[DWARF parser] Fix broken address ranges construction.

Previous algorithm for constructing [Address ranges]->[Compile Units]
mapping was wrong. It somewhat relied on the assumption that address ranges
for different compile units may not overlap. It is not so.
For example, two compile units may contain the definition of the same
linkonce_odr function. These definitions will be merged at link-time,
resulting in equivalent .debug_ranges entries for both these units

Instead of sorting and merging original address ranges (from .debug_ranges
and .debug_aranges), implement a different approach: save endpoints
of all ranges, and then use a sweep-line approach to construct
the desired mapping. If we find that certain address maps to
several compilation units, we just pick any of them.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@210860 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 56 insertions, 60 deletions

diff --git a/lib/DebugInfo/DWARFDebugAranges.cpp b/lib/DebugInfo/DWARFDebugAranges.cpp
index 2524adc25c..fe7e46d63b 100644
--- a/lib/DebugInfo/DWARFDebugAranges.cpp
+++ b/lib/DebugInfo/DWARFDebugAranges.cpp
@@ -15,6 +15,7 @@
 #include "llvm/Support/raw_ostream.h"
 #include <algorithm>
 #include <cassert>
+#include <set>
 using namespace llvm;
 
 void DWARFDebugAranges::extract(DataExtractor DebugArangesData) {
@@ -30,6 +31,7 @@ void DWARFDebugAranges::extract(DataExtractor DebugArangesData) {
       uint64_t HighPC = Desc.getEndAddress();
       appendRange(CUOffset, LowPC, HighPC);
     }
+    ParsedCUOffsets.insert(CUOffset);
   }
 }
 
@@ -56,69 +58,55 @@ void DWARFDebugAranges::generate(DWARFContext *CTX) {
     }
   }
 
-  sortAndMinimize();
+  construct();
 }
 
 void DWARFDebugAranges::clear() {
+  Endpoints.clear();
   Aranges.clear();
   ParsedCUOffsets.clear();
 }
 
 void DWARFDebugAranges::appendRange(uint32_t CUOffset, uint64_t LowPC,
                                     uint64_t HighPC) {
-  if (!Aranges.empty()) {
-    if (Aranges.back().CUOffset == CUOffset &&
-        Aranges.back().HighPC() == LowPC) {
-      Aranges.back().setHighPC(HighPC);
-      return;
-    }
-  }
-  Aranges.push_back(Range(LowPC, HighPC, CUOffset));
-}
-
-void DWARFDebugAranges::sortAndMinimize() {
-  const size_t orig_arange_size = Aranges.size();
-  // Size of one? If so, no sorting is needed
-  if (orig_arange_size <= 1)
+  if (LowPC >= HighPC)
     return;
-  // Sort our address range entries
-  std::stable_sort(Aranges.begin(), Aranges.end());
-
-  // Most address ranges are contiguous from function to function
-  // so our new ranges will likely be smaller. We calculate the size
-  // of the new ranges since although std::vector objects can be resized,
-  // the will never reduce their allocated block size and free any excesss
-  // memory, so we might as well start a brand new collection so it is as
-  // small as possible.
-
-  // First calculate the size of the new minimal arange vector
-  // so we don't have to do a bunch of re-allocations as we
-  // copy the new minimal stuff over to the new collection.
-  size_t minimal_size = 1;
-  for (size_t i = 1; i < orig_arange_size; ++i) {
-    if (!Range::SortedOverlapCheck(Aranges[i-1], Aranges[i]))
-      ++minimal_size;
-  }
+  Endpoints.emplace_back(LowPC, CUOffset, true);
+  Endpoints.emplace_back(HighPC, CUOffset, false);
+}
 
