[gtk+/wip/otte/shader: 14/21] gskslexpression: Add spv writing optimization

[Benjamin Otte <otte src gnome org>]

commit a463947b32a5af595f90241c304df232211d1d8e
Author: Benjamin Otte <otte redhat com>
Date:   Tue Oct 10 04:02:08 2017 +0200

    gskslexpression: Add spv writing optimization
    
    For assignable expressions, we can always use an access chain to query
    the value. Access chains are not just faster, they also contain lots of
    optimizations for merging swizzles and whatnot.

 gsk/gskslexpression.c |   11 +++++++++++
 1 files changed, 11 insertions(+), 0 deletions(-)
---
diff --git a/gsk/gskslexpression.c b/gsk/gskslexpression.c
index 428048a..47d9232 100644
--- a/gsk/gskslexpression.c
+++ b/gsk/gskslexpression.c
@@ -2650,5 +2650,16 @@ guint32
 gsk_sl_expression_write_spv (const GskSlExpression *expression,
                              GskSpvWriter          *writer)
 {
+  if (gsk_sl_expression_is_assignable (expression, NULL))
+    {
+      GskSpvAccessChain *chain;
+      guint result_id;
+      
+      chain = gsk_sl_expression_get_spv_access_chain (expression, writer);
+      result_id = gsk_spv_access_chain_load (chain);
+      gsk_spv_access_chain_free (chain);
+      return result_id;
+    }
+
   return expression->class->write_spv (expression, writer);
 }