DebugInfo: Use base address selection entries for debug_loc

Unify the range and loc emission (for both DWARFv4 and DWARFv5 style lists) and take advantage of that unification to use strategic base addresses for loclists.

Differential Revision: https://reviews.llvm.org/D68620

llvm-svn: 374600

1 files changed, 115 insertions, 150 deletions

diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
index 61a5445ff41..be9ea00973a 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
@@ -2293,14 +2293,121 @@ static MCSymbol *emitLoclistsTableHeader(AsmPrinter *Asm,
   return TableEnd;
 }
 
+template <typename Ranges, typename PayloadEmitter>
+static void emitRangeList(
+    DwarfDebug &DD, AsmPrinter *Asm, MCSymbol *Sym, const Ranges &R,
+    const DwarfCompileUnit &CU, unsigned BaseAddressx, unsigned OffsetPair,
+    unsigned StartxLength, unsigned EndOfList,
+    StringRef (*StringifyEnum)(unsigned),
+    bool ShouldUseBaseAddress,
+    PayloadEmitter EmitPayload) {
+
+  auto Size = Asm->MAI->getCodePointerSize();
+  bool UseDwarf5 = DD.getDwarfVersion() >= 5;
+
+  // Emit our symbol so we can find the beginning of the range.
+  Asm->OutStreamer->EmitLabel(Sym);
+
+  // Gather all the ranges that apply to the same section so they can share
+  // a base address entry.
+  MapVector<const MCSection *, std::vector<decltype(&*R.begin())>> SectionRanges;
+
+  for (const auto &Range : R)
+    SectionRanges[&Range.Begin->getSection()].push_back(&Range);
+
+  const MCSymbol *CUBase = CU.getBaseAddress();
+  bool BaseIsSet = false;
+  for (const auto &P : SectionRanges) {
+    auto *Base = CUBase;
+    if (!Base && ShouldUseBaseAddress) {
+      const MCSymbol *Begin = P.second.front()->Begin;
+      const MCSymbol *NewBase = DD.getSectionLabel(&Begin->getSection());
+      if (!UseDwarf5) {
+        Base = NewBase;
+        BaseIsSet = true;
+        Asm->OutStreamer->EmitIntValue(-1, Size);
+        Asm->OutStreamer->AddComment("  base address");
+        Asm->OutStreamer->EmitSymbolValue(Base, Size);
+      } else if (NewBase != Begin || P.second.size() > 1) {
+        // Only use a base address if
+        //  * the existing pool address doesn't match (NewBase != Begin)
+        //  * or, there's more than one entry to share the base address
+        Base = NewBase;
+        BaseIsSet = true;
+        Asm->OutStreamer->AddComment(StringifyEnum(BaseAddressx));
+        Asm->emitInt8(BaseAddressx);
+        Asm->OutStreamer->AddComment("  base address index");
