[Bug target/115307] [avr] Don't expand isinf() like a built-in

[rguenth at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115307

--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
The issue is that we probably fold isinff early.  On x86 I see already in
.original:

  return !(ABS_EXPR <f> u<= 3.4028234663852885981170418348451692544e+38);

I think your option is to provide optabs for isinf<mode> but make expansion
of them always FAIL; (which is of course a quite ugly way)