From: Piotr Trojanek <troja...@adacore.com>
We save/restore visibility by setting the Is_Immediately_Visible flag
and appending entities to / removing them from the tail of an element
list.
However, the Is_Immediately_Visible flag can be restored in any order,
while the element list is singly-linked and removal from the tail is
inefficient. This change removes a performance hot spot, which accounted
for up to 10% of compilation time of complex applications (e.g. QGen),
at least as measured on GNAT built with profiling support.
gcc/ada/
* sem_ch8.adb (Restore_Scope_Stack): Remove elements from the head
and not the tail of an element list.
Tested on x86_64-pc-linux-gnu, committed on master.
---
gcc/ada/sem_ch8.adb | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/gcc/ada/sem_ch8.adb b/gcc/ada/sem_ch8.adb
index c4812e2a563..e555de915e6 100644
--- a/gcc/ada/sem_ch8.adb
+++ b/gcc/ada/sem_ch8.adb
@@ -9717,10 +9717,10 @@ package body Sem_Ch8 is
-- we saved (we use Remove, since this list will not be used again).
loop
- Elmt := Last_Elmt (List);
+ Elmt := First_Elmt (List);
exit when Elmt = No_Elmt;
Set_Is_Immediately_Visible (Node (Elmt));
- Remove_Last_Elmt (List);
+ Remove_Elmt (List, Elmt);
end loop;
-- Restore use clauses
--
2.34.1
