An unreviewed ARM patch
Kazu Hirata
kazu@codesourcery.com
Tue Jun 8 02:03:00 GMT 2010
Hi Richard,
>> Could someone please review the following patch?
>>
>> [patch] arm: Improve arm_rtx_costs_1 for Thumb2.
>> http://gcc.gnu.org/ml/gcc-patches/2009-12/msg00958.html
>>
>
> Hmm, I agree that there's probably some code in the rest of the MINUS
> case that should be shared. I'm not convinced, however, that we should
> fall through into the PLUS case: most of the code from that point on
> will only apply if we have RSB (and we don't in Thumb-2).
Err, which form of RSB are you talking about? IIRC, ARM has:
RSB <Rd>, <Rn>, <shifter_operand>
Thumb-2 has:
RSB <Rd>,<Rn>,#0
RSB.W <Rd>,<Rn>,#<const>
RSB <Rd>,<Rn>,<Rm>{,<shift>}
So, Thumb-2's RSB supports most of ARM's RSB, except somewhat exotic
operands like variable shifts and rotations in <shifter_operand>.
Did you mean to say Thumb-1 above?
Thanks,
Kazu Hirata
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