[lldb] rm DWARFDebugRanges (#116379)

The class is only used from one place, which is trivial to implement
using the llvm class.

The main difference is that in the new implementation, the ranges are
parsed each time anew (instead of being parsed at startup and cached). I
believe this is fine because:
- this is already how things work with DWARF v5 debug_rnglists
- parsing debug_ranges is fairly fast (definitely faster than rnglists)
- generally, this result will be cached at a higher level anyway.
Browsing the code I did find one instance where that is not the case --
SymbolFileDWARF::ResolveFunctionAndBlock -- which is called each time we
resolve an address (to the block level). However, this function is
already pretty suboptimal: it first traverses the DIE tree (which
involves parsing all the DIE attributes) to find the correct block, then
it parses them again to construct the `lldb_private::Block`
representation, and *then* it uses the ID of the block DIE it found in
the first step to look up the `Block` object. If this turns out to be a
bottleneck, I think there are better ways to optimize it than caching
the debug_ranges parse.

The motiviation for this is that DWARFDebugRanges sorts the block
ranges, even though the order of the ranges is load-bearing (in the
absence of DW_AT_low_pc, the "base address" of a scope is determined by
the first range entry). Delaying the parsing (and sorting) step makes it
easier to access the first entry.

Author: labath

lldb/source/Plugins/SymbolFile/DWARF/CMakeLists.txt

@@ -21,7 +21,6 @@ add_lldb_library(lldbPluginSymbolFileDWARF PLUGIN
   DWARFDebugInfo.cpp
   DWARFDebugInfoEntry.cpp
   DWARFDebugMacro.cpp
-  DWARFDebugRanges.cpp
   DWARFDeclContext.cpp
   DWARFDefines.cpp
   DWARFDIE.cpp

lldb/source/Plugins/SymbolFile/DWARF/DWARFDebugInfoEntry.cpp

@@ -25,7 +25,6 @@
 #include "DWARFCompileUnit.h"
 #include "DWARFDebugAranges.h"
 #include "DWARFDebugInfo.h"
-#include "DWARFDebugRanges.h"
 #include "DWARFDeclContext.h"
 #include "DWARFFormValue.h"
 #include "DWARFUnit.h"

lldb/source/Plugins/SymbolFile/DWARF/DWARFDebugInfoEntry.h

@@ -14,7 +14,6 @@
 
 #include "DWARFAttribute.h"
 #include "DWARFBaseDIE.h"
-#include "DWARFDebugRanges.h"
 #include <map>
 #include <optional>
 #include <set>

lldb/source/Plugins/SymbolFile/DWARF/DWARFDebugRanges.cpp

@@ -13,8 +13,10 @@
 #include "lldb/Utility/LLDBAssert.h"
 #include "lldb/Utility/StreamString.h"
 #include "lldb/Utility/Timer.h"
+#include "llvm/DebugInfo/DWARF/DWARFAddressRange.h"
 #include "llvm/DebugInfo/DWARF/DWARFDebugAbbrev.h"
 #include "llvm/DebugInfo/DWARF/DWARFDebugLoc.h"
+#include "llvm/DebugInfo/DWARF/DWARFDebugRangeList.h"
 #include "llvm/Object/Error.h"
 
 #include "DWARFCompileUnit.h"
@@ -1029,43 +1031,49 @@ DWARFUnit::GetStringOffsetSectionItem(uint32_t index) const {
 
 llvm::Expected<DWARFRangeList>
 DWARFUnit::FindRnglistFromOffset(dw_offset_t offset) {
+  llvm::DWARFAddressRangesVector llvm_ranges;
   if (GetVersion() <= 4) {
-    const DWARFDebugRanges *debug_ranges = m_dwarf.GetDebugRanges();
-    if (!debug_ranges)
-      return llvm::make_error<llvm::object::GenericBinaryError>(
-          "No debug_ranges section");
-    return debug_ranges->FindRanges(this, offset);
+    llvm::DWARFDataExtractor data =
+        m_dwarf.GetDWARFContext().getOrLoadRangesData().GetAsLLVMDWARF();
+    data.setAddressSize(m_header.getAddressByteSize());
+
+    llvm::DWARFDebugRangeList list;
+    if (llvm::Error e = list.extract(data, &offset))
+      return e;
+    llvm_ranges = list.getAbsoluteRanges(
+        llvm::object::SectionedAddress{GetBaseAddress()});
+  } else {
+    if (!GetRnglistTable())
+      return llvm::createStringError(std::errc::invalid_argument,
+                                     "missing or invalid range list table");
+
+    llvm::DWARFDataExtractor data = GetRnglistData().GetAsLLVMDWARF();
+
+    // As DW_AT_rnglists_base may be missing we need to call setAddressSize.
+    data.setAddressSize(m_header.getAddressByteSize());
+    auto range_list_or_error = GetRnglistTable()->findList(data, offset);
+    if (!range_list_or_error)
+      return range_list_or_error.takeError();
+
+    llvm::Expected<llvm::DWARFAddressRangesVector> expected_llvm_ranges =
+        range_list_or_error->getAbsoluteRanges(
+            llvm::object::SectionedAddress{GetBaseAddress()},
+            GetAddressByteSize(), [&](uint32_t index) {
+              uint32_t index_size = GetAddressByteSize();
+              dw_offset_t addr_base = GetAddrBase();
+              lldb::offset_t offset =
+                  addr_base + static_cast<lldb::offset_t>(index) * index_size;
+              return llvm::object::SectionedAddress{
+                  m_dwarf.GetDWARFContext().getOrLoadAddrData().GetMaxU64(
+                      &offset, index_size)};
+            });
+    if (!expected_llvm_ranges)
+      return expected_llvm_ranges.takeError();
+    llvm_ranges = std::move(*expected_llvm_ranges);
   }
 
