Merge bitcoin-core/secp256k1#1053: ecmult: move `_ecmult_odd_multiple…

…s_table_globalz_windowa`

05e049b ecmult: move `_ecmult_odd_multiples_table_globalz_windowa` (siv2r)

Pull request description:

  Fixes bitcoin#1035

  **Changes:**
      - move `secp256k1_ecmult_odd_multiples_table_globalz_windowa` function from ecmult to ecmult_const
      - remove outdated comment

ACKs for top commit:
  robot-dreams:
    utACK 05e049b (`diff` between removed and added lines is exactly as expected)
  real-or-random:
    utACK 05e049b

Tree-SHA512: 3fad4e93c641b642e84f4bbafcb8083d3e63b0523009fe0edcb2c1ebe1571d822320451289c651403ed1dc033ec6a7a3e8c3c56ad93d81bb1590cf9ff15a3b34

src/ecmult_const_impl.h

@@ -12,6 +12,22 @@
 #include "ecmult_const.h"
 #include "ecmult_impl.h"
 
+/** Fill a table 'pre' with precomputed odd multiples of a.
+ *
+ *  The resulting point set is brought to a single constant Z denominator, stores the X and Y
+ *  coordinates as ge_storage points in pre, and stores the global Z in globalz.
+ *  It only operates on tables sized for WINDOW_A wnaf multiples.
+ */
+static void secp256k1_ecmult_odd_multiples_table_globalz_windowa(secp256k1_ge *pre, secp256k1_fe *globalz, const secp256k1_gej *a) {
+    secp256k1_gej prej[ECMULT_TABLE_SIZE(WINDOW_A)];
+    secp256k1_fe zr[ECMULT_TABLE_SIZE(WINDOW_A)];
+
+    /* Compute the odd multiples in Jacobian form. */
+    secp256k1_ecmult_odd_multiples_table(ECMULT_TABLE_SIZE(WINDOW_A), prej, zr, a);
+    /* Bring them to the same Z denominator. */
+    secp256k1_ge_globalz_set_table_gej(ECMULT_TABLE_SIZE(WINDOW_A), pre, globalz, prej, zr);
+}
+
 /* This is like `ECMULT_TABLE_GET_GE` but is constant time */
 #define ECMULT_CONST_TABLE_GET_GE(r,pre,n,w) do { \
     int m = 0; \

src/ecmult_impl.h

@@ -96,25 +96,6 @@ static void secp256k1_ecmult_odd_multiples_table(int n, secp256k1_gej *prej, sec
     secp256k1_fe_mul(&prej[n-1].z, &prej[n-1].z, &d.z);
 }
 
-/** Fill a table 'pre' with precomputed odd multiples of a.
- *
- *  The resulting point set is brought to a single constant Z denominator, stores the X and Y
- *  coordinates as ge_storage points in pre, and stores the global Z in rz.
- *  It only operates on tables sized for WINDOW_A wnaf multiples.
- *
- *  To compute a*P + b*G, we compute a table for P using this function,
- *  and use the precomputed table in <precomputed_ecmult.c> for G.
- */
-static void secp256k1_ecmult_odd_multiples_table_globalz_windowa(secp256k1_ge *pre, secp256k1_fe *globalz, const secp256k1_gej *a) {
-    secp256k1_gej prej[ECMULT_TABLE_SIZE(WINDOW_A)];
-    secp256k1_fe zr[ECMULT_TABLE_SIZE(WINDOW_A)];
-
-    /* Compute the odd multiples in Jacobian form. */
-    secp256k1_ecmult_odd_multiples_table(ECMULT_TABLE_SIZE(WINDOW_A), prej, zr, a);
-    /* Bring them to the same Z denominator. */
-    secp256k1_ge_globalz_set_table_gej(ECMULT_TABLE_SIZE(WINDOW_A), pre, globalz, prej, zr);
-}
-
 /** The following two macro retrieves a particular odd multiple from a table
  *  of precomputed multiples. */
 #define ECMULT_TABLE_GET_GE(r,pre,n,w) do { \