Change ScaleSumSamples to return Sum of Squares

TBR=kjellander@chromium.org
BUG=libyuv:717
TEST=LibYUVPlanarTest.TestScaleSumSamples_Opt

Change-Id: I5208666f3968c5c4b0f1b0c951f24216d78ee3fe
Reviewed-on: https://chromium-review.googlesource.com/607184
Reviewed-by: Cheng Wang <wangcheng@google.com>

1 files changed, 4 insertions, 3 deletions

diff --git a/BUILD.gn b/BUILD.gn
index 7f5f26f6..3eefc361 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -158,10 +158,11 @@ static_library("libyuv_internal") {
   }
 
   # To enable AVX2 or other cpu optimization, pass flag here
-  # cflags = [ "-mavx2" ]
-  # cflags = [ "-mpopcnt" ]
+  # cflags = [ "-mavx2", "-mpopcnt", "-mavx2", "-mfma" ]
+  if (!is_win) {
+    cflags = [ "-ffp-contract=fast" ]   # Enable fma vectorization for NEON.
+  }
 }
-
 if (libyuv_use_neon) {
   static_library("libyuv_neon") {
     sources = [