Re: [patch] Speed up find_pc_section

[Paul Pluzhnikov <ppluzhnikov@google.com>]

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On Mon, Sep 14, 2009 at 10:35 AM, Joel Brobecker <brobecker@adacore.com> wrote:
>> I've just checked in both patches. Hopefully this thread will end here,
>> it's been long enough :-)
>
> There is still the OBJF_NOT_MAPPED patch.

Given this subthread:

  http://sourceware.org/ml/gdb-patches/2009-09/msg00307.html

I don't believe OBJF_NOT_MAPPED is the right way to go.

I agree with Tristan that we should separate the 'read objfile for symbols,
sections, etc.' from read an object file just for its debug bits.

This would allow:
- Darwin "dwarf debug is found in the separate *.o files",
- Solaris cc/CC without '-xs' (dwarf or stabs debug is found in original
  *.o files -- very similar to Darwin),
- We could then use the same on Linux and drop the
  separate_debug_objfile/separate_debug_objfile_backlink objfile members,
  as well as filter_debuginfo_sections().

Note that current checked in code on Darwin does not fail any asserts,
it just doesn't work correctly and issues bazillion of complaints.

Given above, I don't think committing/testing the OBJF_NOT_MAPPED patch
is the right way to go -- it's more of a hack then a solution.

However, if someone needs a hack, attached is the current state of the
patch. Christian Thalinger tested essentially this version on his Darwin/Java
build, and reported success.

Cheers,
-- 
Paul Pluzhnikov

2009-09-14  Paul Pluzhnikov  <ppluzhnikov@google.com>

	* objfiles.h (OBJF_NOT_MAPPED): New define.
	* objfiles.c (update_section_map): Ignore not mapped objfiles.
	* machoread.c (macho_oso_symfile, macho_oso_symfile): Adjust.

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Index: objfiles.h
===================================================================
RCS file: /cvs/src/src/gdb/objfiles.h,v
retrieving revision 1.64
diff -u -p -u -r1.64 objfiles.h
--- objfiles.h	11 Sep 2009 18:51:31 -0000	1.64
+++ objfiles.h	14 Sep 2009 18:04:54 -0000
@@ -414,6 +414,12 @@ struct objfile
 
 #define OBJF_USERLOADED	(1 << 3)	/* User loaded */
 
+/* This objfile is not mapped into the process address space. We only have it
+   for its debug bits.  One example is MACH-O ("other source") object
+   files.  */
+
+#define OBJF_NOT_MAPPED (1 << 4)        /* Not mapped */
+
 /* The object file that the main symbol table was loaded from (e.g. the
    argument to the "symbol-file" or "file" command).  */
 
Index: objfiles.c
===================================================================
RCS file: /cvs/src/src/gdb/objfiles.c,v
retrieving revision 1.96
diff -u -p -u -r1.96 objfiles.c
--- objfiles.c	14 Sep 2009 17:12:07 -0000	1.96
+++ objfiles.c	14 Sep 2009 18:04:54 -0000
@@ -1041,16 +1041,21 @@ update_section_map (struct obj_section *
   xfree (map);
 
   alloc_size = 0;
-  ALL_OBJSECTIONS (objfile, s)
-    if (insert_section_p (objfile->obfd, s->the_bfd_section))
-      alloc_size += 1;
+
+  ALL_OBJFILES (objfile)
+    if ((objfile->flags & OBJF_NOT_MAPPED) == 0)
+      ALL_OBJFILE_OSECTIONS (objfile, s)
+	if (insert_section_p (objfile->obfd, s->the_bfd_section))
+	  alloc_size += 1;
 
   map = xmalloc (alloc_size * sizeof (*map));
 
   i = 0;
-  ALL_OBJSECTIONS (objfile, s)
-    if (insert_section_p (objfile->obfd, s->the_bfd_section))
-      map[i++] = s;
+  ALL_OBJFILES (objfile)
+    if ((objfile->flags & OBJF_NOT_MAPPED) == 0)
+      ALL_OBJFILE_OSECTIONS (objfile, s)
+	if (insert_section_p (objfile->obfd, s->the_bfd_section))
+	  map[i++] = s;
 
   qsort (map, alloc_size, sizeof (*map), qsort_cmp);
   map_size = filter_debuginfo_sections(map, alloc_size);
Index: machoread.c
===================================================================
RCS file: /cvs/src/src/gdb/machoread.c,v
retrieving revision 1.5
diff -u -p -u -r1.5 machoread.c
--- machoread.c	19 Jun 2009 14:30:30 -0000	1.5
+++ machoread.c	14 Sep 2009 18:04:54 -0000
@@ -406,7 +406,8 @@ macho_oso_symfile (struct objfile *main_
 	      bfd_close (member_bfd);
 	    }
 	    else
-	      symbol_file_add_from_bfd (member_bfd, 0, addrs, 0);
+	      symbol_file_add_from_bfd (member_bfd, SYMFILE_DEFER_BP_RESET,
+					addrs, OBJF_NOT_MAPPED);
 	}
       else
 	{
@@ -429,7 +430,8 @@ macho_oso_symfile (struct objfile *main_
 	      continue;
 	    }
   
-	  symbol_file_add_from_bfd (abfd, 0, addrs, 0);
+	  symbol_file_add_from_bfd (abfd, SYMFILE_DEFER_BP_RESET, addrs,
+				    OBJF_NOT_MAPPED);
 	}
       xfree (oso->symbols);
       xfree (oso->offsets);
@@ -592,7 +594,7 @@ macho_symfile_read (struct objfile *objf
 	  oso_vector = NULL;
 
 	  /* Now recurse: read dwarf from dsym.  */
-	  symbol_file_add_from_bfd (dsym_bfd, 0, NULL, 0);
+	  symbol_file_add_from_bfd (dsym_bfd, 0, NULL, OBJF_NOT_MAPPED);
       
 	  /* Don't try to read dwarf2 from main file or shared libraries.  */
 	  return;