[llvm-dev] How to get the value for casting in a bitcast instruction more efficiently?

[Shen Liu via llvm-dev]

I see, thank you! ^_^

On Thu, Dec 15, 2016 at 3:11 PM, Ryan Taylor via llvm-dev <
llvm-dev at lists.llvm.org> wrote:

> I guess I didn't understand your question, my point was that the operand,
> in your example, inherits from value class, it already is a value, most
> everything in IR is a value.
>
> -Ryan
>
> On Thu, Dec 15, 2016 at 3:10 PM, Shen Liu <sxl463 at cse.psu.edu> wrote:
>
>> Hi Ryan,
>>
>> Thanks for your reply!  Yes i can use llvm::Use.get() API to do this, i
>> just want to know whether there's a better way(e.g. an existed API like
>> getValue()) to make my code look more professional.
>>
>> On Thu, Dec 15, 2016 at 2:58 PM, Ryan Taylor via llvm-dev <
>> llvm-dev at lists.llvm.org> wrote:
>>
>>> This might help:
>>>
>>> http://llvm.org/docs/ProgrammersManual.html#the-value-class
>>>
>>> Or maybe I'm misunderstanding what you mean by "efficient way to get the
>>> value". When you say 'value', I'm assuming you mean the class. In your
>>> case, AllocaInst inherits from value.
>>>
>>> -Ryan
>>>
>>> On Thu, Dec 15, 2016 at 10:24 AM, Shen Liu via llvm-dev <
>>> llvm-dev at lists.llvm.org> wrote:
>>>
>>>> Hi everyone,
>>>>
>>>> This is a simple question but is there an efficient way to get the *value for casting* directly from a bitcast instruction?
>>>>
>>>> bitcast format :<result> = bitcast <ty> <*value*> to <ty2>
>>>>
>>>> For example, if i have
>>>>
>>>> MemAddr
>>>> ...
>>>> 0x3d61238   %key = alloca [16 x i8], align 16
>>>> 0x3d612a8   %plain_text = alloca [64 x i8], align 16
>>>> 0x3d61318   %key1 = bitcast [16 x i8]* %key to i8*
>>>> ...
>>>>
>>>> The way i am using is processing all opcodes in %key1, and go back to find %key along the def-use chain. But is there a better way for doing this?
>>>>
>>>> Thanks very much!
>>>>
>>>> Best
>>>>
>>>>
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>>>>
>>>>
>>>
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>>>
>>
>
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