Add a new step to legalization to legalize vector math operations. This

will allow simplifying LegalizeDAG to eliminate type legalization.  (I 
have a patch to do that, but it's not quite finished; I'll commit it 
once it's finished and I've fixed any review comments for this patch.)  
See the comment at the beginning of 
lib/CodeGen/SelectionDAG/LegalizeVectorOps.cpp for more details on the
motivation for this patch.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@72325 91177308-0d34-0410-b5e6-96231b3b80d8

3 files changed, 375 insertions, 0 deletions

diff --git a/include/llvm/CodeGen/SelectionDAG.h b/include/llvm/CodeGen/SelectionDAG.h
index 5fbda87..ec2d1d7 100644
--- a/include/llvm/CodeGen/SelectionDAG.h
+++ b/include/llvm/CodeGen/SelectionDAG.h
@@ -220,6 +220,19 @@ public:
   /// the graph.
   void Legalize(bool TypesNeedLegalizing, CodeGenOpt::Level OptLevel);
 
+  /// LegalizeVectors - This transforms the SelectionDAG into a SelectionDAG
+  /// that only uses vector math operations supported by the target.  This is
+  /// necessary as a separate step from Legalize because unrolling a vector
+  /// operation can introduce illegal types, which requires running
+  /// LegalizeTypes again.
+  ///
+  /// This returns true if it made any changes; in that case, LegalizeTypes
+  /// is called again before Legalize.
+  ///
+  /// Note that this is an involved process that may invalidate pointers into
+  /// the graph.
+  bool LegalizeVectors();
+
   /// RemoveDeadNodes - This method deletes all unreachable nodes in the
   /// SelectionDAG.
   void RemoveDeadNodes();
diff --git a/lib/CodeGen/SelectionDAG/LegalizeVectorOps.cpp b/lib/CodeGen/SelectionDAG/LegalizeVectorOps.cpp
new file mode 100644
index 0000000..b6f74ae
--- /dev/null
+++ b/lib/CodeGen/SelectionDAG/LegalizeVectorOps.cpp
@@ -0,0 +1,332 @@
+//===-- LegalizeVectorOps.cpp - Implement SelectionDAG::LegalizeVectors ---===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements the SelectionDAG::LegalizeVectors method.
+//
+// The vector legalizer looks for vector operations which might need to be
+// unrolled and legalizes them. This is a separate step from Legalize because
+// unrolling can introduce illegal types.  For example, suppose we have an
+// ISD::SDIV of type v2i64 on x86-32.  The type is legal (for example, addition
+// on a v2i64 is legal), but ISD::SDIV isn't legal, so we have to unroll the
+// operation, which introduces nodes with the illegal type i64 which must be
+// expanded.  Similarly, suppose we have an ISD::SRA of type v16i8 on PowerPC;
+// the operation must be unrolled, which introduces nodes with the illegal
+// type i8 which must be promoted.
+//
+// This does not legalize vector manipulations like ISD::BUILD_VECTOR,
+// or operations that happen to take a vector which are custom-lowered like
+// ISD::CALL; the legalization for such operations never produces nodes
+// with illegal types, so it's okay to put off legalizing them until
+// SelectionDAG::Legalize runs.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/CodeGen/SelectionDAG.h"
+#include "llvm/Target/TargetLowering.h"
+using namespace llvm;
+
+namespace {
+class VectorLegalizer {
+  SelectionDAG& DAG;
+  TargetLowering& TLI;
+  bool Changed; // Keep track of whether anything changed
+
+  /// LegalizedNodes - For nodes that are of legal width, and that have more
+  /// than one use, this map indicates what regularized operand to use.  This
+  /// allows us to avoid legalizing the same thing more than once.
+  DenseMap<SDValue, SDValue> LegalizedNodes;
+
+  // Adds a node to the translation cache
+  void AddLegalizedOperand(SDValue From, SDValue To) {
+    LegalizedNodes.insert(std::make_pair(From, To));
+    // If someone requests legalization of the new node, return itself.
+    if (From != To)
+      LegalizedNodes.insert(std::make_pair(To, To));
+  }
+
+  // Legalizes the given node
+  SDValue LegalizeOp(SDValue Op);
+  // Assuming the node is legal, "legalize" the results
+  SDValue TranslateLegalizeResults(SDValue Op, SDValue Result);
+  // Implements unrolling a generic vector operation, i.e. turning it into
+  // scalar operations.
+  SDValue UnrollVectorOp(SDValue Op);
+  // Implements unrolling a VSETCC.
