1.10. Integer Intrinsics
This section describes integer intrinsic functions that are only supported in device code. To use these functions you do not need to include any additional header files in your program.
Functions
 __device__ unsigned int __brev ( unsigned int x )
 Reverse the bit order of a 32bit unsigned integer.
 __device__ unsigned long long int __brevll ( unsigned long long int x )
 Reverse the bit order of a 64bit unsigned integer.
 __device__ unsigned int __byte_perm ( unsigned int x, unsigned int y, unsigned int s )
 Return selected bytes from two 32bit unsigned integers.
 __device__ int __clz ( int x )
 Return the number of consecutive highorder zero bits in a 32bit integer.
 __device__ int __clzll ( long long int x )
 Count the number of consecutive highorder zero bits in a 64bit integer.
 __device__ unsigned int __dp2a_hi ( ushort2 srcA, uchar4 srcB, unsigned int c )
 Twoway unsignedint16 by int8 dot product with unsignedint32 accumulate, taking the upper half of the second input.
 __device__ int __dp2a_hi ( short2 srcA, char4 srcB, int c )
 Twoway signedint16 by int8 dot product with int32 accumulate, taking the upper half of the second input.
 __device__ unsigned int __dp2a_hi ( unsigned int srcA, unsigned int srcB, unsigned int c )
 Twoway unsignedint16 by int8 dot product with unsignedint32 accumulate, taking the upper half of the second input.
 __device__ int __dp2a_hi ( int srcA, int srcB, int c )
 Twoway signedint16 by int8 dot product with int32 accumulate, taking the upper half of the second input.
 __device__ unsigned int __dp2a_lo ( ushort2 srcA, uchar4 srcB, unsigned int c )
 Twoway unsignedint16 by int8 dot product with unsignedint32 accumulate, taking the lower half of the second input.
 __device__ int __dp2a_lo ( short2 srcA, char4 srcB, int c )
 Twoway signedint16 by int8 dot product with int32 accumulate, taking the lower half of the second input.
 __device__ unsigned int __dp2a_lo ( unsigned int srcA, unsigned int srcB, unsigned int c )
 Twoway unsignedint16 by int8 dot product with unsignedint32 accumulate, taking the lower half of the second input.
 __device__ int __dp2a_lo ( int srcA, int srcB, int c )
 Twoway signedint16 by int8 dot product with int32 accumulate, taking the lower half of the second input.
 __device__ unsigned int __dp4a ( uchar4 srcA, uchar4 srcB, unsigned int c )
 Fourway unsignedint8 dot product with unsignedint32 accumulate.
 __device__ int __dp4a ( char4 srcA, char4 srcB, int c )
 Fourway signedint8 dot product with int32 accumulate.
 __device__ unsigned int __dp4a ( unsigned int srcA, unsigned int srcB, unsigned int c )
 Fourway unsignedint8 dot product with unsignedint32 accumulate.
 __device__ int __dp4a ( int srcA, int srcB, int c )
 Fourway signedint8 dot product with int32 accumulate.
 __device__ int __ffs ( int x )
 Find the position of the least significant bit set to 1 in a 32bit integer.
 __device__ int __ffsll ( long long int x )
 Find the position of the least significant bit set to 1 in a 64bit integer.
 __device__ unsigned __fns ( unsigned mask, unsigned base, int offset )
 Find the position of the nth set to 1 bit in a 32bit integer.
 __device__ unsigned int __funnelshift_l ( unsigned int lo, unsigned int hi, unsigned int shift )
 Concatenate hi : lo, shift left by shift & 31 bits, return the most significant 32 bits.
 __device__ unsigned int __funnelshift_lc ( unsigned int lo, unsigned int hi, unsigned int shift )
 Concatenate hi : lo, shift left by min(shift, 32) bits, return the most significant 32 bits.
 __device__ unsigned int __funnelshift_r ( unsigned int lo, unsigned int hi, unsigned int shift )
 Concatenate hi : lo, shift right by shift & 31 bits, return the least significant 32 bits.
 __device__ unsigned int __funnelshift_rc ( unsigned int lo, unsigned int hi, unsigned int shift )
 Concatenate hi : lo, shift right by min(shift, 32) bits, return the least significant 32 bits.
 __device__ int __hadd ( int x, int y )
 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 64bit integers.
 __device__ int __mulhi ( int x, int y )
 Calculate the most significant 32 bits of the product of the two 32bit integers.
 __device__ int __popc ( unsigned int x )
 Count the number of bits that are set to 1 in a 32bit integer.
 __device__ int __popcll ( unsigned long long int x )
 Count the number of bits that are set to 1 in a 64bit integer.
 __device__ int __rhadd ( int x, int y )
 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 x, unsigned int y )
 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 32bit unsigned integers.
 __device__ unsigned int __urhadd ( unsigned int x, unsigned int y )
 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 32bit 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 32bit unsigned integer x.
 __device__ unsigned long long int __brevll ( unsigned long long int x )

