[LegalizeVectorTypes] Create correct memoperands in SplitVecRes_INSERT_SUBVECTOR.

[craig.topper]

Summary

Previously this code just used a default constructed
MachinePointerInfo. But we know the accesses are to a fixed stack
object or at least somewhere on the stack.

I don't think this function is currently exercised in tree so I
don't know how to test it. I just noticed it when I removed
non-constant index support in this function.

[efriedma]

getUnknownStack() doesn't actually do anything at the moment except set the correct address-space. But I guess that's still an improvement.

llvm/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp

1165

While you're here, please pass the alignment consistently to all the load/store operations where it applies.

[craig.topper]

Pass Alignment to all the loads and stores

[efriedma]

llvm/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp

1170

Not sure the alignment of the subvector store is right?

[craig.topper]

llvm/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp

1170

Oops. You're right. I got carried away.

[craig.topper]

-Remove Alignment from the subvector store.
-Add alignment to the very similar code in SplitVecRes_INSERT_VECTOR_ELT

[efriedma]

LGTM

llvm/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp

 //===------- LegalizeVectorTypes.cpp - Legalization of vector types -------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 //
if ((IdxVal == 0) && (IdxVal + SubElems <= VecElems / 2)) {
     EVT LoVT, HiVT;
     std::tie(LoVT, HiVT) = DAG.GetSplitDestVTs(N->getValueType(0));
     Lo = DAG.getNode(ISD::INSERT_SUBVECTOR, dl, LoVT, Lo, SubVec, Idx);
     return;
   }
 
   // Spill the vector to the stack.
   SDValue StackPtr = DAG.CreateStackTemporary(VecVT);
+  auto &MF = DAG.getMachineFunction();
+  auto FrameIndex = cast<FrameIndexSDNode>(StackPtr.getNode())->getIndex();
+  auto PtrInfo = MachinePointerInfo::getFixedStack(MF, FrameIndex);
+  Type *VecType = VecVT.getTypeForEVT(*DAG.getContext());
+  Align Alignment = DAG.getDataLayout().getPrefTypeAlign(VecType);
+
   SDValue Store =
-      DAG.getStore(DAG.getEntryNode(), dl, Vec, StackPtr, MachinePointerInfo());
+      DAG.getStore(DAG.getEntryNode(), dl, Vec, StackPtr, PtrInfo, Alignment);
 
   // Store the new subvector into the specified index.
   SDValue SubVecPtr = TLI.getVectorElementPointer(DAG, StackPtr, VecVT, Idx);
-  Type *VecType = VecVT.getTypeForEVT(*DAG.getContext());
-  Align Alignment = DAG.getDataLayout().getPrefTypeAlign(VecType);
-  Store = DAG.getStore(Store, dl, SubVec, SubVecPtr, MachinePointerInfo());
+  Store = DAG.getStore(Store, dl, SubVec, SubVecPtr,
+                       MachinePointerInfo::getUnknownStack(MF), Alignment);
 
   // Load the Lo part from the stack slot.
-  Lo =
-      DAG.getLoad(Lo.getValueType(), dl, Store, StackPtr, MachinePointerInfo());
+  Lo = DAG.getLoad(Lo.getValueType(), dl, Store, StackPtr, PtrInfo, Alignment);
 
   // Increment the pointer to the other part.
   unsigned IncrementSize = Lo.getValueSizeInBits() / 8;
   StackPtr = DAG.getMemBasePlusOffset(StackPtr, IncrementSize, dl);
 
   // Load the Hi part from the stack slot.
-  Hi =
-      DAG.getLoad(Hi.getValueType(), dl, Store, StackPtr,
-                  MachinePointerInfo().getWithOffset(IncrementSize), Alignment);
+  Hi = DAG.getLoad(Hi.getValueType(), dl, Store, StackPtr,
+                   PtrInfo.getWithOffset(IncrementSize), Alignment);
 }
 
 void DAGTypeLegalizer::SplitVecRes_FPOWI(SDNode *N, SDValue &Lo,
                                          SDValue &Hi) {
   SDLoc dl(N);
   GetSplitVector(N->getOperand(0), Lo, Hi);
   Lo = DAG.getNode(ISD::FPOWI, dl, Lo.getValueType(), Lo, N->getOperand(1));
   Hi = DAG.getNode(ISD::FPOWI, dl, Hi.getValueType(), Hi, N->getOperand(1));