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Heuristically decide whether to use int128_struct

This commit is contained in:
Pieter Wuille 2022-11-16 14:49:17 -05:00
parent 63ff064d2f
commit 9b5f589d30
1 changed files with 16 additions and 3 deletions
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19
src/util.h
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@ -230,21 +230,34 @@ static SECP256K1_INLINE void secp256k1_int_cmov(int *r, const int *a, int flag)
*r = (int)(r_masked | a_masked);
}
/* If USE_FORCE_WIDEMUL_{INT128, INT128_STRUCT, INT64} is set, use that wide multiplication implementation.
* Otherwise use the presence of __SIZEOF_INT128__ to decide.
*/
#if defined(USE_FORCE_WIDEMUL_INT128_STRUCT)
/* If USE_FORCE_WIDEMUL_INT128_STRUCT is set, use int128_struct. */
# define SECP256K1_WIDEMUL_INT128 1
# define SECP256K1_INT128_STRUCT 1
#elif defined(USE_FORCE_WIDEMUL_INT128)
/* If USE_FORCE_WIDEMUL_INT128 is set, use int128. */
# define SECP256K1_WIDEMUL_INT128 1
# define SECP256K1_INT128_NATIVE 1
#elif defined(USE_FORCE_WIDEMUL_INT64)
/* If USE_FORCE_WIDEMUL_INT64 is set, use int64. */
# define SECP256K1_WIDEMUL_INT64 1
#elif defined(UINT128_MAX) || defined(__SIZEOF_INT128__)
/* If a native 128-bit integer type exists, use int128. */
# define SECP256K1_WIDEMUL_INT128 1
# define SECP256K1_INT128_NATIVE 1
#elif defined(_MSC_VER) && (defined(_M_X64) || defined(_M_ARM64))
/* On 64-bit MSVC targets (x86_64 and arm64), use int128_struct
* (which has special logic to implement using intrinsics on those systems). */
# define SECP256K1_WIDEMUL_INT128 1
# define SECP256K1_INT128_STRUCT 1
#elif SIZE_MAX > 0xffffffff
/* Systems with 64-bit pointers (and thus registers) very likely benefit from
* using 64-bit based arithmetic (even if we need to fall back to 32x32->64 based
* multiplication logic). */
# define SECP256K1_WIDEMUL_INT128 1
# define SECP256K1_INT128_STRUCT 1
#else
/* Lastly, fall back to int64 based arithmetic. */
# define SECP256K1_WIDEMUL_INT64 1
#endif