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Re: [wide-int] Fix mode choice in convert_modes
- From: Richard Sandiford <rdsandiford at googlemail dot com>
- To: gcc-patches at gcc dot gnu dot org
- Cc: zadeck at naturalbridge dot com, mikestump at comcast dot net
- Date: Wed, 18 Sep 2013 08:27:23 +0100
- Subject: Re: [wide-int] Fix mode choice in convert_modes
- Authentication-results: sourceware.org; auth=none
- References: <871u4ygmwq dot fsf at talisman dot default>
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);
> }
>