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

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
>
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Am Mi., 12. Dez. 2018 um 17:05 Uhr schrieb Alberto Barbaro
<barbaro.alberto at gmail.com>:
> 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 :)
As Joshua and others already explained, the instruction and the value
it computes are both the same object: the 'Instruction' you are
calling dump() on. For instance, to enumerate where this values is
used, try:

    for (auto &U : Instruction.uses()) { ... }

If you want the name of the value/instruction as string, as it appears
on stdout when calling Instruction::dump()?

Short version: Use Instruction.getName()

Long version: In you example, getName() will return the empty string,
i.e. it has no name. There is some disambiguation going on to print
unique names. You can get the uniqued name using
Instruction.printAsOperand(). You will have to pass a string stream
(such as llvm::raw_string_ostream) and extract the string using
raw_string_ostream::str().

Michael

Michael

Thanks Michael,
Indeed as you said the Instruction.getName() returns an empty string. I
think I should have mentioned that I'm trying to print it from the
visitLoadInst() method of my class that extends Interpreter.

Anyway I'll try as you suggested and get back to you.

Thanks again


On Wed, Dec 12, 2018, 23:29 Michael Kruse <llvmdev at meinersbur.de wrote:
> Am Mi., 12. Dez. 2018 um 17:05 Uhr schrieb Alberto Barbaro
> <barbaro.alberto at gmail.com>:
> > 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 :)
>
> As Joshua and others already explained, the instruction and the value
> it computes are both the same object: the 'Instruction' you are
> calling dump() on. For instance, to enumerate where this values is
> used, try:
>
>     for (auto &U : Instruction.uses()) { ... }
>
> If you want the name of the value/instruction as string, as it appears
> on stdout when calling Instruction::dump()?
>
> Short version: Use Instruction.getName()
>
> Long version: In you example, getName() will return the empty string,
> i.e. it has no name. There is some disambiguation going on to print
> unique names. You can get the uniqued name using
> Instruction.printAsOperand(). You will have to pass a string stream
> (such as llvm::raw_string_ostream) and extract the string using
> raw_string_ostream::str().
>
> Michael
>
> Michael
>
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