1.6. Integer Intrinsics
This section describes integer intrinsic functions that are only supported in device code.
Functions
 __device__ unsigned int __brev ( unsigned int x )
 Reverse the bit order of a 32 bit unsigned integer.
 __device__ unsigned long long int __brevll ( unsigned long long int x )
 Reverse the bit order of a 64 bit unsigned integer.
 __device__ unsigned int __byte_perm ( unsigned int x, unsigned int y, unsigned int s )
 Return selected bytes from two 32 bit unsigned integers.
 __device__ int __clz ( int x )
 Return the number of consecutive highorder zero bits in a 32 bit integer.
 __device__ int __clzll ( long long int x )
 Count the number of consecutive highorder zero bits in a 64 bit integer.
 __device__ int __ffs ( int x )
 Find the position of the least significant bit set to 1 in a 32 bit integer.
 __device__ int __ffsll ( long long int x )
 Find the position of the least significant bit set to 1 in a 64 bit integer.
 __device__ int __hadd ( int , int )
 Compute average of signed input arguments, avoiding overflow in the intermediate sum.
 __device__ int __mul24 ( int x, int y )
 Calculate the least significant 32 bits of the product of the least significant 24 bits of two integers.
 __device__ long long int __mul64hi ( long long int x, long long int y )
 Calculate the most significant 64 bits of the product of the two 64 bit integers.
 __device__ int __mulhi ( int x, int y )
 Calculate the most significant 32 bits of the product of the two 32 bit integers.
 __device__ int __popc ( unsigned int x )
 Count the number of bits that are set to 1 in a 32 bit integer.
 __device__ int __popcll ( unsigned long long int x )
 Count the number of bits that are set to 1 in a 64 bit integer.
 __device__ int __rhadd ( int , int )
 Compute rounded average of signed input arguments, avoiding overflow in the intermediate sum.
 __device__ unsigned int __sad ( int x, int y, unsigned int z )
 Calculate $xy+z$ , the sum of absolute difference.
 __device__ unsigned int __uhadd ( unsigned int, unsigned int )
 Compute average of unsigned input arguments, avoiding overflow in the intermediate sum.
 __device__ unsigned int __umul24 ( unsigned int x, unsigned int y )
 Calculate the least significant 32 bits of the product of the least significant 24 bits of two unsigned integers.
 __device__ unsigned long long int __umul64hi ( unsigned long long int x, unsigned long long int y )
 Calculate the most significant 64 bits of the product of the two 64 unsigned bit integers.
 __device__ unsigned int __umulhi ( unsigned int x, unsigned int y )
 Calculate the most significant 32 bits of the product of the two 32 bit unsigned integers.
 __device__ unsigned int __urhadd ( unsigned int, unsigned int )
 Compute rounded average of unsigned input arguments, avoiding overflow in the intermediate sum.
 __device__ unsigned int __usad ( unsigned int x, unsigned int y, unsigned int z )
 Calculate $xy+z$ , the sum of absolute difference.
Functions
 __device__ unsigned int __brev ( unsigned int x )

Reverse the bit order of a 32 bit unsigned integer.
Returns
Returns the bitreversed value of x. i.e. bit N of the return value corresponds to bit 31N of x.
Description
Reverses the bit order of the 32 bit unsigned integer x.
 __device__ unsigned long long int __brevll ( unsigned long long int x )

Reverse the bit order of a 64 bit unsigned integer.
Returns
Returns the bitreversed value of x. i.e. bit N of the return value corresponds to bit 63N of x.
Description
Reverses the bit order of the 64 bit unsigned integer x.
 __device__ unsigned int __byte_perm ( unsigned int x, unsigned int y, unsigned int s )

Return selected bytes from two 32 bit unsigned integers.
Returns
The returned value r is computed to be: result[n] := input[selector[n]] where result[n] is the nth byte of r.
Description
byte_perm(x,y,s) returns a 32bit integer consisting of four bytes from eight input bytes provided in the two input integers x and y, as specified by a selector, s.
The input bytes are indexed as follows: input[0] = x<7:0> input[1] = x<15:8> input[2] = x<23:16> input[3] = x<31:24> input[4] = y<7:0> input[5] = y<15:8> input[6] = y<23:16> input[7] = y<31:24> The selector indices are as follows (the upper 16bits of the selector are not used): selector[0] = s<2:0> selector[1] = s<6:4> selector[2] = s<10:8> selector[3] = s<14:12>
 __device__ int __clz ( int x )

Return the number of consecutive highorder zero bits in a 32 bit integer.
Returns
Returns a value between 0 and 32 inclusive representing the number of zero bits.
Description
Count the number of consecutive leading zero bits, starting at the most significant bit (bit 31) of x.
 __device__ int __clzll ( long long int x )

Count the number of consecutive highorder zero bits in a 64 bit integer.
Returns
Returns a value between 0 and 64 inclusive representing the number of zero bits.
Description
Count the number of consecutive leading zero bits, starting at the most significant bit (bit 63) of x.
 __device__ int __ffs ( int x )

