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Re: missed optimization, would be very helpful
- To: egcs at egcs dot cygnus dot com
- Subject: Re: missed optimization, would be very helpful
- From: Zack Weinberg <zack at rabi dot columbia dot edu>
- Date: Fri, 01 Jan 1999 13:52:50 -0500
On Thu, 31 Dec 1998 23:03:25 -0400, Horst von Brand wrote:
>Zack Weinberg <zack@rabi.columbia.edu> said:
>> In a loop of the form
>>
>> while (condition) (*int_ptr)++;
>>
>> gcc generates a read-mod-write cycle to the memory location *int_ptr at each
>> iteration of the loop.
>
>It's still there with egcs-19981226. On i586:
>
This is what I see too. rth doesn't get that on Alpha, so it's an i386.md
problem at this point. A guess at a kludge: if the incdi pattern were
changed to not allow memory operands, that might force the optimization.
But that's overkill.
zw