[DAG] computeKnownBits - Replace ISD::SREM handling with KnownBits::srem to reduce code duplication

Author: RKSimon

llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp

@@ -3249,30 +3249,12 @@ KnownBits SelectionDAG::computeKnownBits(SDValue Op, const APInt &DemandedElts,
     Known = KnownBits::computeForAddCarry(Known, Known2, Carry);
     break;
   }
-  case ISD::SREM:
-    if (ConstantSDNode *Rem = isConstOrConstSplat(Op.getOperand(1))) {
-      const APInt &RA = Rem->getAPIntValue().abs();
-      if (RA.isPowerOf2()) {
-        APInt LowBits = RA - 1;
-        Known2 = computeKnownBits(Op.getOperand(0), DemandedElts, Depth + 1);
-
-        // The low bits of the first operand are unchanged by the srem.
-        Known.Zero = Known2.Zero & LowBits;
-        Known.One = Known2.One & LowBits;
-
-        // If the first operand is non-negative or has all low bits zero, then
-        // the upper bits are all zero.
-        if (Known2.isNonNegative() || LowBits.isSubsetOf(Known2.Zero))
-          Known.Zero |= ~LowBits;
-
-        // If the first operand is negative and not all low bits are zero, then
-        // the upper bits are all one.
-        if (Known2.isNegative() && LowBits.intersects(Known2.One))
-          Known.One |= ~LowBits;
-        assert((Known.Zero & Known.One) == 0&&"Bits known to be one AND zero?");
-      }
-    }
+  case ISD::SREM: {
+    Known = computeKnownBits(Op.getOperand(0), DemandedElts, Depth + 1);
+    Known2 = computeKnownBits(Op.getOperand(1), DemandedElts, Depth + 1);
+    Known = KnownBits::srem(Known, Known2);
     break;
+  }
   case ISD::UREM: {
     Known = computeKnownBits(Op.getOperand(0), DemandedElts, Depth + 1);
     Known2 = computeKnownBits(Op.getOperand(1), DemandedElts, Depth + 1);