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Re: how well does gcc support type-specific pointer formats?
- From: Richard Biener <richard dot guenther at gmail dot com>
- To: Mikael Pettersson <mikpelinux at gmail dot com>
- Cc: GCC Development <gcc at gcc dot gnu dot org>
- Date: Wed, 30 Sep 2015 11:33:47 +0200
- Subject: Re: how well does gcc support type-specific pointer formats?
- Authentication-results: sourceware.org; auth=none
- References: <22027 dot 43566 dot 729390 dot 638271 at gargle dot gargle dot HOWL>
On Wed, Sep 30, 2015 at 11:23 AM, Mikael Pettersson
<mikpelinux@gmail.com> wrote:
> Does gcc allow backends to have a say in how pointers are represented
> (bits beyond the address), what happens in conversions between pointer
> types, and what happens in conversions between pointers and uintptr_t?
>
> The target in question has:
> - one pointer format and set of load/store instructions for pointers to int/long
> - another format and set of load/store instructions for pointers to char
> - pointers to short use a third format in general, but can use the int/long
> format IF you know which half of the word you're going to access
>
> What mechanisms, if any, are present in gcc to deal with this?
Basically none. The only thing I could imagine you could use is have
the pointer
formats be different address-spaces. The target controls how to
convert pointers
from/to different address-spaces. I am not aware of specialities for
pointer-to-int
or int-to-pointer conversion though - IIRC they simply use
bit-identical conversions
(thus subregs if the modes differ).
But who would design this kind of weird architecture and think he could get
away with that easily?
Richard.