[DWARF][NFC] Factoring out emission of a single rangelist into a static helper

[wolfgangp]

Summary

This is in preparation for the emission of DWARF v5 range lists (.debug_rnglists section). We move the emission of a single range list to a static helper function for easier emission of v5 range lists later.

[JDevlieghere]

LGTM, Thanks!

lib/CodeGen/AsmPrinter/DwarfDebug.cpp

for (DwarfCompileUnit *CU : CUs) {
     }
 
     Asm->OutStreamer->AddComment("ARange terminator");
     Asm->OutStreamer->EmitIntValue(0, PtrSize);
     Asm->OutStreamer->EmitIntValue(0, PtrSize);
   }
 }
 
-/// Emit address ranges into a debug ranges section.
-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());
-
-  // Size for our labels.
-  unsigned char Size = Asm->MAI->getCodePointerSize();
-
-  // Grab the specific ranges for the compile units in the module.
-  for (const auto &I : CUMap) {
-    DwarfCompileUnit *TheCU = I.second;
-
-    if (auto *Skel = TheCU->getSkeleton())
-      TheCU = Skel;
-
-    // Iterate over the misc ranges for the compile units in the module.
-    for (const RangeSpanList &List : TheCU->getRangeLists()) {
-      // Emit our symbol so we can find the beginning of the range.
-      Asm->OutStreamer->EmitLabel(List.getSym());
-
-      // 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 *>> MV;
-      for (const RangeSpan &Range : List.getRanges()) {
-        MV[&Range.getStart()->getSection()].push_back(&Range);
-      }
+/// Emit a single range list.
+static void emitRangeList(AsmPrinter *Asm, DwarfCompileUnit *CU,
+                          const RangeSpanList &List) {
+  MapVector<const MCSection *, std::vector<const RangeSpan *>> SectionRanges;
+  // Size for our labels.
+  auto Size = Asm->MAI->getCodePointerSize();
 
-      auto *CUBase = TheCU->getBaseAddress();
-      bool BaseIsSet = false;
-      for (const auto &P : MV) {
-        // 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
-        // contrubutions.
-        auto *Base = CUBase;
-        if (!Base && P.second.size() > 1 &&
-            UseDwarfRangesBaseAddressSpecifier) {
-          BaseIsSet = true;
-          // FIXME/use care: This may not be a useful base address if it's not
-          // the lowest address/range in this object.
-          Base = P.second.front()->getStart();
-          Asm->OutStreamer->EmitIntValue(-1, Size);
-          Asm->OutStreamer->EmitSymbolValue(Base, Size);
-        } else if (BaseIsSet) {
-          BaseIsSet = false;
-          Asm->OutStreamer->EmitIntValue(-1, Size);
-          Asm->OutStreamer->EmitIntValue(0, Size);
-        }
+  for (const RangeSpan &Range : List.getRanges())
+    SectionRanges[&Range.getStart()->getSection()].push_back(&Range);
+
+  auto *CUBase = CU->getBaseAddress();
+  for (const auto &P : SectionRanges) {
+    if (!Base && P.second.size() > 1 && UseDwarfRangesBaseAddressSpecifier) {
 
-        for (const auto *RS : P.second) {
-          const MCSymbol *Begin = RS->getStart();
-          const MCSymbol *End = RS->getEnd();
-          assert(Begin && "Range without a begin symbol?");
-          assert(End && "Range without an end symbol?");
-          if (Base) {
-            Asm->EmitLabelDifference(Begin, Base, Size);
-            Asm->EmitLabelDifference(End, Base, Size);
-          } else {
-            Asm->OutStreamer->EmitSymbolValue(Begin, Size);
-            Asm->OutStreamer->EmitSymbolValue(End, Size);
-          }
-        }
-      }
 
-      // And terminate the list with two 0 values.
-      Asm->OutStreamer->EmitIntValue(0, Size);
-      Asm->OutStreamer->EmitIntValue(0, Size);
-    }
+
+/// Emit address ranges into a debug ranges section.
+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());
+
+  // Grab the specific ranges for the compile units in the module.
+  for (const auto &I : CUMap) {
+    DwarfCompileUnit *TheCU = I.second;
+
+    if (auto *Skel = TheCU->getSkeleton())
+      TheCU = Skel;
+
+    // Iterate over the misc ranges for the compile units in the module.
+    for (const RangeSpanList &List : TheCU->getRangeLists())
+      emitRangeList(Asm, TheCU, List);
   }
 }
 
 void DwarfDebug::handleMacroNodes(DIMacroNodeArray Nodes, DwarfCompileUnit &U) {
   for (auto *MN : Nodes) {
     if (auto *M = dyn_cast<DIMacro>(MN))
       emitMacro(*M);
     else if (auto *F = dyn_cast<DIMacroFile>(MN))