Save _normalize_weak calls in group add methods

Co-authored-by: Sebastian Falbesoner <[email protected]>

Author: peterdettman

src/group_impl.h

@@ -495,7 +495,7 @@ static void secp256k1_gej_add_var(secp256k1_gej *r, const secp256k1_gej *a, cons
 }
 
 static void secp256k1_gej_add_ge_var(secp256k1_gej *r, const secp256k1_gej *a, const secp256k1_ge *b, secp256k1_fe *rzr) {
-    /* 8 mul, 3 sqr, 13 add/negate/normalize_weak/normalizes_to_zero (ignoring special cases) */
+    /* Operations: 8 mul, 3 sqr, 11 add/negate/normalizes_to_zero (ignoring special cases) */
     secp256k1_fe z12, u1, u2, s1, s2, h, i, h2, h3, t;
     secp256k1_gej_verify(a);
     secp256k1_ge_verify(b);
@@ -513,11 +513,11 @@ static void secp256k1_gej_add_ge_var(secp256k1_gej *r, const secp256k1_gej *a, c
     }
 
     secp256k1_fe_sqr(&z12, &a->z);
-    u1 = a->x; secp256k1_fe_normalize_weak(&u1);
+    u1 = a->x;
     secp256k1_fe_mul(&u2, &b->x, &z12);
-    s1 = a->y; secp256k1_fe_normalize_weak(&s1);
+    s1 = a->y;
     secp256k1_fe_mul(&s2, &b->y, &z12); secp256k1_fe_mul(&s2, &s2, &a->z);
-    secp256k1_fe_negate(&h, &u1, 1); secp256k1_fe_add(&h, &u2);
+    secp256k1_fe_negate(&h, &u1, 6); secp256k1_fe_add(&h, &u2);
     secp256k1_fe_negate(&i, &s2, 1); secp256k1_fe_add(&i, &s1);
     if (secp256k1_fe_normalizes_to_zero_var(&h)) {
         if (secp256k1_fe_normalizes_to_zero_var(&i)) {
@@ -556,7 +556,7 @@ static void secp256k1_gej_add_ge_var(secp256k1_gej *r, const secp256k1_gej *a, c
 }
 
 static void secp256k1_gej_add_zinv_var(secp256k1_gej *r, const secp256k1_gej *a, const secp256k1_ge *b, const secp256k1_fe *bzinv) {
-    /* 9 mul, 3 sqr, 13 add/negate/normalize_weak/normalizes_to_zero (ignoring special cases) */
+    /* Operations: 9 mul, 3 sqr, 11 add/negate/normalizes_to_zero (ignoring special cases) */
     secp256k1_fe az, z12, u1, u2, s1, s2, h, i, h2, h3, t;
 
     secp256k1_gej_verify(a);
@@ -589,11 +589,11 @@ static void secp256k1_gej_add_zinv_var(secp256k1_gej *r, const secp256k1_gej *a,
     secp256k1_fe_mul(&az, &a->z, bzinv);
 
     secp256k1_fe_sqr(&z12, &az);
-    u1 = a->x; secp256k1_fe_normalize_weak(&u1);
+    u1 = a->x;
     secp256k1_fe_mul(&u2, &b->x, &z12);
-    s1 = a->y; secp256k1_fe_normalize_weak(&s1);
+    s1 = a->y;
     secp256k1_fe_mul(&s2, &b->y, &z12); secp256k1_fe_mul(&s2, &s2, &az);
-    secp256k1_fe_negate(&h, &u1, 1); secp256k1_fe_add(&h, &u2);
+    secp256k1_fe_negate(&h, &u1, 6); secp256k1_fe_add(&h, &u2);
     secp256k1_fe_negate(&i, &s2, 1); secp256k1_fe_add(&i, &s1);
     if (secp256k1_fe_normalizes_to_zero_var(&h)) {
         if (secp256k1_fe_normalizes_to_zero_var(&i)) {
@@ -626,7 +626,7 @@ static void secp256k1_gej_add_zinv_var(secp256k1_gej *r, const secp256k1_gej *a,
 
 
 static void secp256k1_gej_add_ge(secp256k1_gej *r, const secp256k1_gej *a, const secp256k1_ge *b) {
-    /* Operations: 7 mul, 5 sqr, 24 add/cmov/half/mul_int/negate/normalize_weak/normalizes_to_zero */
+    /* Operations: 7 mul, 5 sqr, 21 add/cmov/half/mul_int/negate/normalizes_to_zero */
     secp256k1_fe zz, u1, u2, s1, s2, t, tt, m, n, q, rr;
     secp256k1_fe m_alt, rr_alt;
     int degenerate;
@@ -686,17 +686,17 @@ static void secp256k1_gej_add_ge(secp256k1_gej *r, const secp256k1_gej *a, const
      */
 
