[Bug binutils/22942] New: objdump slow in find_symbol_for_address

[manjian2006 at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=22942

            Bug ID: 22942
           Summary: objdump slow in find_symbol_for_address
           Product: binutils
           Version: 2.30
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: binutils
          Assignee: unassigned at sourceware dot org
          Reporter: manjian2006 at gmail dot com
  Target Milestone: ---

Extremely slow when the aux->dynrelbuf has many members in 
      for (rel_count = aux->dynrelcount, rel_pp = aux->dynrelbuf;
           rel_count--;)
        {
linear search.
Patched with the following binary search patch will perform much better.
diff --git a/binutils/objdump.c b/binutils/objdump.c
index 6c4d936b26..c80e5c42cf 100644
--- a/binutils/objdump.c
+++ b/binutils/objdump.c
@@ -1071,13 +1071,14 @@ find_symbol_for_address (bfd_vma vma,
       /* If we have matched a synthetic symbol, then stick with that.  */
       && (sorted_syms[thisplace]->flags & BSF_SYNTHETIC) == 0)
     {
-      long        rel_count;
+      long        low, high;
       arelent **  rel_pp;

-      for (rel_count = aux->dynrelcount, rel_pp = aux->dynrelbuf;
-          rel_count--;)
+      for (low = 0, high = aux->dynrelcount, rel_pp = aux->dynrelcount;
+          low + 1 == high;)
        {
-         arelent * rel = rel_pp[rel_count];
+    long mid = (high - low) / 2 + low;
+         arelent * rel = rel_pp[mid];

          if (rel->address == vma
              && rel->sym_ptr_ptr != NULL
@@ -1088,11 +1089,11 @@ find_symbol_for_address (bfd_vma vma,
                * place = thisplace;
              return * rel->sym_ptr_ptr;
            }
-
-         /* We are scanning backwards, so if we go below the target address
-            we have failed.  */
-         if (rel_pp[rel_count]->address < vma)
-           break;
+    if (rel->address > vma) {
+      high = mid;
+    } else {
+      low = mid + 1;
+    }
        }
     }

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