Find the position of the least significant bit set to 1 in a 32 bit integer.
Returns
Returns a value between 0 and 32 inclusive representing the position of the first bit set.
 __ffs(0) returns 0.
Description
Find the position of the first (least significant) bit set to 1 in x, where the least significant bit position is 1.
 __device__ int __ffsll ( long long int x )

Find the position of the least significant bit set to 1 in a 64 bit integer.
Returns
Returns a value between 0 and 64 inclusive representing the position of the first bit set.
 __ffsll(0) returns 0.
Description
Find the position of the first (least significant) bit set to 1 in x, where the least significant bit position is 1.
 __device__ int __hadd ( int , int )

Compute average of signed input arguments, avoiding overflow in the intermediate sum.
Returns
Returns a signed integer value representing the signed average value of the two inputs.
Description
Compute average of signed input arguments x and y as ( x + y ) >> 1, avoiding overflow in the intermediate sum.
 __device__ int __mul24 ( int x, int y )

Calculate the least significant 32 bits of the product of the least significant 24 bits of two integers.
Returns
Returns the least significant 32 bits of the product x * y.
Description
Calculate the least significant 32 bits of the product of the least significant 24 bits of x and y. The high order 8 bits of x and y are ignored.
 __device__ long long int __mul64hi ( long long int x, long long int y )

Calculate the most significant 64 bits of the product of the two 64 bit integers.
Returns
Returns the most significant 64 bits of the product x * y.
Description
Calculate the most significant 64 bits of the 128bit product x * y, where x and y are 64bit integers.
 __device__ int __mulhi ( int x, int y )

Calculate the most significant 32 bits of the product of the two 32 bit integers.
Returns
Returns the most significant 32 bits of the product x * y.
Description
Calculate the most significant 32 bits of the 64bit product x * y, where x and y are 32bit integers.
 __device__ int __popc ( unsigned int x )

Count the number of bits that are set to 1 in a 32 bit integer.
Returns
Returns a value between 0 and 32 inclusive representing the number of set bits.
Description
Count the number of bits that are set to 1 in x.
 __device__ int __popcll ( unsigned long long int x )

Count the number of bits that are set to 1 in a 64 bit integer.
Returns
Returns a value between 0 and 64 inclusive representing the number of set bits.
Description
Count the number of bits that are set to 1 in x.
 __device__ int __rhadd ( int , int )

Compute rounded average of signed input arguments, avoiding overflow in the intermediate sum.
Returns
Returns a signed integer value representing the signed rounded average value of the two inputs.
Description
Compute average of signed input arguments x and y as ( x + y + 1 ) >> 1, avoiding overflow in the intermediate sum.
 __device__ unsigned int __sad ( int x, int y, unsigned int z )

Calculate $xy+z$ , the sum of absolute difference.
Returns
Returns $xy+z$ .
Description
Calculate $xy+z$ , the 32bit sum of the third argument z plus and the absolute value of the difference between the first argument, x, and second argument, y.
Inputs x and y are signed 32bit integers, input z is a 32bit unsigned integer.
 __device__ unsigned int __uhadd ( unsigned int, unsigned int )

Compute average of unsigned input arguments, avoiding overflow in the intermediate sum.
Returns
Returns an unsigned integer value representing the unsigned average value of the two inputs.
Description
Compute average of unsigned input arguments x and y as ( x + y ) >> 1, avoiding overflow in the intermediate sum.
 __device__ unsigned int __umul24 ( unsigned int x, unsigned int y )

Calculate the least significant 32 bits of the product of the least significant 24 bits of two unsigned integers.
Returns
Returns the least significant 32 bits of the product x * y.
Description
Calculate the least significant 32 bits of the product of the least significant 24 bits of x and y. The high order 8 bits of x and y are ignored.
 __device__ unsigned long long int __umul64hi ( unsigned long long int x, unsigned long long int y )

Calculate the most significant 64 bits of the product of the two 64 unsigned bit integers.
Returns
Returns the most significant 64 bits of the product x * y.
Description
Calculate the most significant 64 bits of the 128bit product x * y, where x and y are 64bit unsigned integers.
 __device__ unsigned int __umulhi ( unsigned int x, unsigned int y )

Calculate the most significant 32 bits of the product of the two 32 bit unsigned integers.
Returns
Returns the most significant 32 bits of the product x * y.
Description
Calculate the most significant 32 bits of the 64bit product x * y, where x and y are 32bit unsigned integers.
 __device__ unsigned int __urhadd ( unsigned int, unsigned int )

Compute rounded average of unsigned input arguments, avoiding overflow in the intermediate sum.
Returns
Returns an unsigned integer value representing the unsigned rounded average value of the two inputs.
Description
Compute average of unsigned input arguments x and y as ( x + y + 1 ) >> 1, avoiding overflow in the intermediate sum.
 __device__ unsigned int __usad ( unsigned int x, unsigned int y, unsigned int z )

Calculate $xy+z$ , the sum of absolute difference.
Returns
Returns $xy+z$ .
Description
Calculate $xy+z$ , the 32bit sum of the third argument z plus and the absolute value of the difference between the first argument, x, and second argument, y.
Inputs x, y, and z are unsigned 32bit integers.