rand/rand.c (rdrand_quick): Improve the loop.

[catacomb] / rand / rand.c

diff --git a/rand/rand.c b/rand/rand.c
index 29b180d..f9f16d5 100644 (file)
--- a/rand/rand.c
+++ b/rand/rand.c
@@ -165,17 +165,13 @@ static int trivial_quick(rand_pool *r) { return (-1); }
 static int rdrand_quick(rand_pool *r)
 {
   unsigned long rr;
-  unsigned char w;
-  int i;
-
-  for (i = 0; i < 16; i++) {
-    __asm__ ("rdrand %0; setc %1" : "=r" (rr), "=g" (w) : : "cc");
-    if (w) {
-      rand_add(r, &rr, sizeof(rr), 8*sizeof(rr));
-      return (0);
-    }
-  }
-  return (-1);
+  int i = 16;
+
+  __asm__ ("0: rdrand %0; jc 9f; dec %1; jnz 0b; 9:"
+          : "=r" (rr), "=r" (i) : "1" (i) : "cc");
+  if (!i) return (-1);
+  rand_add(r, &rr, sizeof(rr), 8*sizeof(rr));
+  return (0);
 }
 #endif