Assembly Language Examples

Min using cmovle

This code example makes use of the cmovle assembly instruction to compare two 64-bit integer values and return the minimum between integer variables a and b. This code such as this can be useful to reduce branch prediction misses.

min :: (a: int, b: int) -> int {
    ret: int;
    #asm {
        cmp.64     a, b;
        mov.64     ret, b;
        cmovle.64  ret, a;
    }
    return ret;
}

Max using cmovge

This code example makes use of the cmovge assembly instruction to compare two 64-bit integer values and return the maximum between integer variables a and b. This code such as this can be useful to reduce branch prediction misses.

max :: (a: int, b: int) -> int {
    ret: int;
    #asm {
        cmp.64     a, b;
        mov.64     ret, b;
        cmovge.64  ret, a;
    }
    return ret;
}

Abs with cmovs

This code example makes use of the cmovs assembly instruction to compare a value with its negation and return the absolute value of a particular integer number. This code such as this can be useful to reduce branch prediction misses.

abs :: (a: int) -> int {
    ret: int;
    #asm {
        mov     ret, a;
        neg     ret;
        cmovs   ret, a;
    }
    return ret;
}

Popcount

One can use the CPU builtin assembly language instruction popcount to speedup the computation of bits.

Popcount u8

This code example utilizes the x86-64 assembly language to do a popcount on a u8.

popcount_u8 :: (value: u8) -> int {
    result: int;
    #asm {
        bytes: gpr;                // declare a register
        movzxbw    bytes,  value;  // bytes = value
        popcnt.16  result, bytes;  // result = popcount(bytes);
    }
    return result;
}

Popcount u16

This code example utilizes the x86-64 assembly language to do a popcount on a u16.

popcount_u16 :: (value: u16) -> int {
    result: int;
    #asm {
        popcnt.16  result, value;  // result = popcount(value);
    }
    return result;
}

Popcount u32

This code example utilizes the x86-64 assembly language to do a popcount on a u32.

popcount_u32 :: (value: u32) -> int {
    result: int;
    #asm {
        popcnt.32  result, value;  // result = popcount(value);
    }
    return result;
}

Popcount u64

This code example utilizes the x86-64 assembly language to do a popcount on a u64.

popcount_u64 :: (value: u64) -> int {
    result: int;
    #asm {
        popcnt.64  result, value;  // result = popcount(result);
    }
    return result;
}