i965: Use negative relocation deltas to minimse vertex uploads

With relaxed relocation checking in the kernel, we can specify a
negative delta (i.e. pointing outside of the target bo) in order to fake
a range in a large buffer. We only then need to upload the elements used
and adjust the buffer offset such that they correspond with the indices
used in the DrawArrays.

(Depends on libdrm 0209428b3918c4336018da9293cdcbf7f8fedfb6)

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

src/mesa/drivers/dri/i965/brw_context.h

@@ -460,7 +460,7 @@ struct brw_context
    GLboolean has_negative_rhw_bug;
    GLboolean has_aa_line_parameters;
    GLboolean has_pln;
-;
+
    struct {
       struct brw_state_flags dirty;
 

src/mesa/drivers/dri/i965/brw_draw_upload.c

@@ -278,7 +278,7 @@ static void brw_prepare_vertices(struct brw_context *brw)
    GLuint interleaved = 0, total_size = 0;
    unsigned int min_index = brw->vb.min_index;
    unsigned int max_index = brw->vb.max_index;
-   int i, j;
+   int delta, i, j;
 
    struct brw_vertex_element *upload[VERT_ATTRIB_MAX];
    GLuint nr_uploads = 0;
@@ -401,21 +401,25 @@ static void brw_prepare_vertices(struct brw_context *brw)
     * only the used elements [min_index, max_index] so long as we adjust all
     * the values used in the 3DPRIMITIVE i.e. by setting the vertex bias.
     */
+   brw->vb.start_vertex_bias = 0;
+   delta = min_index;
    if (nr_uploads == brw->vb.nr_enabled) {
-      brw->vb.start_vertex_bias = min_index;
-   } else {
-      brw->vb.start_vertex_bias = 0;
-      min_index = 0;
+      brw->vb.start_vertex_bias = -delta;
+      delta = 0;
    }
+   if (delta && !brw->intel.intelScreen->relaxed_relocations)
+      min_index = delta = 0;
 
    /* Handle any arrays to be uploaded. */
    if (nr_uploads > 1) {
       if (interleaved && interleaved <= 2*total_size) {
+	 struct brw_vertex_buffer *buffer = &brw->vb.buffers[j];
 	 /* All uploads are interleaved, so upload the arrays together as
 	  * interleaved.  First, upload the contents and set up upload[0].
 	  */
 	 copy_array_to_vbo_array(brw, upload[0], min_index, max_index,
-				 &brw->vb.buffers[j], interleaved);
+				 buffer, interleaved);
+	 buffer->offset -= delta * interleaved;
 
 	 for (i = 0; i < nr_uploads; i++) {
 	    /* Then, just point upload[i] at upload[0]'s buffer. */
@@ -462,14 +466,17 @@ static void brw_prepare_vertices(struct brw_context *brw)
 	 intel_upload_unmap(&brw->intel, map, offset * count, offset,
 			    &buffer->bo, &buffer->offset);
 	 buffer->stride = offset;
+	 buffer->offset -= delta * offset;
 
 	 nr_uploads = 0;
       }
    }
    /* Upload non-interleaved arrays */
    for (i = 0; i < nr_uploads; i++) {
+      struct brw_vertex_buffer *buffer = &brw->vb.buffers[j];
       copy_array_to_vbo_array(brw, upload[i], min_index, max_index,
-			      &brw->vb.buffers[j], upload[i]->element_size);
+			      buffer, upload[i]->element_size);
+      buffer->offset -= delta * buffer->stride;
       upload[i]->buffer = j++;
       upload[i]->offset = 0;
    }

src/mesa/drivers/dri/intel/intel_screen.c

@@ -309,6 +309,13 @@ intel_get_param(__DRIscreen *psp, int param, int *value)
    return GL_TRUE;
 }
 
+static GLboolean
+intel_get_boolean(__DRIscreen *psp, int param)
+{
+   int value = 0;
+   return intel_get_param(psp, param, &value) && value;
+}
+
 static void
 nop_callback(GLuint key, void *data, void *userData)
 {
@@ -482,6 +489,10 @@ intel_init_bufmgr(struct intel_screen *intelScreen)
 
    intelScreen->named_regions = _mesa_NewHashTable();
 
+   intelScreen->relaxed_relocations = 0;
+   intelScreen->relaxed_relocations |=
+      intel_get_boolean(spriv, I915_PARAM_HAS_RELAXED_DELTA) << 0;
+
    return GL_TRUE;
 }
 

src/mesa/drivers/dri/intel/intel_screen.h

@@ -43,6 +43,7 @@ struct intel_screen
    __DRIscreen *driScrnPriv;
 
    GLboolean no_hw;
+   GLuint relaxed_relocations;
 
    GLboolean no_vbo;
    dri_bufmgr *bufmgr;