Reapply "[SCEV] Fold (C1 * A /u C2) -> A /u (C2 /u C1), if C2 > C1." (llvm#158328)

This reverts commit fd58f23.

The recommit contains an extra check to make sure that D is a multiple of
C2, if C2 > C1. This fixes the issue causing the revert fd58f23. Tests
have been added in 6a726e9.

Original message:
If C2 >u C1 and C1 >u 1, fold to A /u (C2 /u C1).

Depends on llvm#157555.

Alive2 Proof: https://alive2.llvm.org/ce/z/BWvQYN

PR: llvm#157656
(cherry picked from commit f78150d)

Author: fhahn

llvm/lib/Analysis/ScalarEvolution.cpp

@@ -3230,14 +3230,15 @@ const SCEV *ScalarEvolution::getMulExpr(SmallVectorImpl<const SCEV *> &Ops,
           match(Ops[1], m_scev_UDiv(m_SCEV(D), m_SCEVConstant(C2))) &&
           C2->getAPInt().isPowerOf2() &&
           C1V.logBase2() <= getMinTrailingZeros(D)) {
-        const SCEV *NewMul;
+        const SCEV *NewMul = nullptr;
         if (C1V.uge(C2->getAPInt())) {
           NewMul = getMulExpr(getUDivExpr(getConstant(C1V), C2), D);
-        } else {
+        } else if (C2->getAPInt().logBase2() <= getMinTrailingZeros(D)) {
           assert(C1V.ugt(1) && "C1 <= 1 should have been folded earlier");
           NewMul = getUDivExpr(D, getUDivExpr(C2, getConstant(C1V)));
         }
-        return C1V == LHSC->getAPInt() ? NewMul : getNegativeSCEV(NewMul);
+        if (NewMul)
+          return C1V == LHSC->getAPInt() ? NewMul : getNegativeSCEV(NewMul);
       }
     }
   }