Microsoft Specific

Emits the Streaming SIMD Extensions (SSE) instruction cvtsi2ss. This instruction converts a 64-bit signed integer to a single-precision floating point number and inserts it into another 128 bit parameter.

__m128 _mm_cvtsi64_ss( 
   __m128 a,
   __int64 b


  • [in] a
    A 128-bit parameter that contains four 32-bit floating point values.

  • [in] b
    A 64-bit signed integer.

Return value

The result can be expressed with the following equations:

r0 := FLT(b)
r1 := a1
r2 := a2
r3 := a3






Header file <xmmintrin.h>


r0-r3 and a0-a3 are are the sequentially ordered 32-bit components of return value r and parameter a, respectively. r0 and a0 are the least significant 32 bits.

The upper 96 bits of parameter a are passed to the result unchanged.

Before you use this intrinsic, software must ensure that the processor supports the instruction.


#include <stdio.h>
#include <xmmintrin.h>

int main ()
    __m128 a;
    __int64 b = -65535;

    a.m128_f32[0] = 1.5;
    a.m128_f32[1] = -3.25;
    a.m128_f32[2] = 3.0625;
    a.m128_f32[3] = -50.125;

    __m128 res = _mm_cvtsi64_ss(a, b);

    printf_s("Original a: %f\t%f\t%f\t%f\nOriginal b: %I64d\n",
                a.m128_f32[3], a.m128_f32[2], a.m128_f32[1], a.m128_f32[0], b);
    printf_s("Result res: %f\t%f\t%f\t%f\n",
                res.m128_f32[3], res.m128_f32[2], res.m128_f32[1], res.m128_f32[0]);

    return 0;
Original a: -50.125000  3.062500        -3.250000       1.500000
Original b: -65535
Result res: -50.125000  3.062500        -3.250000       -65535.000000

See Also


Compiler Intrinsics