[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

3 files changed, 27 insertions, 4 deletions

diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
index 0ff1b5004d9..2cee47c04d8 100644
--- 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 b9a17d5018c..58ef279a9f6 100644
--- 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 56a1d633729..4459a5051e4 100644
--- 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