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 <brianp@vmware.com>
Signed-off-by: Mathias Fröhlich <Mathias.Froehlich@web.de>

1 files changed, 32 insertions, 33 deletions

diff --git a/src/mesa/tnl/t_vb_program.c b/src/mesa/tnl/t_vb_program.c
index 21fd6cd..55c44d1 100644
--- a/src/mesa/tnl/t_vb_program.c
+++ b/src/mesa/tnl/t_vb_program.c
@@ -40,6 +40,7 @@
 #include "program/prog_statevars.h"
 #include "program/prog_execute.h"
 #include "swrast/s_context.h"
+#include "util/bitscan.h"
 
 #include "tnl/tnl.h"
 #include "tnl/t_context.h"
@@ -84,40 +85,38 @@ userclip( struct gl_context *ctx,
           GLubyte *clipormask,
           GLubyte *clipandmask )
 {
-   GLuint p;
-
-   for (p = 0; p < ctx->Const.MaxClipPlanes; p++) {
-      if (ctx->Transform.ClipPlanesEnabled & (1 << p)) {
-	 GLuint nr, i;
-	 const GLfloat a = ctx->Transform._ClipUserPlane[p][0];
-	 const GLfloat b = ctx->Transform._ClipUserPlane[p][1];
-	 const GLfloat c = ctx->Transform._ClipUserPlane[p][2];
-	 const GLfloat d = ctx->Transform._ClipUserPlane[p][3];
-         GLfloat *coord = (GLfloat *)clip->data;
-         GLuint stride = clip->stride;
-         GLuint count = clip->count;
-
-	 for (nr = 0, i = 0 ; i < count ; i++) {
-	    GLfloat dp = (coord[0] * a + 
-			  coord[1] * b +
-			  coord[2] * c +
-			  coord[3] * d);
-
-	    if (dp < 0) {
-	       nr++;
-	       clipmask[i] |= CLIP_USER_BIT;
-	    }
-
-	    STRIDE_F(coord, stride);
-	 }
+   GLbitfield mask = ctx->Transform.ClipPlanesEnabled;
+   while (mask) {
+      const int p = u_bit_scan(&mask);
+      GLuint nr, i;
+      const GLfloat a = ctx->Transform._ClipUserPlane[p][0];
+      const GLfloat b = ctx->Transform._ClipUserPlane[p][1];
+      const GLfloat c = ctx->Transform._ClipUserPlane[p][2];
+      const GLfloat d = ctx->Transform._ClipUserPlane[p][3];
+      GLfloat *coord = (GLfloat *)clip->data;
+      GLuint stride = clip->stride;
+      GLuint count = clip->count;
+
+      for (nr = 0, i = 0 ; i < count ; i++) {
+         GLfloat dp = (coord[0] * a +
+                       coord[1] * b +
+                       coord[2] * c +
+                       coord[3] * d);
+
+         if (dp < 0) {
+            nr++;
+            clipmask[i] |= CLIP_USER_BIT;
+         }
+
+         STRIDE_F(coord, stride);
+      }
 
-	 if (nr > 0) {
-	    *clipormask |= CLIP_USER_BIT;
-	    if (nr == count) {
-	       *clipandmask |= CLIP_USER_BIT;
-	       return;
-	    }
-	 }
+      if (nr > 0) {
+         *clipormask |= CLIP_USER_BIT;
+         if (nr == count) {
+            *clipandmask |= CLIP_USER_BIT;
+            return;
+         }
       }
    }
 }