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field: serialize elements by word

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The byte assignments replaced nested nibble loops before the endian write helpers existed.
Pack the 5x52 limbs into four 64-bit words and the 10x26 limbs into eight 32-bit words, then use those helpers.
This matches the scalar serializers and keeps the output unchanged.
Benchmarks indicate no measurable performance regression.
This commit is contained in:
Lőrinc
2026-05-28 22:05:08 +02:00
parent ebf594320d
commit e217ead5c4
2 changed files with 12 additions and 64 deletions
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src/field_10x26_impl.h
+8 -32
View File
@@ -303,38 +303,14 @@ static int secp256k1_fe_impl_set_b32_limit(secp256k1_fe *r, const unsigned char
/** Convert a field element to a 32-byte big endian value. Requires the input to be normalized */
static void secp256k1_fe_impl_get_b32(unsigned char *r, const secp256k1_fe *a) {
r[0] = (a->n[9] >> 14) & 0xff;
r[1] = (a->n[9] >> 6) & 0xff;
r[2] = ((a->n[9] & 0x3F) << 2) | ((a->n[8] >> 24) & 0x3);
r[3] = (a->n[8] >> 16) & 0xff;
r[4] = (a->n[8] >> 8) & 0xff;
r[5] = a->n[8] & 0xff;
r[6] = (a->n[7] >> 18) & 0xff;
r[7] = (a->n[7] >> 10) & 0xff;
r[8] = (a->n[7] >> 2) & 0xff;
r[9] = ((a->n[7] & 0x3) << 6) | ((a->n[6] >> 20) & 0x3f);
r[10] = (a->n[6] >> 12) & 0xff;
r[11] = (a->n[6] >> 4) & 0xff;
r[12] = ((a->n[6] & 0xf) << 4) | ((a->n[5] >> 22) & 0xf);
r[13] = (a->n[5] >> 14) & 0xff;
r[14] = (a->n[5] >> 6) & 0xff;
r[15] = ((a->n[5] & 0x3f) << 2) | ((a->n[4] >> 24) & 0x3);
r[16] = (a->n[4] >> 16) & 0xff;
r[17] = (a->n[4] >> 8) & 0xff;
r[18] = a->n[4] & 0xff;
r[19] = (a->n[3] >> 18) & 0xff;
r[20] = (a->n[3] >> 10) & 0xff;
r[21] = (a->n[3] >> 2) & 0xff;
r[22] = ((a->n[3] & 0x3) << 6) | ((a->n[2] >> 20) & 0x3f);
r[23] = (a->n[2] >> 12) & 0xff;
r[24] = (a->n[2] >> 4) & 0xff;
r[25] = ((a->n[2] & 0xf) << 4) | ((a->n[1] >> 22) & 0xf);
r[26] = (a->n[1] >> 14) & 0xff;
r[27] = (a->n[1] >> 6) & 0xff;
r[28] = ((a->n[1] & 0x3f) << 2) | ((a->n[0] >> 24) & 0x3);
r[29] = (a->n[0] >> 16) & 0xff;
r[30] = (a->n[0] >> 8) & 0xff;
r[31] = a->n[0] & 0xff;
secp256k1_write_be32(&r[0], (a->n[9] << 10) | (a->n[8] >> 16));
secp256k1_write_be32(&r[4], (a->n[8] << 16) | (a->n[7] >> 10));
secp256k1_write_be32(&r[8], (a->n[7] << 22) | (a->n[6] >> 4));
secp256k1_write_be32(&r[12], (a->n[6] << 28) | (a->n[5] << 2) | (a->n[4] >> 24));
secp256k1_write_be32(&r[16], (a->n[4] << 8) | (a->n[3] >> 18));
secp256k1_write_be32(&r[20], (a->n[3] << 14) | (a->n[2] >> 12));
secp256k1_write_be32(&r[24], (a->n[2] << 20) | (a->n[1] >> 6));
secp256k1_write_be32(&r[28], (a->n[1] << 26) | a->n[0]);
}
SECP256K1_INLINE static void secp256k1_fe_impl_negate_unchecked(secp256k1_fe *r, const secp256k1_fe *a, int m) {
src/field_5x52_impl.h
+4 -32
View File
@@ -269,38 +269,10 @@ static int secp256k1_fe_impl_set_b32_limit(secp256k1_fe *r, const unsigned char
/** Convert a field element to a 32-byte big endian value. Requires the input to be normalized */
static void secp256k1_fe_impl_get_b32(unsigned char *r, const secp256k1_fe *a) {
r[0] = (a->n[4] >> 40) & 0xFF;
r[1] = (a->n[4] >> 32) & 0xFF;
r[2] = (a->n[4] >> 24) & 0xFF;
r[3] = (a->n[4] >> 16) & 0xFF;
r[4] = (a->n[4] >> 8) & 0xFF;
r[5] = a->n[4] & 0xFF;
r[6] = (a->n[3] >> 44) & 0xFF;
r[7] = (a->n[3] >> 36) & 0xFF;
r[8] = (a->n[3] >> 28) & 0xFF;
r[9] = (a->n[3] >> 20) & 0xFF;
r[10] = (a->n[3] >> 12) & 0xFF;
r[11] = (a->n[3] >> 4) & 0xFF;
r[12] = ((a->n[2] >> 48) & 0xF) | ((a->n[3] & 0xF) << 4);
r[13] = (a->n[2] >> 40) & 0xFF;
r[14] = (a->n[2] >> 32) & 0xFF;
r[15] = (a->n[2] >> 24) & 0xFF;
r[16] = (a->n[2] >> 16) & 0xFF;
r[17] = (a->n[2] >> 8) & 0xFF;
r[18] = a->n[2] & 0xFF;
r[19] = (a->n[1] >> 44) & 0xFF;
r[20] = (a->n[1] >> 36) & 0xFF;
r[21] = (a->n[1] >> 28) & 0xFF;
r[22] = (a->n[1] >> 20) & 0xFF;
r[23] = (a->n[1] >> 12) & 0xFF;
r[24] = (a->n[1] >> 4) & 0xFF;
r[25] = ((a->n[0] >> 48) & 0xF) | ((a->n[1] & 0xF) << 4);
r[26] = (a->n[0] >> 40) & 0xFF;
r[27] = (a->n[0] >> 32) & 0xFF;
r[28] = (a->n[0] >> 24) & 0xFF;
r[29] = (a->n[0] >> 16) & 0xFF;
r[30] = (a->n[0] >> 8) & 0xFF;
r[31] = a->n[0] & 0xFF;
secp256k1_write_be64(&r[0], (a->n[4] << 16) | (a->n[3] >> 36));
secp256k1_write_be64(&r[8], (a->n[3] << 28) | (a->n[2] >> 24));
secp256k1_write_be64(&r[16], (a->n[2] << 40) | (a->n[1] >> 12));
secp256k1_write_be64(&r[24], (a->n[1] << 52) | a->n[0]);
}
SECP256K1_INLINE static void secp256k1_fe_impl_negate_unchecked(secp256k1_fe *r, const secp256k1_fe *a, int m) {