Remove c-11 memcpy checks from perf-critical code

Change-Id: Id4f37f5d4a03160572954a416efa1ef9b3d79ad1
Signed-off-by: Dave Barach <dave@barachs.net>

1 files changed, 17 insertions, 7 deletions

diff --git a/src/vppinfra/string.h b/src/vppinfra/string.h
index 5c1d8267742..b00c0cfbcc2 100644
--- a/src/vppinfra/string.h
+++ b/src/vppinfra/string.h
@@ -78,10 +78,10 @@ void clib_memswap (void *_a, void *_b, uword bytes);
 #elif __SSSE3__
 #include <vppinfra/memcpy_sse3.h>
 #else
-#define _clib_memcpy(a,b,c) memcpy(a,b,c)
+#define clib_memcpy_fast(a,b,c) memcpy(a,b,c)
 #endif
 #else /* __COVERITY__ */
-#define _clib_memcpy(a,b,c) memcpy(a,b,c)
+#define clib_memcpy_fast(a,b,c) memcpy(a,b,c)
 #endif
 
 /* c-11 string manipulation variants */
@@ -108,6 +108,16 @@ memcpy_s_inline (void *__restrict__ dest, rsize_t dmax,
   u8 bad;
 
   /*
+   * Optimize constant-number-of-bytes calls without asking
+   * "too many questions for someone from New Jersey"
+   */
+  if (__builtin_constant_p (n))
+    {
+      clib_memcpy_fast (dest, src, n);
+      return EOK;
+    }
+
+  /*
    * call bogus if: src or dst NULL, trying to copy
    * more data than we have space in dst, or src == dst.
    * n == 0 isn't really "bad", so check first in the
@@ -140,7 +150,7 @@ memcpy_s_inline (void *__restrict__ dest, rsize_t dmax,
       return EINVAL;
     }
 
-  _clib_memcpy (dest, src, n);
+  clib_memcpy_fast (dest, src, n);
   return EOK;
 }
 
@@ -247,10 +257,10 @@ clib_memcpy64_x4 (void *d0, void *d1, void *d2, void *d3, void *s)
   _mm_storeu_si128 ((__m128i *) (d3 + 3 * 16), r3);
 
 #else
-  clib_memcpy (d0, s, 64);
-  clib_memcpy (d1, s, 64);
-  clib_memcpy (d2, s, 64);
-  clib_memcpy (d3, s, 64);
+  clib_memcpy_fast (d0, s, 64);
+  clib_memcpy_fast (d1, s, 64);
+  clib_memcpy_fast (d2, s, 64);
+  clib_memcpy_fast (d3, s, 64);
 #endif
 }