It's on by default, but can be disabled with the below cmake argument.
Index: Makefile =================================================================== RCS file: /cvs/ports/graphics/opencv/Makefile,v retrieving revision 1.37 diff -u -p -u -r1.37 Makefile --- Makefile 15 Apr 2016 08:53:49 -0000 1.37 +++ Makefile 20 Apr 2016 04:59:34 -0000 @@ -13,6 +13,7 @@ DISTNAME = opencv-$V PKGNAME-main = ${PKGNAME} PKGNAME-docs = opencv-docs-$V PKGNAME-java = opencv-java-$V +REVISION = 0 REVISION-docs = 0 HOMEPAGE = http://www.opencv.org/ @@ -122,6 +123,7 @@ CONFIGURE_ARGS = -DBUILD_opencv_nonfree: -DWITH_PNG:Bool=On \ -DWITH_TIFF:Bool=On \ -DWITH_V4L:Bool=Off \ + -DENABLE_SSE3:Bool=Off \ -DPYTHON_EXECUTABLE:FILEPATH=${MODPY_BIN} .if ${BUILD_PACKAGES:M-java}