Unroll keycompare

git-svn-id: file:///svn/tokudb@133 c7de825b-a66e-492c-adef-691d508d4ae1

newbrt/key.c

@@ -46,12 +46,36 @@ int keycompare (bytevec key1, ITEMLEN key1len, bytevec key2, ITEMLEN key2len) {
 	else return -1;
     }
 }
+#elif 0
+/* This one looks tighter, but it does use memcmp... */
+int keycompare (bytevec key1, ITEMLEN key1len, bytevec key2, ITEMLEN key2len) {
+    int comparelen = key1len<key2len ? key1len : key2len;
+    const unsigned char *k1;
+    const unsigned char *k2;
+    for (k1=key1, k2=key2;
+	 comparelen>0;
+	 k1++, k2++, comparelen--) {
+	if (*k1 != *k2) {
+	    return (int)*k1-(int)*k2;
+	}
+    }
+    return key1len-key2len;
+}
 #else
+/* unroll that one twice */
 int keycompare (bytevec key1, ITEMLEN key1len, bytevec key2, ITEMLEN key2len) {
     int comparelen = key1len<key2len ? key1len : key2len;
     const unsigned char *k1;
     const unsigned char *k2;
     for (k1=key1, k2=key2;
+	 comparelen>4;
+	 k1+=4, k2+=4, comparelen-=4) {
+	{ int v1=k1[0], v2=k2[0]; if (v1!=v2) return v1-v2; }
+	{ int v1=k1[1], v2=k2[1]; if (v1!=v2) return v1-v2; }
+	{ int v1=k1[2], v2=k2[2]; if (v1!=v2) return v1-v2; }
+	{ int v1=k1[3], v2=k2[3]; if (v1!=v2) return v1-v2; }
+    }
+    for (;
 	 comparelen>0;
 	 k1++, k2++, comparelen--) {
 	if (*k1 != *k2) {
@@ -60,6 +84,7 @@ int keycompare (bytevec key1, ITEMLEN key1len, bytevec key2, ITEMLEN key2len) {
     }
     return key1len-key2len;
 }
+
 #endif
 
 void test_keycompare (void) {