+        Asm->EmitULEB128(DD.getAddressPool().getIndex(Base));
+      }
+    } else if (BaseIsSet && !UseDwarf5) {
+      BaseIsSet = false;
+      assert(!Base);
+      Asm->OutStreamer->EmitIntValue(-1, Size);
+      Asm->OutStreamer->EmitIntValue(0, Size);
+    }
+
+    for (const auto *RS : P.second) {
+      const MCSymbol *Begin = RS->Begin;
+      const MCSymbol *End = RS->End;
+      assert(Begin && "Range without a begin symbol?");
+      assert(End && "Range without an end symbol?");
+      if (Base) {
+        if (UseDwarf5) {
+          // Emit offset_pair when we have a base.
+          Asm->OutStreamer->AddComment(StringifyEnum(OffsetPair));
+          Asm->emitInt8(OffsetPair);
+          Asm->OutStreamer->AddComment("  starting offset");
+          Asm->EmitLabelDifferenceAsULEB128(Begin, Base);
+          Asm->OutStreamer->AddComment("  ending offset");
+          Asm->EmitLabelDifferenceAsULEB128(End, Base);
+        } else {
+          Asm->EmitLabelDifference(Begin, Base, Size);
+          Asm->EmitLabelDifference(End, Base, Size);
+        }
+      } else if (UseDwarf5) {
+        Asm->OutStreamer->AddComment(StringifyEnum(StartxLength));
+        Asm->emitInt8(StartxLength);
+        Asm->OutStreamer->AddComment("  start index");
+        Asm->EmitULEB128(DD.getAddressPool().getIndex(Begin));
+        Asm->OutStreamer->AddComment("  length");
+        Asm->EmitLabelDifferenceAsULEB128(End, Begin);
+      } else {
+        Asm->OutStreamer->EmitSymbolValue(Begin, Size);
+        Asm->OutStreamer->EmitSymbolValue(End, Size);
+      }
+      EmitPayload(*RS);
+    }
+  }
+
+  if (UseDwarf5) {
+    Asm->OutStreamer->AddComment(StringifyEnum(EndOfList));
+    Asm->emitInt8(EndOfList);
+  } else {
+    // Terminate the list with two 0 values.
+    Asm->OutStreamer->EmitIntValue(0, Size);
+    Asm->OutStreamer->EmitIntValue(0, Size);
+  }
+}
+
+static void emitLocList(DwarfDebug &DD, AsmPrinter *Asm, const DebugLocStream::List &List) {
+  emitRangeList(
+      DD, Asm, List.Label, DD.getDebugLocs().getEntries(List), *List.CU,
+      dwarf::DW_LLE_base_addressx, dwarf::DW_LLE_offset_pair,
+      dwarf::DW_LLE_startx_length, dwarf::DW_LLE_end_of_list,
+      llvm::dwarf::LocListEncodingString,
+      /* ShouldUseBaseAddress */ true,
+      [&](const DebugLocStream::Entry &E) {
+        DD.emitDebugLocEntryLocation(E, List.CU);
+      });
+}
+
 // Emit locations into the .debug_loc/.debug_rnglists section.
 void DwarfDebug::emitDebugLoc() {
   if (DebugLocs.getLists().empty())
     return;
 
