bitops.h: Provide hswap32(), hswap64(), wswap64() swapping operations

Currently the ARM SVE helper code defines locally some utility
functions for swapping 16-bit halfwords within 32-bit or 64-bit
values and for swapping 32-bit words within 64-bit values,
parallel to the byte-swapping bswap16/32/64 functions.

We want these also for the ARM MVE code, and they're potentially
generally useful for other targets, so move them to bitops.h.
(We don't put them in bswap.h with the bswap* functions because
they are implemented in terms of the rotate operations also
defined in bitops.h, and including bitops.h from bswap.h seems
better avoided.)

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-id: 20210614151007.4545-17-peter.maydell@linaro.org

include/qemu/bitops.h

@@ -291,6 +291,35 @@ static inline uint64_t ror64(uint64_t word, unsigned int shift)
     return (word >> shift) | (word << ((64 - shift) & 63));
 }
 
+/**
+ * hswap32 - swap 16-bit halfwords within a 32-bit value
+ * @h: value to swap
+ */
+static inline uint32_t hswap32(uint32_t h)
+{
+    return rol32(h, 16);
+}
+
+/**
+ * hswap64 - swap 16-bit halfwords within a 64-bit value
+ * @h: value to swap
+ */
+static inline uint64_t hswap64(uint64_t h)
+{
+    uint64_t m = 0x0000ffff0000ffffull;
+    h = rol64(h, 32);
+    return ((h & m) << 16) | ((h >> 16) & m);
+}
+
+/**
+ * wswap64 - swap 32-bit words within a 64-bit value
+ * @h: value to swap
+ */
+static inline uint64_t wswap64(uint64_t h)
+{
+    return rol64(h, 32);
+}
+
 /**
  * extract32:
  * @value: the value to extract the bit field from