llvm dev - Apr 2010 - [LLVMdev] Check the location of the definition of a Value object

Hello,

How to check whether a value object is within a particular basic block or not.

I have the following LLVM bytecode:

------------------------
entry:
  ...
  %2 = call i32 (...)* @atoi(i8*%1) nounwind
  ...

--
bb1:
  ..
  %5 = icmp sgt i32 %2, %i.0
  ...
-----------------

Here I got the corresponding pointer of the Value object of *%2*. How
can I check whether it is defined in *entry* or not?

I tried:
---------------------
//Value* pb corresponding to %2
for (BasicBlock::iterator I=entry->begin(), e=entry.end(); I != e; I++)
{
       if (I == pb)
          return true;
}
return false;
----------------------

However, I got  errors when compiled the code. Could anyone give some
simple examples about this issue?

Thanks.

Cheers,
Zheng

Zheng Wang wrote:
> Hello,
>
> How to check whether a value object is within a particular basic block or
not.
>   
There is a much simpler way to do this.  Assuming that Value * pb holds 
the pointer to the value of %2, you do the following:

1) Check to see if %2 is an instruction (use dyn_cast<Instruction>(pb) 
and see if the result is NULL).  If it's not an instruction, then it's 
definitely not defined in the entry block.

2) Use the result of dyn_cast<Instruction>(pb) to get the basic block in 
which the instruction is defined.

So, you do

// Entry is a Basic Block pointer pointing to the function's entry block
if (Instruction * PBI = dyn_cast<Instruction>(pb)) {
    if (PBI->getParent() == Entry)
       // pb is an instruction defined in the entry basic block.


-- John T.
> I have the following LLVM bytecode:
>
> ------------------------
> entry:
>   ...
>   %2 = call i32 (...)* @atoi(i8*%1) nounwind
>   ...
>
> --
> bb1:
>   ..
>   %5 = icmp sgt i32 %2, %i.0
>   ...
> -----------------
>
> Here I got the corresponding pointer of the Value object of *%2*. How
> can I check whether it is defined in *entry* or not?
>
> I tried:
> ---------------------
> //Value* pb corresponding to %2
> for (BasicBlock::iterator I=entry->begin(), e=entry.end(); I != e; I++)
> {
>        if (I == pb)
>           return true;
> }
> return false;
> ----------------------
>
> However, I got  errors when compiled the code. Could anyone give some
> simple examples about this issue?
>
> Thanks.
>
> Cheers,
> Zheng
> _______________________________________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>

Cheers John!


On 8 April 2010 17:25, John Criswell <criswell at uiuc.edu>
wrote:
> Zheng Wang wrote:
>>
>> Hello,
>>
>> How to check whether a value object is within a particular basic block
or
>> not.
>>
>
> There is a much simpler way to do this.  Assuming that Value * pb holds the
> pointer to the value of %2, you do the following:
>
> 1) Check to see if %2 is an instruction (use
dyn_cast<Instruction>(pb) and
> see if the result is NULL).  If it's not an instruction, then it's
> definitely not defined in the entry block.
>
> 2) Use the result of dyn_cast<Instruction>(pb) to get the basic block
in
> which the instruction is defined.
>
> So, you do
>
> // Entry is a Basic Block pointer pointing to the function's entry
block
> if (Instruction * PBI = dyn_cast<Instruction>(pb)) {
>   if (PBI->getParent() == Entry)
>      // pb is an instruction defined in the entry basic block.
>
>
> -- John T.
>
>> I have the following LLVM bytecode:
>>
>> ------------------------
>> entry:
>>  ...
>>  %2 = call i32 (...)* @atoi(i8*%1) nounwind
>>  ...
>>
>> --
>> bb1:
>>  ..
>>  %5 = icmp sgt i32 %2, %i.0
>>  ...
>> -----------------
>>
>> Here I got the corresponding pointer of the Value object of *%2*. How
>> can I check whether it is defined in *entry* or not?
>>
>> I tried:
>> ---------------------
>> //Value* pb corresponding to %2
>> for (BasicBlock::iterator I=entry->begin(), e=entry.end(); I != e;
I++)
>> {
>>       if (I == pb)
>>          return true;
>> }
>> return false;
>> ----------------------
>>
>> However, I got  errors when compiled the code. Could anyone give some
>> simple examples about this issue?
>>
>> Thanks.
>>
>> Cheers,
>> Zheng
>> _______________________________________________
>> LLVM Developers mailing list
>> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
>> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>>
>
>


-- 
Best regards,

WANG Zheng