-  bool IsLocLists = getDwarfVersion() >= 5;
   MCSymbol *TableEnd = nullptr;
-  if (IsLocLists) {
+  if (getDwarfVersion() >= 5) {
     Asm->OutStreamer->SwitchSection(
         Asm->getObjFileLowering().getDwarfLoclistsSection());
     TableEnd = emitLoclistsTableHeader(Asm, useSplitDwarf() ? SkeletonHolder
@@ -2310,63 +2417,8 @@ void DwarfDebug::emitDebugLoc() {
         Asm->getObjFileLowering().getDwarfLocSection());
   }
 
-  unsigned char Size = Asm->MAI->getCodePointerSize();
-  for (const auto &List : DebugLocs.getLists()) {
-    Asm->OutStreamer->EmitLabel(List.Label);
-
-    const DwarfCompileUnit *CU = List.CU;
-    const MCSymbol *Base = CU->getBaseAddress();
-    for (const auto &Entry : DebugLocs.getEntries(List)) {
-      if (Base) {
-        // Set up the range. This range is relative to the entry point of the
-        // compile unit. This is a hard coded 0 for low_pc when we're emitting
-        // ranges, or the DW_AT_low_pc on the compile unit otherwise.
-        if (IsLocLists) {
-          Asm->OutStreamer->AddComment("DW_LLE_offset_pair");
-          Asm->OutStreamer->EmitIntValue(dwarf::DW_LLE_offset_pair, 1);
-          Asm->OutStreamer->AddComment("  starting offset");
-          Asm->EmitLabelDifferenceAsULEB128(Entry.Begin, Base);
-          Asm->OutStreamer->AddComment("  ending offset");
-          Asm->EmitLabelDifferenceAsULEB128(Entry.End, Base);
-        } else {
-          Asm->EmitLabelDifference(Entry.Begin, Base, Size);
-          Asm->EmitLabelDifference(Entry.End, Base, Size);
-        }
-
-        emitDebugLocEntryLocation(Entry, CU);
-        continue;
-      }
-
-      // We have no base address.
-      if (IsLocLists) {
-        // TODO: Use DW_LLE_base_addressx + DW_LLE_offset_pair, or
-        // DW_LLE_startx_length in case if there is only a single range.
-        // That should reduce the size of the debug data emited.
-        // For now just use the DW_LLE_startx_length for all cases.
-        Asm->OutStreamer->AddComment("DW_LLE_startx_length");
-        Asm->emitInt8(dwarf::DW_LLE_startx_length);
-        Asm->OutStreamer->AddComment("  start idx");
-        Asm->EmitULEB128(AddrPool.getIndex(Entry.Begin));
-        Asm->OutStreamer->AddComment("  length");
-        Asm->EmitLabelDifferenceAsULEB128(Entry.End, Entry.Begin);
-      } else {
-        Asm->OutStreamer->EmitSymbolValue(Entry.Begin, Size);
-        Asm->OutStreamer->EmitSymbolValue(Entry.End, Size);
-      }
-
-      emitDebugLocEntryLocation(Entry, CU);
-    }
-
-    if (IsLocLists) {
-      // .debug_loclists section ends with DW_LLE_end_of_list.
-      Asm->OutStreamer->AddComment("DW_LLE_end_of_list");
-      Asm->OutStreamer->EmitIntValue(dwarf::DW_LLE_end_of_list, 1);
-    } else {
-      // Terminate the .debug_loc list with two 0 values.
-      Asm->OutStreamer->EmitIntValue(0, Size);
-      Asm->OutStreamer->EmitIntValue(0, Size);
-    }
-  }
+  for (const auto &List : DebugLocs.getLists())
+    emitLocList(*this, Asm, List);
 
   if (TableEnd)
     Asm->OutStreamer->EmitLabel(TableEnd);
@@ -2556,103 +2608,16 @@ void DwarfDebug::emitDebugARanges() {
   }
 }
 
