[wide-int] Fix mode choice in convert_modes

[Kenneth Zadeck]

On 09/09/2013 09:56 AM, Richard Sandiford wrote:
> Richard Biener <richard.guenther@gmail.com> writes:
>> On Mon, Sep 9, 2013 at 3:11 PM, Richard Sandiford
>> <rdsandiford@googlemail.com> wrote:
>>> 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.
>> If consuming code assumes CONST_INTs are canonical we better leave it
>> in though.
> Yeah, I think the patch Kenny's working on is going to canonise CONST_INTs
> via the scratch array, to avoid making any assumptions.  I think we should
> keep that for the merge and only swap it for an assert later.
>
> Thanks,
> Richard
yes, this is what my patch does now.