Commit: Improve the performance of objcopy's note merging algorithm

[Nick Clifton <nickc@redhat.com>]

Hi Guys,

  I am applying the patch below to speed up objcopy's note-merging
  algorithm.  With this patch applied the time taken to merge the notes
  in Firefox's libxul.so went down from 10 minutes to 5 minutes, on the
  machine that I was using for testing.

Cheers
  Nick

binutils/ChangeLog
2023-01-18  Nick Clifton  <nickc@redhat.com>

	PR 29993
	* objcopy.c (merge_gnu_build_notes): Remember the last non-deleted
	note in order to speed up the scan for matching notes.

diff --git a/binutils/objcopy.c b/binutils/objcopy.c
index b8958bcab57..eb2e54b9602 100644
--- a/binutils/objcopy.c
+++ b/binutils/objcopy.c
@@ -2403,6 +2403,8 @@ merge_gnu_build_notes (bfd *          abfd,
 	    other note then if they are both of the same type (open
 	    or func) then they can be merged and one deleted.  If
 	    they are of different types then they cannot be merged.  */
+  objcopy_internal_note * prev_note = NULL;
+
   for (pnote = pnotes; pnote < pnotes_end; pnote ++)
     {
       /* Skip already deleted notes.
@@ -2424,7 +2426,9 @@ merge_gnu_build_notes (bfd *          abfd,
       objcopy_internal_note * back;
 
       /* Rule 2: Check to see if there is an identical previous note.  */
-      for (iter = 0, back = pnote - 1; back >= pnotes; back --)
+      for (iter = 0, back = prev_note ? prev_note : pnote - 1;
+	   back >= pnotes;
+	   back --)
 	{
 	  if (is_deleted_note (back))
 	    continue;
@@ -2486,11 +2490,17 @@ merge_gnu_build_notes (bfd *          abfd,
 	      break;
 	    }
 	}
-#if DEBUG_MERGE
+
       if (! is_deleted_note (pnote))
-	merge_debug ("Unable to do anything with note at %#08lx\n",
-		     (pnote->note.namedata - (char *) contents) - 12);
+	{
+	  /* Keep a pointer to this note, so that we can
+	     start the next search for rule 2 matches here.  */
+	  prev_note = pnote;
+#if DEBUG_MERGE
+	  merge_debug ("Unable to do anything with note at %#08lx\n",
+		       (pnote->note.namedata - (char *) contents) - 12);
 #endif
+	}
     }
 
   /* Resort the notes.  */