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

Craig Topper via llvm-dev llvm-dev at lists.llvm.org
Thu Jun 17 17:37:36 PDT 2021

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.


On Thu, Jun 17, 2021 at 5:25 PM 周书林 via llvm-dev <llvm-dev at lists.llvm.org>

> 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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