DwarfDebug: Simplify debug_loc merging

No functional change intended.

Merging up-front rather than delaying this task until later. This just
seems simpler and more efficient (avoiding growing the debug loc list
only to have to skip over those post-merged entries, etc).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@204679 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/AsmPrinter/DIEHash.cpp

@@ -296,8 +296,6 @@ void DIEHash::hashLocList(const DIELocList &LocList) {
     // which is the next empty entry.
     if (Entry.isEmpty())
       return;
-    else if (Entry.isMerged())
-      continue;
     else
       AP->getDwarfDebug()->emitDebugLocEntry(Streamer, Entry);
   }

lib/CodeGen/AsmPrinter/DwarfDebug.cpp

@@ -1297,8 +1297,9 @@ DwarfDebug::collectVariableInfo(SmallPtrSet<const MDNode *, 16> &Processed) {
       // The value is valid until the next DBG_VALUE or clobber.
       LexicalScope *FnScope = LScopes.getCurrentFunctionScope();
       DwarfCompileUnit *TheCU = SPMap.lookup(FnScope->getScopeNode());
-      DotDebugLocEntries.push_back(
-          getDebugLocEntry(Asm, FLabel, SLabel, Begin, TheCU));
+      DebugLocEntry Loc = getDebugLocEntry(Asm, FLabel, SLabel, Begin, TheCU);
+      if (DotDebugLocEntries.empty() || !DotDebugLocEntries.back().Merge(Loc))
+        DotDebugLocEntries.push_back(std::move(Loc));
     }
     DotDebugLocEntries.push_back(DebugLocEntry());
   }
@@ -2378,15 +2379,6 @@ void DwarfDebug::emitDebugLoc() {
   if (DotDebugLocEntries.empty())
     return;
 
-  for (SmallVectorImpl<DebugLocEntry>::iterator
-           I = DotDebugLocEntries.begin(),
-           E = DotDebugLocEntries.end();
-       I != E; ++I) {
-    DebugLocEntry &Entry = *I;
-    if (I + 1 != DotDebugLocEntries.end())
-      Entry.Merge(I + 1);
-  }
-
   // Start the dwarf loc section.
   Asm->OutStreamer.SwitchSection(
       Asm->getObjFileLowering().getDwarfLocSection());
@@ -2398,8 +2390,6 @@ void DwarfDebug::emitDebugLoc() {
            E = DotDebugLocEntries.end();
        I != E; ++I, ++index) {
     const DebugLocEntry &Entry = *I;
-    if (Entry.isMerged())
-      continue;
 
     if (Entry.isEmpty()) {
       Asm->OutStreamer.EmitIntValue(0, Size);

lib/CodeGen/AsmPrinter/DwarfDebug.h

@@ -84,47 +84,43 @@ class DebugLocEntry {
   // The compile unit to which this location entry is referenced by.
   const DwarfCompileUnit *Unit;
 
-  // Whether this location has been merged.
-  bool Merged;
-
 public:
-  DebugLocEntry() : Begin(0), End(0), Variable(0), Unit(0), Merged(false) {
+  DebugLocEntry() : Begin(0), End(0), Variable(0), Unit(0) {
     Constants.Int = 0;
   }
   DebugLocEntry(const MCSymbol *B, const MCSymbol *E, MachineLocation &L,
                 const MDNode *V, const DwarfCompileUnit *U)
-      : Begin(B), End(E), Loc(L), Variable(V), Unit(U), Merged(false) {
+      : Begin(B), End(E), Loc(L), Variable(V), Unit(U) {
     Constants.Int = 0;
     EntryKind = E_Location;
   }
   DebugLocEntry(const MCSymbol *B, const MCSymbol *E, int64_t i,
                 const DwarfCompileUnit *U)
-      : Begin(B), End(E), Variable(0), Unit(U), Merged(false) {
+      : Begin(B), End(E), Variable(0), Unit(U) {
     Constants.Int = i;
     EntryKind = E_Integer;
   }
   DebugLocEntry(const MCSymbol *B, const MCSymbol *E, const ConstantFP *FPtr,
                 const DwarfCompileUnit *U)
-      : Begin(B), End(E), Variable(0), Unit(U), Merged(false) {
+      : Begin(B), End(E), Variable(0), Unit(U) {
     Constants.CFP = FPtr;
     EntryKind = E_ConstantFP;
   }
   DebugLocEntry(const MCSymbol *B, const MCSymbol *E, const ConstantInt *IPtr,
                 const DwarfCompileUnit *U)
-      : Begin(B), End(E), Variable(0), Unit(U), Merged(false) {
+      : Begin(B), End(E), Variable(0), Unit(U) {
     Constants.CIP = IPtr;
     EntryKind = E_ConstantInt;
   }
 
   /// \brief Empty entries are also used as a trigger to emit temp label. Such
   /// labels are referenced is used to find debug_loc offset for a given DIE.
   bool isEmpty() const { return Begin == 0 && End == 0; }
-  bool isMerged() const { return Merged; }
-  void Merge(DebugLocEntry *Next) {
-    if (!(Begin && Loc == Next->Loc && End == Next->Begin))
-      return;
-    Next->Begin = Begin;
-    Merged = true;
+  bool Merge(const DebugLocEntry &Next) {
+    if (!(Begin && Loc == Next.Loc && End == Next.Begin))
+      return false;
+    End = Next.End;
+    return true;
   }
   bool isLocation() const { return EntryKind == E_Location; }
   bool isInt() const { return EntryKind == E_Integer; }