diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
index 6fc6eb1..5a58273 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -3448,30 +3448,21 @@
       Ty = StTy->getElementType(Field);
     } else {
       Ty = cast<SequentialType>(Ty)->getElementType();
+      MVT PtrTy = DAG.getTargetLoweringInfo().getPointerTy(AS);
+      unsigned PtrSize = PtrTy.getSizeInBits();
+      APInt ElementSize(PtrSize, DL->getTypeAllocSize(Ty));
 
       // If this is a constant subscript, handle it quickly.
-      const TargetLowering &TLI = DAG.getTargetLoweringInfo();
-      if (const ConstantInt *CI = dyn_cast<ConstantInt>(Idx)) {
-        if (CI->isZero()) continue;
-        uint64_t Offs =
-            DL->getTypeAllocSize(Ty)*cast<ConstantInt>(CI)->getSExtValue();
-        SDValue OffsVal;
-        EVT PTy = TLI.getPointerTy(AS);
-        unsigned PtrBits = PTy.getSizeInBits();
-        if (PtrBits < 64)
-          OffsVal = DAG.getNode(ISD::TRUNCATE, getCurSDLoc(), PTy,
-                                DAG.getConstant(Offs, MVT::i64));
-        else
-          OffsVal = DAG.getConstant(Offs, PTy);
-
-        N = DAG.getNode(ISD::ADD, getCurSDLoc(), N.getValueType(), N,
-                        OffsVal);
+      if (const auto *CI = dyn_cast<ConstantInt>(Idx)) {
+        if (CI->isZero())
+          continue;
+        APInt Offs = ElementSize * CI->getValue().sextOrTrunc(PtrSize);
+        SDValue OffsVal = DAG.getConstant(Offs, PtrTy);
+        N = DAG.getNode(ISD::ADD, getCurSDLoc(), N.getValueType(), N, OffsVal);
         continue;
       }
 
       // N = N + Idx * ElementSize;
-      APInt ElementSize =
-          APInt(TLI.getPointerSizeInBits(AS), DL->getTypeAllocSize(Ty));
       SDValue IdxN = getValue(Idx);
 
       // If the index is smaller or larger than intptr_t, truncate or extend