Re: push r1, pop r0

Matthijs Kooijman <[email protected]> Wed, 8 Nov 2017 14:14:12 +0100

Newsgroups	gmane.comp.hardware.avr.gcc
Message-ID	<[email protected]>

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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