[llvm-dev] Efficient way to identify an instruction

[Alberto Barbaro via llvm-dev]

Hi Tim,
as always thanks for your help. Unfortunately I made a mistake in my email
but apart from that I still have problems.

Il giorno sab 27 lug 2019 alle ore 11:53 Tim Northover <
t.p.northover at gmail.com> ha scritto:

> Hi Alberto,
>
> On Sat, 27 Jul 2019 at 10:09, Alberto Barbaro via llvm-dev
> <llvm-dev at lists.llvm.org> wrote:
> > Having the reference I to the instruction in bold.Can i efficiently know
> that the variable %11 was "created" by the %3 = alloca [40 x i8], align 16.
>
> Yes, I.getOperand(0) *is* the AllocaInst in this case. So for example
> isa<AllocaInst>(I.getOperand(0)) will return true. And if you care
> about more details you can dyn_cast<AllocaInst> it and check any other
> properties you want.
>
>
I would like to use the approach you described considering I to be a
reference to the icmp instruction ( %13 = icmp eq i32 %12, 66 ). From what
I understood i should do something like:

Instruction* source;

if(source = dyn_cast<AllocaInst>(I.getOperand(0))) {
    cout << "Alloca Inst" << endl;
    I.dump();
    getchar();
}

I thought I.getOperand(0) was a reference to the instruction that have
created %12. What am I missing?


> Cheers.
>
> Tim.
>

Thanks again
Alberto
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