st/mesa: small optimization in swizzle_swizzle()

Usually, there's no user-specified texture swizzle so we can optimize
the swizzle_swizzle() function and skip the loop/switch.

Reviewed-by: Charmaine Lee <charmainel@vmware.com>

diff --git a/src/mesa/state_tracker/st_atom_texture.c b/src/mesa/state_tracker/st_atom_texture.c
index a6135333b3e72fe8ea42f1a5897517769f1bb56b..19df6622ef115109abbda29a7c1b0a5739b4faa9 100644 (file)
--- a/src/mesa/state_tracker/st_atom_texture.c
+++ b/src/mesa/state_tracker/st_atom_texture.c
@@ -59,6 +59,11 @@ swizzle_swizzle(unsigned swizzle1, unsigned swizzle2)
 {
    unsigned i, swz[4];
 
+   if (swizzle1 == SWIZZLE_XYZW) {
+      /* identity swizzle, no change to swizzle2 */
+      return swizzle2;
+   }
+
    for (i = 0; i < 4; i++) {
       unsigned s = GET_SWZ(swizzle1, i);
       switch (s) {