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rsa: add msvc intrinsic for non x64 platforms

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_umul128() is x86_64 (x64) only, while __umulh() works everywhere, but
doesn't generate optimal code on x64

Reviewed-by: Dmitry Belyavskiy <beldmit@gmail.com>
Reviewed-by: Paul Dale <pauli@openssl.org>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/20244)
This commit is contained in:
Hubert Kario 2023-02-08 14:13:24 +01:00 committed by Tomas Mraz
parent 4596c20b86
commit 075652f224
1 changed files with 23 additions and 1 deletions
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24
crypto/bn/rsa_sup_mul.c
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@ -110,12 +110,34 @@ static ossl_inline void _mul_limb(limb_t *hi, limb_t *lo, limb_t a, limb_t b)
*lo = (limb_t)t;
}
#elif (BN_BYTES == 8) && (defined _MSC_VER)
/* https://learn.microsoft.com/en-us/cpp/intrinsics/umul128?view=msvc-170 */
# if defined(_M_X64)
/*
* on x86_64 (x64) we can use the _umul128 intrinsic to get one `mul`
* instruction to get both high and low 64 bits of the multiplication.
* https://learn.microsoft.com/en-us/cpp/intrinsics/umul128?view=msvc-140
*/
#include <intrin.h>
#pragma intrinsic(_umul128)
static ossl_inline void _mul_limb(limb_t *hi, limb_t *lo, limb_t a, limb_t b)
{
*lo = _umul128(a, b, hi);
}
# elif defined(_M_ARM64) || defined (_M_IA64)
/*
* We can't use the __umulh() on x86_64 as then msvc generates two `mul`
* instructions; so use this more portable intrinsic on platforms that
* don't support _umul128 (like aarch64 (ARM64) or ia64)
* https://learn.microsoft.com/en-us/cpp/intrinsics/umulh?view=msvc-140
*/
#include <intrin.h>
static ossl_inline void _mul_limb(limb_t *hi, limb_t *lo, limb_t a, limb_t b)
{
*lo = a * b;
*hi = __umulh(a, b);
}
# else
# error Only x64, ARM64 and IA64 supported.
# endif /* defined(_M_X64) */
#else
/*
* if the compiler doesn't have either a 128bit data type nor a "return