Revert 336426 (and follow-ups 428, 440), it very likely caused PR38084.

llvm-svn: 336453

1 files changed, 0 insertions, 105 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 59c9026ebdd..e6b4f13a474 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -447,7 +447,6 @@ namespace {
     SDNode *MatchRotate(SDValue LHS, SDValue RHS, const SDLoc &DL);
     SDValue MatchLoadCombine(SDNode *N);
     SDValue ReduceLoadWidth(SDNode *N);
-    SDValue foldRedundantShiftedMasks(SDNode *N);
     SDValue ReduceLoadOpStoreWidth(SDNode *N);
     SDValue splitMergedValStore(StoreSDNode *ST);
     SDValue TransformFPLoadStorePair(SDNode *N);
@@ -4379,9 +4378,6 @@ SDValue DAGCombiner::visitAND(SDNode *N) {
     }
   }
 
-  if (SDValue R = foldRedundantShiftedMasks(N))
-    return R;
-
   if (Level >= AfterLegalizeTypes) {
     // Attempt to propagate the AND back up to the leaves which, if they're
     // loads, can be combined to narrow loads and the AND node can be removed.
@@ -5948,107 +5944,6 @@ SDValue DAGCombiner::visitRotate(SDNode *N) {
   return SDValue();
 }
 
-// fold expressions x1 and x2 alike:
-// x1 = ( and, x, 0x00FF )
-// x2 = (( shl x, 8 ) and 0xFF00 )
-// into
-// x2 = shl x1, 8 ; reuse the computation of x1
-SDValue DAGCombiner::foldRedundantShiftedMasks(SDNode *AND) {
-  if (!AND)
-    return SDValue();
-
-  const SDValue &SHIFT = AND->getOperand(0);
-  if ((SHIFT.getNumOperands() != 2) || (!SHIFT.hasOneUse()))
-    return SDValue();
-
-  const ConstantSDNode *ShiftAmount =
-      dyn_cast<ConstantSDNode>(SHIFT.getOperand(1));
-  if (!ShiftAmount)
-    return SDValue();
-
-  const ConstantSDNode *Mask = dyn_cast<ConstantSDNode>(AND->getOperand(1));
-  if (!Mask)
-    return SDValue();
-
-  SDValue MASKED = SHIFT.getOperand(0);
-  const auto &MaskedValue = dyn_cast<SDNode>(MASKED);
-  unsigned N0Opcode = SHIFT.getOpcode();
-  for (SDNode *OtherUser : MaskedValue->uses()) {
-    if ((&(*OtherUser) == ShiftAmount) || (OtherUser->getOpcode() != ISD::AND))
-      continue;
-
-    ConstantSDNode *OtherMask =
-        dyn_cast<ConstantSDNode>(OtherUser->getOperand(1));
-
-    if (!OtherMask)
-      continue;
-
-    bool CanReduce = false;
-
-    const APInt &MaskValue = Mask->getAPIntValue();
-    const APInt &ShiftValue = ShiftAmount->getAPIntValue();
-    const APInt &OtherMaskValue = OtherMask->getAPIntValue();
-
-    KnownBits MaskedValueBits;
-    DAG.computeKnownBits(MASKED, MaskedValueBits);
-    KnownBits ShiftedValueBits;
-    DAG.computeKnownBits(SHIFT, ShiftedValueBits);
-
-    const APInt EffectiveOtherMask = OtherMaskValue & ~MaskedValueBits.Zero;
-    const APInt EffectiveMask = MaskValue & ~ShiftedValueBits.Zero;
-
-    LLVM_DEBUG(
-        dbgs() << "\tValue being masked and shift-masked: "; MASKED.dump();
-        dbgs() << "\t\tValue zero bits: 0x"
-               << MaskedValueBits.Zero.toString(16, false)
-               << "\n\n\t\tApplied mask: 0x"
-               << OtherMaskValue.toString(16, false) << " : ";
-        OtherUser->dump();
-        dbgs() << "\t\tEffective mask: 0x"
-               << EffectiveOtherMask.toString(16, false)
-               << "\n\n\tShifted by: " << ShiftValue.getZExtValue() << " : ";
-        SHIFT.dump(); dbgs() << "\t\tAnd masked by: 0x"
-                             << MaskValue.toString(16, false) << " : ";
-        AND->dump(); dbgs() << "\t\tEffective mask to shifted value: 0x"
-                            << EffectiveMask.toString(16, false) << '\n';);
-
-    switch (N0Opcode) {
-    case ISD::SHL:
-      CanReduce = (EffectiveOtherMask.shl(EffectiveMask) == EffectiveMask) ||
-                  (EffectiveMask.lshr(ShiftValue) == EffectiveOtherMask);
-      break;
-    case ISD::SRA:
-      if (!MaskedValueBits.Zero.isSignBitSet()) {
-        CanReduce = (EffectiveOtherMask.ashr(ShiftValue) == EffectiveMask);
-        break;
-      } else // Same as SRL
-        N0Opcode = ISD::SRL;
-      LLVM_FALLTHROUGH;
-    case ISD::SRL:
-      CanReduce = (EffectiveOtherMask.lshr(ShiftValue) == EffectiveMask) ||
-                  (EffectiveMask.shl(ShiftValue) == EffectiveOtherMask);
-      break;
-    case ISD::ROTR:
-      CanReduce = (EffectiveOtherMask.rotr(ShiftValue) == EffectiveMask);
-      break;
-    default:
-      return SDValue();
-    }
-    if (CanReduce) {
-      LLVM_DEBUG(dbgs() << "\tCan just shift the masked value\n");
-
-      SDValue ShiftTheAND(OtherUser, 0);
-      const SDLoc DL(SHIFT);
-      EVT VT = AND->getValueType(0);
-      SDValue NewShift =
-          DAG.getNode(N0Opcode, DL, VT, ShiftTheAND, SHIFT.getOperand(1));
-      AddToWorklist(OtherUser);
-      return NewShift;
-    }
-  }
-  return SDValue();
-}
-
 SDValue DAGCombiner::visitSHL(SDNode *N) {
   SDValue N0 = N->getOperand(0);
   SDValue N1 = N->getOperand(1);