From 98f9a401c3964c7ff0e6ca048685e28a2a6401d4 Mon Sep 17 00:00:00 2001 From: Hubert Kario Date: Wed, 8 Feb 2023 14:13:24 +0100 Subject: [PATCH] rsa: add msvc intrinsic for non x64 platforms _umul128() is x86_64 (x64) only, while __umulh() works everywhere, but doesn't generate optimal code on x64 Reviewed-by: Dmitry Belyavskiy Reviewed-by: Paul Dale Reviewed-by: Tomas Mraz (Merged from https://github.com/openssl/openssl/pull/20244) (cherry picked from commit 075652f224479dad2e64b92e791b296177af8705) --- crypto/bn/rsa_sup_mul.c | 24 +++++++++++++++++++++++- 1 file changed, 23 insertions(+), 1 deletion(-) diff --git a/crypto/bn/rsa_sup_mul.c b/crypto/bn/rsa_sup_mul.c index 0e0d02e1946e..3b57161b4589 100644 --- a/crypto/bn/rsa_sup_mul.c +++ b/crypto/bn/rsa_sup_mul.c @@ -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 #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 +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