[lto-wrapper] Don't pre-link the early-debug objects.

Hi,

As there was some discussion of this on IRC - I believe that Honza might want this patch sooner, rather than later

I constructed it as part of the series to support LTO debug [PR 82005] on Darwin (it’s still needed there).

The patch has been reg-strapped on x86_64-darwin, x86_64-linux, powerpc-linux and AIX-7.2.

There are some small tidy-ups in this too, which can be split out (but posting what I tested, anyway).

OK for trunk?
thoughts?

Iain

* I don’t think to mention the PR for this patch alone - the simple object stuff needs to be included too.

gcc/

	* lto-wrapper.c (tool_cleanup): Don’t report ficticious temp files.
	(debug_objcopy): Improve temp filenames.  Append the early
	debug objects to the outfiles.  Remove the phase prelinking the
	early debug. Emit the early debug filenames for ld.

 gcc/lto-wrapper.c | 135 +++++++++++++++++-----------------------------
 1 file changed, 50 insertions(+), 85 deletions(-)

On December 23, 2018 12:41:04 PM GMT+01:00, Iain Sandoe <iain@sandoe.co.uk> wrote:
>Hi,
>
>As there was some discussion of this on IRC - I believe that Honza
>might want this patch sooner, rather than later
>
>I constructed it as part of the series to support LTO debug [PR 82005]
>on Darwin (it’s still needed there).
>
>The patch has been reg-strapped on x86_64-darwin, x86_64-linux,
>powerpc-linux and AIX-7.2.
>
>There are some small tidy-ups in this too, which can be split out (but
>posting what I tested, anyway).
>
>OK for trunk?

OK. 

Richard. 

