[LLVMdev] Is address space 1 reserved?

[David Majnemer]

I was repeating something that Nick told me a while ago, he mentioned it
again on the list:
http://lists.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20150105/251080.html

Nick asked for it to get documented but it looks like there is disagreement
as to whether or not it really does (or perhaps should) exist.

On Wed, Jan 7, 2015 at 11:25 AM, Owen Anderson <resistor at mac.com> wrote:

> I'm not aware of any such restriction, and I know of several LLVM based
> systems that use address space 1 for something other than that.
>
> -Owen
>
> On Jan 7, 2015, at 1:18 PM, Philip Reames <listmail at philipreames.com>
> wrote:
>
> On the review for http://reviews.llvm.org/D6808, majnemer
> <http://reviews.llvm.org/p/majnemer/> commented that:
> "Address space 1 has a special meaning in LLVM, it's identical to address
> space 0 except for the fact that "null" may be dereferenced. You might want
> to consider a different address space."
>
> This is the first I've heard of this and I can't find any documentation
> about it being reserved, either in general, or specifically for x86.  Can
> anyone clarify?
>
> The only address spaces with special meanings I know of are:
> - 0 (the normal address space, null is not dereferencable)
> - 256 - TLS, GS relative addressing
> - 257 - FS relative addressing
>
> Philip
>
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