[LLVMdev] Pointer Constant?

[Jim Grosbach]

I believe lldb does something similar to #2 for  complex expression evaluation. It might be worth having a look there for some examples.

Jim

On Jul 2, 2011, at 7:19 AM, Kenneth Uildriks <kennethuil at gmail.com> wrote:

> 1. Create an extern global variable of the type being pointed to.  Use
> ExecutionEngine::addGlobalMapping to map that extern global variable
> to the pointer.  Then your IR code can refer to the extern global
> variable and get the pointer.
> 2. Convert the pointer to an int.  Create an int constant in IR.  Then
> add an inttoptr instruction, and your IR has the pointer constant.
> Last I checked, though, the generated X86 code doesn't treat the
> resulting pointer as a constant... for instance, if you use it as a
> function pointer, the X86 code ends up being an indirect call through
> a function pointer in a register, rather than a direct call.
> 
> On Fri, Jul 1, 2011 at 9:30 AM, Timothy Baldridge <tbaldridge at gmail.com> wrote:
>> I'm writing a JIT for my toy language, and I'm confused by one thing.
>> How do I, with IR Builder, Insert a pointer constant? For the first
>> version of my jit, I really only need LLVM to pass around opaque types
>> and then pass those variables to C functions that return other opaque
>> types. So for instance, I have a Int object that wraps the GNU GMP
>> routines. A want to be able to tell IRBuilder "create a pointer named
>> x and set it's value to this memory location".
>> 
>> I know I'd have to re-compile everytime I reload my project, but for
>> now, and considering it is a JIT, I don't really care.
>> 
>> Timothy
>> 
>> --
>> “One of the main causes of the fall of the Roman Empire was
>> that–lacking zero–they had no way to indicate successful termination
>> of their C programs.”
>> (Robert Firth)
>> 
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