[gtk+/wip/otte/shader: 21/23] gskspvwriter: Add optimization for access chain

[Benjamin Otte <otte src gnome org>]

commit 1a7f9dd96f401d3569d36561d8aa9d6b70e5d9d4
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 0aa188e..052d96e 100644
--- a/gsk/gskspvwriter.c
+++ b/gsk/gskspvwriter.c
@@ -744,6 +744,27 @@ 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);