[gtk+/wip/otte/shader: 113/156] gskspvwriter: Add optimization for access chain

[Benjamin Otte <otte src gnome org>]

commit 3c5cd300b4cdd83059c07984e8891058180b5576
Author: Benjamin Otte <otte redhat com>
Date:   Tue Oct 10 03:55:45 2017 +0200

    gskspvwriter: Add optimization for access chain
    
    A single swizzle can be reduced to an access chain lookup. This is
    especially useful during assignments, because it means we don't need to
    load the whole vector and OpVectorShuffle it.

 gsk/gskspvwriter.c |   21 +++++++++++++++++++++
 1 files changed, 21 insertions(+), 0 deletions(-)
---
diff --git a/gsk/gskspvwriter.c b/gsk/gskspvwriter.c
index 83afefb..64a986a 100644
--- a/gsk/gskspvwriter.c
+++ b/gsk/gskspvwriter.c
@@ -749,6 +749,27 @@ gsk_spv_access_chain_swizzle (GskSpvAccessChain *chain,
   guint tmp[4];
   guint i;
 
+  if (length == 1)
+    {
+      GskSlValue *value;
+      guint32 new_index;
+
+      if (chain->swizzle_length != 0)
+        new_index = chain->swizzle[indexes[0]];
+      else
+        new_index = indexes[0];
+      chain->swizzle_length = 0;
+
+      value = gsk_sl_value_new_for_data (gsk_sl_type_get_scalar (GSK_SL_UINT),
+                                         &new_index,
+                                         NULL, NULL);
+      gsk_spv_access_chain_add_index (chain,
+                                      gsk_sl_type_get_index_type (chain->type),
+                                      gsk_spv_writer_get_id_for_value (chain->writer, value));
+      gsk_sl_value_free (value);
+      return;
+    }
+
   if (chain->swizzle_length != 0)
     {
       g_assert (length <= chain->swizzle_length);