[LLVMdev] L->isLoopInvariant giving wrong results?

[Sreeraj a]

Hi,
I'm trying to write a simple pass to print out Loop invariant instructions,
using the
Loop::isLoopInvariant(Instruction *I)
function. it is giving me false value on instructions which should be loop
invariant.

the code i am using is:

bool MyLoopPass::runOnLoop(Loop * L, LPPassManager &lpm){
BasicBlock* lat=L->getLoopLatch();
for (BasicBlock::iterator i = lat->begin(), e = lat->end(); i != e; ++i){
  Instruction* hijk= i;
  if(L->isLoopInvariant(hijk))
    errs() << "hurray " << *hijk << " is loop invariant\n";
  else
    errs() << "bad luck\n";
 }
 return false;
}

the loop latch prints as:
bb:                                               ; preds = %bb1
  store i32 21, i32* %ij, align 4
  store i32 10, i32* %j, align 4
  %0 = load i32* %i, align 4
  %1 = call i32 (i8*, ...)* @printf(i8* noalias getelementptr inbounds ([4 x
i8]* @.str, i32 0, i32 0), i32 %0) nounwind
  %2 = load i32* %i, align 4
  %3 = sub nsw i32 %2, 1
  store i32 %3, i32* %i, align 4
  br label %bb1

the first instruction "  store i32 21, i32* %ij, align 4"
is clearly loop invariant (corresponds to j=10; in c-code)
but all i am getting is "bad luck".

am i doing something wrong here? or is the function incomplete/wrong?
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