[Mesa-dev] [PATCH 11/29] mesa: Use bitmask/ffs to iterate enabled lights for building ff shader keys.

[Mathias.Froehlich at gmx.net]

From: Mathias Fröhlich <mathias.froehlich at web.de>

Replaces a loop that iterates all lights and test
which of them is enabled by a loop only iterating over
the bits set in the enabled bitmask.

Signed-off-by: Mathias Fröhlich <Mathias.Froehlich at web.de>
---
 src/mesa/main/ffvertex_prog.c | 28 +++++++++++++++-------------
 1 file changed, 15 insertions(+), 13 deletions(-)

diff --git a/src/mesa/main/ffvertex_prog.c b/src/mesa/main/ffvertex_prog.c
index ecdd018..bcfc999 100644
--- a/src/mesa/main/ffvertex_prog.c
+++ b/src/mesa/main/ffvertex_prog.c
@@ -148,6 +148,7 @@ static GLboolean check_active_shininess( struct gl_context *ctx,
 static void make_state_key( struct gl_context *ctx, struct state_key *key )
 {
    const struct gl_fragment_program *fp;
+   GLbitfield mask;
    GLuint i;
 
    memset(key, 0, sizeof(struct state_key));
@@ -183,23 +184,24 @@ static void make_state_key( struct gl_context *ctx, struct state_key *key )
 	 key->light_color_material_mask = ctx->Light._ColorMaterialBitmask;
       }
 
-      for (i = 0; i < MAX_LIGHTS; i++) {
-	 struct gl_light *light = &ctx->Light.Light[i];
+      mask = ctx->Light._EnabledLights;
+      while (mask) {
+         const int i = ffs(mask) - 1;
+         struct gl_light *light = &ctx->Light.Light[i];
+         mask ^= (1u << i);
 
-	 if (light->Enabled) {
-	    key->unit[i].light_enabled = 1;
+         key->unit[i].light_enabled = 1;
 
-	    if (light->EyePosition[3] == 0.0F)
-	       key->unit[i].light_eyepos3_is_zero = 1;
+         if (light->EyePosition[3] == 0.0F)
+            key->unit[i].light_eyepos3_is_zero = 1;
 
-	    if (light->SpotCutoff == 180.0F)
-	       key->unit[i].light_spotcutoff_is_180 = 1;
+         if (light->SpotCutoff == 180.0F)
+            key->unit[i].light_spotcutoff_is_180 = 1;
 
-	    if (light->ConstantAttenuation != 1.0F ||
-		light->LinearAttenuation != 0.0F ||
-		light->QuadraticAttenuation != 0.0F)
-	       key->unit[i].light_attenuated = 1;
-	 }
+         if (light->ConstantAttenuation != 1.0F ||
+             light->LinearAttenuation != 0.0F ||
+             light->QuadraticAttenuation != 0.0F)
+            key->unit[i].light_attenuated = 1;
       }
 
       if (check_active_shininess(ctx, key, 0)) {
-- 
2.5.5