[Patch:H8/300] Absolute address mode support for bit_operand predicate

[Jeff Law]

On 04/16/10 09:25, Jeff Law wrote:
> On 04/16/10 01:19, Kaushik Phatak wrote:
>>> 2010-04-12  Kaushik Phatak<kaushik.phatak@kpitcummins.com>
>>>
>>>     * config/h8300/predicate.md (bit_operand): Allow immediate 
>>> values that
>>>     satisfy 'U' constraint.
>>>
>>>> OK.  Please install.
>> Thanks for approval.
>> I do not have check-in rights. Could you apply this to 4.6?
> OK.  I installed it for you.
>
>> Also, could you please apply the following approved patch to 4.6,
>>
>> http://gcc.gnu.org/ml/gcc-patches/2010-03/msg00373.html
> I was looking at it yesterday; I'm investigating a codesize regression 
> with that patch.  I'll post to the list once I've got a handle on what 
> the problem is.
OK.  The problem is rearranging alternatives in the logical patterns 
(and, ior, xor) to prefer the bit variants inhibits the elimination of 
tst insns as the bit versions do not set the condition codes and the 
condition codes need to be set so that redundant tst insns can be 
detected and eliminated.

ISTM that we want to avoid the bit variants when they directly feed a 
tst insn.   I think the attribute mechanisms are powerful enough to 
describe this, but I haven't tried it myself.

For now, I'm going to install the new patterns, but leave the existing 
and/ior/xor patterns alone until we can resolve this issue.

Jeff