[Bug tree-optimization/91734] gcc skip an if statement with "-O1 -ffast-math"

[chinoune.mehdi at hotmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91734

--- Comment #2 from Chinoune <chinoune.mehdi at hotmail dot com> ---
Replacing `if( az<FLT_MIN)` with `if( az==0.f )` gives a correct result.