[gcc r13-1689] libcpp: Avoid pessimizing std::move [PR106272]

[gcc r13-1689] libcpp: Avoid pessimizing std::move [PR106272]

[Marek Polacek]

https://gcc.gnu.org/g:86a15b266a7284f3aa1b12494a475f31416b981d

commit r13-1689-g86a15b266a7284f3aa1b12494a475f31416b981d
Author: Marek Polacek <polacek@redhat.com>
Date:   Tue Jul 12 20:18:56 2022 -0400

    libcpp: Avoid pessimizing std::move [PR106272]
    
    std::move in a return statement can prevent the NRVO:
    <https://developers.redhat.com/blog/2019/04/12/understanding-when-not-to-stdmove-in-c>
    
    PR106272 reports that we have two such cases in class label_text's
    member functions.  We have -Wpessimizing-move that's supposed to detect
    problematic std::move uses, but in this case it didn't trigger.  I've filed
    PR106276 to track that.
    
            PR preprocessor/106272
    
    libcpp/ChangeLog:
    
            * include/line-map.h (class label_text): Don't std::move in a return
            statement.

Diff:
---
 libcpp/include/line-map.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/libcpp/include/line-map.h b/libcpp/include/line-map.h
index c6379ce25b8..c434a246b13 100644
--- a/libcpp/include/line-map.h
+++ b/libcpp/include/line-map.h
@@ -1873,13 +1873,13 @@ public:
      longer-lived owner.  */
   static label_text borrow (const char *buffer)
   {
-    return std::move (label_text (const_cast <char *> (buffer), false));
+    return label_text (const_cast <char *> (buffer), false);
   }
 
   /* Create a label_text instance that takes ownership of BUFFER.  */
   static label_text take (char *buffer)
   {
-    return std::move (label_text (buffer, true));
+    return label_text (buffer, true);
   }
 
   /* Take ownership of the buffer, copying if necessary.  */