[LLVMdev] A weird problem when try to output operand of instruction involving function pointer in a struct

[Robert Sandra]

Hi all,

I just start to learn llvm. I am trying to get the operand's name of some
instruction that invokes a function field of a struct. While,  I found in
the result that there is a sequence number attached to the function field
name. Below is an example:

/******source code t2.c*******/

#include <stdio.h>


void F(){printf("F\n");}

void E(){printf("E\n");}

void D(){printf("D\n");}

void C(){D();E();printf("C\n");}

void B(){C();printf("C\n");}

void A(){B();printf("A\n");}


int main(){

struct s{

int vvv;

void (*ff)();

void (*tt)();

int value ;

}sss;


void (*ppp)();

void (*kkk)();

A();


sss.tt = &A;

sss.tt();

sss.ff = &C;

sss.ff();

sss.tt = &F;

sss.tt();


kkk = &B;

ppp = &C;

(*ppp)();

(*kkk)();

}


I use the following command to generate the .bc file:

clang -O0 -c -emit-llvm t2.c -o t2.bc


Then I create a FunctionPass, inside the runOnFunction() I use the
following codes to find direct and indirect function calls:


for (Function::iterator b = F.begin(), be = F.end(); b != be; ++b) {

for (BasicBlock::iterator i = b->begin(), ie = b->end(); i != ie; ++i) {

if (CallInst* callInst = dyn_cast<CallInst>(&*i)) {

 Function *fun = callInst->getCalledFunction();

 if(fun){

 errs().write_escaped(fun->getName());

 }

 else{

 errs() <<"indirect call: ";

 Instruction* pinst = &*i;

 for(User::op_iterator opi=pinst->op_begin(), opie=pinst->op_end();
opi!=opie; ++opi){

 if (Instruction *Op = dyn_cast<Instruction>(*opi)){

 errs() <<Op->getOperand(0)->getName() <<", ";

 }else{

 errs() <<"noti\n";

 }

 }

 }

 }

}

}


The output is:
In function: main
A,
indirect call: tt1,
indirect call: ff2,
indirect call: tt4,
indirect call: ppp,
indirect call: kkk,


You can find that there is a number after tt and ff, I have no idea where
they are coming from. Can anyone give some hint?

Thanks.
Robert
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