[X86][SSE] Combine shuffle nodes with multiple uses if all the users are being combined.

Currently we only combine shuffle nodes if they have a single user to prevent us from causing code bloat by splitting the shuffles into several different combines.

We don't take into account that in some cases we will already have combined all the users during recursively calling up the shuffle tree.

This patch keeps a list of all the shuffle nodes that have been combined so far and permits combining of further shuffle nodes if all its users are in that list.

Differential Revision: https://reviews.llvm.org/D29399

llvm-svn: 294183

2 files changed, 34 insertions, 9 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index 46dde01970b..dc5c8baaabc 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -7125,6 +7125,21 @@ bool SDNode::isOnlyUserOf(const SDNode *N) const {
   return Seen;
 }
 
+/// Return true if the only users of N are contained in Nodes.
+bool SDNode::areOnlyUsersOf(ArrayRef<const SDNode *> Nodes, const SDNode *N) {
+  bool Seen = false;
+  for (SDNode::use_iterator I = N->use_begin(), E = N->use_end(); I != E; ++I) {
+    SDNode *User = *I;
+    if (llvm::any_of(Nodes,
+                     [&User](const SDNode *Node) { return User == Node; }))
+      Seen = true;
+    else
+      return false;
+  }
+
+  return Seen;
+}
+
 /// isOperand - Return true if this node is an operand of N.
 ///
 bool SDValue::isOperandOf(const SDNode *N) const {
diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index af06cd3a719..83b340a1b5c 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -27333,6 +27333,7 @@ static bool combineX86ShufflesConstants(const SmallVectorImpl<SDValue> &Ops,
 static bool combineX86ShufflesRecursively(ArrayRef<SDValue> SrcOps,
                                           int SrcOpIndex, SDValue Root,
                                           ArrayRef<int> RootMask,
+                                          ArrayRef<const SDNode*> SrcNodes,
                                           int Depth, bool HasVariableMask,
                                           SelectionDAG &DAG,
                                           TargetLowering::DAGCombinerInfo &DCI,
@@ -27469,11 +27470,20 @@ static bool combineX86ShufflesRecursively(ArrayRef<SDValue> SrcOps,
 
   HasVariableMask |= isTargetShuffleVariableMask(Op.getOpcode());
 
-  // See if we can recurse into each shuffle source op (if it's a target shuffle).
+  // Update the list of shuffle nodes that have been combined so far.
+  SmallVector<const SDNode *, 8> CombinedNodes(SrcNodes.begin(),
+                                               SrcNodes.end());
+  CombinedNodes.push_back(Op.getNode());
+
+  // See if we can recurse into each shuffle source op (if it's a target
+  // shuffle). The source op should only be combined if it either has a
+  // single use (i.e. current Op) or all its users have already been combined.
   for (int i = 0, e = Ops.size(); i < e; ++i)
-    if (Ops[i].getNode()->hasOneUse() || Op->isOnlyUserOf(Ops[i].getNode()))
-      if (combineX86ShufflesRecursively(Ops, i, Root, Mask, Depth + 1,
-                                        HasVariableMask, DAG, DCI, Subtarget))
+    if (Ops[i].getNode()->hasOneUse() ||
+        SDNode::areOnlyUsersOf(CombinedNodes, Ops[i].getNode()))
+      if (combineX86ShufflesRecursively(Ops, i, Root, Mask, CombinedNodes,
+                                        Depth + 1, HasVariableMask, DAG, DCI,
+                                        Subtarget))
         return true;
 
   // Attempt to constant fold all of the constant source ops.
@@ -28270,7 +28280,7 @@ static SDValue combineShuffle(SDNode *N, SelectionDAG &DAG,
     // a particular chain.
     SmallVector<int, 1> NonceMask; // Just a placeholder.
     NonceMask.push_back(0);
-    if (combineX86ShufflesRecursively({Op}, 0, Op, NonceMask,
+    if (combineX86ShufflesRecursively({Op}, 0, Op, NonceMask, {},
                                       /*Depth*/ 1, /*HasVarMask*/ false, DAG,
                                       DCI, Subtarget))
       return SDValue(); // This routine will use CombineTo to replace N.
@@ -30541,7 +30551,7 @@ static SDValue combineVectorShift(SDNode *N, SelectionDAG &DAG,
     SDValue Op(N, 0);
     SmallVector<int, 1> NonceMask; // Just a placeholder.
     NonceMask.push_back(0);
-    if (combineX86ShufflesRecursively({Op}, 0, Op, NonceMask,
+    if (combineX86ShufflesRecursively({Op}, 0, Op, NonceMask, {},
                                       /*Depth*/ 1, /*HasVarMask*/ false, DAG,
                                       DCI, Subtarget))
       return SDValue(); // This routine will use CombineTo to replace N.
@@ -30582,7 +30592,7 @@ static SDValue combineVectorInsert(SDNode *N, SelectionDAG &DAG,
   SDValue Op(N, 0);
   SmallVector<int, 1> NonceMask; // Just a placeholder.
   NonceMask.push_back(0);
-  combineX86ShufflesRecursively({Op}, 0, Op, NonceMask,
+  combineX86ShufflesRecursively({Op}, 0, Op, NonceMask, {},
                                 /*Depth*/ 1, /*HasVarMask*/ false, DAG,
                                 DCI, Subtarget);
   return SDValue();
@@ -30895,7 +30905,7 @@ static SDValue combineAnd(SDNode *N, SelectionDAG &DAG,
     SDValue Op(N, 0);
     SmallVector<int, 1> NonceMask; // Just a placeholder.
     NonceMask.push_back(0);
-    if (combineX86ShufflesRecursively({Op}, 0, Op, NonceMask,
+    if (combineX86ShufflesRecursively({Op}, 0, Op, NonceMask, {},
                                       /*Depth*/ 1, /*HasVarMask*/ false, DAG,
                                       DCI, Subtarget))
       return SDValue(); // This routine will use CombineTo to replace N.
@@ -33053,7 +33063,7 @@ static SDValue combineAndnp(SDNode *N, SelectionDAG &DAG,
     SDValue Op(N, 0);
     SmallVector<int, 1> NonceMask; // Just a placeholder.
     NonceMask.push_back(0);
-    if (combineX86ShufflesRecursively({Op}, 0, Op, NonceMask,
+    if (combineX86ShufflesRecursively({Op}, 0, Op, NonceMask, {},
                                       /*Depth*/ 1, /*HasVarMask*/ false, DAG,
                                       DCI, Subtarget))
       return SDValue(); // This routine will use CombineTo to replace N.