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41 lines
1.4 KiB
Diff
41 lines
1.4 KiB
Diff
diff --git a/crypto/bn/rsa_sup_mul.c b/crypto/bn/rsa_sup_mul.c
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index 0e0d02e1946e..3b57161b4589 100644
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--- a/crypto/bn/rsa_sup_mul.c
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+++ b/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)
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*lo = (limb_t)t;
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}
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#elif (BN_BYTES == 8) && (defined _MSC_VER)
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-/* https://learn.microsoft.com/en-us/cpp/intrinsics/umul128?view=msvc-170 */
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+# if defined(_M_X64)
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+/*
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+ * on x86_64 (x64) we can use the _umul128 intrinsic to get one `mul`
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+ * instruction to get both high and low 64 bits of the multiplication.
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+ * https://learn.microsoft.com/en-us/cpp/intrinsics/umul128?view=msvc-140
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+ */
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+#include <intrin.h>
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#pragma intrinsic(_umul128)
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static ossl_inline void _mul_limb(limb_t *hi, limb_t *lo, limb_t a, limb_t b)
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{
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*lo = _umul128(a, b, hi);
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}
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+# elif defined(_M_ARM64) || defined (_M_IA64)
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+/*
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+ * We can't use the __umulh() on x86_64 as then msvc generates two `mul`
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+ * instructions; so use this more portable intrinsic on platforms that
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+ * don't support _umul128 (like aarch64 (ARM64) or ia64)
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+ * https://learn.microsoft.com/en-us/cpp/intrinsics/umulh?view=msvc-140
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+ */
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+#include <intrin.h>
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+static ossl_inline void _mul_limb(limb_t *hi, limb_t *lo, limb_t a, limb_t b)
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+{
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+ *lo = a * b;
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+ *hi = __umulh(a, b);
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+}
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+# else
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+# error Only x64, ARM64 and IA64 supported.
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+# endif /* defined(_M_X64) */
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#else
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/*
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* if the compiler doesn't have either a 128bit data type nor a "return
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