Optimize comparisions in file sort functions.

Use three-valued comparison macro from gnulib
efa15594e17fc20827dba66414fb391e99905394.

Signed-off-by: Andrew Borodin <aborodin@vmail.ru>

lib/util.h

@@ -38,6 +38,22 @@
 #define MC_PIPE_ERROR_CREATE_PIPE_STREAM -4
 #define MC_PIPE_ERROR_READ -5
 
+/* gnulib efa15594e17fc20827dba66414fb391e99905394
+
+ *_GL_CMP (n1, n2) performs a three-valued comparison on n1 vs. n2.
+ *  It returns
+ *    1  if n1 > n2
+ *    0  if n1 == n2
+ *    -1 if n1 < n2
+ *  The native code   (n1 > n2 ? 1 : n1 < n2 ? -1 : 0)  produces a conditional
+ *  jump with nearly all GCC versions up to GCC 10.
+ *  This variant      (n1 < n2 ? -1 : n1 > n2)  produces a conditional with many
+ *  GCC versions up to GCC 9.
+ *  The better code  (n1 > n2) - (n1 < n2)  from Hacker's Delight para 2-9
+ *  avoids conditional jumps in all GCC versions >= 3.4.
+ */
+#define _GL_CMP(n1, n2) (((n1) > (n2)) - ((n1) < (n2)))
+
 /*** enums ***************************************************************************************/
 
 /* Pathname canonicalization */

src/filemanager/dir.c

@@ -393,7 +393,7 @@ sort_time (file_entry_t * a, file_entry_t * b)
 
     if (ad == bd || panels_options.mix_all_files)
     {
-        int result = a->st.st_mtime < b->st.st_mtime ? -1 : a->st.st_mtime > b->st.st_mtime;
+        int result = _GL_CMP (a->st.st_mtime, b->st.st_mtime);
 
         if (result != 0)
             return result * reverse;
@@ -414,7 +414,7 @@ sort_ctime (file_entry_t * a, file_entry_t * b)
 
     if (ad == bd || panels_options.mix_all_files)
     {
-        int result = a->st.st_ctime < b->st.st_ctime ? -1 : a->st.st_ctime > b->st.st_ctime;
+        int result = _GL_CMP (a->st.st_ctime, b->st.st_ctime);
 
         if (result != 0)
             return result * reverse;
@@ -435,7 +435,7 @@ sort_atime (file_entry_t * a, file_entry_t * b)
 
     if (ad == bd || panels_options.mix_all_files)
     {
-        int result = a->st.st_atime < b->st.st_atime ? -1 : a->st.st_atime > b->st.st_atime;
+        int result = _GL_CMP (a->st.st_atime, b->st.st_atime);
 
         if (result != 0)
             return result * reverse;
@@ -470,7 +470,7 @@ sort_size (file_entry_t * a, file_entry_t * b)
 
     if (ad == bd || panels_options.mix_all_files)
     {
-        int result = a->st.st_size < b->st.st_size ? -1 : a->st.st_size > b->st.st_size;
+        int result = _GL_CMP (a->st.st_size, b->st.st_size);
 
         if (result != 0)
             return result * reverse;