>thoughts?
>
>Iain
>
>* I don’t think to mention the PR for this patch alone - the simple
>object stuff needs to be included too.
>
>gcc/
>
>	* lto-wrapper.c (tool_cleanup): Don’t report ficticious temp files.
>	(debug_objcopy): Improve temp filenames.  Append the early
>	debug objects to the outfiles.  Remove the phase prelinking the
>	early debug. Emit the early debug filenames for ld.
>
> gcc/lto-wrapper.c | 135 +++++++++++++++++-----------------------------
> 1 file changed, 50 insertions(+), 85 deletions(-)
>
>diff --git a/gcc/lto-wrapper.c b/gcc/lto-wrapper.c
>index 90d8c1c7fb..15cf6edb5b 100644
>--- a/gcc/lto-wrapper.c
>+++ b/gcc/lto-wrapper.c
>@@ -71,7 +71,8 @@ static char **output_names;
> static char **offload_names;
> static char *offload_objects_file_name;
> static char *makefile;
>-static char *debug_obj;
>+static unsigned int num_deb_objs;
>+static const char **early_debug_object_names;
> 
> const char tool_name[] = "lto-wrapper";
> 
>@@ -90,8 +91,10 @@ tool_cleanup (bool)
>     maybe_unlink (offload_objects_file_name);
>   if (makefile)
>     maybe_unlink (makefile);
>-  if (debug_obj)
>-    maybe_unlink (debug_obj);
>+  if (early_debug_object_names)
>+    for (i = 0; i < num_deb_objs; ++i)
>+      if (early_debug_object_names[i])
>+	maybe_unlink (early_debug_object_names[i]);
>   for (i = 0; i < nr; ++i)
>     {
>       maybe_unlink (input_names[i]);
>@@ -1036,7 +1039,7 @@ find_and_merge_options (int fd, off_t
>file_offset, const char *prefix,
> const char *
> debug_objcopy (const char *infile, bool rename)
> {
>-  const char *outfile;
>+  char *outfile;
>   const char *errmsg;
>   int err;
> 
>@@ -1075,7 +1078,15 @@ debug_objcopy (const char *infile, bool rename)
>       return NULL;
>     }
> 
>-  outfile = make_temp_file ("debugobjtem");
>+  if (save_temps)
>+    {
>+      outfile = (char *) xmalloc (strlen (infile)
>+				  + sizeof (".debug.temp.o") + 1);
>+      strcpy (outfile, infile);
>+      strcat (outfile, ".debug.temp.o");
>+    }
>+  else
>+    outfile = make_temp_file (".debug.temp.o");
>errmsg = simple_object_copy_lto_debug_sections (inobj, outfile, &err,
>rename);
>   if (errmsg)
>     {
>@@ -1412,9 +1423,16 @@ cont1:
> 
>   if (lto_mode == LTO_MODE_LTO)
>     {
>-      flto_out = make_temp_file (".lto.o");
>       if (linker_output)
>-	obstack_ptr_grow (&argv_obstack, linker_output);
>+	{
>+	  obstack_ptr_grow (&argv_obstack, linker_output);
>+	  flto_out = (char *) xmalloc (strlen (linker_output)
>+				       + sizeof (".lto.o") + 1);
>+	  strcpy (flto_out, linker_output);
>+	  strcat (flto_out, ".lto.o");
>+	}
>+      else
>+	flto_out = make_temp_file (".lto.o");
>       obstack_ptr_grow (&argv_obstack, "-o");
>       obstack_ptr_grow (&argv_obstack, flto_out);
>     }
>@@ -1487,95 +1505,39 @@ cont1:
>   argv_ptr = &new_argv[new_head_argc];
>   fork_execute (new_argv[0], CONST_CAST (char **, new_argv), true);
> 
>-  /* Handle early generated debug information.  At compile-time
>-     we output early DWARF debug info into .gnu.debuglto_ prefixed
>-     sections.  LTRANS object DWARF debug info refers to that.
>-     So we need to transfer the .gnu.debuglto_ sections to the final
>-     link.  Ideally the linker plugin interface would allow us to
>-     not claim those sections and instruct the linker to keep
>-     them, renaming them in the process.  For now we extract and
>-     rename those sections via a simple-object interface to produce
>-     regular objects containing only the early debug info.  We
>-     then partially link those to a single early debug info object
>-     and pass that as additional output back to the linker plugin.  */
>-
>-  /* Prepare the partial link to gather the compile-time generated
>-     debug-info into a single input for the final link.  */
>-  debug_obj = make_temp_file ("debugobj");
>-  obstack_ptr_grow (&argv_obstack, collect_gcc);
>-  for (i = 1; i < decoded_options_count; ++i)
>-    {
>-      /* Retain linker choice and -B.  */
>-      if (decoded_options[i].opt_index == OPT_B
>-	  || decoded_options[i].opt_index == OPT_fuse_ld_bfd
>-	  || decoded_options[i].opt_index == OPT_fuse_ld_gold)
>-	append_linker_options (&argv_obstack, &decoded_options[i-1], 2);
>-      /* Retain all target options, this preserves -m32 for example. 
>*/
>-      if (cl_options[decoded_options[i].opt_index].flags & CL_TARGET)
>-	append_linker_options (&argv_obstack, &decoded_options[i-1], 2);
>-      /* Recognize -g0.  */
>-      if (decoded_options[i].opt_index == OPT_g
>-	  && strcmp (decoded_options[i].arg, "0") == 0)
>-	skip_debug = true;
>-    }
>-  obstack_ptr_grow (&argv_obstack, "-r");
>-  obstack_ptr_grow (&argv_obstack, "-nostdlib");
>-  obstack_ptr_grow (&argv_obstack, "-o");
>-  obstack_ptr_grow (&argv_obstack, debug_obj);
>-
>   /* Copy the early generated debug info from the objects to temporary
>      files and append those to the partial link commandline.  */
>   n_debugobj = 0;
>+  early_debug_object_names = NULL;
>   if (! skip_debug)
>-    for (i = 0; i < ltoobj_argc; ++i)
>-      {
>-	const char *tem;
>-	if ((tem = debug_objcopy (ltoobj_argv[i], !linker_output_rel)))
>-	  {
>-	    obstack_ptr_grow (&argv_obstack, tem);
>-	    n_debugobj++;
>-	  }
>-      }
>-
>-  /* Link them all into a single object.  Ideally this would reduce
>-     disk space usage mainly due to .debug_str merging but
>unfortunately
>-     GNU ld doesn't perform this with -r.  */
>-  if (n_debugobj)
>     {
>-      obstack_ptr_grow (&argv_obstack, NULL);
>-      const char **debug_link_argv = XOBFINISH (&argv_obstack, const
>char **);
>-      fork_execute (debug_link_argv[0],
>-		    CONST_CAST (char **, debug_link_argv), false);
>-
>-      /* And dispose the temporaries.  */
>-      for (i = 0; debug_link_argv[i]; ++i)
>-	;
>-      for (--i; i > 0; --i)
>+      early_debug_object_names = XCNEWVEC (const char *, ltoobj_argc+
>1);
>+      num_deb_objs = ltoobj_argc;
>+      for (i = 0; i < ltoobj_argc; ++i)
> 	{
>-	  if (strcmp (debug_link_argv[i], debug_obj) == 0)
>-	    break;
>-	  maybe_unlink (debug_link_argv[i]);
>+	  const char *tem;
>+	  if ((tem = debug_objcopy (ltoobj_argv[i], !linker_output_rel)))
>+	    {
>+	      early_debug_object_names[i] = tem;
>+	      n_debugobj++;
>+	    }
> 	}
>     }
>-  else
>-    {
>-      unlink_if_ordinary (debug_obj);
>-      free (debug_obj);
>-      debug_obj = NULL;
>-      skip_debug = true;
>-    }
> 
>   if (lto_mode == LTO_MODE_LTO)
>     {
>       printf ("%s\n", flto_out);
>       if (!skip_debug)
> 	{
>-	  printf ("%s\n", debug_obj);
>-	  free (debug_obj);
>-	  debug_obj = NULL;
>+	  for (i = 0; i < ltoobj_argc; ++i)
>+	    if (early_debug_object_names[i] != NULL)
>+	      printf ("%s\n", early_debug_object_names[i]);	      
> 	}
>+      /* These now belong to collect2.  */
>       free (flto_out);
>       flto_out = NULL;
>+      free (early_debug_object_names);
>+      early_debug_object_names = NULL;
>     }
>   else
>     {
>@@ -1739,21 +1701,24 @@ cont:
> 	  for (i = 0; i < nr; ++i)
> 	    maybe_unlink (input_names[i]);
> 	}
>-      if (!skip_debug)
>-	{
>-	  printf ("%s\n", debug_obj);
>-	  free (debug_obj);
>-	  debug_obj = NULL;
>-	}
>       for (i = 0; i < nr; ++i)
> 	{
> 	  fputs (output_names[i], stdout);
> 	  putc ('\n', stdout);
> 	  free (input_names[i]);
> 	}
>+      if (!skip_debug)
>+	{
>+	  for (i = 0; i < ltoobj_argc; ++i)
>+	    if (early_debug_object_names[i] != NULL)
>+	      printf ("%s\n", early_debug_object_names[i]);	      
>+	}
>       nr = 0;
>       free (ltrans_priorities);
>       free (output_names);
>+      output_names = NULL;
>+      free (early_debug_object_names);
>+      early_debug_object_names = NULL;
>       free (input_names);
>       free (list_option_full);
>       obstack_free (&env_obstack, NULL);