memset:optimizate speed.

Signed-off-by: yangguangcai <[email protected]>

libs/libc/string/lib_memset.c

@@ -95,6 +95,18 @@ FAR void *memset(FAR void *s, int c, size_t n)
             }
 
 #ifndef CONFIG_MEMSET_64BIT
+          /* Loop while there are at least 16-bytes left to be written */
+
+          while (n >= 16)
+            {
+              *(FAR uint32_t *)(addr +  0) = val32;
+              *(FAR uint32_t *)(addr +  4) = val32;
+              *(FAR uint32_t *)(addr +  8) = val32;
+              *(FAR uint32_t *)(addr + 12) = val32;
+              addr += 16;
+              n    -= 16;
+            }
+
           /* Loop while there are at least 32-bits left to be written */
 
           while (n >= 4)
@@ -119,6 +131,22 @@ FAR void *memset(FAR void *s, int c, size_t n)
                   n    -= 4;
                 }
 
+              /* Loop while there are at least 64-bytes left to be written */
+
+              while (n >= 64)
+                {
+                  *(FAR uint64_t *)(addr +  0) = val64;
+                  *(FAR uint64_t *)(addr +  8) = val64;
+                  *(FAR uint64_t *)(addr + 16) = val64;
+                  *(FAR uint64_t *)(addr + 24) = val64;
+                  *(FAR uint64_t *)(addr + 32) = val64;
+                  *(FAR uint64_t *)(addr + 40) = val64;
+                  *(FAR uint64_t *)(addr + 48) = val64;
+                  *(FAR uint64_t *)(addr + 56) = val64;
+                  addr += 64;
+                  n    -= 64;
+                }
+
               /* Loop while there are at least 64-bits left to be written */
 
               while (n >= 8)