Cycles: Add an AVX kernel for CPU rendering.

* AVX is available on Intel Sandy Bridge and newer and AMD Bulldozer and newer.
* We don't use dedicated AVX intrinsics yet, but gcc auto vectorization gives a 3% performance improvement for Caminandes. Tested on an i5-3570, Linux x64.
* No change for Windows yet, MSVC 2008 does not support AVX.

Reviewed by: brecht
Differential Revision: https://developer.blender.org/D216

intern/cycles/kernel/kernel_avx.cpp

@@ -0,0 +1,82 @@
+/*
+ * Copyright 2011-2013 Blender Foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License
+ */
+
+/* Optimized CPU kernel entry points. This file is compiled with AVX
+ * optimization flags and nearly all functions inlined, while kernel.cpp
+ * is compiled without for other CPU's. */
+ 
+/* SSE optimization disabled for now on 32 bit, see bug #36316 */
+#if !(defined(__GNUC__) && (defined(i386) || defined(_M_IX86)))
+#define __KERNEL_SSE2__
+#define __KERNEL_SSE3__
+#define __KERNEL_SSSE3__
+#define __KERNEL_SSE41__
+#endif
+ 
+#include "util_optimization.h"
+ 
+#ifdef WITH_CYCLES_OPTIMIZED_KERNEL_AVX
+
+#include "kernel.h"
+#include "kernel_compat_cpu.h"
+#include "kernel_math.h"
+#include "kernel_types.h"
+#include "kernel_globals.h"
+#include "kernel_film.h"
+#include "kernel_path.h"
+#include "kernel_displace.h"
+
+CCL_NAMESPACE_BEGIN
+
+/* Path Tracing */
+
+void kernel_cpu_avx_path_trace(KernelGlobals *kg, float *buffer, unsigned int *rng_state, int sample, int x, int y, int offset, int stride)
+{
+#ifdef __BRANCHED_PATH__
+	if(kernel_data.integrator.branched)
+		kernel_branched_path_trace(kg, buffer, rng_state, sample, x, y, offset, stride);
+	else
+#endif
+		kernel_path_trace(kg, buffer, rng_state, sample, x, y, offset, stride);
+}
+
+/* Film */
+
+void kernel_cpu_avx_convert_to_byte(KernelGlobals *kg, uchar4 *rgba, float *buffer, float sample_scale, int x, int y, int offset, int stride)
+{
+	kernel_film_convert_to_byte(kg, rgba, buffer, sample_scale, x, y, offset, stride);
+}
+
+void kernel_cpu_avx_convert_to_half_float(KernelGlobals *kg, uchar4 *rgba, float *buffer, float sample_scale, int x, int y, int offset, int stride)
+{
+	kernel_film_convert_to_half_float(kg, rgba, buffer, sample_scale, x, y, offset, stride);
+}
+
+/* Shader Evaluate */
+
+void kernel_cpu_avx_shader(KernelGlobals *kg, uint4 *input, float4 *output, int type, int i)
+{
+	kernel_shader_evaluate(kg, input, output, (ShaderEvalType)type, i);
+}
+
+CCL_NAMESPACE_END
+#else
+
+/* needed for some linkers in combination with scons making empty compilation unit in a library */
+void __dummy_function_cycles_avx(void);
+void __dummy_function_cycles_avx(void){}
+
+#endif