2 files changed, 20 insertions, 46 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/ScheduleDAGSDNodes.cpp b/llvm/lib/CodeGen/SelectionDAG/ScheduleDAGSDNodes.cpp
index 559265a3ac8..93c5c34b67a 100644
--- a/llvm/lib/CodeGen/SelectionDAG/ScheduleDAGSDNodes.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/ScheduleDAGSDNodes.cpp
@@ -205,6 +205,19 @@ void ScheduleDAGSDNodes::ClusterNeighboringLoads(SDNode *Node) {
   if (!Chain)
     return;
 
+  // Skip any load instruction that has a tied input. There may be an additional
+  // dependency requiring a different order than by increasing offsets, and the
+  // added glue may introduce a cycle.
+  auto hasTiedInput = [this](const SDNode *N) {
+    const MCInstrDesc &MCID = TII->get(N->getMachineOpcode());
+    for (unsigned I = 0; I != MCID.getNumOperands(); ++I) {
+      if (MCID.getOperandConstraint(I, MCOI::TIED_TO) != -1)
+        return true;
+    }
+
+    return false;
+  };
+
   // Look for other loads of the same chain. Find loads that are loading from
   // the same base pointer and different offsets.
   SmallPtrSet<SDNode*, 16> Visited;
@@ -212,6 +225,10 @@ void ScheduleDAGSDNodes::ClusterNeighboringLoads(SDNode *Node) {
   DenseMap<long long, SDNode*> O2SMap;  // Map from offset to SDNode.
   bool Cluster = false;
   SDNode *Base = Node;
+
+  if (hasTiedInput(Base))
+    return;
+
   // This algorithm requires a reasonably low use count before finding a match
   // to avoid uselessly blowing up compile time in large blocks.
   unsigned UseCount = 0;
@@ -222,10 +239,12 @@ void ScheduleDAGSDNodes::ClusterNeighboringLoads(SDNode *Node) {
       continue;
     int64_t Offset1, Offset2;
     if (!TII->areLoadsFromSameBasePtr(Base, User, Offset1, Offset2) ||
-        Offset1 == Offset2)
+        Offset1 == Offset2 ||
+        hasTiedInput(User)) {
       // FIXME: Should be ok if they addresses are identical. But earlier
       // optimizations really should have eliminated one of the loads.
       continue;
+    }
     if (O2SMap.insert(std::make_pair(Offset1, Base)).second)
       Offsets.push_back(Offset1);
     O2SMap.insert(std::make_pair(Offset2, User));
diff --git a/llvm/lib/Target/AMDGPU/SIISelLowering.cpp b/llvm/lib/Target/AMDGPU/SIISelLowering.cpp
index 3873c46b44e..69e05c311d2 100644
--- a/llvm/lib/Target/AMDGPU/SIISelLowering.cpp
+++ b/llvm/lib/Target/AMDGPU/SIISelLowering.cpp
@@ -9367,51 +9367,6 @@ SDNode *SITargetLowering::PostISelFolding(MachineSDNode *Node,
     Ops.push_back(ImpDef.getValue(1));
     return DAG.getMachineNode(Opcode, SDLoc(Node), Node->getVTList(), Ops);
   }
-  case AMDGPU::FLAT_LOAD_UBYTE_D16_HI:
-  case AMDGPU::FLAT_LOAD_SBYTE_D16_HI:
-  case AMDGPU::FLAT_LOAD_SHORT_D16_HI:
-  case AMDGPU::GLOBAL_LOAD_UBYTE_D16_HI:
-  case AMDGPU::GLOBAL_LOAD_SBYTE_D16_HI:
-  case AMDGPU::GLOBAL_LOAD_SHORT_D16_HI:
-  case AMDGPU::DS_READ_U16_D16_HI:
-  case AMDGPU::DS_READ_I8_D16_HI:
-  case AMDGPU::DS_READ_U8_D16_HI:
-  case AMDGPU::BUFFER_LOAD_SHORT_D16_HI_OFFSET:
-  case AMDGPU::BUFFER_LOAD_UBYTE_D16_HI_OFFSET:
-  case AMDGPU::BUFFER_LOAD_SBYTE_D16_HI_OFFSET:
-  case AMDGPU::BUFFER_LOAD_SHORT_D16_HI_OFFEN:
-  case AMDGPU::BUFFER_LOAD_UBYTE_D16_HI_OFFEN:
-  case AMDGPU::BUFFER_LOAD_SBYTE_D16_HI_OFFEN: {
-    // For these loads that write to the HI part of a register,
-    // we should chain them to the op that writes to the LO part
-    // of the register to maintain the order.
-    unsigned NumOps = Node->getNumOperands();
-    SDValue OldChain = Node->getOperand(NumOps-1);
-
-    if (OldChain.getValueType() != MVT::Other)
-      break;
-
-    // Look for the chain to replace to.
-    SDValue Lo = Node->getOperand(NumOps-2);
-    SDNode *LoNode = Lo.getNode();
-    if (LoNode->getNumValues() == 1 ||
-        LoNode->getValueType(LoNode->getNumValues() - 1) != MVT::Other)
-      break;
-
-    SDValue NewChain = Lo.getValue(LoNode->getNumValues() - 1);
-    if (NewChain == OldChain) // Already replaced.
-      break;
-
-    SmallVector<SDValue, 16> Ops;
-    for (unsigned I = 0; I < NumOps-1; ++I)
-      Ops.push_back(Node->getOperand(I));
-    // Repalce the Chain.
-    Ops.push_back(NewChain);
-    MachineSDNode *NewNode = DAG.getMachineNode(Opcode, SDLoc(Node),
-                                                Node->getVTList(), Ops);
-    DAG.setNodeMemRefs(NewNode, Node->memoperands());
-    return NewNode;
-  }
   default:
     break;
   }