Revert "[CodeGenPrepare] Fix isIVIncrement (PR49466)"

This reverts commit cf82700af8c658ae09b14c3d01bb1e73e48d3bd3 due to a compile timeout when building the following with `clang -O2`:

```
template <class, class = int> class a;
struct b {
  using d = int *;
};
struct e {
  using f = b::d;
};
class g {
public:
  e::f h;
  e::f i;
};
template <class, class> class a : g {
public:
  long j() const { return i - h; }
  long operator[](long) const noexcept;
};
template <class c, class k> long a<c, k>::operator[](long l) const noexcept {
  return h[l];
}
template <typename m, typename n> int fn1(m, n, const char *);
int o, p;
class D {
  void q(const a<long> &);
  long r;
};
void D::q(const a<long> &l) {
  int s;
  if (l[0])
    for (; l.j(); ++s) {
      if (l[s])
        while (fn1(o, 0, ""))
          ;
      r = l[s] / p;
    }
}
```

1 files changed, 1 insertions, 2 deletions

diff --git a/llvm/lib/CodeGen/CodeGenPrepare.cpp b/llvm/lib/CodeGen/CodeGenPrepare.cpp
index 0f698dd..0b1156e 100644
--- a/llvm/lib/CodeGen/CodeGenPrepare.cpp
+++ b/llvm/lib/CodeGen/CodeGenPrepare.cpp
@@ -1332,7 +1332,7 @@ getIVIncrement(const PHINode *PN, const LoopInfo *LI) {
 
 static bool isIVIncrement(const BinaryOperator *BO, const LoopInfo *LI) {
   auto *PN = dyn_cast<PHINode>(BO->getOperand(0));
-  if (!PN || LI->getLoopFor(BO->getParent()) != LI->getLoopFor(PN->getParent()))
+  if (!PN)
     return false;
   if (auto IVInc = getIVIncrement(PN, LI))
     return IVInc->first == BO;
@@ -1347,7 +1347,6 @@ bool CodeGenPrepare::replaceMathCmpWithIntrinsic(BinaryOperator *BO,
     if (!isIVIncrement(BO, LI))
       return false;
     const Loop *L = LI->getLoopFor(BO->getParent());
-    assert(L && "L should not be null after isIVIncrement()");
     // Do not risk on moving increment into a child loop.
     if (LI->getLoopFor(Cmp->getParent()) != L)
       return false;