* dwarf_reader.cc (next_generation_count): New static var.

	(Addr2line_cache_entry): New struct.
	(addr2line_cache): New static var.
	(Dwarf_line_info::one_addr2line): Added caching.
	(Dwarf_line_info::clear_addr2line_cache): New function.
	* dwarf_reader.h (Dwarf_line_info::one_addr2line): Add
	cache-size parameter.
	(Dwarf_line_info::one_addr2line_cache): New function.
	* symtab.cc (Symbol_table::detect_odr_violations): Pass
	new cache-size argument to one_addr2line(), and clear cache.

1 files changed, 102 insertions, 16 deletions

diff --git a/gold/dwarf_reader.cc b/gold/dwarf_reader.cc
index d3faeeb..ec697e4 100644
--- a/gold/dwarf_reader.cc
+++ b/gold/dwarf_reader.cc
@@ -23,6 +23,7 @@
 #include "gold.h"
 
 #include <algorithm>
+#include <vector>
 
 #include "elfcpp_swap.h"
 #include "dwarf.h"
@@ -799,35 +800,120 @@ Sized_dwarf_line_info<size, big_endian>::do_addr2line(unsigned int shndx,
 
 // Dwarf_line_info routines.
 
+static unsigned int next_generation_count = 0;
+
+struct Addr2line_cache_entry
+{
+  Object* object;
+  unsigned int shndx;
+  Dwarf_line_info* dwarf_line_info;
+  unsigned int generation_count;
+  unsigned int access_count;
+
+  Addr2line_cache_entry(Object* o, unsigned int s, Dwarf_line_info* d)
+      : object(o), shndx(s), dwarf_line_info(d),
+        generation_count(next_generation_count), access_count(0)
+  {
+    if (next_generation_count < (1U << 31))
+      ++next_generation_count;
+  }
+};
+// We expect this cache to be small, so don't bother with a hashtable
+// or priority queue or anything: just use a simple vector.
+static std::vector<Addr2line_cache_entry> addr2line_cache;
+
 std::string
 Dwarf_line_info::one_addr2line(Object* object,
-                               unsigned int shndx, off_t offset)
+                               unsigned int shndx, off_t offset,
+                               size_t cache_size)
 {
-  switch (parameters->size_and_endianness())
+  Dwarf_line_info* lineinfo = NULL;
+  std::vector<Addr2line_cache_entry>::iterator it;
+
+  // First, check the cache.  If we hit, update the counts.
+  for (it = addr2line_cache.begin(); it != addr2line_cache.end(); ++it)
     {
+      if (it->object == object && it->shndx == shndx)
+        {
+          lineinfo = it->dwarf_line_info;
+          it->generation_count = next_generation_count;
+          // We cap generation_count at 2^31 -1 to avoid overflow.
+          if (next_generation_count < (1U << 31))
+            ++next_generation_count;
+          // We cap access_count at 31 so 2^access_count doesn't overflow
+          if (it->access_count < 31)
+            ++it->access_count;
+          break;
+        }
+    }
+
+  // If we don't hit the cache, create a new object and insert into the
+  // cache.
+  if (lineinfo == NULL)
+  {
+    switch (parameters->size_and_endianness())
+      {
 #ifdef HAVE_TARGET_32_LITTLE
-    case Parameters::TARGET_32_LITTLE:
-      return Sized_dwarf_line_info<32, false>(object, shndx).addr2line(shndx,
-                                                                       offset);
+        case Parameters::TARGET_32_LITTLE:
+          lineinfo = new Sized_dwarf_line_info<32, false>(object, shndx); break;
 #endif
 #ifdef HAVE_TARGET_32_BIG
-    case Parameters::TARGET_32_BIG:
-      return Sized_dwarf_line_info<32, true>(object, shndx).addr2line(shndx,
-                                                                      offset);
+        case Parameters::TARGET_32_BIG:
+          lineinfo = new Sized_dwarf_line_info<32, true>(object, shndx); break;
 #endif
 #ifdef HAVE_TARGET_64_LITTLE
-    case Parameters::TARGET_64_LITTLE:
-      return Sized_dwarf_line_info<64, false>(object, shndx).addr2line(shndx,
-                                                                       offset);
+        case Parameters::TARGET_64_LITTLE:
+          lineinfo = new Sized_dwarf_line_info<64, false>(object, shndx); break;
 #endif
 #ifdef HAVE_TARGET_64_BIG
-    case Parameters::TARGET_64_BIG:
-      return Sized_dwarf_line_info<64, true>(object, shndx).addr2line(shndx,
-                                                                      offset);
+        case Parameters::TARGET_64_BIG:
+          lineinfo = new Sized_dwarf_line_info<64, true>(object, shndx); break;
 #endif
-    default:
-      gold_unreachable();
+        default:
+          gold_unreachable();
+      }
+    addr2line_cache.push_back(Addr2line_cache_entry(object, shndx, lineinfo));
+  }
+
+  // Now that we have our object, figure out the answer
+  std::string retval = lineinfo->addr2line(shndx, offset);
+
+  // Finally, if our cache has grown too big, delete old objects.  We
+  // assume the common (probably only) case is deleting only one object.
+  // We use a pretty simple scheme to evict: function of LRU and MFU.
+  while (addr2line_cache.size() > cache_size)
+    {
+      unsigned int lowest_score = ~0U;
+      std::vector<Addr2line_cache_entry>::iterator lowest
+          = addr2line_cache.end();
+      for (it = addr2line_cache.begin(); it != addr2line_cache.end(); ++it)
+        {
+          const unsigned int score = (it->generation_count
+                                      + (1U << it->access_count));
+          if (score < lowest_score)
+            {
+              lowest_score = score;
+              lowest = it;
+            }
+        }
+      if (lowest != addr2line_cache.end())
+        {
+          delete lowest->dwarf_line_info;
+          addr2line_cache.erase(lowest);
+        }
     }
+
+  return retval;
+}
+
+void
+Dwarf_line_info::clear_addr2line_cache()
+{
+  for (std::vector<Addr2line_cache_entry>::iterator it = addr2line_cache.begin();
+       it != addr2line_cache.end();
+       ++it)
+    delete it->dwarf_line_info;
+  addr2line_cache.clear();
 }
 
 #ifdef HAVE_TARGET_32_LITTLE