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Re: RFA: Fix rtl-optimization/22258


Bernd Schmidt wrote:

Ok, I see. I must say I'm not very fond of introducing hard reg references into complex insns during combine; I'd prefer cant_combine_insn_p to just reject any moves involving hardregs. My initial version of that function did that, but in
http://gcc.gnu.org/ml/gcc-patches/2002-05/msg01216.html
Dale Johannesen claims that restricting the test to CLASS_LIKELY_SPILLED_P is a win on PPC. I'm curious why.

It is also a win on the SH, because arguments that are passed in registers can be put directly into the right register.


It would also make sense to allow combinations with a CLASS_LIKELY_SPILLED_P destination in i3,
except that since your last reload rewrite this won't work if a spill in that class is needed for that insn
(yes, what we had before was unsafe, but it did get this case right) - we could make it work if we didn't
put the newly set register into bad_spill_regs and instead tracked the actual hard reg use. At least if
we have an actual operand with a constraint, we know if this is an earlyclobber operand or not.



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