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[Bug tree-optimization/19703] Poor optimisation of loop test
- From: "andrewhutchinson at cox dot net" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: 30 Jan 2005 04:58:41 -0000
- Subject: [Bug tree-optimization/19703] Poor optimisation of loop test
- References: <20050130025905.19703.andrewhutchinson@cox.net>
- Reply-to: gcc-bugzilla at gcc dot gnu dot org
------- Additional Comments From andrewhutchinson at cox dot net 2005-01-30 04:58 -------
Subject: Re: Poor optimisation of loop test
I am not sure what makes you think that. Compare with ZERO is
invariabley cheaper than compare with "n".
The former is "free" sign status following any conditioning setting
instruction - like subtract!
Its even the sign bit of the result!
subi r28,10
cpi r28, -10
brpl looptop
subi r28,10
brpl looptop
or did I miss something?
pinskia at gcc dot gnu dot org wrote:
>------- Additional Comments From pinskia at gcc dot gnu dot org 2005-01-30 03:17 -------
>Hmm, on most targets it is true that != is the same case as >=.
>
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19703