From: Jason Merrill <jason@redhat.com>
To: gcc-patches@gcc.gnu.org, jakub@redhat.com, richard.sandiford@arm.com
Subject: Re: [PATCH] Remove poly_int_pod
Date: Thu, 28 Sep 2023 13:26:30 -0400 [thread overview]
Message-ID: <8673fdfc-4b16-ff4a-8906-c47403cde825@redhat.com> (raw)
In-Reply-To: <mptil7utye5.fsf@arm.com>
On 9/28/23 05:55, Richard Sandiford wrote:
> poly_int was written before the switch to C++11 and so couldn't
> use explicit default constructors. This led to an awkward split
> between poly_int_pod and poly_int. poly_int simply inherited from
> poly_int_pod and added constructors, with the argumentless constructor
> having an empty body. But inheritance meant that poly_int had to
> repeat the assignment operators from poly_int_pod (again, no C++11,
> so no "using" to inherit base-class implementations).
>
> All that goes away if we switch to using default constructors.
>
> The main complication is ensuring that braced initialisation still
> gives a constexpr, so that static variables can be initialised without
> runtime code. The two problems here are:
>
> (1) When initialising a poly_int<N, wide_int> with fewer than N
> coefficients, the other coefficients need to be a zero of
> the same precision as the explicit coefficients. This was
> previously done in a for loop using wi::ints_for<...>::zero,
> but C++11 constexpr constructors can't have function bodies.
> The patch instead uses a series of delegated initialisers to
> fill in the implicit coefficients.
Perhaps it's time to update the bootstrap requirement to C++14 (i.e. GCC
5, from eight years ago). Not that this would affect this particular patch.
Jason
next prev parent reply other threads:[~2023-09-28 17:26 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-09-28 9:55 Richard Sandiford
2023-09-28 14:06 ` Jakub Jelinek
2023-09-28 17:26 ` Jason Merrill [this message]
2023-09-28 19:09 ` Jeff Law
2023-09-29 6:31 ` Richard Biener
2023-09-29 8:14 ` Jakub Jelinek
2023-10-02 7:47 ` Jan-Benedict Glaw
2023-10-02 7:50 ` Richard Sandiford
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