[llvm-dev] Computing unique ID of IR instructions that can be mapped back

[Dipanjan Das via llvm-dev]

Thank you very much to you all. I got the idea. Only problem is now to
relate the ID back to a specific IR instruction in case I want to trace
back which ID an instruction corresponds to. I can either write the mapping
on disk or augment the bitcode format to accommodate an ID field (may be).

On 8 May 2017 at 22:19, Daniel Berlin <dberlin at dberlin.org> wrote:

> Right.
> As folks have told you, the following loop will always give the same
> instructions in the same order given the same input IR:
>
>
> for (auto &BB : F)
>   for (auto &I : BB)
>       Instruction *IPtr = &I;
>
> Thus, you only need to give them an id based on the order you see them.
>
> If you need something you can access outside of llvm as well, you could
> also rename each instruction to the id number using setName.
>
>
> On Mon, May 8, 2017 at 10:12 PM, George Burgess IV via llvm-dev <
> llvm-dev at lists.llvm.org> wrote:
>
>> > Isn't Instruction* a pointer to the instruction in memory? If so, it'll
>> change across runs
>>
>> Correct, but none of this is meant to be stored across runs, so the
>> actual address doesn't matter. You recompute the map every time your IR is
>> loaded.
>>
>> On Mon, May 8, 2017 at 7:34 PM, Dipanjan Das via llvm-dev <
>> llvm-dev at lists.llvm.org> wrote:
>>
>>>
>>>
>>> On 8 May 2017 at 18:14, Jonathan Roelofs <jonathan at codesourcery.com>
>>> wrote:
>>>
>>>> An alternative way to do it, which would be less invasive and more
>>>> upstreaming friendly, would be to implement this as an analysis pass.
>>>>
>>>> In the pass, calculate a map<Instruction*,ID>, and use that as the
>>>> analysis result. Then query that result for the ID where you need it. If
>>>> you've written the analysis correctly, then you'll always get the same IDs
>>>> for the same instructions given the same input IR.
>>>>
>>>
>>> Isn't Instruction* a pointer to the instruction in memory? If so, it'll
>>> change across runs.
>>>
>>>
>>> --
>>>
>>> Thanks & Regards,
>>> Dipanjan
>>>
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>>>
>>
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>>
>


-- 

Thanks & Regards,
Dipanjan
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