[SCEV] Generalize (C * A /u C) -> A fold to (C1 * A /u C2) -> C1/C2 * A.

Generalize fold added in 74ec38f to support multiplying and dividing
by different constants, given they are both powers-of-2 and C1 is a
multiple of C2, checked via their trailing zeros.

https://alive2.llvm.org/ce/z/eqJ2xj

Author: fhahn

llvm/lib/Analysis/ScalarEvolution.cpp

@@ -3216,13 +3216,16 @@ const SCEV *ScalarEvolution::getMulExpr(SmallVectorImpl<const SCEV *> &Ops,
         };
       }
 
-      // Try to fold (C * D /u C) -> D, if C is a power-of-2 and D is a multiple
-      //  of C.
+      // Try to fold (C1 * D /u C2) -> C1/C2 * D, if C1 and C2 are powers-of-2,
+      // D is a multiple of C2, and C1 is a multiple of C1.
       const SCEV *D;
-      if (match(Ops[1], m_scev_UDiv(m_SCEV(D), m_scev_Specific(LHSC))) &&
-          LHSC->getAPInt().isPowerOf2() &&
-          LHSC->getAPInt().logBase2() <= getMinTrailingZeros(D)) {
-        return D;
+      const SCEVConstant *C2;
+      if (LHSC->getAPInt().isPowerOf2() &&
+          match(Ops[1], m_scev_UDiv(m_SCEV(D), m_SCEVConstant(C2))) &&
+          C2->getAPInt().isPowerOf2() &&
+          getMinTrailingZeros(LHSC) >= getMinTrailingZeros(C2) &&
+          getMinTrailingZeros(LHSC) <= getMinTrailingZeros(D)) {
+        return getMulExpr(getUDivExpr(LHSC, C2), D);
       }
     }
   }