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Re: RFA: Fix rtl-optimization/22258


Joern RENNECKE wrote:
Bernd Schmidt wrote:

Example? Why isn't this caught by cant_combine_insn_p?



Look at the rtl dumps in the PR. none of the combined insns mentions a CLASS_LIKELY_SPILLED_P register. i3 is insn 31, which is preceded by insn 30. insn30 is not included in the combination attempt, put it sets fr0, which is CLASS_LIKLEY_SPILLED_P. insn 30 and insn 31 (and to some extent the clobber in insn 29) together implement the return value copy.

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.



Bernd



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