[Mesa-dev] [PATCH 12/29] tnl: Use bitmask/ffs to iterate enabled lights

[Mathias.Froehlich at gmx.net]

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

Replaces loops that iterate all lights and test
which of them is enabled by a loop only iterating over
the bits set in the enabled bitmask.
---
 src/mesa/tnl/t_vb_light.c    |  2 +-
 src/mesa/tnl/t_vb_lighttmp.h | 27 ++++++++++++++++++++-------
 2 files changed, 21 insertions(+), 8 deletions(-)

diff --git a/src/mesa/tnl/t_vb_light.c b/src/mesa/tnl/t_vb_light.c
index 029265a..0cdb925 100644
--- a/src/mesa/tnl/t_vb_light.c
+++ b/src/mesa/tnl/t_vb_light.c
@@ -394,7 +394,7 @@ static void validate_lighting( struct gl_context *ctx,
 	 tab = _tnl_light_tab;
    }
    else {
-      if (ctx->Light.EnabledList.next == ctx->Light.EnabledList.prev)
+      if (_mesa_bitcount(ctx->Light._EnabledLights) == 1)
 	 tab = _tnl_light_fast_single_tab;
       else
 	 tab = _tnl_light_fast_tab;
diff --git a/src/mesa/tnl/t_vb_lighttmp.h b/src/mesa/tnl/t_vb_lighttmp.h
index 3aebcd4..191f65c 100644
--- a/src/mesa/tnl/t_vb_lighttmp.h
+++ b/src/mesa/tnl/t_vb_lighttmp.h
@@ -87,7 +87,7 @@ static void TAG(light_rgba_spec)( struct gl_context *ctx,
 
    for (j = 0; j < nr; j++,STRIDE_F(vertex,vstride),STRIDE_F(normal,nstride)) {
       GLfloat sum[2][3], spec[2][3];
-      struct gl_light *light;
+      GLbitfield mask;
 
 #if IDX & LIGHT_MATERIAL
       update_materials( ctx, store );
@@ -106,7 +106,10 @@ static void TAG(light_rgba_spec)( struct gl_context *ctx,
 #endif
 
       /* Add contribution from each enabled light source */
-      foreach (light, &ctx->Light.EnabledList) {
+      mask = ctx->Light._EnabledLights;
+      while (mask) {
+         int l = ffs(mask) - 1;
+         struct gl_light *light = &ctx->Light.Light[l];
 	 GLfloat n_dot_h;
 	 GLfloat correction;
 	 GLint side;
@@ -115,6 +118,7 @@ static void TAG(light_rgba_spec)( struct gl_context *ctx,
 	 GLfloat VP[3];          /* unit vector from vertex to light */
 	 GLfloat n_dot_VP;       /* n dot VP */
 	 GLfloat *h;
+         mask ^= (1u << l);
 
 	 /* compute VP and attenuation */
 	 if (!(light->_Flags & LIGHT_POSITIONAL)) {
@@ -265,7 +269,7 @@ static void TAG(light_rgba)( struct gl_context *ctx,
 
    for (j = 0; j < nr; j++,STRIDE_F(vertex,vstride),STRIDE_F(normal,nstride)) {
       GLfloat sum[2][3];
-      struct gl_light *light;
+      GLbitfield mask;
 
 #if IDX & LIGHT_MATERIAL
       update_materials( ctx, store );
@@ -282,7 +286,10 @@ static void TAG(light_rgba)( struct gl_context *ctx,
 #endif
 
       /* Add contribution from each enabled light source */
-      foreach (light, &ctx->Light.EnabledList) {
+      mask = ctx->Light._EnabledLights;
+      while (mask) {
+         int l = ffs(mask) - 1;
+         struct gl_light *light = &ctx->Light.Light[l];
 	 GLfloat n_dot_h;
 	 GLfloat correction;
 	 GLint side;
@@ -291,6 +298,7 @@ static void TAG(light_rgba)( struct gl_context *ctx,
 	 GLfloat VP[3];          /* unit vector from vertex to light */
 	 GLfloat n_dot_VP;       /* n dot VP */
 	 GLfloat *h;
+         mask ^= (1u << l);
 
 	 /* compute VP and attenuation */
 	 if (!(light->_Flags & LIGHT_POSITIONAL)) {
@@ -417,7 +425,8 @@ static void TAG(light_fast_rgba_single)( struct gl_context *ctx,
 #if IDX & LIGHT_TWOSIDE
    GLfloat (*Bcolor)[4] = (GLfloat (*)[4]) store->LitColor[1].data;
 #endif
-   const struct gl_light *light = ctx->Light.EnabledList.next;
+   const struct gl_light *light =
+      &ctx->Light.Light[ffs(ctx->Light._EnabledLights) - 1];
    GLuint j = 0;
    GLfloat base[2][4];
 #if IDX & LIGHT_MATERIAL
@@ -528,7 +537,6 @@ static void TAG(light_fast_rgba)( struct gl_context *ctx,
 #else
    const GLuint nr = VB->AttribPtr[_TNL_ATTRIB_NORMAL]->count;
 #endif
-   const struct gl_light *light;
 
 #ifdef TRACE
    fprintf(stderr, "%s %d\n", __func__, nr );
@@ -556,6 +564,7 @@ static void TAG(light_fast_rgba)( struct gl_context *ctx,
    for (j = 0; j < nr; j++, STRIDE_F(normal,nstride)) {
 
       GLfloat sum[2][3];
+      GLbitfield mask;
 
 #if IDX & LIGHT_MATERIAL
       update_materials( ctx, store );
@@ -572,8 +581,12 @@ static void TAG(light_fast_rgba)( struct gl_context *ctx,
       COPY_3V(sum[1], ctx->Light._BaseColor[1]);
 #endif
 
-      foreach (light, &ctx->Light.EnabledList) {
+      mask = ctx->Light._EnabledLights;
+      while (mask) {
+         int l = ffs(mask) - 1;
+         const struct gl_light *light = &ctx->Light.Light[l];
 	 GLfloat n_dot_h, n_dot_VP, spec;
+         mask ^= (1u << l);
 
 	 ACC_3V(sum[0], light->_MatAmbient[0]);
 #if IDX & LIGHT_TWOSIDE
-- 
2.5.5