[Qemu-devel] [RFC][PATCH 4/9] buffer_is_zero: use vector optimizations if possible

[Peter Lieven <pl@dlhnet.de>]

performance gain on SSE2 is approx. 20-25%. altivec
is not tested. performance for unsigned long arithmetic
is unchanged.

Signed-off-by: Peter Lieven <pl@kamp.de>
---
  util/cutils.c |    5 +++++
  1 file changed, 5 insertions(+)

diff --git a/util/cutils.c b/util/cutils.c
index a09d8e8..23f0cd6 100644
--- a/util/cutils.c
+++ b/util/cutils.c
@@ -186,6 +186,11 @@ bool buffer_is_zero(const void *buf, size_t len)
       * latency.
       */

+    if (((uintptr_t) buf) % sizeof(VECTYPE) == 0
+          && len % 8*sizeof(VECTYPE) == 0) {
+        return buffer_find_nonzero_offset(buf, len)==len;
+    }
+
      size_t i;
      long d0, d1, d2, d3;
      const long * const data = buf;
-- 
1.7.9.5