float xfermodes (burn, dodge, softlight) in Sk8f, possibly using AVX.

Xfermode_ColorDodge_aa	10.3ms -> 7.85ms	0.76x
 Xfermode_SoftLight_aa	13.8ms -> 10.2ms	0.74x
 Xfermode_ColorBurn_aa	10.7ms -> 7.82ms	0.73x
    Xfermode_SoftLight	33.6ms -> 23.2ms	0.69x
   Xfermode_ColorDodge	  25ms -> 16.5ms	0.66x
    Xfermode_ColorBurn	26.1ms -> 16.6ms	0.63x

Ought to be no pixel diffs:
https://gold.skia.org/search2?issue=1432903002&unt=true&query=source_type%3Dgm&master=false

Incidental stuff:

I made the SkNx(T) constructors implicit to make writing math expressions simpler.
This allows us to write expressions like
  Sk4f v;
  ...
  v = v*4;
rather than
  Sk4f v;
  ...
  v = v * Sk4f(4);

As written it only works when the constant is on the right-hand side,
so expressions like `(Sk4f(1) - da)` have to stay for now.  I plan on
following up with a CL that lets those become `(1 - da)` too.

BUG=skia:4117
CQ_EXTRA_TRYBOTS=client.skia:Test-Ubuntu-GCC-GCE-CPU-AVX2-x86_64-Release-SKNX_NO_SIMD-Trybot

Review URL: https://codereview.chromium.org/1432903002

1 files changed, 17 insertions, 0 deletions

diff --git a/src/opts/SkOpts_avx.cpp b/src/opts/SkOpts_avx.cpp
new file mode 100644
index 0000000000..8802153002
--- /dev/null
+++ b/src/opts/SkOpts_avx.cpp
@@ -0,0 +1,17 @@
+/*
+ * Copyright 2015 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "SkOpts.h"
+#define SK_OPTS_NS sk_avx
+#include "SkXfermode_opts.h"
+
+namespace SkOpts {
+    void Init_avx() {
+        create_xfermode = sk_avx::create_xfermode;
+    }
+}
+