[wide-int] Fix mode choice in convert_modes

[Kenneth Zadeck]

this is fine with me.

kenny

On 09/18/2013 03:27 AM, Richard Sandiford wrote:
> Ping
>
> Richard Sandiford <rdsandiford@googlemail.com> writes:
>> Enabling the CONST_INT assert showed that this branch-local code was
>> passing the wrong mode to std::make_pair.  The mode of X is OLDMODE,
>> and we're supposed to be converting it to MODE.
>>
>> In the case where OLDMODE is VOIDmode, I think we have to assume
>> that every bit of the input is significant.
>>
>> Tested on x86_64-linux-gnu.  OK to install?
>>
>> This and the other patches that I just committed to trunk are enough
>> for a bootstrap and regression test to pass on x86_64-linux-gnu with
>> the assertion for a canonical CONST_INT enabled.  I think it would be
>> better to leave the assertion out until after the merge though,
>> so we can deal with any fallout separately.
>>
>> Thanks,
>> Richard
>>
>>
>> Index: gcc/expr.c
>> ===================================================================
>> --- gcc/expr.c	2013-09-09 11:32:33.734617409 +0100
>> +++ gcc/expr.c	2013-09-09 11:45:27.381001353 +0100
>> @@ -714,13 +714,14 @@ convert_modes (enum machine_mode mode, e
>>         && GET_MODE_CLASS (mode) == MODE_INT
>>         && (oldmode == VOIDmode || GET_MODE_CLASS (oldmode) == MODE_INT))
>>       {
>> -      wide_int w = std::make_pair (x, mode);
>>         /* If the caller did not tell us the old mode, then there is
>> -	 not much to do with respect to canonization.  */
>> -      if (oldmode != VOIDmode
>> -	  && GET_MODE_PRECISION (mode) > GET_MODE_PRECISION (oldmode))
>> -	w = wi::ext (w, GET_MODE_PRECISION (oldmode),
>> -		     unsignedp ? UNSIGNED : SIGNED);
>> +	 not much to do with respect to canonization.  We have to assume
>> +	 that all the bits are significant.  */
>> +      if (oldmode == VOIDmode)
>> +	oldmode = MAX_MODE_INT;
>> +      wide_int w = wide_int::from (std::make_pair (x, oldmode),
>> +				   GET_MODE_PRECISION (mode),
>> +				   unsignedp ? UNSIGNED : SIGNED);
>>         return immed_wide_int_const (w, mode);
>>       }
>>