From: Greg Kurz Date: Fri, 5 Feb 2016 10:46:18 +0000 (+0100) Subject: virtio: optimize virtio_access_is_big_endian() for little-endian targets X-Git-Tag: v2.6.0-rc0~99^2~7 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=e5157e313cd9c2d57f28873318d0bb29c77a9b1a;p=thirdparty%2Fqemu.git virtio: optimize virtio_access_is_big_endian() for little-endian targets When adding cross-endian support, we introduced the TARGET_IS_BIENDIAN macro and the virtio_access_is_big_endian() helper to have a branchless fast path in the virtio memory accessors for targets that don't switch endian. This was considered as a strong requirement at the time. Now we have added a runtime check for virtio 1.0, which ruins the benefit of the virtio_access_is_big_endian() helper for always little-endian targets. With this patch, always little-endian targets stop checking for virtio 1.0, since the result is little-endian in all cases. Reviewed-by: Cornelia Huck Reviewed-by: Laurent Vivier Signed-off-by: Greg Kurz Reviewed-by: Michael S. Tsirkin Signed-off-by: Michael S. Tsirkin Reviewed-by: Laurent Vivier --- diff --git a/include/hw/virtio/virtio-access.h b/include/hw/virtio/virtio-access.h index f1f12afe908..8dc84f52031 100644 --- a/include/hw/virtio/virtio-access.h +++ b/include/hw/virtio/virtio-access.h @@ -19,13 +19,13 @@ static inline bool virtio_access_is_big_endian(VirtIODevice *vdev) { +#if defined(TARGET_IS_BIENDIAN) + return virtio_is_big_endian(vdev); +#elif defined(TARGET_WORDS_BIGENDIAN) if (virtio_vdev_has_feature(vdev, VIRTIO_F_VERSION_1)) { /* Devices conforming to VIRTIO 1.0 or later are always LE. */ return false; } -#if defined(TARGET_IS_BIENDIAN) - return virtio_is_big_endian(vdev); -#elif defined(TARGET_WORDS_BIGENDIAN) return true; #else return false;