#x86_64 Linux machine language, 5 bytes 0: f3 0f 53 c0 rcpss %xmm0,%xmm0 4: c3 retq To test this, you can compile and run the following C program

#include<stdio.h>
#include<math.h>
const char f[]="\xf3\xf\x53\xc0\xc3";
int main(){
  for( float i = .1; i < 2; i+= .1 ) {
    printf( "%f %f\n", i, ((float(*)(float))f)(i) );
  }
}

Try it online!

x86_64 Linux machine language, 5 bytes

0:       f3 0f 53 c0             rcpss  %xmm0,%xmm0
4:       c3                      retq

To test this, you can compile and run the following C program

#include<stdio.h>
#include<math.h>
const char f[]="\xf3\xf\x53\xc0\xc3";
int main(){
  for( float i = .1; i < 2; i+= .1 ) {
    printf( "%f %f\n", i, ((float(*)(float))f)(i) );
  }
}

Try it online!

#x86_64 Linux machine language, 5 bytes 0: f3 0f 53 c0 rcpss %xmm0,%xmm0 4: c3 retq To test this, you can compile and run the following C program

#include<stdio.h>
#include<math.h>
const char f[]="\xf3\xf\x53\xc0\xc3";
int main(){
  for( double i = .1; i < 2; i+= .1 ) {
    printf( "%f %f\n", i, ((float(*)(float))f)(i) );
  }
}

Try it online!

#x86_64 Linux machine language, 5 bytes 0: f3 0f 53 c0 rcpss %xmm0,%xmm0 4: c3 retq To test this, you can compile and run the following C program

#include<stdio.h>
#include<math.h>
const char f[]="\xf3\xf\x53\xc0\xc3";
int main(){
  for( float i = .1; i < 2; i+= .1 ) {
    printf( "%f %f\n", i, ((float(*)(float))f)(i) );
  }
}

Try it online!