protect fast tanh against FPE in codegen
protect fast tanh against FPE in codegen

this is porting 1ae659bb7036bb93ca389c4616ded2f6d5b567f9 to the codegen

olifre/root,root-mirror/root,root-mirror/root,olifre/root,karies/root,root-mirror/root,olifre/root,karies/root,olifre/root,root-mirror/root,root-mirror/root,olifre/root,root-mirror/root,karies/root,karies/root,olifre/root,olifre/root,root-mirror/root,olifre/root,root-mirror/root,karies/root,karies/root,karies/root,root-mirror/root,olifre/root,karies/root,root-mirror/root,root-mirror/root,karies/root,olifre/root,olifre/root,karies/root,karies/root