+  SDValue UnrollVSETCC(SDValue Op);
+  // Implements expansion for FNEG; falls back to UnrollVectorOp if FSUB
+  // isn't legal.
+  SDValue ExpandFNEG(SDValue Op);
+  // Implements vector promotion; this is essentially just bitcasting the
+  // operands to a different type and bitcasting the result back to the
+  // original type.
+  SDValue PromoteVectorOp(SDValue Op);
+
+  public:
+  bool Run();
+  VectorLegalizer(SelectionDAG& dag) :
+      DAG(dag), TLI(dag.getTargetLoweringInfo()), Changed(false) {}
+};
+
+bool VectorLegalizer::Run() {
+  // The legalize process is inherently a bottom-up recursive process (users
+  // legalize their uses before themselves).  Given infinite stack space, we
+  // could just start legalizing on the root and traverse the whole graph.  In
+  // practice however, this causes us to run out of stack space on large basic
+  // blocks.  To avoid this problem, compute an ordering of the nodes where each
+  // node is only legalized after all of its operands are legalized.
+  DAG.AssignTopologicalOrder();
+  for (SelectionDAG::allnodes_iterator I = DAG.allnodes_begin(),
+       E = prior(DAG.allnodes_end()); I != next(E); ++I)
+    LegalizeOp(SDValue(I, 0));
+
+  // Finally, it's possible the root changed.  Get the new root.
+  SDValue OldRoot = DAG.getRoot();
+  assert(LegalizedNodes.count(OldRoot) && "Root didn't get legalized?");
+  DAG.setRoot(LegalizedNodes[OldRoot]);
+
+  LegalizedNodes.clear();
+
+  // Remove dead nodes now.
+  DAG.RemoveDeadNodes();
+
+  return Changed;
+}
+
+SDValue VectorLegalizer::TranslateLegalizeResults(SDValue Op, SDValue Result) {
+  // Generic legalization: just pass the operand through.
+  for (unsigned i = 0, e = Op.getNode()->getNumValues(); i != e; ++i)
+    AddLegalizedOperand(Op.getValue(i), Result.getValue(i));
+  return Result.getValue(Op.getResNo());
+}
+
+SDValue VectorLegalizer::LegalizeOp(SDValue Op) {
+  // Note that LegalizeOp may be reentered even from single-use nodes, which
+  // means that we always must cache transformed nodes.
+  DenseMap<SDValue, SDValue>::iterator I = LegalizedNodes.find(Op);
+  if (I != LegalizedNodes.end()) return I->second;
+
+  SDNode* Node = Op.getNode();
+
+  // Legalize the operands
+  SmallVector<SDValue, 8> Ops;
+  for (unsigned i = 0, e = Node->getNumOperands(); i != e; ++i)
+    Ops.push_back(LegalizeOp(Node->getOperand(i)));
+
+  SDValue Result =
+      DAG.UpdateNodeOperands(Op.getValue(0), Ops.data(), Ops.size());
+
+  bool HasVectorValue = false;
+  for (SDNode::value_iterator J = Node->value_begin(), E = Node->value_end();
+       J != E;
+       ++J)
+    HasVectorValue |= J->isVector();
+  if (!HasVectorValue)
+    return TranslateLegalizeResults(Op, Result);
+
+  switch (Op.getOpcode()) {
+  default:
+    return TranslateLegalizeResults(Op, Result);
+  case ISD::ADD:
+  case ISD::SUB:
+  case ISD::MUL:
+  case ISD::SDIV:
+  case ISD::UDIV:
+  case ISD::SREM:
+  case ISD::UREM:
+  case ISD::FADD:
+  case ISD::FSUB:
+  case ISD::FMUL:
+  case ISD::FDIV:
+  case ISD::FREM:
+  case ISD::AND:
+  case ISD::OR:
+  case ISD::XOR:
+  case ISD::SHL:
+  case ISD::SRA:
+  case ISD::SRL:
+  case ISD::ROTL:
+  case ISD::ROTR:
+  case ISD::CTTZ:
+  case ISD::CTLZ:
+  case ISD::CTPOP:
+  case ISD::SELECT:
+  case ISD::SELECT_CC:
+  case ISD::VSETCC:
+  case ISD::ZERO_EXTEND:
+  case ISD::ANY_EXTEND:
+  case ISD::TRUNCATE:
+  case ISD::SIGN_EXTEND:
+  case ISD::SINT_TO_FP:
+  case ISD::UINT_TO_FP:
+  case ISD::FP_TO_SINT:
+  case ISD::FP_TO_UINT:
+  case ISD::FNEG:
+  case ISD::FABS:
+  case ISD::FSQRT:
+  case ISD::FSIN:
+  case ISD::FCOS:
+  case ISD::FPOWI:
+  case ISD::FPOW:
+  case ISD::FLOG:
+  case ISD::FLOG2:
+  case ISD::FLOG10:
+  case ISD::FEXP:
