; Function Attrs: noinline nounwind optnone uwtable
+define void @_Z2f1v() #0 section "a" !dbg !7 {
+entry:
+  ret void, !dbg !10
+}
+
+; Function Attrs: noinline nounwind optnone uwtable
+define void @_Z2f2v() #0 section "b" !dbg !11 {
+entry:
+  ret void, !dbg !12
+}
+
+attributes #0 = { noinline nounwind optnone uwtable "correctly-rounded-divide-sqrt-fp-math"="false" "disable-tail-calls"="false" "less-precise-fpmad"="false" "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf" "no-infs-fp-math"="false" "no-jump-tables"="false" "no-nans-fp-math"="false" "no-signed-zeros-fp-math"="false" "no-trapping-math"="false" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+fxsr,+mmx,+sse,+sse2,+x87" "unsafe-fp-math"="false" "use-soft-float"="false" }
+
+!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 6.0.0 (trunk 309523) (llvm/trunk 309526)", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !2)
+!1 = !DIFile(filename: "funcs.cpp", directory: "/usr/local/google/home/blaikie/dev/scratch")
+!2 = !{}
+!3 = !{i32 2, !"Dwarf Version", i32 4}
+!4 = !{i32 2, !"Debug Info Version", i32 3}
+!5 = !{i32 1, !"wchar_size", i32 4}
+!6 = !{!"clang version 6.0.0 (trunk 309523) (llvm/trunk 309526)"}
+!7 = distinct !DISubprogram(name: "f1", linkageName: "_Z2f1v", scope: !1, file: !1, line: 1, type: !8, isLocal: false, isDefinition: true, scopeLine: 1, flags: DIFlagPrototyped, isOptimized: false, unit: !0, variables: !2)
+!8 = !DISubroutineType(types: !9)
+!9 = !{null}
+!10 = !DILocation(line: 1, column: 42, scope: !7)
+!11 = 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, variables: !2)
+!12 = !DILocation(line: 2, column: 42, scope: !11)