[Bug target/106562] PRU: Inefficient code for zero check of 64-bit (boolean) AND result

[dimitar at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106562

--- Comment #1 from Dimitar Dimitrov <dimitar at gcc dot gnu.org> ---
I explored setting REGMODE_NATURAL_SIZE=4 for PRU.  This required adjustments
in many places in middle end to use REGMODE_NATURAL_SIZE instead of word_mode.
That however proved too intrusive. And I don't see how other targets would
benefit.

I'll instead go with defining an expansion of cbranchdi4 for PRU. That would be
contained in the PRU backend only, and thus safer.