bitops: Add MAKE_64BIT_MASK macro

Add a macro that creates a 64bit value which has length number of ones
shifted across by the value of shift.

Signed-off-by: Alistair Francis <alistair.francis@xilinx.com>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Message-id: 9773244aa1c8c26b8b82cb261d8f5dd4b7b9fcf9.1467053537.git.alistair.francis@xilinx.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

diff --git a/include/qemu/bitops.h b/include/qemu/bitops.h
index 15418a8..98fb005 100644 (file)
--- a/include/qemu/bitops.h
+++ b/include/qemu/bitops.h
@@ -24,6 +24,9 @@
 #define BIT_WORD(nr)            ((nr) / BITS_PER_LONG)
 #define BITS_TO_LONGS(nr)       DIV_ROUND_UP(nr, BITS_PER_BYTE * sizeof(long))
 
+#define MAKE_64BIT_MASK(shift, length) \
+    (((~0ULL) >> (64 - (length))) << (shift))
+
 /**
  * set_bit - Set a bit in memory
  * @nr: the bit to set