Use __shiftright128 intrinsic in secp256k1_u128_rshift on MSVC

hebasto · hebasto · commit 3e9d8c87b6e2 · 2023-06-01T13:11:10.000+01:00
diff --git a/src/int128_struct_impl.h b/src/int128_struct_impl.h
@@ -80,7 +80,11 @@ static SECP256K1_INLINE void secp256k1_u128_rshift(secp256k1_uint128 *r, unsigne
      r->lo = r->hi >> (n-64);
      r->hi = 0;
    } else if (n > 0) {
+#if defined(_MSC_VER) && defined(_M_X64)
+     r->lo = __shiftright128(r->lo, r->hi, n);
+#else
      r->lo = ((1U * r->hi) << (64-n)) | r->lo >> n;
+#endif
      r->hi >>= n;
    }
 }

Original file line number	Diff line number	Diff line change
`@@ -80,7 +80,11 @@ static SECP256K1_INLINE void secp256k1_u128_rshift(secp256k1_uint128 *r, unsigne`
`80`	`80`	`r->lo = r->hi >> (n-64);`
`81`	`81`	`r->hi = 0;`
`82`	`82`	`} else if (n > 0) {`
	`83`	`+#if defined(_MSC_VER) && defined(_M_X64)`
	`84`	`+ r->lo = __shiftright128(r->lo, r->hi, n);`
	`85`	`+#else`
`83`	`86`	`r->lo = ((1U * r->hi) << (64-n)) \| r->lo >> n;`
	`87`	`+#endif`
`84`	`88`	`r->hi >>= n;`
`85`	`89`	`}`
`86`	`90`	`}`