[PATCH 3/4] libstdc++/regex: Reduce space usage of _M_rep_once_more [PR86164]

[Patrick Palka]

If __rep_count.second is already 1 we don't need to add a cleanup frame
to restore it to 1.

This reduces the maximum size of the __frames stack by 12% for
regex_match(string(200000, 'a'), "(a|b|c)*").

	PR libstdc++/86164

libstdc++-v3/ChangeLog:

	* include/bits/regex_executor.tcc: Only add a
	restore_rep_count_val frame when necessary.
---
 libstdc++-v3/include/bits/regex_executor.tcc | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/libstdc++-v3/include/bits/regex_executor.tcc b/libstdc++-v3/include/bits/regex_executor.tcc
index 0e78cb2e2c87..ca631fb77ce9 100644
--- a/libstdc++-v3/include/bits/regex_executor.tcc
+++ b/libstdc++-v3/include/bits/regex_executor.tcc
@@ -181,12 +181,15 @@ namespace __detail
       auto& __rep_count = _M_rep_count[__i];
       if (__rep_count.second == 0 || __rep_count.first != _M_current)
 	{
-	  __frames.emplace_back(_S_fopcode_restore_rep_count_val,
-				__i, __rep_count.second);
+	  if (__rep_count.second != 1)
+	    {
+	      __frames.emplace_back(_S_fopcode_restore_rep_count_val,
+				    __i, __rep_count.second);
+	      __rep_count.second = 1;
+	    }
 	  __frames.emplace_back(_S_fopcode_restore_rep_count_pos,
 				__i, __rep_count.first);
 	  __rep_count.first = _M_current;
-	  __rep_count.second = 1;
 	  __frames.emplace_back(_S_fopcode_next, __state._M_alt);
 	}
       else
-- 
2.53.0.rc0.25.gb5c409c40f