llvm dev - Apr 2020 - Various Intermediate Representations. IR

Hi,

I am looking for an IR that is similar to LLVM IR, with its SSA form,
module->function->block->instruction etc.
But, I wish a much reduced type model.
I wish only three types:
1) An Integer of various bit-widths.
2) A pointer, but a pointer that does not need to point to a known
type. A sort of "pointer to unknown type".
3) Floats of various varieties.

For example, if we were using a pointer to step through an array of
32bit integers.
We would use: pointer = pointer + 4;   (I.e. step over 4 octets at a time)

Is anyone aware of such an IR, or is there some way for trick LLVM IR
into only using the above 2 types?
IR already does (1) and (3). It does not seem to be able to do (2).

Kind Regards

James

Currently, LLVM often uses the *i8 type (pointer to char) to represent
a pointer to some not-specified type. We are also working on replacing
the pointer-to-type pointer types by a single pointer type without a
specific pointee-type. Look for "opaque pointer" on llvm-dev and the
repository commits.

Michael

Am Di., 14. Apr. 2020 um 15:06 Uhr schrieb James Courtier-Dutton via
llvm-dev <llvm-dev at lists.llvm.org>:
>
> Hi,
>
> I am looking for an IR that is similar to LLVM IR, with its SSA form,
> module->function->block->instruction etc.
> But, I wish a much reduced type model.
> I wish only three types:
> 1) An Integer of various bit-widths.
> 2) A pointer, but a pointer that does not need to point to a known
> type. A sort of "pointer to unknown type".
> 3) Floats of various varieties.
>
> For example, if we were using a pointer to step through an array of
> 32bit integers.
> We would use: pointer = pointer + 4;   (I.e. step over 4 octets at a time)
>
> Is anyone aware of such an IR, or is there some way for trick LLVM IR
> into only using the above 2 types?
> IR already does (1) and (3). It does not seem to be able to do (2).
>
> Kind Regards
>
> James
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev

People are actually working on 2) (for a while now). Progress was made
but I'm unsure where we are. If you search for "llvm opaque
pointers"
you find the original LLVM-Dev talk, mailing list discussions, and
various patch reviews. I guess one way of achieving what you need is to
accelerate the transition in LLVM-IR ;)

Cheers,
   Johannes



On 4/14/20 3:05 PM, James Courtier-Dutton via llvm-dev wrote:
 > Hi,
 >
 > I am looking for an IR that is similar to LLVM IR, with its SSA form,
 > module->function->block->instruction etc.
 > But, I wish a much reduced type model.
 > I wish only three types:
 > 1) An Integer of various bit-widths.
 > 2) A pointer, but a pointer that does not need to point to a known
 > type. A sort of "pointer to unknown type".
 > 3) Floats of various varieties.
 >
 > For example, if we were using a pointer to step through an array of
 > 32bit integers.
 > We would use: pointer = pointer + 4;   (I.e. step over 4 octets at a 
time)
 >
 > Is anyone aware of such an IR, or is there some way for trick LLVM IR
 > into only using the above 2 types?
 > IR already does (1) and (3). It does not seem to be able to do (2).
 >
 > Kind Regards
 >
 > James
 > _______________________________________________
 > LLVM Developers mailing list
 > llvm-dev at lists.llvm.org
 > https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev

On Tue, 14 Apr 2020 at 21:24, Michael Kruse <llvmdev at meinersbur.de>
wrote:
>
> Currently, LLVM often uses the *i8 type (pointer to char) to represent
> a pointer to some not-specified type. We are also working on replacing
> the pointer-to-type pointer types by a single pointer type without a
> specific pointee-type. Look for "opaque pointer" on llvm-dev and
the
> repository commits.
>
Hi Michael,
Thank you for your reply.

Does the LLVM IRBuilder currently allow adding an opaque pointer to a
LLVM .bc file?
Even if it does not compile, just being able to add it, would be helpful.
I could then run my own experimental passes against it.

Does using opaque pointers, adversely affect alias analysis?

Kind Regards

James