mesa: Use bitmask/ffs to iterate enabled clip planes.

Replaces an iterate and test bit in a bitmask loop by a
loop only iterating over the bits set in the bitmask.

v2: Use _mesa_bit_scan{,64} instead of open coding.
v3: Use u_bit_scan{,64} instead of _mesa_bit_scan{,64}.

Reviewed-by: Brian Paul <[email protected]>
Signed-off-by: Mathias Fröhlich <[email protected]>

1 files changed, 10 insertions, 11 deletions

diff --git a/src/mesa/main/rastpos.c b/src/mesa/main/rastpos.c
index 8f971f5b8d4..4fddad16f1b 100644
--- a/src/mesa/main/rastpos.c
+++ b/src/mesa/main/rastpos.c
@@ -91,17 +91,16 @@ viewclip_point_z( const GLfloat v[] )
 static GLuint
 userclip_point( struct gl_context *ctx, const GLfloat v[] )
 {
-   GLuint p;
-
-   for (p = 0; p < ctx->Const.MaxClipPlanes; p++) {
-      if (ctx->Transform.ClipPlanesEnabled & (1 << p)) {
-	 GLfloat dot = v[0] * ctx->Transform._ClipUserPlane[p][0]
-		     + v[1] * ctx->Transform._ClipUserPlane[p][1]
-		     + v[2] * ctx->Transform._ClipUserPlane[p][2]
-		     + v[3] * ctx->Transform._ClipUserPlane[p][3];
-         if (dot < 0.0F) {
-            return 0;
-         }
+   GLbitfield mask = ctx->Transform.ClipPlanesEnabled;
+   while (mask) {
+      const int p = u_bit_scan(&mask);
+      GLfloat dot = v[0] * ctx->Transform._ClipUserPlane[p][0]
+         + v[1] * ctx->Transform._ClipUserPlane[p][1]
+         + v[2] * ctx->Transform._ClipUserPlane[p][2]
+         + v[3] * ctx->Transform._ClipUserPlane[p][3];
+
+      if (dot < 0.0F) {
+         return 0;
       }
    }