[Mesa-dev] [PATCH 4/4] i965: Orphan storage in MapBufferRange if invalidating all valid data.

[Kenneth Graunke]

We can promote INVALIDATE_RANGE_BIT to INVALIDATE_BUFFER_BIT if the
range contains the only valid data in the buffer.  This allows us to
orphan the storage, instead of doing stall avoidance blits.
---
 src/mesa/drivers/dri/i965/intel_buffer_objects.c | 7 +++++++
 1 file changed, 7 insertions(+)

I don't have any performance data for this.

diff --git a/src/mesa/drivers/dri/i965/intel_buffer_objects.c b/src/mesa/drivers/dri/i965/intel_buffer_objects.c
index 09c18db1afe..c305539e1b5 100644
--- a/src/mesa/drivers/dri/i965/intel_buffer_objects.c
+++ b/src/mesa/drivers/dri/i965/intel_buffer_objects.c
@@ -371,6 +371,13 @@ brw_map_buffer_range(struct gl_context *ctx,
       return NULL;
    }
 
+   if ((access & GL_MAP_INVALIDATE_RANGE_BIT) &&
+       (length == obj->Size ||
+        (intel_obj->valid_data_start >= offset &&
+         intel_obj->valid_data_end <= offset + length))) {
+      access |= GL_MAP_INVALIDATE_BUFFER_BIT;
+   }
+
    /* If the access is synchronized (like a normal buffer mapping), then get
     * things flushed out so the later mapping syncs appropriately through GEM.
     * If the user doesn't care about existing buffer contents and mapping would
-- 
2.13.1