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>

2 files changed, 12 insertions, 0 deletions

diff --git a/src/mesa/drivers/dri/intel/intel_screen.c b/src/mesa/drivers/dri/intel/intel_screen.c
index 746da462ee..5c95c72732 100644
--- a/src/mesa/drivers/dri/intel/intel_screen.c
+++ b/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;
 }
 
diff --git a/src/mesa/drivers/dri/intel/intel_screen.h b/src/mesa/drivers/dri/intel/intel_screen.h
index 5863093f00..0f0b5be56d 100644
--- a/src/mesa/drivers/dri/intel/intel_screen.h
+++ b/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;