llvm dev - Apr 2013 - [LLVMdev] How to retrieve IntToPtr from StoreInst?

hi,

i am writing a simple LLVM pass to analyze the Store instruction.
my pass derives from InstVisitor class, and the method to handle Store
instruction is like this:

void MyPass::visitStoreInst(StoreInst &I) {
...
}

It is pretty simple to handle Store. however, in on test i got an
instruction like below:

  store i8 %tmp5, i8* inttoptr (i32 301959828 to i8*)

the second operand is "i8* inttoptr (i32 301959828 to i8*)", and i
have no
idea how i can retrieve the address 301959828, given the StoreInst argument
of visitStoreInst.

i am looking in the the code of LLVM, but still fail to see how to extract
this information.

any suggestion is very appreciated. i am really struggling here now ...

thanks so much.
Jun
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On 4/18/13 9:56 AM, Jun Koi wrote:
> hi,
>
> i am writing a simple LLVM pass to analyze the Store instruction.
> my pass derives from InstVisitor class, and the method to handle Store 
> instruction is like this:
>
> void MyPass::visitStoreInst(StoreInst &I) {
> ...
> }
>
> It is pretty simple to handle Store. however, in on test i got an 
> instruction like below:
>
>   store i8 %tmp5, i8* inttoptr (i32 301959828 to i8*)
The inttoptr used here is a Constant Expression (llvm::ConstantExpr).  
You'll need to take the operand to the store, cast it to 
llvm::ConstantExpr, and then examine the opcode and operands of the 
constant expression.

The ConstantExpr class is documented at 
http://llvm.org/doxygen/classllvm_1_1ConstantExpr.html and is described 
in the LLVM Language Reference Manual.

-- John T.
>
> the second operand is "i8* inttoptr (i32 301959828 to i8*)", and
i
> have no idea how i can retrieve the address 301959828, given the 
> StoreInst argument of visitStoreInst.
>
> i am looking in the the code of LLVM, but still fail to see how to 
> extract this information.
>
> any suggestion is very appreciated. i am really struggling here now ...
>
> thanks so much.
> Jun
>
>
>
> _______________________________________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
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On Thu, Apr 18, 2013 at 11:11 PM, John Criswell <criswell at
illinois.edu>wrote:
>  On 4/18/13 9:56 AM, Jun Koi wrote:
>
>   hi,
>
> i am writing a simple LLVM pass to analyze the Store instruction.
> my pass derives from InstVisitor class, and the method to handle Store
> instruction is like this:
>
> void MyPass::visitStoreInst(StoreInst &I) {
> ...
> }
>
> It is pretty simple to handle Store. however, in on test i got an
> instruction like below:
>
>   store i8 %tmp5, i8* inttoptr (i32 301959828 to i8*)
>
>
> The inttoptr used here is a Constant Expression (llvm::ConstantExpr).
> You'll need to take the operand to the store, cast it to
> llvm::ConstantExpr, and then examine the opcode and operands of the
> constant expression.
>
> The ConstantExpr class is documented at
> http://llvm.org/doxygen/classllvm_1_1ConstantExpr.html and is described
> in the LLVM Language Reference Manual.
>
>
OK, I tried my best, and come up with code like below:

void MyPass::visitStoreInst(StoreInst &I)
{
    Value *op2 = I.getOperand(1);    // the address where we store data

    if (const ConstantExpr *c = dyn_cast <ConstantExpr>(op2)) {
    // how to extract the Int Constant here?
    }
}

The problem is that given ConstantExpr, i am not sure how to extract the
Int Constant operand.
According to http://llvm.org/doxygen/classllvm_1_1ConstantExpr.html, this
class only provides method such as getWithOperands(), but this method
doesnt seem to do what I want.

I grep through the code of LLVM, but cannot find any example doing this.

any more hint, please?

Thanks,
Jun
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