ec_cvt.c: avoid EC_GFp_nist_method on platforms with bn_mul_mont [see

commentary for details].

crypto/ec/ec_cvt.c

@@ -80,10 +80,29 @@ EC_GROUP *EC_GROUP_new_curve_GFp(const BIGNUM *p, const BIGNUM *a, const BIGNUM
 	const EC_METHOD *meth;
 	EC_GROUP *ret;
 
+#if defined(OPENSSL_BN_ASM_MONT) && !defined(__sparc)
+	/*
+	 * This might appear controversial, but the fact is that generic
+	 * prime method was observed to deliver better performance even
+	 * for NIST primes on a range of platforms, e.g.: 60%-15%
+	 * improvement on IA-64, 50%-20% on ARM, 30%-90% on P4, 20%-25%
+	 * in 32-bit build and 35%--12% in 64-bit build on Core2...
+	 * Coefficients are relative to optimized bn_nist.c for most
+	 * intensive ECDSA verify and ECDH operations for 192- and 521-
+	 * bit keys respectively. What effectively happens is that loop
+	 * with bn_mul_add_words is put against bn_mul_mont, and latter
+	 * wins on short vectors. Correct solution should be implementing
+	 * dedicated NxN multiplication subroutines for small N. But till
+	 * it materializes, let's stick to generic prime method...
+	 *						<appro>
+	 */
+	meth = EC_GFp_mont_method();
+#else
 	if (BN_nist_mod_func(p))
 		meth = EC_GFp_nist_method();
 	else
 		meth = EC_GFp_mont_method();
+#endif
 	
 	ret = EC_GROUP_new(meth);
 	if (ret == NULL)