-template <typename Ranges>
-static void emitRangeList(DwarfDebug &DD, AsmPrinter *Asm, MCSymbol *Sym,
-                          const Ranges &R, const DwarfCompileUnit &CU,
-                          unsigned BaseAddressx, unsigned OffsetPair,
-                          unsigned StartxLength, unsigned EndOfList,
-                          StringRef (*StringifyEnum)(unsigned)) {
-  auto DwarfVersion = DD.getDwarfVersion();
-  // Emit our symbol so we can find the beginning of the range.
-  Asm->OutStreamer->EmitLabel(Sym);
-  // Gather all the ranges that apply to the same section so they can share
-  // a base address entry.
-  MapVector<const MCSection *, std::vector<const RangeSpan *>> SectionRanges;
-  // Size for our labels.
-  auto Size = Asm->MAI->getCodePointerSize();
-
-  for (const RangeSpan &Range : R)
-    SectionRanges[&Range.Begin->getSection()].push_back(&Range);
-
-  const MCSymbol *CUBase = CU.getBaseAddress();
-  bool BaseIsSet = false;
-  for (const auto &P : SectionRanges) {
-    // Don't bother with a base address entry if there's only one range in
-    // this section in this range list - for example ranges for a CU will
-    // usually consist of single regions from each of many sections
-    // (-ffunction-sections, or just C++ inline functions) except under LTO
-    // or optnone where there may be holes in a single CU's section
-    // contributions.
-    auto *Base = CUBase;
-    if (!Base && (P.second.size() > 1 || DwarfVersion < 5) &&
-        (CU.getCUNode()->getRangesBaseAddress() || DwarfVersion >= 5)) {
-      BaseIsSet = true;
-      Base = DD.getSectionLabel(&P.second.front()->Begin->getSection());
-      if (DwarfVersion >= 5) {
-        Asm->OutStreamer->AddComment(StringifyEnum(BaseAddressx));
-        Asm->OutStreamer->EmitIntValue(BaseAddressx, 1);
-        Asm->OutStreamer->AddComment("  base address index");
-        Asm->EmitULEB128(DD.getAddressPool().getIndex(Base));
-      } else {
-        Asm->OutStreamer->EmitIntValue(-1, Size);
-        Asm->OutStreamer->AddComment("  base address");
-        Asm->OutStreamer->EmitSymbolValue(Base, Size);
-      }
-    } else if (BaseIsSet && DwarfVersion < 5) {
-      BaseIsSet = false;
-      assert(!Base);
-      Asm->OutStreamer->EmitIntValue(-1, Size);
-      Asm->OutStreamer->EmitIntValue(0, Size);
-    }
-
-    for (const auto *RS : P.second) {
-      const MCSymbol *Begin = RS->Begin;
-      const MCSymbol *End = RS->End;
-      assert(Begin && "Range without a begin symbol?");
-      assert(End && "Range without an end symbol?");
-      if (Base) {
-        if (DwarfVersion >= 5) {
-          // Emit DW_RLE_offset_pair when we have a base.
-          Asm->OutStreamer->AddComment(StringifyEnum(OffsetPair));
-          Asm->emitInt8(OffsetPair);
-          Asm->OutStreamer->AddComment("  starting offset");
-          Asm->EmitLabelDifferenceAsULEB128(Begin, Base);
-          Asm->OutStreamer->AddComment("  ending offset");
-          Asm->EmitLabelDifferenceAsULEB128(End, Base);
-        } else {
-          Asm->EmitLabelDifference(Begin, Base, Size);
-          Asm->EmitLabelDifference(End, Base, Size);
-        }
-      } else if (DwarfVersion >= 5) {
-        Asm->OutStreamer->AddComment(StringifyEnum(StartxLength));
-        Asm->emitInt8(StartxLength);
-        Asm->OutStreamer->AddComment("  start index");
-        Asm->EmitULEB128(DD.getAddressPool().getIndex(Begin));
-        Asm->OutStreamer->AddComment("  length");
-        Asm->EmitLabelDifferenceAsULEB128(End, Begin);
-      } else {
-        Asm->OutStreamer->EmitSymbolValue(Begin, Size);
-        Asm->OutStreamer->EmitSymbolValue(End, Size);
-      }
-    }
-  }
-  if (DwarfVersion >= 5) {
-    Asm->OutStreamer->AddComment(StringifyEnum(EndOfList));
-    Asm->emitInt8(EndOfList);
-  } else {
-    // Terminate the list with two 0 values.
-    Asm->OutStreamer->EmitIntValue(0, Size);
-    Asm->OutStreamer->EmitIntValue(0, Size);
-  }
-}
-
 /// Emit a single range list. We handle both DWARF v5 and earlier.
 static void emitRangeList(DwarfDebug &DD, AsmPrinter *Asm,
                           const RangeSpanList &List) {
   emitRangeList(DD, Asm, List.getSym(), List.getRanges(), List.getCU(),
                 dwarf::DW_RLE_base_addressx, dwarf::DW_RLE_offset_pair,
                 dwarf::DW_RLE_startx_length, dwarf::DW_RLE_end_of_list,
-                llvm::dwarf::RangeListEncodingString);
+                llvm::dwarf::RangeListEncodingString,
+                List.getCU().getCUNode()->getRangesBaseAddress() ||
+                    DD.getDwarfVersion() >= 5,
+                [](auto) {});
 }
 
 static void emitDebugRangesImpl(DwarfDebug &DD, AsmPrinter *Asm,