[gtk+/wip/otte/shader: 113/127] gskspvwriter: Add optimization for access chain

[Benjamin Otte <otte src gnome org>]

commit 7fb5324699afee588a17e90992791b8d481eeb13
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 b971d64..fb1459b 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);