[Bug rtl-optimization/91865] Combine misses opportunity to remove (sign_extend (zero_extend)) before searching for insn patterns

[segher at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91865

Segher Boessenkool <segher at gcc dot gnu.org> changed:

           What    |Removed                     |Added
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           Assignee|unassigned at gcc dot gnu.org      |segher at gcc dot gnu.org

--- Comment #4 from Segher Boessenkool <segher at gcc dot gnu.org> ---
Created attachment 47550
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=47550&action=edit
simplify-rtx patch for extends of AND of hard reg

So I did a patch to make this work (in simplify-rtx) also for hard registers
(see attachment).

But, we should not have this problem at all if make_more_copies would have
done its job.  It turns out that msp430 does not do register copies for the
arguments, but zero_extends instead.  Let me see how we can handle that
easily.