[llvm-dev] Cast a function parameter to GEP

[Alberto Barbaro via llvm-dev]

Thanks Tim,
I'll try to solve my problem ASAP, if I cannot maybe I'll some other
clarifications.

Thanks again

On Sat, Mar 9, 2019, 06:03 Tim Northover <t.p.northover at gmail.com> wrote:

> Hi Alberto,
>
> On Sat, 9 Mar 2019 at 05:50, Alberto Barbaro via llvm-dev
> <llvm-dev at lists.llvm.org> wrote:
> > i8* getelementptr inbounds ([7 x i8], [7 x i8]* @.str1, i32 0, i32 0)
>
> Because all of its inputs are Constants, this is actually a
> GetElementPtrConstantExpr instead of a GetElementPtrInst (the easiest
> way to tell on sight without context is the extra parens, which the
> instruction variant never has).
>
> The main practical difference between the two is that instances of
> Constant don't live in a BasicBlock independently, but are referenced
> directly by each user. When printing the IR this is shown by
> "inlining" them into the parent Instruction.
>
> LLVM has a GEPOperator class to help deal with this issue; it can be
> used to access the common features of Instructions and Constants.
> There are similar Operators for other operations because this is quite
> a common situation.
>
> > I think it does not work because str1 is a "private constant". Is there
> a way to solve it?
>
> Broadly true, but the same would apply to any global, not just ones
> declared constant.
>
> Cheers.
>
> Tim.
>
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