Reverse the bit order of a 64bit 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 64bit unsigned integer x.
 __device__ unsigned int __byte_perm ( unsigned int x, unsigned int y, unsigned int s )

Return selected bytes from two 32bit unsigned integers.
Returns
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.
Description
Create 8byte source

uint64_t tmp64 = ((uint64_t)y << 32)  x;
Extract selector bits

selector0 = (s >> 0) & 0x7;

selector1 = (s >> 4) & 0x7;

selector2 = (s >> 8) & 0x7;

selector3 = (s >> 12) & 0x7;
Return 4 selected bytes from 8byte source:

res[07:00] = tmp64[selector0];

res[15:08] = tmp64[selector1];

res[23:16] = tmp64[selector2];

res[31:24] = tmp64[selector3];

 __device__ int __clz ( int x )

Return the number of consecutive highorder zero bits in a 32bit 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 64bit 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__ unsigned int __dp2a_hi ( ushort2 srcA, uchar4 srcB, unsigned int c )

Twoway unsignedint16 by int8 dot product with unsignedint32 accumulate, taking the upper half of the second input.
Description
Takes two packed 16bit integers from scrA vector and two packed 8bit integers from the upper 16 bits of srcB vector, then creates two pairwise 8x16 products and adds them together to an unsigned 32bit integer c.
 __device__ int __dp2a_hi ( short2 srcA, char4 srcB, int c )

Twoway signedint16 by int8 dot product with int32 accumulate, taking the upper half of the second input.
Description
Takes two packed 16bit integers from scrA vector and two packed 8bit integers from the upper 16 bits of srcB vector, then creates two pairwise 8x16 products and adds them together to a signed 32bit integer c.
 __device__ unsigned int __dp2a_hi ( unsigned int srcA, unsigned int srcB, unsigned int c )

Twoway unsignedint16 by int8 dot product with unsignedint32 accumulate, taking the upper half of the second input.
Description
Extracts two packed 16bit integers from scrA and two packed 8bit integers from the upper 16 bits of srcB, then creates two pairwise 8x16 products and adds them together to an unsigned 32bit integer c.
 __device__ int __dp2a_hi ( int srcA, int srcB, int c )

Twoway signedint16 by int8 dot product with int32 accumulate, taking the upper half of the second input.
Description
Extracts two packed 16bit integers from scrA and two packed 8bit integers from the upper 16 bits of srcB, then creates two pairwise 8x16 products and adds them together to a signed 32bit integer c.
 __device__ unsigned int __dp2a_lo ( ushort2 srcA, uchar4 srcB, unsigned int c )

Twoway unsignedint16 by int8 dot product with unsignedint32 accumulate, taking the lower half of the second input.
Description
Takes two packed 16bit integers from scrA vector and two packed 8bit integers from the lower 16 bits of srcB vector, then creates two pairwise 8x16 products and adds them together to an unsigned 32bit integer c.
 __device__ int __dp2a_lo ( short2 srcA, char4 srcB, int c )

Twoway signedint16 by int8 dot product with int32 accumulate, taking the lower half of the second input.
Description
Takes two packed 16bit integers from scrA vector and two packed 8bit integers from the lower 16 bits of srcB vector, then creates two pairwise 8x16 products and adds them together to a signed 32bit integer c.
 __device__ unsigned int __dp2a_lo ( unsigned int srcA, unsigned int srcB, unsigned int c )

Twoway unsignedint16 by int8 dot product with unsignedint32 accumulate, taking the lower half of the second input.
Description
Extracts two packed 16bit integers from scrA and two packed 8bit integers from the lower 16 bits of srcB, then creates two pairwise 8x16 products and adds them together to an unsigned 32bit integer c.
 __device__ int __dp2a_lo ( int srcA, int srcB, int c )

Twoway signedint16 by int8 dot product with int32 accumulate, taking the lower half of the second input.
Description
Extracts two packed 16bit integers from scrA and two packed 8bit integers from the lower 16 bits of srcB, then creates two pairwise 8x16 products and adds them together to a signed 32bit integer c.
 __device__ unsigned int __dp4a ( uchar4 srcA, uchar4 srcB, unsigned int c )

