[binutils-gdb] section-select: Fix performance problem (PR30367)

[binutils-gdb] section-select: Fix performance problem (PR30367)

[Michael Matz]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=8f5cd47bee6c07c33aeda758d8d8db5f81ae03e7

commit 8f5cd47bee6c07c33aeda758d8d8db5f81ae03e7
Author: Michael Matz <matz@suse.de>
Date:   Tue Apr 18 16:16:01 2023 +0200

    section-select: Fix performance problem (PR30367)
    
    when using many wild-statements with non-wildcard filenames we
    were running into quadraticness via repeatedly using lookup_name
    on a long list of loaded files.  I've originally retained using
    lookup_name because that preserved existing behaviour most obviously.
    In particular in matching wild-statements when using a non-wildcard
    filename it matches against local_sym_name, not the filename member.
    If the wildspec would have an archive-spec or a wildcard it would use
    the filename member, though.  Also it would load the named file
    (and ignore it, as being not equal to the currently considered
    input-statement).
    
    Rewrite this to not use lookup_name but retain the comparison
    against local_sym_name with a comment to that effect.
    
            PR 30367
            * ldlang.c (walk_wild_section_match): Don't use lookup_name
            but directly compare spec and local_sym_name.

Diff:
---
 ld/ldlang.c | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/ld/ldlang.c b/ld/ldlang.c
index 006031b5a65..9ad405aa06c 100644
--- a/ld/ldlang.c
+++ b/ld/ldlang.c
@@ -433,10 +433,18 @@ walk_wild_section_match (lang_wild_statement_type *ptr,
     }
   else
     {
-      lang_input_statement_type *f;
-      /* Perform the iteration over a single file.  */
-      f = lookup_name (file_spec);
-      if (f != file)
+      /* XXX Matching against non-wildcard filename in wild statements
+	 was done by going through lookup_name, which uses
+	 ->local_sym_name to compare against, not ->filename.  We retain
+	 this behaviour even though the above code paths use filename.
+	 It would be more logical to use it here as well, in which
+	 case the above wildcard() arm could be folded into this by using
+	 name_match.  This would also solve the worry of what to do
+	 about unset local_sym_name (in which case lookup_name simply adds
+	 the input file again).  */
+      const char *filename = file->local_sym_name;
+      if (filename == NULL
+	  || filename_cmp (filename, file_spec) != 0)
 	return;
     }