Re: [RFA] [PATCH] Fix invalid redundant extension elimination for rl78 port

[Jeff Law <law@redhat.com>]

On 12/01/2015 12:32 PM, Richard Sandiford wrote:
> Jeff Law <law@redhat.com> writes:
>> @@ -1080,6 +1070,18 @@ add_removable_extension (const_rtx expr, rtx_insn *insn,
>>   	      }
>>   	  }
>>
>> +      /* Fourth, if the extended version occupies more registers than the
>> +	 original and the source of the extension is the same hard register
>> +	 as the destination of the extension, then we can not eliminate
>> +	 the extension without deep analysis, so just punt.
>> +
>> +	 We allow this when the registers are different because the
>> +	 code in combine_reaching_defs will handle that case correctly.  */
>> +      if ((HARD_REGNO_NREGS (REGNO (dest), mode)
>> +	   != HARD_REGNO_NREGS (REGNO (reg), GET_MODE (reg)))
>> +	  && REGNO (dest) == REGNO (reg))
>> +	return;
>> +
>>         /* Then add the candidate to the list and insert the reaching definitions
>>            into the definition map.  */
>>         ext_cand e = {expr, code, mode, insn};
>
> I might be wrong, but the check looks specific to little-endian.  Would
> it make sense to use reg_overlap_mentioned_p instead of the REGNO check?
Agreed.  Testing in progress now...

jeff