Re: [avr-gcc-list] push r1, pop r0

[Matthijs Kooijman]

Hi Szikra,

> So it is 2017, but the compiler still cannot optimize away bitwise or
> zero... :(
I think this is https://gcc.gnu.org/bugzilla/show_bug.cgi?id=41076
(which should be fixed in gcc 7 according to the comments). The fix
contains a peephole optimization that I think catches exactly this case:

         6831           (define_peephole2
         6832              [(set (match_operand:QI 0 "register_operand")
         6833                    (const_int 0))
         6834               (set (match_dup 0)
         6835                    (ior:QI (match_dup 0)
         6836                            (match_operand:QI 1 
"register_operand")))]
         6837              ""
         6838              [(set (match_dup 0)
         6839                    (match_dup 1))])

https://gcc.gnu.org/viewcvs/gcc/trunk/gcc/config/avr/avr.md?r1=242907&r2=242906&pathrev=242907

Gr.

Matthijs

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