Set correct MMO offset on scalarized load pieces

[greened]

Summary

When scalarizing a load, be sure to update the offset in the MachineMemOperand
for each scalar load.

[greened]

Found this by inspection, so no testcase.

[craig.topper]

lib/Target/X86/X86ISelLowering.cpp

19890

I'm not sure if this is needed. getAlignment for loads defers to MachineMemOperand::getAlignment which calls MinAlign(getBaseAlignment(), Offset)

[arsenm]

lib/Target/X86/X86ISelLowering.cpp

19889

Why doesn't this use TLI::scalarizeVectorLoad?

[greened]

lib/Target/X86/X86ISelLowering.cpp

19889

I don't know. Perhaps we can look at refactoring after fixing this bug.

19890

I was just following the example of similar code in the file. If we think it's unnecessary, I guess that's ok but it seems good to me to make this kind of thing explicit, if for no other reason than to make others feel comfortable when they look at this code two years from now.

[greened]

Ping?

[craig.topper]

LGTM

[greened]

Closed with r343776.

lib/Target/X86/X86ISelLowering.cpp

assert(WideVecVT.getSizeInBits() == LoadUnitVecVT.getSizeInBits() &&
          "Invalid vector type");
 
   // We can't shuffle using an illegal type.
   assert(TLI.isTypeLegal(WideVecVT) &&
          "We only lower types that form legal widened vector types");
 
   SmallVector<SDValue, 8> Chains;
   SDValue Ptr = Ld->getBasePtr();
-  SDValue Increment = DAG.getConstant(SclrLoadTy.getSizeInBits() / 8, dl,
+  unsigned OffsetInc = SclrLoadTy.getSizeInBits() / 8;
+  SDValue Increment = DAG.getConstant(OffsetInc, dl,
                                       TLI.getPointerTy(DAG.getDataLayout()));
   SDValue Res = DAG.getUNDEF(LoadUnitVecVT);
 
+  unsigned Offset = 0;
   for (unsigned i = 0; i < NumLoads; ++i) {
+    unsigned NewAlign = MinAlign(Ld->getAlignment(), Offset);
+
     // Perform a single load.
     SDValue ScalarLoad =
-        DAG.getLoad(SclrLoadTy, dl, Ld->getChain(), Ptr, Ld->getPointerInfo(),
-                    Ld->getAlignment(), Ld->getMemOperand()->getFlags());
+      DAG.getLoad(SclrLoadTy, dl, Ld->getChain(), Ptr,
+                  Ld->getPointerInfo().getWithOffset(Offset),
+                  NewAlign, Ld->getMemOperand()->getFlags());
     Chains.push_back(ScalarLoad.getValue(1));
     // Create the first element type using SCALAR_TO_VECTOR in order to avoid
     // another round of DAGCombining.
     if (i == 0)
       Res = DAG.getNode(ISD::SCALAR_TO_VECTOR, dl, LoadUnitVecVT, ScalarLoad);
     else
       Res = DAG.getNode(ISD::INSERT_VECTOR_ELT, dl, LoadUnitVecVT, Res,
                         ScalarLoad, DAG.getIntPtrConstant(i, dl));
 
     Ptr = DAG.getNode(ISD::ADD, dl, Ptr.getValueType(), Ptr, Increment);
+    Offset += OffsetInc;
   }
 
   SDValue TF = DAG.getNode(ISD::TokenFactor, dl, MVT::Other, Chains);
 
   // Bitcast the loaded value to a vector of the original element type, in
   // the size of the target vector type.
   SDValue SlicedVec = DAG.getBitcast(WideVecVT, Res);
   unsigned SizeRatio = RegSz / MemSz;