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<p>Ed, it sounds like you have an idea for a new language with a new
execution model and a special object representation. I was merely
trying to point out that these ideas have little to do with what
C++ compilers do today. <br>
</p>
<p>Oleg.<br>
</p>
<div class="moz-cite-prefix">On 2018-11-28 15:28, Edward Givelberg
wrote:<br>
</div>
<blockquote type="cite"
cite="mid:CAORUK-xy0fjiTc4FrjFTo-kXdaYRoZZyLjpWQgzNgq7Z4r2mHw@mail.gmail.com">
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<div>Oleg,</div>
<div><br>
</div>
<div>May be I am misunderstanding what you're saying... <br>
</div>
<div>
<div>Since I am proposing a different framework for execution,</div>
</div>
<div>the architecture which has an abstract machine <br>
</div>
<div>and a memory model will have to change. <br>
</div>
<div>Since I'd like to have remote objects,</div>
<div>which are native to C++, unlike the existing objects, which
are all local,</div>
<div>I am proposing this IOR layer. Access to objects will have
to change.</div>
<div>An object access will not longer be a memory access, unless
some</div>
<div>compiler optimization determines that the object is local.</div>
<div>
<div>So this probably means that it requires changes to the
LLVM IR?</div>
<div>As I said, I don't know enough about the current LLVM
architecture</div>
<div>to make a detailed plan, but I think it is an interesting
problem.<br>
</div>
</div>
<div><br>
</div>
<div>Ed<br>
</div>
<div><br>
</div>
</div>
<br>
<div class="gmail_quote">
<div dir="ltr">On Wed, Nov 28, 2018 at 5:42 PM Oleg Smolsky <<a
href="mailto:oleg@cohesity.com" moz-do-not-send="true">oleg@cohesity.com</a>>
wrote:<br>
</div>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">On
2018-11-28 13:14, Edward Givelberg via cfe-dev wrote:<br>
><br>
> [...]<br>
> Naively, it seems to me that LLVM is a sequential VM, so
perhaps its <br>
> architecture needs be extended.<br>
> I am proposing an intermediate representation which
encodes object <br>
> operations,<br>
> let's call it IOR. IOR is translated to interconnect
hardware <br>
> instructions, as well as LLVM's IR.<br>
> I am proposing a dedicated back end to generate code for
the <br>
> interconnect fabric.<br>
<br>
Edward, it sounds to me like you are trying to reinvent
Smalltalk. Its <br>
core is really about message passing and perhaps people have
made <br>
attempts to make it parallel already.<br>
<br>
On a more serious and specific note, I think you are ignoring
the <br>
"abstract C machine" on which both C and C++ languages are
built. <br>
Fundamentally, objects are laid out in memory (let's ignore
the stack <br>
for now) and are built off primitive and user-defined types.
These types <br>
are known (and stable) throughout the compilation process of a
single <br>
program and so are the offsets of various fields that comprise
the <br>
objects. All these objects (and often their sub-objects) can
be read and <br>
written anywhere in a single-threaded program. Multi-threaded
programs <br>
must be data-race-free, but essentially follow the same model.<br>
<br>
The point I am trying to make is that the whole model is built
on memory <br>
accesses that are eventually lowered to the ISA. There is no
rigid <br>
protocol for invoking a member function or reading a member
variable - <br>
things just happen in the program's address space. And then
there is <br>
code optimizer. The memory accesses (expressed via LLVM IR,
for example) <br>
go through various techniques that reduce and eliminate
pointless <br>
work... at which point you have the target's ISA and
absolutely no <br>
notion of a "method" or "object" (as a well-formed program
cannot tell <br>
that the code has been re-arranged, reduced, reordered etc).<br>
<br>
I suggest that you take a look at <a
href="https://godbolt.org" rel="noreferrer" target="_blank"
moz-do-not-send="true">https://godbolt.org</a> and see what
the <br>
compiler emits with -O3 for a few short class/function
templates as well <br>
as normal procedural code.<br>
<br>
Oleg.<br>
<br>
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