With previous behaviour, multiple mapping symbols within the same
function would result in all the mapping symbols being searched.
This could slow down disassembly dramatically.

Multiple mapping symbols within a function can be a result of encoding
instructions as data, like sometimes seen in random instruction
generators.

opcodes/ChangeLog:

        * riscv-dis.c (riscv_search_mapping_symbol): Use last mapping
          symbol if it exists.

Note for reviewers:
I don't see why the previous check 'n >= last_map_symbol exists'. Why do we force starting from the start of the function if the last mapping symbol was found after it? If I'm missing something, please let me know!

---
 opcodes/riscv-dis.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/opcodes/riscv-dis.c b/opcodes/riscv-dis.c
index 684098d386a..24286702dd3 100644
--- a/opcodes/riscv-dis.c
+++ b/opcodes/riscv-dis.c
@@ -1076,11 +1076,12 @@ riscv_search_mapping_symbol (bfd_vma memaddr,
   from_last_map_symbol = (last_map_symbol >= 0
                          && info->stop_offset == last_stop_offset);

-  /* Start scanning at the start of the function, or wherever
-     we finished last time.  */
-  n = info->symtab_pos + 1;
-  if (from_last_map_symbol && n >= last_map_symbol)
+  /* Start scanning from wherever we finished last time, or the start
+     of the function.  */
+  if (from_last_map_symbol)
     n = last_map_symbol;
+  else
+    n = info->symtab_pos + 1;

   /* Find the suitable mapping symbol to dump.  */
   for (; n < info->symtab_size; n++)
--
2.34.1