blowfish: invert branch and loop precedence

Should slightly improve performance depending on the compiler used.

libavutil/blowfish.c

@@ -381,8 +381,8 @@ void av_blowfish_crypt(AVBlowfish *ctx, uint8_t *dst, const uint8_t *src,
     uint32_t v0, v1;
     int i;
 
-    while (count > 0) {
-        if (decrypt) {
+    if (decrypt) {
+        while (count > 0) {
             v0 = AV_RB32(src);
             v1 = AV_RB32(src + 4);
 
@@ -396,7 +396,13 @@ void av_blowfish_crypt(AVBlowfish *ctx, uint8_t *dst, const uint8_t *src,
                     dst[i] = dst[i] ^ iv[i];
                 memcpy(iv, src, 8);
             }
-        } else {
+
+            src   += 8;
+            dst   += 8;
+            count -= 8;
+        }
+    } else {
+        while (count > 0) {
             if (iv) {
                 for (i = 0; i < 8; i++)
                     dst[i] = src[i] ^ iv[i];
@@ -414,11 +420,11 @@ void av_blowfish_crypt(AVBlowfish *ctx, uint8_t *dst, const uint8_t *src,
 
             if (iv)
                 memcpy(iv, dst, 8);
-        }
 
-        src   += 8;
-        dst   += 8;
-        count -= 8;
+            src   += 8;
+            dst   += 8;
+            count -= 8;
+        }
     }
 }