### Description
Compute 1/sqrt(a) and store the result in d.
### Syntax
```
rsqrt.approx{.ftz}.f32 d, a;
rsqrt.approx.f64 d, a;
```
### Semantics
```
d = 1/sqrt(a);
```
### Examples
```
rsqrt.approx.ftz.f32 isr, x;
rsqrt.approx.f64 ISR, X;
```