-  if (!GetRnglistTable())
-    return llvm::createStringError(std::errc::invalid_argument,
-                                   "missing or invalid range list table");
-
-  llvm::DWARFDataExtractor data = GetRnglistData().GetAsLLVMDWARF();
-
-  // As DW_AT_rnglists_base may be missing we need to call setAddressSize.
-  data.setAddressSize(m_header.getAddressByteSize());
-  auto range_list_or_error = GetRnglistTable()->findList(data, offset);
-  if (!range_list_or_error)
-    return range_list_or_error.takeError();
-
-  llvm::Expected<llvm::DWARFAddressRangesVector> llvm_ranges =
-      range_list_or_error->getAbsoluteRanges(
-          llvm::object::SectionedAddress{GetBaseAddress()},
-          GetAddressByteSize(), [&](uint32_t index) {
-            uint32_t index_size = GetAddressByteSize();
-            dw_offset_t addr_base = GetAddrBase();
-            lldb::offset_t offset =
-                addr_base + static_cast<lldb::offset_t>(index) * index_size;
-            return llvm::object::SectionedAddress{
-                m_dwarf.GetDWARFContext().getOrLoadAddrData().GetMaxU64(
-                    &offset, index_size)};
-          });
-  if (!llvm_ranges)
-    return llvm_ranges.takeError();
-
   DWARFRangeList ranges;
-  for (const llvm::DWARFAddressRange &llvm_range : *llvm_ranges) {
+  for (const llvm::DWARFAddressRange &llvm_range : llvm_ranges) {
     ranges.Append(DWARFRangeList::Entry(llvm_range.LowPC,
                                         llvm_range.HighPC - llvm_range.LowPC));
   }

lldb/source/Plugins/SymbolFile/DWARF/DWARFDebugRanges.h

@@ -63,7 +63,6 @@
 #include "DWARFDebugAranges.h"
 #include "DWARFDebugInfo.h"
 #include "DWARFDebugMacro.h"
-#include "DWARFDebugRanges.h"
 #include "DWARFDeclContext.h"
 #include "DWARFFormValue.h"
 #include "DWARFTypeUnit.h"
@@ -737,19 +736,6 @@ DWARFCompileUnit *SymbolFileDWARF::GetDWARFCompileUnit(CompileUnit *comp_unit) {
   return llvm::cast_or_null<DWARFCompileUnit>(dwarf_cu);
 }
 
-DWARFDebugRanges *SymbolFileDWARF::GetDebugRanges() {
-  if (!m_ranges) {
-    LLDB_SCOPED_TIMER();
-
-    if (m_context.getOrLoadRangesData().GetByteSize() > 0)
-      m_ranges = std::make_unique<DWARFDebugRanges>();
-
-    if (m_ranges)
-      m_ranges->Extract(m_context);
-  }
-  return m_ranges.get();
-}
-
 /// Make an absolute path out of \p file_spec and remap it using the
 /// module's source remapping dictionary.
 static void MakeAbsoluteAndRemap(FileSpec &file_spec, DWARFUnit &dwarf_cu,

lldb/source/Plugins/SymbolFile/DWARF/DWARFUnit.cpp

@@ -54,7 +54,6 @@ class DWARFDebugAranges;
 class DWARFDebugInfo;
 class DWARFDebugInfoEntry;
 class DWARFDebugLine;
-class DWARFDebugRanges;
 class DWARFDeclContext;
 class DWARFFormValue;
 class DWARFTypeUnit;
@@ -212,8 +211,6 @@ class SymbolFileDWARF : public SymbolFileCommon {
 
   DWARFDebugInfo &DebugInfo();
 
-  DWARFDebugRanges *GetDebugRanges();
-
   static bool SupportedVersion(uint16_t version);
 
   DWARFDIE
@@ -533,7 +530,6 @@ class SymbolFileDWARF : public SymbolFileCommon {
   typedef std::set<DIERef> DIERefSet;
   typedef llvm::StringMap<DIERefSet> NameToOffsetMap;
   NameToOffsetMap m_function_scope_qualified_name_map;
-  std::unique_ptr<DWARFDebugRanges> m_ranges;
   UniqueDWARFASTTypeMap m_unique_ast_type_map;
   // A map from DIE to lldb_private::Type. For record type, the key might be
   // either declaration DIE or definition DIE.

lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp

@@ -2,7 +2,7 @@
 # RUN: %lldb %t -o "image lookup -v -s lookup_ranges" -o exit 2>%t.error | FileCheck %s
 # RUN: cat %t.error | FileCheck %s --check-prefix ERROR
 
-# ERROR: DIE has DW_AT_ranges(DW_FORM_sec_offset 0x0000000000000047) attribute, but range extraction failed (No debug_ranges section),
+# ERROR: DIE has DW_AT_ranges(DW_FORM_sec_offset 0x0000000000000047) attribute, but range extraction failed (invalid range list offset 0x47),
 # CHECK:  Function: id = {0x0000001c}, name = "ranges", range = [0x0000000000000000-0x0000000000000004)
 # CHECK:    Blocks: id = {0x0000001c}, range = [0x00000000-0x00000004)