Half float neon port, enable O2 for neon, and denormal test.

BUILD.gn

 # Copyright 2014 The LibYuv Project Authors. All rights reserved.
 #
 # Use of this source code is governed by a BSD-style license
 # that can be found in the LICENSE file in the root of the source
 # tree. An additional intellectual property rights grant can be found
 # in the file PATENTS. All contributing project authors may
 # be found in the AUTHORS file in the root of the source tree.
 
 import("libyuv.gni")
 import("//testing/test.gni")
@@ skipping 104 matching lines @@
     deps += [ ":libyuv_msa" ]
   }
 
   # Always enable optimization for Release and NaCl builds (to workaround
   # crbug.com/538243).
   if (!is_debug || is_nacl) {
     configs -= [ "//build/config/compiler:default_optimization" ]
     # Enable optimize for speed (-O2) over size (-Os).
     configs += [ "//build/config/compiler:optimize_max" ]
   }
+
+  # To enable AVX2 or other cpu optimization, pass flag here
+  #  cflags = [ "-mavx2" ]
+
 }
 
 if (libyuv_use_neon) {
   static_library("libyuv_neon") {
     sources = [
       # ARM Source Files
       "source/compare_neon.cc",
       "source/compare_neon64.cc",
       "source/rotate_neon.cc",
       "source/rotate_neon64.cc",
       "source/row_neon.cc",
       "source/row_neon64.cc",
       "source/scale_neon.cc",
       "source/scale_neon64.cc",
     ]
 
     public_configs = [ ":libyuv_config" ]
 
+    # Always enable optimization for Release and NaCl builds (to workaround
+    # crbug.com/538243).
+    if (!is_debug) {
+      configs -= [ "//build/config/compiler:default_optimization" ]
+      # Enable optimize for speed (-O2) over size (-Os).
+      configs += [ "//build/config/compiler:optimize_max" ]
+    }
+
     if (current_cpu != "arm64") {
       configs -= [ "//build/config/compiler:compiler_arm_fpu" ]
       cflags = [ "-mfpu=neon" ]
     }
   }
 }
 
 if (libyuv_use_msa) {
   static_library("libyuv_msa") {
     sources = [
@@ skipping 130 matching lines @@
   }
 
   executable("cpuid") {
     sources = [
       # sources
       "util/cpuid.c"
     ]
     deps = [ ":libyuv" ]
   }
 }