[llvm] r215383 - Debug info: Refactor DebugLocEntry's Merge function to make

[Adrian Prantl]

Author: adrian
Date: Mon Aug 11 15:59:28 2014
New Revision: 215383

URL: http://llvm.org/viewvc/llvm-project?rev=215383&view=rev
Log:
Debug info: Refactor DebugLocEntry's Merge function to make
buildLocationLists easier to read.

The previous implementation conflated the merging of individual pieces
and the merging of entire DebugLocEntries.

By splitting this functionality into two separate functions the intention
of the code should be clearer.

Modified:
    llvm/trunk/lib/CodeGen/AsmPrinter/DebugLocEntry.h
    llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp

Modified: llvm/trunk/lib/CodeGen/AsmPrinter/DebugLocEntry.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/AsmPrinter/DebugLocEntry.h?rev=215383&r1=215382&r2=215383&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/AsmPrinter/DebugLocEntry.h (original)
+++ llvm/trunk/lib/CodeGen/AsmPrinter/DebugLocEntry.h Mon Aug 11 15:59:28 2014
@@ -97,14 +97,11 @@ public:
     Values.push_back(std::move(Val));
   }
 
-  /// \brief Attempt to merge this DebugLocEntry with Next and return
-  /// true if the merge was successful. Entries can be merged if they
-  /// share the same Loc/Constant and if Next immediately follows this
-  /// Entry.
-  bool Merge(const DebugLocEntry &Next) {
-    // If this and Next are describing different pieces of the same
-    // variable, merge them by appending next's values to the current
-    // list of values.
+  /// \brief If this and Next are describing different pieces of the same
+  // variable, merge them by appending Next's values to the current
+  // list of values.
+  // Return true if the merge was successful.
+  bool MergeValues(const DebugLocEntry &Next) {
     if (Begin == Next.Begin && Values.size() > 0 && Next.Values.size() > 0) {
       DIVariable Var(Values[0].Variable);
       DIVariable NextVar(Next.Values[0].Variable);
@@ -115,6 +112,14 @@ public:
         return true;
       }
     }
+    return false;
+  }
+
+  /// \brief Attempt to merge this DebugLocEntry with Next and return
+  /// true if the merge was successful. Entries can be merged if they
+  /// share the same Loc/Constant and if Next immediately follows this
+  /// Entry.
+  bool MergeRanges(const DebugLocEntry &Next) {
     // If this and Next are describing the same variable, merge them.
     if ((End == Next.Begin && Values == Next.Values)) {
       End = Next.End;

Modified: llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp?rev=215383&r1=215382&r2=215383&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp (original)
+++ llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp Mon Aug 11 15:59:28 2014
@@ -1272,18 +1272,36 @@ DwarfDebug::buildLocationList(SmallVecto
 
     auto Value = getDebugLocValue(Begin);
     DebugLocEntry Loc(StartLabel, EndLabel, Value);
-    if (DebugLoc.empty() || !DebugLoc.back().Merge(Loc)) {
-      // Add all values from still valid non-overlapping pieces.
+    bool couldMerge = false;
+
+    // If this is a piece, it may belong to the current DebugLocEntry.
+    if (DIVar.isVariablePiece()) {
+      // Add this value to the list of open ranges.
+      OpenRanges.push_back(std::make_pair(DIVar, Value));
+
+      // Attempt to add the piece to the last entry.
+      if (!DebugLoc.empty())
+        if (DebugLoc.back().MergeValues(Loc))
+          couldMerge = true;
+    }
+
+    if (!couldMerge) {
+      // Need to add a new DebugLocEntry. Add all values from still
+      // valid non-overlapping pieces.
       for (auto Range : OpenRanges)
         Loc.addValue(Range.second);
       DebugLoc.push_back(std::move(Loc));
     }
-    // Add this value to the list of open ranges.
-    if (DIVar.isVariablePiece())
-      OpenRanges.push_back(std::make_pair(DIVar, Value));
+
+    // Attempt to coalesce the ranges of two otherwise identical
+    // DebugLocEntries.
+    auto CurEntry = DebugLoc.rbegin();
+    auto PrevEntry = std::next(CurEntry);
+    if (PrevEntry != DebugLoc.rend() && PrevEntry->MergeRanges(*CurEntry))
+      DebugLoc.pop_back();
 
     DEBUG(dbgs() << "Values:\n";
-          for (auto Value : DebugLoc.back().getValues())
+          for (auto Value : CurEntry->getValues())
             Value.getVariable()->dump();
           dbgs() << "-----\n");
   }