[X86] combineLoad - begun making the load split code more generic. NFCI.

This is currently only used for ymm->xmm splitting but we shouldn't hardcode the offsets/alignment.

This is necessary for an upcoming patch to split under-aligned non-temporal vector loads.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@363570 91177308-0d34-0410-b5e6-96231b3b80d8

Author: RKSimon

lib/Target/X86/X86ISelLowering.cpp

@@ -39111,27 +39111,26 @@ static SDValue combineLoad(SDNode *N, SelectionDAG &DAG,
       Ext == ISD::NON_EXTLOAD &&
       ((Ld->isNonTemporal() && !Subtarget.hasInt256() && Alignment >= 16) ||
        (TLI.allowsMemoryAccess(*DAG.getContext(), DAG.getDataLayout(), RegVT,
-                               *Ld->getMemOperand(), &Fast) && !Fast))) {
+                               *Ld->getMemOperand(), &Fast) &&
+        !Fast))) {
     unsigned NumElems = RegVT.getVectorNumElements();
     if (NumElems < 2)
       return SDValue();
 
-    SDValue Ptr = Ld->getBasePtr();
-
+    unsigned HalfAlign = 16;
+    SDValue Ptr1 = Ld->getBasePtr();
+    SDValue Ptr2 = DAG.getMemBasePlusOffset(Ptr1, HalfAlign, dl);
     EVT HalfVT = EVT::getVectorVT(*DAG.getContext(), MemVT.getScalarType(),
-                                  NumElems/2);
+                                  NumElems / 2);
     SDValue Load1 =
-        DAG.getLoad(HalfVT, dl, Ld->getChain(), Ptr, Ld->getPointerInfo(),
+        DAG.getLoad(HalfVT, dl, Ld->getChain(), Ptr1, Ld->getPointerInfo(),
                     Alignment, Ld->getMemOperand()->getFlags());
-
-    Ptr = DAG.getMemBasePlusOffset(Ptr, 16, dl);
-    SDValue Load2 =
-        DAG.getLoad(HalfVT, dl, Ld->getChain(), Ptr,
-                    Ld->getPointerInfo().getWithOffset(16),
-                    MinAlign(Alignment, 16U), Ld->getMemOperand()->getFlags());
+    SDValue Load2 = DAG.getLoad(HalfVT, dl, Ld->getChain(), Ptr2,
+                                Ld->getPointerInfo().getWithOffset(HalfAlign),
+                                MinAlign(Alignment, HalfAlign),
+                                Ld->getMemOperand()->getFlags());
     SDValue TF = DAG.getNode(ISD::TokenFactor, dl, MVT::Other,
-                             Load1.getValue(1),
-                             Load2.getValue(1));
+                             Load1.getValue(1), Load2.getValue(1));
 
     SDValue NewVec = DAG.getNode(ISD::CONCAT_VECTORS, dl, RegVT, Load1, Load2);
     return DCI.CombineTo(N, NewVec, TF, true);