Implement review feedback for vector shuffle work.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@70372 91177308-0d34-0410-b5e6-96231b3b80d8

3 files changed, 20 insertions, 6 deletions

diff --git a/include/llvm/CodeGen/SelectionDAG.h b/include/llvm/CodeGen/SelectionDAG.h
index d2d17cf..9060376 100644
--- a/include/llvm/CodeGen/SelectionDAG.h
+++ b/include/llvm/CodeGen/SelectionDAG.h
@@ -356,7 +356,7 @@ public:
   
   /// getVectorShuffle - Return an ISD::VECTOR_SHUFFLE node.  The number of
   /// elements in VT, which must be a vector type, must match the number of
-  /// mask elements NumElts.  A negative integer mask element is treated as
+  /// mask elements NumElts.  A integer mask element equal to -1 is treated as
   /// undefined.
   SDValue getVectorShuffle(MVT VT, DebugLoc dl, SDValue N1, SDValue N2, 
                            const int *MaskElts);
@@ -822,7 +822,7 @@ public:
 
   /// getShuffleScalarElt - Returns the scalar element that will make up the ith
   /// element of the result of the vector shuffle.
-  SDValue getShuffleScalarElt(const SDNode *N, unsigned Idx);
+  SDValue getShuffleScalarElt(const ShuffleVectorSDNode *N, unsigned Idx);
 
 private:
   bool RemoveNodeFromCSEMaps(SDNode *N);
diff --git a/include/llvm/CodeGen/SelectionDAGNodes.h b/include/llvm/CodeGen/SelectionDAGNodes.h
index 34d877a..dc7112c 100644
--- a/include/llvm/CodeGen/SelectionDAGNodes.h
+++ b/include/llvm/CodeGen/SelectionDAGNodes.h
@@ -1704,12 +1704,24 @@ public:
   }
 };
 
+/// ShuffleVectorSDNode - This SDNode is used to implement the code generator
+/// support for the llvm IR shufflevector instruction.  It combines elements
+/// from two input vectors into a new input vector, with the selection and
+/// ordering of elements determined by an array of integers, referred to as
+/// the shuffle mask.  For input vectors of width N, mask indices of 0..N-1
+/// refer to elements from the LHS input, and indices from N to 2N-1 the RHS.
+/// An index of -1 is treated as undef, such that the code generator may put
+/// any value in the corresponding element of the result.
 class ShuffleVectorSDNode : public SDNode {
   SDUse Ops[2];
-  int *Mask;
+
+  // The memory for Mask is owned by the SelectionDAG's OperandAllocator, and
+  // is freed when the SelectionDAG object is destroyed.
+  const int *Mask;
 protected:
   friend class SelectionDAG;
-  ShuffleVectorSDNode(MVT VT, DebugLoc dl, SDValue N1, SDValue N2, int *M)
+  ShuffleVectorSDNode(MVT VT, DebugLoc dl, SDValue N1, SDValue N2, 
+                      const int *M)
     : SDNode(ISD::VECTOR_SHUFFLE, dl, getSDVTList(VT)), Mask(M) {
     InitOperands(Ops, N1, N2);
   }
diff --git a/include/llvm/Target/TargetLowering.h b/include/llvm/Target/TargetLowering.h
index 3dbe89d..624f9fc 100644
--- a/include/llvm/Target/TargetLowering.h
+++ b/include/llvm/Target/TargetLowering.h
@@ -329,7 +329,8 @@ public:
   /// support *some* VECTOR_SHUFFLE operations, those with specific masks.
   /// By default, if a target supports the VECTOR_SHUFFLE node, all mask values
   /// are assumed to be legal.
-  virtual bool isShuffleMaskLegal(SmallVectorImpl<int> &Mask, MVT VT) const {
+  virtual bool isShuffleMaskLegal(const SmallVectorImpl<int> &Mask,
+                                  MVT VT) const {
     return true;
   }
 
@@ -337,7 +338,8 @@ public:
   /// used by Targets can use this to indicate if there is a suitable
   /// VECTOR_SHUFFLE that can be used to replace a VAND with a constant
   /// pool entry.
-  virtual bool isVectorClearMaskLegal(SmallVectorImpl<int> &M, MVT VT) const {
+  virtual bool isVectorClearMaskLegal(const SmallVectorImpl<int> &Mask,
+                                      MVT VT) const {
     return false;
   }