Mailing List Archive

* mpi/mpi-add.c (_gcry_mpi_add): Rename function...
(_gcry_mpi_add_inv_sign): ... to this and add parameter for inverting
sign of second operand.
(_gcry_mpi_add): New.
(_gcry_mpi_sub): Remove mpi_copy and instead use new
'_gcry_mpi_add_inv_sign' function with inverted sign for second
operand.
--

Benchmark on AMD Ryzen 9 7900X:

Before:
| nanosecs/byte mebibytes/sec cycles/byte auto Mhz
add | 0.052 ns/B 18301 MiB/s 0.287 c/B 5500
sub | 0.098 ns/B 9768 MiB/s 0.537 c/B 5500

After:
| nanosecs/byte mebibytes/sec cycles/byte auto Mhz
add | 0.030 ns/B 31771 MiB/s 0.165 c/B 5500
sub | 0.031 ns/B 31187 MiB/s 0.168 c/B 5500

Signed-off-by: Jussi Kivilinna <jussi.kivilinna@iki.fi>
---
mpi/mpi-add.c | 19 +++++++++++--------
1 file changed, 11 insertions(+), 8 deletions(-)

diff --git a/mpi/mpi-add.c b/mpi/mpi-add.c
index 38dd352f..2fd19e55 100644
--- a/mpi/mpi-add.c
+++ b/mpi/mpi-add.c
@@ -84,8 +84,8 @@ _gcry_mpi_add_ui (gcry_mpi_t w, gcry_mpi_t u, unsigned long v )
}


-void
-_gcry_mpi_add(gcry_mpi_t w, gcry_mpi_t u, gcry_mpi_t v)
+static void
+_gcry_mpi_add_inv_sign(gcry_mpi_t w, gcry_mpi_t u, gcry_mpi_t v, int inv_v_sign)
{
mpi_ptr_t wp, up, vp;
mpi_size_t usize, vsize, wsize;
@@ -93,7 +93,7 @@ _gcry_mpi_add(gcry_mpi_t w, gcry_mpi_t u, gcry_mpi_t v)

if( u->nlimbs < v->nlimbs ) { /* Swap U and V. */
usize = v->nlimbs;
- usign = v->sign;
+ usign = v->sign ^ inv_v_sign;
vsize = u->nlimbs;
vsign = u->sign;
wsize = usize + 1;
@@ -106,7 +106,7 @@ _gcry_mpi_add(gcry_mpi_t w, gcry_mpi_t u, gcry_mpi_t v)
usize = u->nlimbs;
usign = u->sign;
vsize = v->nlimbs;
- vsign = v->sign;
+ vsign = v->sign ^ inv_v_sign;
wsize = usize + 1;
RESIZE_IF_NEEDED(w, wsize);
/* These must be after realloc (u or v may be the same as w). */
@@ -211,13 +211,16 @@ _gcry_mpi_sub_ui(gcry_mpi_t w, gcry_mpi_t u, unsigned long v )
w->sign = wsign;
}

+void
+_gcry_mpi_add(gcry_mpi_t w, gcry_mpi_t u, gcry_mpi_t v)
+{
+ _gcry_mpi_add_inv_sign (w, u, v, 0);
+}
+
void
_gcry_mpi_sub(gcry_mpi_t w, gcry_mpi_t u, gcry_mpi_t v)
{
- gcry_mpi_t vv = mpi_copy (v);
- vv->sign = ! vv->sign;
- mpi_add (w, u, vv);
- mpi_free (vv);
+ _gcry_mpi_add_inv_sign (w, u, v, 1);
}


--
2.39.2


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