Mailing List Archive

* mpi/mpi-internal.h (mpih_limb_is_zero): New.
* mpi/mpih-const-time.c (_gcry_mpih_cmp_ui): Use mpih_limb_is_zero
instead of comparison.
--

Signed-off-by: Jussi Kivilinna <jussi.kivilinna@iki.fi>
---
mpi/mpi-internal.h | 9 +++++++++
mpi/mpih-const-time.c | 2 +-
2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/mpi/mpi-internal.h b/mpi/mpi-internal.h
index 79a6cce7..bb12e86c 100644
--- a/mpi/mpi-internal.h
+++ b/mpi/mpi-internal.h
@@ -267,6 +267,15 @@ mpi_limb_t _gcry_mpih_rshift( mpi_ptr_t wp, mpi_ptr_t up, mpi_size_t usize,
#define mpih_abs_cond(w,u,s,o) _gcry_mpih_abs_cond ((w),(u),(s),(o))
#define mpih_mod(v,vs,u,us) _gcry_mpih_mod ((v),(vs),(u),(us))

+static inline int
+mpih_limb_is_zero (mpi_limb_t a)
+{
+ /* Sign bit set if A == 0. */
+ a = ~a & ~(-a);
+
+ return a >> (BITS_PER_MPI_LIMB - 1);
+}
+
void _gcry_mpih_set_cond (mpi_ptr_t wp, mpi_ptr_t up, mpi_size_t usize,
unsigned long op_enable);
mpi_limb_t _gcry_mpih_add_n_cond (mpi_ptr_t wp, mpi_ptr_t up, mpi_ptr_t vp,
diff --git a/mpi/mpih-const-time.c b/mpi/mpih-const-time.c
index 85dba389..3d854e8c 100644
--- a/mpi/mpih-const-time.c
+++ b/mpi/mpih-const-time.c
@@ -202,7 +202,7 @@ _gcry_mpih_cmp_ui (mpi_ptr_t up, mpi_size_t usize, unsigned long v)
mpi_size_t i;

for (i = 1; i < usize; i++)
- is_all_zero &= (up[i] == 0);
+ is_all_zero &= mpih_limb_is_zero (up[i]);

if (is_all_zero)
{
--
2.40.1


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