Fourway unsignedint8 dot product with unsignedint32 accumulate.
Description
Takes four pairs of packed bytesized integers from scrA and srcB vectors, then creates four pairwise products and adds them together to an unsigned 32bit integer c.
 __device__ int __dp4a ( char4 srcA, char4 srcB, int c )

Fourway signedint8 dot product with int32 accumulate.
Description
Takes four pairs of packed bytesized integers from scrA and srcB vectors, then creates four pairwise products and adds them together to a signed 32bit integer c.
 __device__ unsigned int __dp4a ( unsigned int srcA, unsigned int srcB, unsigned int c )

Fourway unsignedint8 dot product with unsignedint32 accumulate.
Description
Extracts four pairs of packed bytesized integers from scrA and srcB, then creates four pairwise products and adds them together to an unsigned 32bit integer c.
 __device__ int __dp4a ( int srcA, int srcB, int c )

Fourway signedint8 dot product with int32 accumulate.
Description
Extracts four pairs of packed bytesized integers from scrA and srcB, then creates four pairwise products and adds them together to a signed 32bit integer c.
 __device__ int __ffs ( int x )

Find the position of the least significant bit set to 1 in a 32bit 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 64bit 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__ unsigned __fns ( unsigned mask, unsigned base, int offset )

Find the position of the nth set to 1 bit in a 32bit integer.
Returns
Returns a value between 0 and 32 inclusive representing the position of the nth set bit.
 parameter base must be <=31, otherwise behavior is undefined.
Description
Given a 32bit value mask and an integer value base (between 0 and 31), find the nth (given by offset) set bit in mask from the base bit. If not found, return 0xFFFFFFFF.
See also https://docs.nvidia.com/cuda/parallelthreadexecution/index.html#integerarithmeticinstructionsfns for more information.
 __device__ unsigned int __funnelshift_l ( unsigned int lo, unsigned int hi, unsigned int shift )

Concatenate hi : lo, shift left by shift & 31 bits, return the most significant 32 bits.
Returns
Returns the most significant 32 bits of the shifted 64bit value.
Description
Shift the 64bit value formed by concatenating argument lo and hi left by the amount specified by the argument shift. Argument lo holds bits 31:0 and argument hi holds bits 63:32 of the 64bit source value. The source is shifted left by the wrapped value of shift (shift & 31). The most significant 32bits of the result are returned.
 __device__ unsigned int __funnelshift_lc ( unsigned int lo, unsigned int hi, unsigned int shift )

Concatenate hi : lo, shift left by min(shift, 32) bits, return the most significant 32 bits.
Returns
Returns the most significant 32 bits of the shifted 64bit value.
Description
Shift the 64bit value formed by concatenating argument lo and hi left by the amount specified by the argument shift. Argument lo holds bits 31:0 and argument hi holds bits 63:32 of the 64bit source value. The source is shifted left by the clamped value of shift (min(shift, 32)). The most significant 32bits of the result are returned.
 __device__ unsigned int __funnelshift_r ( unsigned int lo, unsigned int hi, unsigned int shift )

Concatenate hi : lo, shift right by shift & 31 bits, return the least significant 32 bits.
Returns
Returns the least significant 32 bits of the shifted 64bit value.
Description
Shift the 64bit value formed by concatenating argument lo and hi right by the amount specified by the argument shift. Argument lo holds bits 31:0 and argument hi holds bits 63:32 of the 64bit source value. The source is shifted right by the wrapped value of shift (shift & 31). The least significant 32bits of the result are returned.
 __device__ unsigned int __funnelshift_rc ( unsigned int lo, unsigned int hi, unsigned int shift )

Concatenate hi : lo, shift right by min(shift, 32) bits, return the least significant 32 bits.
Returns
Returns the least significant 32 bits of the shifted 64bit value.
Description
Shift the 64bit value formed by concatenating argument lo and hi right by the amount specified by the argument shift. Argument lo holds bits 31:0 and argument hi holds bits 63:32 of the 64bit source value. The source is shifted right by the clamped value of shift (min(shift, 32)). The least significant 32bits of the result are returned.
 __device__ int __hadd ( int x, int y )

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 64bit 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 32bit 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 32bit 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 64bit 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 x, int y )

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 x, unsigned int y )

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 32bit 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 x, unsigned int y )

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.