1 files changed, 49 insertions, 0 deletions
diff --git a/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp b/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
index 4e7094bf210..017db41fa9e 100644
--- a/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
@@ -4142,6 +4142,55 @@ SDValue TargetLowering::expandFMINNUM_FMAXNUM(SDNode *Node,
   return SDValue();
 }
 
+bool TargetLowering::expandCTPOP(SDNode *Node, SDValue &Result,
+                                 SelectionDAG &DAG) const {
+  SDLoc dl(Node);
+  EVT VT = Node->getValueType(0);
+  EVT ShVT = getShiftAmountTy(VT, DAG.getDataLayout());
+  SDValue Op = Node->getOperand(0);
+  unsigned Len = VT.getScalarSizeInBits();
+  assert(VT.isInteger() && Len <= 128 && Len % 8 == 0 &&
+         "CTPOP not implemented for this type.");
+
+  // This is the "best" algorithm from
+  // http://graphics.stanford.edu/~seander/bithacks.html#CountBitsSetParallel
+  SDValue Mask55 =
+      DAG.getConstant(APInt::getSplat(Len, APInt(8, 0x55)), dl, VT);
+  SDValue Mask33 =
+      DAG.getConstant(APInt::getSplat(Len, APInt(8, 0x33)), dl, VT);
+  SDValue Mask0F =
+      DAG.getConstant(APInt::getSplat(Len, APInt(8, 0x0F)), dl, VT);
+  SDValue Mask01 =
+      DAG.getConstant(APInt::getSplat(Len, APInt(8, 0x01)), dl, VT);
+
+  // v = v - ((v >> 1) & 0x55555555...)
+  Op = DAG.getNode(ISD::SUB, dl, VT, Op,
+                   DAG.getNode(ISD::AND, dl, VT,
+                               DAG.getNode(ISD::SRL, dl, VT, Op,
+                                           DAG.getConstant(1, dl, ShVT)),
+                               Mask55));
+  // v = (v & 0x33333333...) + ((v >> 2) & 0x33333333...)
+  Op = DAG.getNode(ISD::ADD, dl, VT, DAG.getNode(ISD::AND, dl, VT, Op, Mask33),
+                   DAG.getNode(ISD::AND, dl, VT,
+                               DAG.getNode(ISD::SRL, dl, VT, Op,
+                                           DAG.getConstant(2, dl, ShVT)),
+                               Mask33));
+  // v = (v + (v >> 4)) & 0x0F0F0F0F...
+  Op = DAG.getNode(ISD::AND, dl, VT,
+                   DAG.getNode(ISD::ADD, dl, VT, Op,
+                               DAG.getNode(ISD::SRL, dl, VT, Op,
+                                           DAG.getConstant(4, dl, ShVT))),
+                   Mask0F);
+  // v = (v * 0x01010101...) >> (Len - 8)
+  if (Len > 8)
+    Op =
+        DAG.getNode(ISD::SRL, dl, VT, DAG.getNode(ISD::MUL, dl, VT, Op, Mask01),
+                    DAG.getConstant(Len - 8, dl, ShVT));
+
+  Result = Op;
+  return true;
+}
+
 bool TargetLowering::expandCTLZ(SDNode *Node, SDValue &Result,
                                 SelectionDAG &DAG) const {
   SDLoc dl(Node);