llvm dev - Jun 2021 - When I got a Operator by iterating a Value's User, how can I got the relevant Instruction?

Hi Michael,

Thank you very much!
I have a further question: if I want to get the dataflow of a target Value,
is there any way to handle these situations when iterate the Users?Or only
by iterator all the instructions and their operands?

Sincerely,
Shulin

Michael Kruse <llvmdev at meinersbur.de> 于2021年6月18日周五 上午5:11写道：
> Am Do., 17. Juni 2021 um 10:24 Uhr schrieb 周书林 via llvm-dev
> <llvm-dev at lists.llvm.org>:
> > %39 = load i32, i32* getelementptr inbounds (%struct.TTT, %struct.TTT*
> @ttt, i32 0, i32 2), align 8, !dbg !971
>
> %39 is the LoadInst, while getelementptr is its second operand. It is
> inlined because it is an llvm::Constant, not an instruction. Constants
> do not participate in use/user-chains and hence there is no link from
> GEP to the LoadInst that is using it. The constant GEP object may be
> used by an arbitrary number of other instructions, other constants in
> the same or other functions.
>
> Node that there "GEPOperator" can represent either a
GetElementPtrInst
> (i.e. an instruction) or a GEP constant expression (derived from
> ConstantExpr)
>
> Michael
>
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How did you choose where you started from? An Instruction can only be used
by another Instruction, but it seems you've started from a Constant which
can be used by ConstantExprs.

~Craig


On Thu, Jun 17, 2021 at 5:25 PM 周书林 via llvm-dev <llvm-dev at
lists.llvm.org>
wrote:
> Hi Michael,
>
> Thank you very much!
> I have a further question: if I want to get the dataflow of a target
> Value, is there any way to handle these situations when iterate the
> Users?Or only by iterator all the instructions and their operands?
>
> Sincerely,
> Shulin
>
> Michael Kruse <llvmdev at meinersbur.de> 于2021年6月18日周五 上午5:11写道：
>
>> Am Do., 17. Juni 2021 um 10:24 Uhr schrieb 周书林 via llvm-dev
>> <llvm-dev at lists.llvm.org>:
>> > %39 = load i32, i32* getelementptr inbounds (%struct.TTT,
%struct.TTT*
>> @ttt, i32 0, i32 2), align 8, !dbg !971
>>
>> %39 is the LoadInst, while getelementptr is its second operand. It is
>> inlined because it is an llvm::Constant, not an instruction. Constants
>> do not participate in use/user-chains and hence there is no link from
>> GEP to the LoadInst that is using it. The constant GEP object may be
>> used by an arbitrary number of other instructions, other constants in
>> the same or other functions.
>>
>> Node that there "GEPOperator" can represent either a
GetElementPtrInst
>> (i.e. an instruction) or a GEP constant expression (derived from
>> ConstantExpr)
>>
>> Michael
>>
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
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