* sort.c (backtrace_qsort): Use middle element as pivot.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@208403 138bc75d-0d04-0410-961f-82ee72b054a4

1 files changed, 6 insertions, 0 deletions

diff --git a/libbacktrace/sort.c b/libbacktrace/sort.c
index 88f92314224..8c4760f8aa3 100644
--- a/libbacktrace/sort.c
+++ b/libbacktrace/sort.c
@@ -69,6 +69,12 @@ backtrace_qsort (void *basearg, size_t count, size_t size,
   if (count < 2)
     return;
 
+  /* The symbol table and DWARF tables, which is all we use this
+     routine for, tend to be roughly sorted.  Pick the middle element
+     in the array as our pivot point, so that we are more likely to
+     cut the array in half for each recursion step.  */
+  swap (base, base + (count / 2) * size, size);
+
   mid = 0;
   for (i = 1; i < count; i++)
     {