llvm dev - Nov 2008 - [LLVMdev] How do I get the result of an instruction?

Thanks!

How do I cast the result to a string? I basically need to store the results of
some instructions in a file.

Thanks,
Bhavani


--- On Sun, 11/16/08, John Criswell <criswell at uiuc.edu> wrote:
> From: John Criswell <criswell at uiuc.edu>
> Subject: Re: [LLVMdev] How do I get the result of an instruction?
> To: "bhavi63 at yahoo.com" <bhavi63 at yahoo.com>,
"LLVM Developers Mailing List" <llvmdev at cs.uiuc.edu>
> Date: Sunday, November 16, 2008, 10:55 AM
> bhavani krishnan wrote:
> > Hi all,
> > 
> > I probably have a stupid question but I could not find
> out so please help me out here. I can use getOperand to get
> the operands of an instruction. Similarly, How do I get the
> result of an instruction?   
> The instruction itself is its result.
> 
> For example, if I wanted to generate code that does a
> getlemeneptr instruction (GEP) and then uses the result of
> the GEP as the pointer to a load instruction, I would do the
> following:
> 
> Instruction * GEP = new GetElementPtrInst (Value, ....);
> Instruction * LI = new LoadInst (GEP, "name",
> ...);
> 
> -- John T.
> 
> > Thanks,
> > Bhavani
> > 
> > 
> >       _______________________________________________
> > LLVM Developers mailing list
> > LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> > http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
> >

On Sat, Nov 15, 2008 at 3:58 PM, bhavani krishnan <bhavi63 at yahoo.com>
wrote:
> Thanks!
>
> How do I cast the result to a string? I basically need to store the results
of some instructions in a file.
If you're confused about how the IR works, http://llvm.org/demo/ can
be useful.  The question you're asking doesn't really seem to make
sense.

-Eli

Hi,

I am writing an optimization pass where I need to instrument the code such that
I need to store the results of some instructions in file. Using llc -march=cpp
option I figured out how to add a function(say writeToFile) which takes char*
parameter and writes to file. Now, I need put in a CallInst which calls
writeToFile passing the Instruction result as parameter. How do I do this?

So, in my optimization pass...
Func *myprint = makewriteToFile() //creates a function which writes to file
for (Function::iterator i = func->begin(), e = func->end(); i != e; ++i)
{
        blk=i;
        for (BasicBlock::iterator j = blk->begin(), k = blk->end(); j !=
k; ++j){
            Instruction *inst = j;
            //if inst satisfies my condition, write reults to file
            CallInst *CallPrint = CallInst::Create(myprint, ???, "",
j);
            CallPrint->setTailCall(true);
       }
}       
What do I put in the ???. How do I cast Instruction *inst into char * which can
be passed into the function?


Hope this is clear.
Thanks,
Bhavani


--- On Sun, 11/16/08, Eli Friedman <eli.friedman at gmail.com> wrote:
> From: Eli Friedman <eli.friedman at gmail.com>
> Subject: Re: [LLVMdev] How do I get the result of an instruction?
> To: bhavi63 at yahoo.com, "LLVM Developers Mailing List"
<llvmdev at cs.uiuc.edu>
> Cc: "John Criswell" <criswell at uiuc.edu>
> Date: Sunday, November 16, 2008, 6:35 AM
> On Sat, Nov 15, 2008 at 3:58 PM, bhavani krishnan
> <bhavi63 at yahoo.com> wrote:
> > Thanks!
> >
> > How do I cast the result to a string? I basically need
> to store the results of some instructions in a file.
> 
> If you're confused about how the IR works,
> http://llvm.org/demo/ can
> be useful.  The question you're asking doesn't
> really seem to make
> sense.
> 
> -Eli