vendor/llvm-project/llvmorg-12.0.0-0-gd28af7c654d8

1 files changed, 11 insertions, 4 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 89670d708264..6a6f83827f72 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -6517,8 +6517,11 @@ static SDValue extractShiftForRotate(SelectionDAG &DAG, SDValue OppShift,
 // reduces to a rotate in direction shift2 by Pos or (equivalently) a rotate
 // in direction shift1 by Neg.  The range [0, EltSize) means that we only need
 // to consider shift amounts with defined behavior.
+//
+// The IsRotate flag should be set when the LHS of both shifts is the same.
+// Otherwise if matching a general funnel shift, it should be clear.
 static bool matchRotateSub(SDValue Pos, SDValue Neg, unsigned EltSize,
-                           SelectionDAG &DAG) {
+                           SelectionDAG &DAG, bool IsRotate) {
   // If EltSize is a power of 2 then:
   //
   //  (a) (Pos == 0 ? 0 : EltSize - Pos) == (EltSize - Pos) & (EltSize - 1)
@@ -6550,8 +6553,11 @@ static bool matchRotateSub(SDValue Pos, SDValue Neg, unsigned EltSize,
   // always invokes undefined behavior for 32-bit X.
   //
   // Below, Mask == EltSize - 1 when using [A] and is all-ones otherwise.
+  //
+  // NOTE: We can only do this when matching an AND and not a general
+  // funnel shift.
   unsigned MaskLoBits = 0;
-  if (Neg.getOpcode() == ISD::AND && isPowerOf2_64(EltSize)) {
+  if (IsRotate && Neg.getOpcode() == ISD::AND && isPowerOf2_64(EltSize)) {
     if (ConstantSDNode *NegC = isConstOrConstSplat(Neg.getOperand(1))) {
       KnownBits Known = DAG.computeKnownBits(Neg.getOperand(0));
       unsigned Bits = Log2_64(EltSize);
@@ -6641,7 +6647,8 @@ SDValue DAGCombiner::MatchRotatePosNeg(SDValue Shifted, SDValue Pos,
   //          (srl x, (*ext y))) ->
   //   (rotr x, y) or (rotl x, (sub 32, y))
   EVT VT = Shifted.getValueType();
-  if (matchRotateSub(InnerPos, InnerNeg, VT.getScalarSizeInBits(), DAG)) {
+  if (matchRotateSub(InnerPos, InnerNeg, VT.getScalarSizeInBits(), DAG,
+                     /*IsRotate*/ true)) {
     bool HasPos = TLI.isOperationLegalOrCustom(PosOpcode, VT);
     return DAG.getNode(HasPos ? PosOpcode : NegOpcode, DL, VT, Shifted,
                        HasPos ? Pos : Neg);
@@ -6670,7 +6677,7 @@ SDValue DAGCombiner::MatchFunnelPosNeg(SDValue N0, SDValue N1, SDValue Pos,
   // fold (or (shl x0, (*ext (sub 32, y))),
   //          (srl x1, (*ext y))) ->
   //   (fshr x0, x1, y) or (fshl x0, x1, (sub 32, y))
-  if (matchRotateSub(InnerPos, InnerNeg, EltBits, DAG)) {
+  if (matchRotateSub(InnerPos, InnerNeg, EltBits, DAG, /*IsRotate*/ N0 == N1)) {
     bool HasPos = TLI.isOperationLegalOrCustom(PosOpcode, VT);
     return DAG.getNode(HasPos ? PosOpcode : NegOpcode, DL, VT, N0, N1,
                        HasPos ? Pos : Neg);