Optimise sswap for POWER9

Use lxvd2x instruction instead of lxvw4x.
lxvd2x performs far better on the new POWER architecture than lxvw4x.

kernel/power/sswap_microk_power8.c

@@ -42,43 +42,43 @@ static void sswap_kernel_32 (long n, float *x, float *y)
        ".p2align	5		\n"
      "1:				\n\t"
 
-       "lxvw4x		32, 0, %4	\n\t"
-       "lxvw4x		33, %5, %4	\n\t"
-       "lxvw4x		34, %6, %4	\n\t"
-       "lxvw4x		35, %7, %4	\n\t"
-       "lxvw4x		36, %8, %4	\n\t"
-       "lxvw4x		37, %9, %4	\n\t"
-       "lxvw4x		38, %10, %4	\n\t"
-       "lxvw4x		39, %11, %4	\n\t"
+       "lxvd2x		32, 0, %4	\n\t"
+       "lxvd2x		33, %5, %4	\n\t"
+       "lxvd2x		34, %6, %4	\n\t"
+       "lxvd2x		35, %7, %4	\n\t"
+       "lxvd2x		36, %8, %4	\n\t"
+       "lxvd2x		37, %9, %4	\n\t"
+       "lxvd2x		38, %10, %4	\n\t"
+       "lxvd2x		39, %11, %4	\n\t"
 
-       "lxvw4x		40, 0, %3	\n\t"
-       "lxvw4x		41, %5, %3	\n\t"
-       "lxvw4x		42, %6, %3	\n\t"
-       "lxvw4x		43, %7, %3	\n\t"
-       "lxvw4x		44, %8, %3	\n\t"
-       "lxvw4x		45, %9, %3	\n\t"
-       "lxvw4x		46, %10, %3	\n\t"
-       "lxvw4x		47, %11, %3	\n\t"
+       "lxvd2x		40, 0, %3	\n\t"
+       "lxvd2x		41, %5, %3	\n\t"
+       "lxvd2x		42, %6, %3	\n\t"
+       "lxvd2x		43, %7, %3	\n\t"
+       "lxvd2x		44, %8, %3	\n\t"
+       "lxvd2x		45, %9, %3	\n\t"
+       "lxvd2x		46, %10, %3	\n\t"
+       "lxvd2x		47, %11, %3	\n\t"
 
-       "stxvw4x		32, 0, %3	\n\t"
-       "stxvw4x		33, %5, %3	\n\t"
-       "stxvw4x		34, %6, %3	\n\t"
-       "stxvw4x		35, %7, %3	\n\t"
-       "stxvw4x		36, %8, %3	\n\t"
-       "stxvw4x		37, %9, %3	\n\t"
-       "stxvw4x		38, %10, %3	\n\t"
-       "stxvw4x		39, %11, %3	\n\t"
+       "stxvd2x		32, 0, %3	\n\t"
+       "stxvd2x		33, %5, %3	\n\t"
+       "stxvd2x		34, %6, %3	\n\t"
+       "stxvd2x		35, %7, %3	\n\t"
+       "stxvd2x		36, %8, %3	\n\t"
+       "stxvd2x		37, %9, %3	\n\t"
+       "stxvd2x		38, %10, %3	\n\t"
+       "stxvd2x		39, %11, %3	\n\t"
 
        "addi		%3, %3, 128	\n\t"
 
-       "stxvw4x		40, 0, %4	\n\t"
-       "stxvw4x		41, %5, %4	\n\t"
-       "stxvw4x		42, %6, %4	\n\t"
-       "stxvw4x		43, %7, %4	\n\t"
-       "stxvw4x		44, %8, %4	\n\t"
-       "stxvw4x		45, %9, %4	\n\t"
-       "stxvw4x		46, %10, %4	\n\t"
-       "stxvw4x		47, %11, %4	\n\t"
+       "stxvd2x		40, 0, %4	\n\t"
+       "stxvd2x		41, %5, %4	\n\t"
+       "stxvd2x		42, %6, %4	\n\t"
+       "stxvd2x		43, %7, %4	\n\t"
+       "stxvd2x		44, %8, %4	\n\t"
+       "stxvd2x		45, %9, %4	\n\t"
+       "stxvd2x		46, %10, %4	\n\t"
+       "stxvd2x		47, %11, %4	\n\t"
 
        "addi		%4, %4, 128	\n\t"