[Mesa-dev] [v3 4/5] i965: Add helper for lossless compression support

[Topi Pohjolainen]

v2: Check explicitly against base type of GL_FLOAT instead of
    using _mesa_is_format_integer_color(). Otherwise we miss
    GL_UNSIGNED_NORMALIZED.

Signed-off-by: Topi Pohjolainen <topi.pohjolainen at intel.com>
---
 src/mesa/drivers/dri/i965/intel_mipmap_tree.c | 22 ++++++++++++++++++++++
 src/mesa/drivers/dri/i965/intel_mipmap_tree.h |  3 +++
 2 files changed, 25 insertions(+)

diff --git a/src/mesa/drivers/dri/i965/intel_mipmap_tree.c b/src/mesa/drivers/dri/i965/intel_mipmap_tree.c
index 6c233d8..e9fbeeb 100644
--- a/src/mesa/drivers/dri/i965/intel_mipmap_tree.c
+++ b/src/mesa/drivers/dri/i965/intel_mipmap_tree.c
@@ -294,6 +294,28 @@ intel_miptree_is_lossless_compressed(const struct brw_context *brw,
    return mt->num_samples <= 1;
 }
 
+bool
+intel_miptree_supports_lossless_compressed(mesa_format format)
+{
+   /* For now compression is only enabled for integer formats even though
+    * there exist supported floating point formats also. This is a heuristic
+    * decision based on current public benchmarks. In none of the cases these
+    * formats provided any improvement but a few cases were seen to regress.
+    * Hence these are left to to be enabled in the future when they are known
+    * to improve things.
+    */
+   if (_mesa_get_format_datatype(format) == GL_FLOAT)
+      return false;
+
+   /* In principle, fast clear mechanism and lossless compression go hand in
+    * hand. However, fast clear can be also used to clear srgb surfaces by
+    * using equivalent linear format. This trick, however, can't be extended
+    * to be used with lossless compression and therefore a check is needed to
+    * see if the format really is linear.
+    */
+   return _mesa_get_srgb_format_linear(format) == format;
+}
+
 /**
  * Determine depth format corresponding to a depth+stencil format,
  * for separate stencil.
diff --git a/src/mesa/drivers/dri/i965/intel_mipmap_tree.h b/src/mesa/drivers/dri/i965/intel_mipmap_tree.h
index 7cdfb37..6ce9f75 100644
--- a/src/mesa/drivers/dri/i965/intel_mipmap_tree.h
+++ b/src/mesa/drivers/dri/i965/intel_mipmap_tree.h
@@ -679,6 +679,9 @@ intel_miptree_supports_non_msrt_fast_clear(struct brw_context *brw,
                                            const struct intel_mipmap_tree *mt);
 
 bool
+intel_miptree_supports_lossless_compressed(mesa_format format);
+
+bool
 intel_miptree_alloc_non_msrt_mcs(struct brw_context *brw,
                                  struct intel_mipmap_tree *mt);
 
-- 
2.5.0