llvm dev - Dec 2018 - How to get the destination in a LoadInst

Hi all,
I have %5 = load i32, i32* %3, align 4 LoadInst and I would like to get
reference to the destination ( in this case %5 ). How can I do that?

Thanks
-------------- next part --------------
An HTML attachment was scrubbed...
URL:
<http://lists.llvm.org/pipermail/llvm-dev/attachments/20181212/1d0bd00c/attachment.html>

The LoadInst is %5. I'm not sure what you mean by reference though.

On 12/12, Alberto Barbaro via llvm-dev wrote:
> Hi all,
> I have %5 = load i32, i32* %3, align 4 LoadInst and I would like to get
> reference to the destination ( in this case %5 ). How can I do that?
> 
> Thanks
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev

-- 

Johannes Doerfert
Researcher

Argonne National Laboratory
Lemont, IL 60439, USA

jdoerfert at anl.gov
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 228 bytes
Desc: not available
URL:
<http://lists.llvm.org/pipermail/llvm-dev/attachments/20181212/05a2d469/attachment.sig>

Hi,
I would like to get the '5'. I would like to know where the loaded value
is
stored. I don't know which method I should use of the LoadInst class.

Hope this clarifies

Thanks

On Wed, Dec 12, 2018, 20:37 Doerfert, Johannes Rudolf <jdoerfert at anl.gov
wrote:
> The LoadInst is %5. I'm not sure what you mean by reference though.
>
> On 12/12, Alberto Barbaro via llvm-dev wrote:
> > Hi all,
> > I have %5 = load i32, i32* %3, align 4 LoadInst and I would like to
get
> > reference to the destination ( in this case %5 ). How can I do that?
> >
> > Thanks
>
> > _______________________________________________
> > LLVM Developers mailing list
> > llvm-dev at lists.llvm.org
> > http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
>
> --
>
> Johannes Doerfert
> Researcher
>
> Argonne National Laboratory
> Lemont, IL 60439, USA
>
> jdoerfert at anl.gov
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL:
<http://lists.llvm.org/pipermail/llvm-dev/attachments/20181212/fcdfba8a/attachment.html>

I suspect you have some confusion as to how LLVM works.

In LLVM terms, an Instruction is essentially an opcode, some opcode-specific
flags, and a list of Value operands that it uses. Instructions are themselves
Values, so that means that to use the result of an instruction, you pass the
Instruction itself to the method that accepts a Value. There is no “destination”
of an Instruction in structural terms.

In the textual format of LLVM, Instructions are represented by printing out
%<name> = <textual representation of an instruction>, and subsequent
uses of the instruction are referred to in the %<name> format. Names of
instructions (and a few other values) must be unique, with the exception of the
empty string. The %<name> representation for an empty name string is
replaced with a unique autoincrementing integer that is not readily accessible
via the APIs (you need to go through the ModuleSlotTracker to get to it). If
you’re really trying to get that exact string for an instruction, you are
generally doing something wrong and there is an easier way to go about whatever
it is you want to do.

From: llvm-dev [mailto:llvm-dev-bounces at lists.llvm.org] On Behalf Of Alberto
Barbaro via llvm-dev
Sent: Wednesday, December 12, 2018 13:24
To: llvm-dev at lists.llvm.org
Subject: [llvm-dev] How to get the destination in a LoadInst

Hi all,
I have %5 = load i32, i32* %3, align 4 LoadInst and I would like to get
reference to the destination ( in this case %5 ). How can I do that?

Thanks
-------------- next part --------------
An HTML attachment was scrubbed...
URL:
<http://lists.llvm.org/pipermail/llvm-dev/attachments/20181212/f906a499/attachment.html>

Am Mi., 12. Dez. 2018 um 12:24 Uhr schrieb Alberto Barbaro via
llvm-dev <llvm-dev at lists.llvm.org>:
> I have %5 = load i32, i32* %3, align 4 LoadInst and I would like to get
reference to the destination ( in this case %5 ). How can I do that?
Once you have a 'reference to %5' what do you intend to do with it?
This might help to understand question.

Michael

Thanks Joshua and Michael,
Just to to clarify, I'm experimenting with the Interpreter class and
observing the instructions that are executed by it. Just for becoming more
confident with LLVM in general I'd like for each instruction to access to
the various parts of it. In this instance I would like to access to the
%Name that is shown in the textual representation. When I call
Instruction.dump() all is printed correctly so I thought there was a way to
get the %Name ( in my case 5). So my final goal is to obtain it. I
understand that is dinamically generated based on. The execution but I
think that in my case I could access to it. Am I wrong? I hope now all is
more clear :)

Thanks again

On Wed, Dec 12, 2018, 22:41 Michael Kruse <llvmdev at meinersbur.de wrote:
> Am Mi., 12. Dez. 2018 um 12:24 Uhr schrieb Alberto Barbaro via
> llvm-dev <llvm-dev at lists.llvm.org>:
> > I have %5 = load i32, i32* %3, align 4 LoadInst and I would like to
get
> reference to the destination ( in this case %5 ). How can I do that?
>
> Once you have a 'reference to %5' what do you intend to do with it?
> This might help to understand question.
>
> Michael
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL:
<http://lists.llvm.org/pipermail/llvm-dev/attachments/20181212/88b5fea3/attachment.html>

"Doerfert, Johannes Rudolf via llvm-dev" <llvm-dev at
lists.llvm.org>
writes:
> The LoadInst is %5. I'm not sure what you mean by reference though.
This is a common misunderstanding, one that I think is encouraged by the
textual form of IR.  "%5 = load" makes it looks like %5 is a
destination
operand in LoadInst.  LLVM IR looks like assembly and in (most) assembly
syntax, destinations are instruction operands.

Something like "%5 -> load" might have made things more clear, but
of
course it's too late for that.  :)

                            -David