FCurve: optimize search from an RNA path + index.

By checking the index value first instead of a full fledge string
comparision in `BKE_fcurve_find`, we can make that code significatly
faster (from about 10% in a Heist production file to over 45% in a
heavily animated test file).

While this code was already very fast (a few microseconds per call
typically), it gets called a lot from the UI (several hundreds of time
per refresh), among other things.

NOTE: the `UNLIKELY` hint is responsible for 25% to 30% of the
speed improvement.

1 files changed, 4 insertions, 5 deletions

diff --git a/source/blender/blenkernel/intern/fcurve.c b/source/blender/blenkernel/intern/fcurve.c
index 48ba6a851d2..0203620df84 100644
--- a/source/blender/blenkernel/intern/fcurve.c
+++ b/source/blender/blenkernel/intern/fcurve.c
@@ -256,12 +256,11 @@ FCurve *BKE_fcurve_find(ListBase *list, const char rna_path[], const int array_i
 
   /* Check paths of curves, then array indices... */
   for (fcu = list->first; fcu; fcu = fcu->next) {
+    /* Check indices first, much cheaper than a string comparison. */
     /* Simple string-compare (this assumes that they have the same root...) */
-    if (fcu->rna_path && STREQ(fcu->rna_path, rna_path)) {
-      /* Now check indices. */
-      if (fcu->array_index == array_index) {
-        return fcu;
-      }
+    if (UNLIKELY(fcu->array_index == array_index && fcu->rna_path &&
+                 fcu->rna_path[0] == rna_path[0] && STREQ(fcu->rna_path, rna_path))) {
+      return fcu;
     }
   }