v1.6.1, when `--math-mode=fast`

:

```
julia> f() = exp(1.0);
julia> f() - exp(1.0)
0.002427216033242807
```

which is obviously wrong. It’s wrong **even** in fastmath mode!

while when `--math-mode=ieee`

, no problem:

```
julia> f() = exp(1.0);
julia> f() - exp(1.0)
0.0
```