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Re: regrename creates invalid insn


On 03/13/2012 12:41 AM, Andreas Schwab wrote:
> Andreas Schwab <schwab@linux-m68k.org> writes:
> 
>> Ian Lance Taylor <iant@google.com> writes:
>>
>>> Andreas Schwab <schwab@linux-m68k.org> writes:
>>>
>>>> Ian Lance Taylor <iant@google.com> writes:
>>>>
>>>>> But it also looks like the pattern should use a match_scratch.
>>>>
>>>> It is also used as input in operand 2.
>>>
>>> Sorry, I missed that.
>>
>> That appears not to be an issue actually, there is already one use of
>> match_scratch together with a matching constraint in *cmpdi_internal.
>> But then, using match_scratch instead of match_operand doesn't really
>> fix the bug either (it only helps a simplified test case, but not the
>> original one).
> 
> It doesn't actually change anything (I was confused because 4.7/4.8 no
> longer generates the overlapping output for the simplified testcase).

Does 4.7 still have the failure at all? I've checked with the 4.6
branch, and regrename gets confused because there's a REG_DEAD note for
the register, and another REG_UNUSED for the same reg. As far as I
remember, it used to be the case that there should not be a REG_DEAD
note for a register that gets set in the insn, but maybe df changed the
rules? Or maybe it was a df bug in 4.6?


Bernd


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