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Subject: Re: [PATCH][combine] PR rtl-optimization/68651 Try changing rtx from (r + r) to (r << 1) to aid recognition
To: Richard Earnshaw <Richard.Earnshaw@foss.arm.com>,        Kyrill Tkachov <kyrylo.tkachov@foss.arm.com>,        GCC Patches <gcc-patches@gcc.gnu.org>
References: <566EB527.6070305@foss.arm.com> <56702223.80702@redhat.com> <567024C4.2080208@foss.arm.com>
Cc: Segher Boessenkool <segher@kernel.crashing.org>
From: Bernd Schmidt <bschmidt@redhat.com>
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Date: Tue, 15 Dec 2015 14:37:00 -0000
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On 12/15/2015 03:33 PM, Richard Earnshaw wrote:
>
> It's also possible that this would explicitly break some other
> optimization passes (such as the way in which multiplies are synthesised
> with shift/add operations).

How so? IMO such a change would make cost calculations more accurate and 
should help rather than break anything.


Bernd