[gdb/symtab] Make gold index workaround more precise

There's a PR binutils/15646 - "gold-generated .gdb_index has duplicated
symbols that gdb-generated index doesn't", that causes gold to generate
duplicate symbols in the index.

F.i., a namespace N1 declared in a header file can be listed for two CUs that
include the header file:
...
[759] N1:
        2 [global type]
        3 [global type]
...

This causes a gdb performance problem: f.i. when attempting to set a
breakpoint on a non-existing function N1::misspelled, the symtab for both CUs
will be expanded.

Gdb contains a workaround for this, added in commit 8943b87476 "Work around
gold/15646", that skips duplicate global symbols in the index.

However, the workaround does not check for the symbol kind ("type" in the
example above).

Make the workaround more precise by taking symbol kind into account in the
check for duplicates.

Tested on x86_64-linux, with native and target board gold-gdb-index.

gdb/ChangeLog:

2020-05-26  Tom de Vries  <tdevries@suse.de>

	* dwarf2/read.c (NR_GDB_INDEX_SYMBOL_KINDS): Define.
	(struct dw2_symtab_iterator): Make seen_before a bool array.
	(dw2_symtab_iter_init): Update seen_before initialization.
	(dw2_symtab_iter_next, dw2_expand_marked_cus): Check for symbol_kind
	in duplicate check.

---
 gdb/dwarf2/read.c | 20 +++++++++++++-------
 1 file changed, 13 insertions(+), 7 deletions(-)

diff --git a/gdb/dwarf2/read.c b/gdb/dwarf2/read.c
index ec3844188e..4a93cad301 100644
--- a/gdb/dwarf2/read.c
+++ b/gdb/dwarf2/read.c
@@ -3344,6 +3344,8 @@ dw2_map_symtabs_matching_filename
   return false;
 }
 
+#define NR_GDB_INDEX_SYMBOL_KINDS (GDB_INDEX_SYMBOL_KIND_MASK + 1)
+
 /* Struct used to manage iterating over all CUs looking for a symbol.  */
 
 struct dw2_symtab_iterator
@@ -3366,7 +3368,7 @@ struct dw2_symtab_iterator
      If so we can ignore all further global instances.
      This is to work around gold/15646, inefficient gold-generated
      indices.  */
-  int global_seen;
+  bool global_seen[NR_GDB_INDEX_SYMBOL_KINDS];
 };
 
 /* Initialize the index symtab iterator ITER.  */
@@ -3382,7 +3384,8 @@ dw2_symtab_iter_init (struct dw2_symtab_iterator *iter,
   iter->block_index = block_index;
   iter->domain = domain;
   iter->next = 0;
-  iter->global_seen = 0;
+  for (unsigned i = 0; i < NR_GDB_INDEX_SYMBOL_KINDS; ++i)
+    iter->global_seen[i] = false;
 
   mapped_index *index = dwarf2_per_objfile->index_table.get ();
 
@@ -3448,10 +3451,10 @@ dw2_symtab_iter_next (struct dw2_symtab_iterator *iter)
 	    }
 
 	  /* Work around gold/15646.  */
-	  if (!is_static && iter->global_seen)
+	  if (!is_static && iter->global_seen[symbol_kind])
 	    continue;
 	  if (!is_static)
-	    iter->global_seen = 1;
+	    iter->global_seen[symbol_kind] = true;
 	}
 
       /* Only check the symbol's kind if it has one.  */
@@ -4514,9 +4517,12 @@ dw2_expand_marked_cus
    search_domain kind)
 {
   offset_type *vec, vec_len, vec_idx;
-  bool global_seen = false;
+  bool global_seen[NR_GDB_INDEX_SYMBOL_KINDS];
   mapped_index &index = *dwarf2_per_objfile->index_table;
 
+  for (unsigned i = 0; i < NR_GDB_INDEX_SYMBOL_KINDS; ++i)
+    global_seen[i] = false;
+
   vec = (offset_type *) (index.constant_pool
 			 + MAYBE_SWAP (index.symbol_table[idx].vec));
   vec_len = MAYBE_SWAP (vec[0]);
@@ -4539,10 +4545,10 @@ dw2_expand_marked_cus
       /* Work around gold/15646.  */
       if (attrs_valid)
 	{
-	  if (!is_static && global_seen)
+	  if (!is_static && global_seen[symbol_kind])
 	    continue;
 	  if (!is_static)
-	    global_seen = true;
+	    global_seen[symbol_kind] = true;
 	}
 
       /* Only check the symbol's kind if it has one.  */