+  case ISD::FEXP2:
+  case ISD::FCEIL:
+  case ISD::FTRUNC:
+  case ISD::FRINT:
+  case ISD::FNEARBYINT:
+  case ISD::FFLOOR:
+    break;
+  }
+
+  switch (TLI.getOperationAction(Node->getOpcode(), Node->getValueType(0))) {
+  case TargetLowering::Promote:
+    // "Promote" the operation by bitcasting
+    Result = PromoteVectorOp(Op);
+    Changed = true;
+    break;
+  case TargetLowering::Legal: break;
+  case TargetLowering::Custom: {
+    SDValue Tmp1 = TLI.LowerOperation(Op, DAG);
+    if (Tmp1.getNode()) {
+      Result = Tmp1;
+      break;
+    }
+    // FALL THROUGH
+  }
+  case TargetLowering::Expand:
+    if (Node->getOpcode() == ISD::FNEG)
+      Result = ExpandFNEG(Op);
+    else if (Node->getOpcode() == ISD::VSETCC)
+      Result = UnrollVSETCC(Op);
+    else
+      Result = UnrollVectorOp(Op);
+    break;
+  }
+
+  // Make sure that the generated code is itself legal.
+  if (Result != Op) {
+    Result = LegalizeOp(Result);
+    Changed = true;
+  }
+
+  // Note that LegalizeOp may be reentered even from single-use nodes, which
+  // means that we always must cache transformed nodes.
+  AddLegalizedOperand(Op, Result);
+  return Result;
+}
+
+SDValue VectorLegalizer::PromoteVectorOp(SDValue Op) {
+  MVT VT = Op.getValueType();
+  assert(Op.getNode()->getNumValues() == 1 &&
+         "Can't promote a vector with multiple results!");
+  MVT NVT = TLI.getTypeToPromoteTo(Op.getOpcode(), VT);
+  DebugLoc dl = Op.getDebugLoc();
+  SmallVector<SDValue, 4> Operands(Op.getNumOperands());
+
+  for (unsigned j = 0; j != Op.getNumOperands(); ++j) {
+    if (Op.getOperand(j).getValueType().isVector())
+      Operands[j] = DAG.getNode(ISD::BIT_CONVERT, dl, NVT, Op.getOperand(j));
+    else
+      Operands[j] = Op.getOperand(j);
+  }
+
+  Op = DAG.getNode(Op.getOpcode(), dl, NVT, &Operands[0], Operands.size());
+
+  return DAG.getNode(ISD::BIT_CONVERT, dl, VT, Op);
+}
+
+SDValue VectorLegalizer::ExpandFNEG(SDValue Op) {
+  if (TLI.isOperationLegalOrCustom(ISD::FSUB, Op.getValueType())) {
+    SDValue Zero = DAG.getConstantFP(-0.0, Op.getValueType());
+    return DAG.getNode(ISD::FSUB, Op.getDebugLoc(), Op.getValueType(),
+                       Zero, Op.getOperand(0));
+  }
+  return UnrollVectorOp(Op);
+}
+
+SDValue VectorLegalizer::UnrollVSETCC(SDValue Op) {
+  MVT VT = Op.getValueType();
+  unsigned NumElems = VT.getVectorNumElements();
+  MVT EltVT = VT.getVectorElementType();
+  SDValue LHS = Op.getOperand(0), RHS = Op.getOperand(1), CC = Op.getOperand(2);
+  MVT TmpEltVT = LHS.getValueType().getVectorElementType();
+  DebugLoc dl = Op.getDebugLoc();
+  SmallVector<SDValue, 8> Ops(NumElems);
+  for (unsigned i = 0; i < NumElems; ++i) {
+    SDValue LHSElem = DAG.getNode(ISD::EXTRACT_VECTOR_ELT, dl, TmpEltVT, LHS,
+                                  DAG.getIntPtrConstant(i));
+    SDValue RHSElem = DAG.getNode(ISD::EXTRACT_VECTOR_ELT, dl, TmpEltVT, RHS,
+                                  DAG.getIntPtrConstant(i));
+    Ops[i] = DAG.getNode(ISD::SETCC, dl, TLI.getSetCCResultType(TmpEltVT),
+                         LHSElem, RHSElem, CC);
+    Ops[i] = DAG.getNode(ISD::SELECT, dl, EltVT, Ops[i],
+                         DAG.getConstant(APInt::getAllOnesValue
+                                         (EltVT.getSizeInBits()), EltVT),
+                         DAG.getConstant(0, EltVT));
+  }
+  return DAG.getNode(ISD::BUILD_VECTOR, dl, VT, &Ops[0], NumElems);
+}
+
+/// UnrollVectorOp - We know that the given vector has a legal type, however
+/// the operation it performs is not legal, and the target has requested that
+/// the operation be expanded.  "Unroll" the vector, splitting out the scalars
+/// and operating on each element individually.
