[PATCH] Add --devel-skip-producer

[Tom de Vries]

Hi,

In PR27588 a test-case was reported where dwz did not optimize due
to illegal DWARF produced by nasm:
...
$ dwz libxul.so -o libxul.so.z
dwz: libxul.so: loclistptr attribute, yet no .debug_loc section
...

Add an option --devel-skip-producer <producer> such that we can filter out
CUs coming from a particular producer, such that we have instead:
...
$ readelf -wi libxul.so | grep DW_AT_producer \
    | sed 's/.*: //' | sort | uniq -c
    176 clang LLVM (rustc version 1.50.0)
      2 GNU AS 2.36.1
      2 GNU C11 11.0.1 20210315 (experimental) <SNIP>
     16 NASM 2.15.05
     76 yasm 1.3.0
$ dwz libxul.so -o libxul.so.z --devel-skip-producer NASM
$ readelf -wi libxul.so.z | grep DW_AT_producer \
    | sed 's/.*: //' | sort | uniq -c
    176 clang LLVM (rustc version 1.50.0)
      2 GNU AS 2.36.1
      2 GNU C11 11.0.1 20210315 (experimental) <SNIP>
     76 yasm 1.3.0
...

Any comments?

Thanks,
- Tom

Add --devel-skip-producer

2021-03-16  Tom de Vries  <tdevries@suse.de>

	* dwz.c (add_skip_producer, skip_producer): New function.
	(read_debug_info): Skip CUs fi DW_AT_producer in skip_producers list.
	(dwz_options, usage): Add --devel-skip-producer entries.
	(parse_args): Handle skip_producer_parsed.

---
 dwz.c | 57 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 56 insertions(+), 1 deletion(-)

diff --git a/dwz.c b/dwz.c
index 54b4bda..06e73bc 100644
--- a/dwz.c
+++ b/dwz.c
@@ -289,6 +289,8 @@ static enum odr_mode odr_mode = ODR_LINK;
 static int odr_mode_parsed = 0;
 static bool odr_active_p = false;
 
+static int skip_producer_parsed = 0;
+
 /* Struct to gather statistics.  */
 struct stats
 {
@@ -6648,6 +6650,49 @@ read_lang (unsigned char *ptr, enum dwarf_form form,
   return ptr;
 }
 
+static const char **skip_producers;
+static size_t skip_producers_size;
+static size_t nr_skip_producers;
+
+static void
+add_skip_producer (const char *producer)
+{
+  size_t alloc_size;
+  if (skip_producers == NULL)
+    {
+      skip_producers_size = 10;
+      alloc_size = skip_producers_size * sizeof (const char *);
+      skip_producers = malloc (alloc_size);
+    }
+  else if (nr_skip_producers == skip_producers_size)
+    {
+      skip_producers_size += 10;
+      alloc_size = skip_producers_size * sizeof (const char *);
+      skip_producers = realloc (skip_producers, alloc_size);
+    }
+
+  skip_producers[nr_skip_producers] = producer;
+  nr_skip_producers++;
+}
+
+static bool
+skip_producer (const char *producer)
+{
+  size_t i;
+
+  if (producer == NULL)
+    return false;
+
+  for (i = 0; i < nr_skip_producers; ++i)
+    {
+      const char *skip = skip_producers[i];
+      if (strncmp (skip, producer, strlen (skip)) == 0)
+	return true;
+    }
+
+  return false;
+}
+
 /* First phase of the DWARF compression.  Parse .debug_info section
    (for kind == DEBUG_INFO) or .debug_types section (for kind == DEBUG_TYPES)
    for each CU in it construct internal representation for the CU
@@ -7320,6 +7365,11 @@ read_debug_info (DSO *dso, int kind, unsigned int *die_count)
 	}
 
       cu->cu_comp_dir = get_AT_string (cu->cu_die, DW_AT_comp_dir);
+      if (skip_producer (get_AT_string (cu->cu_die, DW_AT_producer)))
+	{
+	  cu->cu_die->die_remove = 1;
+	  continue;
+	}
       enum dwarf_form form;
       debug_line_off
 	= get_AT_int (cu->cu_die, DW_AT_stmt_list, &present, &form);
@@ -16374,6 +16424,8 @@ static struct option dwz_options[] =
 			 no_argument,	    &checksum_cycle_opt, 1 },
   { "devel-no-checksum-cycle-opt",
 			 no_argument,	    &checksum_cycle_opt, 0 },
+  { "devel-skip-producer",
+			 required_argument, &skip_producer_parsed, 1},
 #endif
   { "odr",		 no_argument,	    &odr, 1 },
   { "no-odr",		 no_argument,	    &odr, 0 },
@@ -16630,7 +16682,8 @@ usage (const char *progname, int failing)
 	    "  --devel-die-count-method\n"
 	    "  --devel-deduplication-mode={none,intra-cu,inter-cu}\n"
 	    "  --devel-uni-lang / --devel-no-uni-lang\n"
-	    "  --devel-gen-cu / --devel-no-gen-cu\n"));
+	    "  --devel-gen-cu / --devel-no-gen-cu\n"
+	    "  --devel-skip-producer <producer>\n"));
 #endif
 
   exit (failing);
@@ -16726,6 +16779,8 @@ parse_args (int argc, char *argv[], bool *hardlink, const char **outfile)
 	      error (1, 0, "invalid argument --odr-mode %s",
 		     optarg);
 	    }
+	  if (skip_producer_parsed)
+	    add_skip_producer (optarg);
 	  break;
 
 	case 'o':