[DebugInfo][DivRemPairs] Missing debug location updates

[Apochens]

DivRemPairs-L207
The newly created binary operator RealRem, which replaces original rem instruction RemInst, has no debug location update.

Instruction *RealRem = E.isSigned() ? BinaryOperator::CreateSRem(X, Y)
                                    : BinaryOperator::CreateURem(X, Y);

RealRem->setName(RemInst->getName() + ".recomposed");
RealRem->insertAfter(RemInst);
Instruction *OrigRemInst = RemInst;
RemInst = RealRem;

OrigRemInst->replaceAllUsesWith(RealRem);
OrigRemInst->eraseFromParent();

DivRemPairs-L333, L334
New mul (Mul) and sub (Sub) instructions, which replace the original rem instruction (RemInst), have no debug location update.

Instruction *Mul = BinaryOperator::CreateMul(DivInst, Y);
Instruction *Sub = BinaryOperator::CreateSub(X, Mul);

Mul->insertAfter(RemInst);
Sub->insertAfter(Mul);

Instruction *OrigRemInst = RemInst;
// Update AssertingVH<> with new instruction so it doesn't assert.
RemInst = Sub;
// And replace the original instruction with the new one.
OrigRemInst->replaceAllUsesWith(Sub);
OrigRemInst->eraseFromParent();

DivRemPairs-L385, L393
Two new freeze instruction (FrX and FrY) used by other instructions have no debug location.

if (!isGuaranteedNotToBeUndef(X, nullptr, DivInst, &DT)) {
  auto *FrX =
      new FreezeInst(X, X->getName() + ".frozen", DivInst->getIterator());
  DivInst->setOperand(0, FrX);
  Sub->setOperand(0, FrX);
}

if (!isGuaranteedNotToBeUndef(Y, nullptr, DivInst, &DT)) {
  auto *FrY =
     new FreezeInst(Y, Y->getName() + ".frozen", DivInst->getIterator());
  DivInst->setOperand(1, FrY);
  Mul->setOperand(1, FrY);
}

[llvmbot]

@llvm/issue-subscribers-debuginfo

Author: Shan Huang (Apochens)

**DivRemPairs-[L207](https://github.com/llvm/llvm-project/blob/3417ff6b1c6b165fce92e7c647c65466092cf638/llvm/lib/Transforms/Scalar/DivRemPairs.cpp#L207)** The newly created binary operator `RealRem`, which replaces original rem instruction `RemInst`, has no debug location update. ```c++ Instruction *RealRem = E.isSigned() ? BinaryOperator::CreateSRem(X, Y) : BinaryOperator::CreateURem(X, Y);

RealRem->setName(RemInst->getName() + ".recomposed");
RealRem->insertAfter(RemInst);
Instruction *OrigRemInst = RemInst;
RemInst = RealRem;

OrigRemInst->replaceAllUsesWith(RealRem);
OrigRemInst->eraseFromParent();

**DivRemPairs-[L333](https://github.com/llvm/llvm-project/blob/3417ff6b1c6b165fce92e7c647c65466092cf638/llvm/lib/Transforms/Scalar/DivRemPairs.cpp#L333), [L334](https://github.com/llvm/llvm-project/blob/3417ff6b1c6b165fce92e7c647c65466092cf638/llvm/lib/Transforms/Scalar/DivRemPairs.cpp#L334)**
New mul (`Mul`) and sub (`Sub`) instructions, which replace the original rem instruction (`RemInst`), have no debug location update.
```cpp
Instruction *Mul = BinaryOperator::CreateMul(DivInst, Y);
Instruction *Sub = BinaryOperator::CreateSub(X, Mul);

Mul->insertAfter(RemInst);
Sub->insertAfter(Mul);

Instruction *OrigRemInst = RemInst;
// Update AssertingVH<> with new instruction so it doesn't assert.
RemInst = Sub;
// And replace the original instruction with the new one.
OrigRemInst->replaceAllUsesWith(Sub);
OrigRemInst->eraseFromParent();

DivRemPairs-L385, L393
Two new freeze instruction (FrX and FrY) used by other instructions have no debug location.

if (!isGuaranteedNotToBeUndef(X, nullptr, DivInst, &DT)) {
  auto *FrX =
      new FreezeInst(X, X->getName() + ".frozen", DivInst->getIterator());
  DivInst->setOperand(0, FrX);
  Sub->setOperand(0, FrX);
}

if (!isGuaranteedNotToBeUndef(Y, nullptr, DivInst, &DT)) {
  auto *FrY =
     new FreezeInst(Y, Y->getName() + ".frozen", DivInst->getIterator());
  DivInst->setOperand(1, FrY);
  Mul->setOperand(1, FrY);
}