+SDValue VectorLegalizer::UnrollVectorOp(SDValue Op) {
+  MVT VT = Op.getValueType();
+  assert(Op.getNode()->getNumValues() == 1 &&
+         "Can't unroll a vector with multiple results!");
+  unsigned NE = VT.getVectorNumElements();
+  MVT EltVT = VT.getVectorElementType();
+  DebugLoc dl = Op.getDebugLoc();
+
+  SmallVector<SDValue, 8> Scalars;
+  SmallVector<SDValue, 4> Operands(Op.getNumOperands());
+  for (unsigned i = 0; i != NE; ++i) {
+    for (unsigned j = 0; j != Op.getNumOperands(); ++j) {
+      SDValue Operand = Op.getOperand(j);
+      MVT OperandVT = Operand.getValueType();
+      if (OperandVT.isVector()) {
+        // A vector operand; extract a single element.
+        MVT OperandEltVT = OperandVT.getVectorElementType();
+        Operands[j] = DAG.getNode(ISD::EXTRACT_VECTOR_ELT, dl,
+                                  OperandEltVT,
+                                  Operand,
+                                  DAG.getConstant(i, MVT::i32));
+      } else {
+        // A scalar operand; just use it as is.
+        Operands[j] = Operand;
+      }
+    }
+
+    switch (Op.getOpcode()) {
+    default:
+      Scalars.push_back(DAG.getNode(Op.getOpcode(), dl, EltVT,
+                                    &Operands[0], Operands.size()));
+      break;
+    case ISD::SHL:
+    case ISD::SRA:
+    case ISD::SRL:
+    case ISD::ROTL:
+    case ISD::ROTR:
+      Scalars.push_back(DAG.getNode(Op.getOpcode(), dl, EltVT, Operands[0],
+                                    DAG.getShiftAmountOperand(Operands[1])));
+      break;
+    }
+  }
+
+  return DAG.getNode(ISD::BUILD_VECTOR, dl, VT, &Scalars[0], Scalars.size());
+}
+
+}
+
+bool SelectionDAG::LegalizeVectors() {
+  return VectorLegalizer(*this).Run();
+}
diff --git a/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp b/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
index ba61c88..9d72a12 100644
--- a/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
@@ -611,6 +611,36 @@ void SelectionDAGISel::CodeGenAndEmitDAG() {
       DOUT << "Optimized type-legalized selection DAG:\n";
       DEBUG(CurDAG->dump());
     }
+
+    if (TimePassesIsEnabled) {
+      NamedRegionTimer T("Vector Legalization", GroupName);
+      Changed = CurDAG->LegalizeVectors();
+    } else {
+      Changed = CurDAG->LegalizeVectors();
+    }
+
+    if (Changed) {
+      if (TimePassesIsEnabled) {
+        NamedRegionTimer T("Type Legalization 2", GroupName);
+        Changed = CurDAG->LegalizeTypes();
+      } else {
+        Changed = CurDAG->LegalizeTypes();
+      }
+
+      if (ViewDAGCombineLT)
+        CurDAG->viewGraph("dag-combine-lv input for " + BlockName);
+
+      // Run the DAG combiner in post-type-legalize mode.
+      if (TimePassesIsEnabled) {
+        NamedRegionTimer T("DAG Combining after legalize vectors", GroupName);
+        CurDAG->Combine(NoIllegalOperations, *AA, OptLevel);
+      } else {
+        CurDAG->Combine(NoIllegalOperations, *AA, OptLevel);
+      }
+
+      DOUT << "Optimized vector-legalized selection DAG:\n";
+      DEBUG(CurDAG->dump());
+    }
   }
   
   if (ViewLegalizeDAGs) CurDAG->viewGraph("legalize input for " + BlockName);