1 files changed, 28 insertions, 17 deletions

diff --git a/src/gallium/drivers/i915/i915_state.c b/src/gallium/drivers/i915/i915_state.c
index f5b60ed5942..4a1a4a04f6d 100644
--- a/src/gallium/drivers/i915/i915_state.c
+++ b/src/gallium/drivers/i915/i915_state.c
@@ -525,29 +525,40 @@ static void i915_set_constant_buffer(struct pipe_context *pipe,
                                      struct pipe_resource *buf)
 {
    struct i915_context *i915 = i915_context(pipe);
-   draw_flush(i915->draw);
+   unsigned new_num = 0;
+   boolean diff = TRUE;
 
-   /* Make a copy of shader constants.
-    * During fragment program translation we may add additional
-    * constants to the array.
-    *
-    * We want to consider the situation where some user constants
-    * (ex: a material color) may change frequently but the shader program
-    * stays the same.  In that case we should only be updating the first
-    * N constants, leaving any extras from shader translation alone.
-    */
+
+   /* XXX don't support geom shaders now */
+   if (shader == PIPE_SHADER_GEOMETRY)
+      return;
+
+   /* if we have a new buffer compare it with the old one */
    if (buf) {
       struct i915_buffer *ir = i915_buffer(buf);
-      memcpy(i915->current.constants[shader], ir->data, ir->b.b.width0);
-      i915->current.num_user_constants[shader] = (ir->b.b.width0 /
-						  4 * sizeof(float));
-   }
-   else {
-      i915->current.num_user_constants[shader] = 0;
+      struct pipe_resource *old_buf = i915->constants[shader];
+      struct i915_buffer *old = old_buf ? i915_buffer(old_buf) : NULL;
+
+      new_num = ir->b.b.width0 / 4 * sizeof(float);
+
+      if (old && new_num != i915->current.num_user_constants[shader])
+         diff = memcmp(old->data, ir->data, ir->b.b.width0);
+   } else {
+      diff = i915->current.num_user_constants[shader] != 0;
    }
 
+   /*
+    * flush before updateing the state.
+    * XXX: looks like its okay to skip the flush for vertex cbufs
+    */
+   if (diff && shader == PIPE_SHADER_FRAGMENT)
+      draw_flush(i915->draw);
+
+   pipe_resource_reference(&i915->constants[shader], buf);
+   i915->current.num_user_constants[shader] = new_num;
 
-   i915->dirty |= I915_NEW_CONSTANTS;
+   if (diff)
+      i915->dirty |= shader == PIPE_SHADER_VERTEX ? I915_NEW_VS_CONSTANTS : I915_NEW_FS_CONSTANTS;
 }