Add a constant time zero check function for 64-bit integers

Signed-off-by: Amitay Isaacs <amitay@ozlabs.org>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/14784)

diff --git a/include/internal/constant_time.h b/include/internal/constant_time.h
index cb4ce80830fadf3f876f28b825e5fcc0e185eccd..0ed6f823c11edccba1eef58490adabcbddafb368 100644 (file)
--- a/include/internal/constant_time.h
+++ b/include/internal/constant_time.h
@@ -182,6 +182,11 @@ static ossl_inline uint32_t constant_time_is_zero_32(uint32_t a)
     return constant_time_msb_32(~a & (a - 1));
 }
 
+static ossl_inline uint64_t constant_time_is_zero_64(uint64_t a)
+{
+    return constant_time_msb_64(~a & (a - 1));
+}
+
 static ossl_inline unsigned int constant_time_eq(unsigned int a,
                                                  unsigned int b)
 {