Use try_emplace in index-write.c

index-write.c has a comment indicating that C++17's try_emplace could
be used.  This patch makes the change.

Approved-By: Pedro Alves <pedro@palves.net>

diff --git a/gdb/dwarf2/index-write.c b/gdb/dwarf2/index-write.c
index b77f4f965855a5b3f844c2d10ac475e047ffd179..b4a0117330e79f9ee3982561270c6f82fc3199a1 100644 (file)
--- a/gdb/dwarf2/index-write.c
+++ b/gdb/dwarf2/index-write.c
@@ -515,24 +515,17 @@ write_hash_table (mapped_symtab *symtab, data_buf &output, data_buf &cpool)
          continue;
        gdb_assert (entry.index_offset == 0);
 
-       /* Finding before inserting is faster than always trying to
-          insert, because inserting always allocates a node, does the
-          lookup, and then destroys the new node if another node
-          already had the same key.  C++17 try_emplace will avoid
-          this.  */
-       const auto found
-         = symbol_hash_table.find (entry.cu_indices);
-       if (found != symbol_hash_table.end ())
+       auto [iter, inserted]
+         = symbol_hash_table.try_emplace (entry.cu_indices,
+                                          cpool.size ());
+       entry.index_offset = iter->second;
+       if (inserted)
          {
-           entry.index_offset = found->second;
-           continue;
+           /* Newly inserted.  */
+           cpool.append_offset (entry.cu_indices.size ());
+           for (const auto index : entry.cu_indices)
+             cpool.append_offset (index);
          }
-
-       symbol_hash_table.emplace (entry.cu_indices, cpool.size ());
-       entry.index_offset = cpool.size ();
-       cpool.append_offset (entry.cu_indices.size ());
-       for (const auto index : entry.cu_indices)
-         cpool.append_offset (index);
       }
   }