     secp256k1_fe_sqr(&zz, &a->z);                       /* z = Z1^2 */
-    u1 = a->x; secp256k1_fe_normalize_weak(&u1);        /* u1 = U1 = X1*Z2^2 (1) */
+    u1 = a->x;                                          /* u1 = U1 = X1*Z2^2 (6) */
     secp256k1_fe_mul(&u2, &b->x, &zz);                  /* u2 = U2 = X2*Z1^2 (1) */
-    s1 = a->y; secp256k1_fe_normalize_weak(&s1);        /* s1 = S1 = Y1*Z2^3 (1) */
+    s1 = a->y;                                          /* s1 = S1 = Y1*Z2^3 (4) */
     secp256k1_fe_mul(&s2, &b->y, &zz);                  /* s2 = Y2*Z1^2 (1) */
     secp256k1_fe_mul(&s2, &s2, &a->z);                  /* s2 = S2 = Y2*Z1^3 (1) */
-    t = u1; secp256k1_fe_add(&t, &u2);                  /* t = T = U1+U2 (2) */
-    m = s1; secp256k1_fe_add(&m, &s2);                  /* m = M = S1+S2 (2) */
+    t = u1; secp256k1_fe_add(&t, &u2);                  /* t = T = U1+U2 (7) */
+    m = s1; secp256k1_fe_add(&m, &s2);                  /* m = M = S1+S2 (5) */
     secp256k1_fe_sqr(&rr, &t);                          /* rr = T^2 (1) */
-    secp256k1_fe_negate(&m_alt, &u2, 1);                /* Malt = -X2*Z1^2 */
-    secp256k1_fe_mul(&tt, &u1, &m_alt);                 /* tt = -U1*U2 (2) */
-    secp256k1_fe_add(&rr, &tt);                         /* rr = R = T^2-U1*U2 (3) */
+    secp256k1_fe_negate(&m_alt, &u2, 1);                /* Malt = -X2*Z1^2 (2) */
+    secp256k1_fe_mul(&tt, &u1, &m_alt);                 /* tt = -U1*U2 (1) */
+    secp256k1_fe_add(&rr, &tt);                         /* rr = R = T^2-U1*U2 (2) */
     /* If lambda = R/M = R/0 we have a problem (except in the "trivial"
      * case that Z = z1z2 = 0, and this is special-cased later on). */
     degenerate = secp256k1_fe_normalizes_to_zero(&m);
@@ -706,34 +706,34 @@ static void secp256k1_gej_add_ge(secp256k1_gej *r, const secp256k1_gej *a, const
      * non-indeterminate expression for lambda is (y1 - y2)/(x1 - x2),
      * so we set R/M equal to this. */
     rr_alt = s1;
-    secp256k1_fe_mul_int(&rr_alt, 2);       /* rr = Y1*Z2^3 - Y2*Z1^3 (2) */
-    secp256k1_fe_add(&m_alt, &u1);          /* Malt = X1*Z2^2 - X2*Z1^2 */
+    secp256k1_fe_mul_int(&rr_alt, 2);       /* rr_alt = Y1*Z2^3 - Y2*Z1^3 (8) */
+    secp256k1_fe_add(&m_alt, &u1);          /* Malt = X1*Z2^2 - X2*Z1^2 (8) */
 
-    secp256k1_fe_cmov(&rr_alt, &rr, !degenerate);
-    secp256k1_fe_cmov(&m_alt, &m, !degenerate);
+    secp256k1_fe_cmov(&rr_alt, &rr, !degenerate);       /* rr_alt (8) */
+    secp256k1_fe_cmov(&m_alt, &m, !degenerate);         /* m_alt (5) */
     /* Now Ralt / Malt = lambda and is guaranteed not to be Ralt / 0.
      * From here on out Ralt and Malt represent the numerator
      * and denominator of lambda; R and M represent the explicit
      * expressions x1^2 + x2^2 + x1x2 and y1 + y2. */
     secp256k1_fe_sqr(&n, &m_alt);                       /* n = Malt^2 (1) */
-    secp256k1_fe_negate(&q, &t, 2);                     /* q = -T (3) */
+    secp256k1_fe_negate(&q, &t, 7);                     /* q = -T (8) */
     secp256k1_fe_mul(&q, &q, &n);                       /* q = Q = -T*Malt^2 (1) */
     /* These two lines use the observation that either M == Malt or M == 0,
      * so M^3 * Malt is either Malt^4 (which is computed by squaring), or
      * zero (which is "computed" by cmov). So the cost is one squaring
      * versus two multiplications. */
-    secp256k1_fe_sqr(&n, &n);
-    secp256k1_fe_cmov(&n, &m, degenerate);              /* n = M^3 * Malt (2) */
+    secp256k1_fe_sqr(&n, &n);                           /* n = Malt^4 (1) */
+    secp256k1_fe_cmov(&n, &m, degenerate);              /* n = M^3 * Malt (5) */
     secp256k1_fe_sqr(&t, &rr_alt);                      /* t = Ralt^2 (1) */
     secp256k1_fe_mul(&r->z, &a->z, &m_alt);             /* r->z = Z3 = Malt*Z (1) */
     secp256k1_fe_add(&t, &q);                           /* t = Ralt^2 + Q (2) */
     r->x = t;                                           /* r->x = X3 = Ralt^2 + Q (2) */
     secp256k1_fe_mul_int(&t, 2);                        /* t = 2*X3 (4) */
     secp256k1_fe_add(&t, &q);                           /* t = 2*X3 + Q (5) */
     secp256k1_fe_mul(&t, &t, &rr_alt);                  /* t = Ralt*(2*X3 + Q) (1) */
-    secp256k1_fe_add(&t, &n);                           /* t = Ralt*(2*X3 + Q) + M^3*Malt (3) */
-    secp256k1_fe_negate(&r->y, &t, 3);                  /* r->y = -(Ralt*(2*X3 + Q) + M^3*Malt) (4) */
-    secp256k1_fe_half(&r->y);                           /* r->y = Y3 = -(Ralt*(2*X3 + Q) + M^3*Malt)/2 (3) */
+    secp256k1_fe_add(&t, &n);                           /* t = Ralt*(2*X3 + Q) + M^3*Malt (6) */
+    secp256k1_fe_negate(&r->y, &t, 6);                  /* r->y = -(Ralt*(2*X3 + Q) + M^3*Malt) (7) */
+    secp256k1_fe_half(&r->y);                           /* r->y = Y3 = -(Ralt*(2*X3 + Q) + M^3*Malt)/2 (4) */
 
     /* In case a->infinity == 1, replace r with (b->x, b->y, 1). */
     secp256k1_fe_cmov(&r->x, &b->x, a->infinity);