[Bug target/106701] Compiler does not take into account number range limitation to avoid subtract from immediate

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106701

--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> ---
I'd say all single-operation magic shouldn't happen in match.pd, this really
looks like something for RTL expansion to decide.  For example some targets
might have instructions that can either do cst - a or cst ^ a with an immediate
(when integer_pow2p (cst + 1)).

match.pd should be about canonicalization here (none of the two is "simpler"),
but canonicalization based on value-range looks a bit iffy.