[llvm-dev] How to get the address of a global variable in LLVM?

Dipanjan Das via llvm-dev llvm-dev at lists.llvm.org
Fri Apr 28 15:06:19 PDT 2017

Thank you so much to you both. I got it working.

On 28 April 2017 at 14:49, Tim Northover <t.p.northover at gmail.com> wrote:

> On 28 April 2017 at 14:38, Dipanjan Das via llvm-dev
> <llvm-dev at lists.llvm.org> wrote:
> > I want to insert a call to `func` just before the store instruction with
> the
> > address `x` of global variable `g` as parameter.
> Your error is because the function you create is "void @func(i32)" but
> you're trying to pass it an i32* (the address of the global). This
> mismatch is spotted by LLVM's verifier and it quits.
> So you have to make them match up somehow. IMO the best way to do this
> would be to instead create "void @func(i8*)" (as Joel explained) and
> then use IRBuilder::CreateBitCast on "po" to convert it from an i32*
> to an i8*. Then you can pass that result to @func instead of "po".
> Incidentally, the "i32  call void bitcast (void (i64)* @func to void
> (i32)*)(i32* @a)" line in the output suggests you're being
> inconsistent about how you call getOrCreateFunction for @func
> elsewhere in your code: the first time it's told to expect an i64 so
> when you getOrCreateFunction a second time LLVM "helpfully" inserts a
> constant bitcast of its own. This is almost certainly not a good idea.
> Tim.


Thanks & Regards,
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