Generate random single instructions

gen/rand.go

@@ -11,14 +11,24 @@ func RandBiasedUint64() uint64 {
 
 // Generate a random int64 with an even distribution of the tuple
 // {sign, bits.Len64(math.Abs())}
-func RandBiasedInt64() int64 {
+func RandBiasedInt64() uint64 {
 	shift := rand.Intn(127)
 	// [0,62]: positive
 	// [63,63]: zero
 	// [64,126]: negative
 	if shift < 64 {
-		return int64((rand.Uint64() | 0x8000000000000000) >> (shift + 1))
+		return uint64(int64((rand.Uint64() | 0x8000000000000000) >> (shift + 1)))
 	} else {
-		return int64((rand.Uint64() | 0x8000000000000000) >> (shift - 63)) * -1
+		return uint64(int64((rand.Uint64() | 0x8000000000000000) >> (shift - 63)) * -1)
+	}
+}
+
+// Mixture of RandBiasedUint64() and RandBiasedInt64(), with probability shifted
+// toward more unsigned values.
+func RandBiasedUSint64() uint64 {
+	if rand.Intn(2) == 0 {
+		return RandBiasedUint64()
+	} else {
+		return RandBiasedInt64()
 	}
 }