diff --git a/qemu/include/qemu/bitops.h b/qemu/include/qemu/bitops.h index 9dfcba57..9f3995ec 100644 --- a/qemu/include/qemu/bitops.h +++ b/qemu/include/qemu/bitops.h @@ -419,4 +419,112 @@ static inline uint64_t deposit64(uint64_t value, int start, int length, return (value & ~mask) | ((fieldval << start) & mask); } +/** + * half_shuffle32: + * @value: 32-bit value (of which only the bottom 16 bits are of interest) + * + * Given an input value: + * xxxx xxxx xxxx xxxx ABCD EFGH IJKL MNOP + * return the value where the bottom 16 bits are spread out into + * the odd bits in the word, and the even bits are zeroed: + * 0A0B 0C0D 0E0F 0G0H 0I0J 0K0L 0M0N 0O0P + * + * Any bits set in the top half of the input are ignored. + * + * Returns: the shuffled bits. + */ +static inline uint32_t half_shuffle32(uint32_t x) +{ + /* This algorithm is from _Hacker's Delight_ section 7-2 "Shuffling Bits". + * It ignores any bits set in the top half of the input. + */ + x = ((x & 0xFF00) << 8) | (x & 0x00FF); + x = ((x << 4) | x) & 0x0F0F0F0F; + x = ((x << 2) | x) & 0x33333333; + x = ((x << 1) | x) & 0x55555555; + return x; +} + +/** + * half_shuffle64: + * @value: 64-bit value (of which only the bottom 32 bits are of interest) + * + * Given an input value: + * xxxx xxxx xxxx .... xxxx xxxx ABCD EFGH IJKL MNOP QRST UVWX YZab cdef + * return the value where the bottom 32 bits are spread out into + * the odd bits in the word, and the even bits are zeroed: + * 0A0B 0C0D 0E0F 0G0H 0I0J 0K0L 0M0N .... 0U0V 0W0X 0Y0Z 0a0b 0c0d 0e0f + * + * Any bits set in the top half of the input are ignored. + * + * Returns: the shuffled bits. + */ +static inline uint64_t half_shuffle64(uint64_t x) +{ + /* This algorithm is from _Hacker's Delight_ section 7-2 "Shuffling Bits". + * It ignores any bits set in the top half of the input. + */ + x = ((x & 0xFFFF0000ULL) << 16) | (x & 0xFFFF); + x = ((x << 8) | x) & 0x00FF00FF00FF00FFULL; + x = ((x << 4) | x) & 0x0F0F0F0F0F0F0F0FULL; + x = ((x << 2) | x) & 0x3333333333333333ULL; + x = ((x << 1) | x) & 0x5555555555555555ULL; + return x; +} + +/** + * half_unshuffle32: + * @value: 32-bit value (of which only the odd bits are of interest) + * + * Given an input value: + * xAxB xCxD xExF xGxH xIxJ xKxL xMxN xOxP + * return the value where all the odd bits are compressed down + * into the low half of the word, and the high half is zeroed: + * 0000 0000 0000 0000 ABCD EFGH IJKL MNOP + * + * Any even bits set in the input are ignored. + * + * Returns: the unshuffled bits. + */ +static inline uint32_t half_unshuffle32(uint32_t x) +{ + /* This algorithm is from _Hacker's Delight_ section 7-2 "Shuffling Bits". + * where it is called an inverse half shuffle. + */ + x &= 0x55555555; + x = ((x >> 1) | x) & 0x33333333; + x = ((x >> 2) | x) & 0x0F0F0F0F; + x = ((x >> 4) | x) & 0x00FF00FF; + x = ((x >> 8) | x) & 0x0000FFFF; + return x; +} + +/** + * half_unshuffle64: + * @value: 64-bit value (of which only the odd bits are of interest) + * + * Given an input value: + * xAxB xCxD xExF xGxH xIxJ xKxL xMxN .... xUxV xWxX xYxZ xaxb xcxd xexf + * return the value where all the odd bits are compressed down + * into the low half of the word, and the high half is zeroed: + * 0000 0000 0000 .... 0000 0000 ABCD EFGH IJKL MNOP QRST UVWX YZab cdef + * + * Any even bits set in the input are ignored. + * + * Returns: the unshuffled bits. + */ +static inline uint64_t half_unshuffle64(uint64_t x) +{ + /* This algorithm is from _Hacker's Delight_ section 7-2 "Shuffling Bits". + * where it is called an inverse half shuffle. + */ + x &= 0x5555555555555555ULL; + x = ((x >> 1) | x) & 0x3333333333333333ULL; + x = ((x >> 2) | x) & 0x0F0F0F0F0F0F0F0FULL; + x = ((x >> 4) | x) & 0x00FF00FF00FF00FFULL; + x = ((x >> 8) | x) & 0x0000FFFF0000FFFFULL; + x = ((x >> 16) | x) & 0x00000000FFFFFFFFULL; + return x; +} + #endif