LLVM "Instruction does not dominate all uses" - Inserting new Instruction - llvm

Question

I am getting the following error while inserting an instruction using an llvm pass:
Instruction does not dominate all uses!
%add = add nsw i32 10, 2
%cmp3 = icmp ne i32 %a.01, %add
Broken module found, compilation aborted!
I have the source code in a bitcode file whose snippet is:
if.then: ; preds = %entry
%add = add nsw i32 10, 2
br label %if.end
if.else: ; preds = %entry
%sub = sub nsw i32 10, 2
br label %if.end
if.end: ; preds = %if.else, %if.then
%a.0 = phi i32 [ %add, %if.then ], [ %sub, %if.else ]
%a.01 = call i32 #tauInt32Ty(i32 %a.0) ; line A
%add3 = add nsw i32 %a.01, 2
%add4 = add nsw i32 %a.01, 3
%call5 = call i32 (i8*, ...)* #printf(i8* getelementptr inbounds ([7 x i8]* #.str2, i32 0, i32 0), i32 %add3, i32 %add4)
I want to insert a new instruction after "line A" which is :
%cmp3 = icmp ne i32 %a.01, %add
And I have written a function pass whose snippet of the code which does this task is :
for (Function::iterator bb = F.begin(), e = F.end(); bb != e; ++bb) {
for (BasicBlock::iterator i = bb->begin(), e = bb->end(); i != e; ++i) {
std::string str;
if(isa<CallInst>(i))// || true) {
BasicBlock::iterator next_it = i;
next_it++;
Instruction* next = dyn_cast<Instruction>(&*next_it);
CallInst* ci = dyn_cast<CallInst>(&*i);
Function* ff = ci->getCalledFunction();
str = ff->getName();
errs()<<"> "<<str<<"\n";
if(!str.compare("tauInt32Ty")) {
hotPathSSA1::varVersionWithPathsSet::iterator start = tauArguments[&*ci].begin();
hotPathSSA1::varVersionWithPathsSet::iterator end = tauArguments[&*ci].end();
Value* specArgs = start->second; // specArgs points to %add
ICmpInst* int1_cmp_56 = new ICmpInst(next, ICmpInst::ICMP_NE, ci, specArgs, "cmp3");
}
}
}
}

Answer 1

I have not encountered such a problem jet but I think your problem is the if statement. %add belonges to the if.then BasicBlock and it is not accessable from the if.end block. This is why the phi instruction "chooses" which value is available %add or %sub. So you have to take %a.0 for your IcmpInst as argument not %add.