-  // Else, make a new RangeColl that _only_ contains what we need.
-  RangeColl minimal_aranges;
-  minimal_aranges.resize(minimal_size);
-  uint32_t j = 0;
-  minimal_aranges[j] = Aranges[0];
-  for (size_t i = 1; i < orig_arange_size; ++i) {
-    if (Range::SortedOverlapCheck(minimal_aranges[j], Aranges[i])) {
-      minimal_aranges[j].setHighPC(Aranges[i].HighPC());
+void DWARFDebugAranges::construct() {
+  std::multiset<uint32_t> ValidCUs;  // Maintain the set of CUs describing
+                                     // a current address range.
+  std::sort(Endpoints.begin(), Endpoints.end());
+  uint64_t PrevAddress = -1ULL;
+  for (const auto &E : Endpoints) {
+    if (PrevAddress < E.Address && ValidCUs.size() > 0) {
+      // If the address range between two endpoints is described by some
+      // CU, first try to extend the last range in Aranges. If we can't
+      // do it, start a new range.
+      if (!Aranges.empty() && Aranges.back().HighPC() == PrevAddress &&
+          ValidCUs.find(Aranges.back().CUOffset) != ValidCUs.end()) {
+        Aranges.back().setHighPC(E.Address);
+      } else {
+        Aranges.emplace_back(PrevAddress, E.Address, *ValidCUs.begin());
+      }
+    }
+    // Update the set of valid CUs.
+    if (E.IsRangeStart) {
+      ValidCUs.insert(E.CUOffset);
     } else {
-      // Only increment j if we aren't merging
-      minimal_aranges[++j] = Aranges[i];
+      auto CUPos = ValidCUs.find(E.CUOffset);
+      assert(CUPos != ValidCUs.end());
+      ValidCUs.erase(CUPos);
     }
+    PrevAddress = E.Address;
   }
-  assert(j+1 == minimal_size);
+  assert(ValidCUs.empty());
 
-  // Now swap our new minimal aranges into place. The local
-  // minimal_aranges will then contian the old big collection
-  // which will get freed.
-  minimal_aranges.swap(Aranges);
+  // Endpoints are not needed now.
+  std::vector<RangeEndpoint> EmptyEndpoints;
+  EmptyEndpoints.swap(Endpoints);
 }
 
 uint32_t DWARFDebugAranges::findAddress(uint64_t Address) const {
diff --git a/lib/DebugInfo/DWARFDebugAranges.h b/lib/DebugInfo/DWARFDebugAranges.h
index de96d7fb81..a9f37fe772 100644
--- a/lib/DebugInfo/DWARFDebugAranges.h
+++ b/lib/DebugInfo/DWARFDebugAranges.h
@@ -27,9 +27,9 @@ private:
   void clear();
   void extract(DataExtractor DebugArangesData);
 
-  // Use appendRange multiple times and then call sortAndMinimize.
+  // Call appendRange multiple times and then call construct.
   void appendRange(uint32_t CUOffset, uint64_t LowPC, uint64_t HighPC);
-  void sortAndMinimize();
+  void construct();
 
   struct Range {
     explicit Range(uint64_t LowPC = -1ULL, uint64_t HighPC = -1ULL,
@@ -47,31 +47,39 @@ private:
         return LowPC + Length;
       return -1ULL;
     }
+
     bool containsAddress(uint64_t Address) const {
       return LowPC <= Address && Address < HighPC();
     }
-
-    bool operator <(const Range &other) const {
+    bool operator<(const Range &other) const {
       return LowPC < other.LowPC;
     }
 
-    static bool SortedOverlapCheck(const Range &Left, const Range &Right) {
-      if (Left.CUOffset != Right.CUOffset)
-        return false;
-      return Left.HighPC() >= Right.LowPC;
-    }
-
     uint64_t LowPC; // Start of address range.
     uint32_t Length; // End of address range (not including this address).
     uint32_t CUOffset; // Offset of the compile unit or die.
   };
 
+  struct RangeEndpoint {
+    uint64_t Address;
+    uint32_t CUOffset;
+    bool IsRangeStart;
+
+    RangeEndpoint(uint64_t Address, uint32_t CUOffset, bool IsRangeStart)
+        : Address(Address), CUOffset(CUOffset), IsRangeStart(IsRangeStart) {}
+
+    bool operator<(const RangeEndpoint &Other) const {
+      return Address < Other.Address;
+    }
+  };
+
+
   typedef std::vector<Range>              RangeColl;
   typedef RangeColl::const_iterator       RangeCollIterator;
-  typedef DenseSet<uint32_t>              ParsedCUOffsetColl;
 
+  std::vector<RangeEndpoint> Endpoints;
   RangeColl Aranges;
-  ParsedCUOffsetColl ParsedCUOffsets;
+  DenseSet<uint32_t> ParsedCUOffsets;
 };
 
 }