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

周书林 via llvm-dev llvm-dev at lists.llvm.org
Thu Jun 17 19:06:28 PDT 2021

Hi Craig,

I started from GlobalVaribles, so there are situations that I met the
ConstantExprs, i.e. some Operators.

Craig Topper <craig.topper at gmail.com> 于2021年6月18日周五 上午8:37写道:

> 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
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