diff --git a/llvm/lib/IR/Constants.cpp b/llvm/lib/IR/Constants.cpp
--- a/llvm/lib/IR/Constants.cpp
+++ b/llvm/lib/IR/Constants.cpp
@@ -1518,6 +1518,27 @@
     return CV->getSplatValue();
   if (const ConstantVector *CV = dyn_cast<ConstantVector>(this))
     return CV->getSplatValue(AllowUndefs);
+
+  // Check if this is a constant expression splat of the form returned by
+  // ConstantVector::getSplat()
+  auto *Shuf = dyn_cast<ConstantExpr>(this);
+  if (Shuf && Shuf->getOpcode() == Instruction::ShuffleVector &&
+      isa<UndefValue>(Shuf->getOperand(1))) {
+
+    auto *IElt = dyn_cast<ConstantExpr>(Shuf->getOperand(0));
+    if (IElt && IElt->getOpcode() == Instruction::InsertElement &&
+        isa<UndefValue>(IElt->getOperand(0))) {
+
+      ArrayRef<int> Mask = Shuf->getShuffleMask();
+      Constant *SplatVal = IElt->getOperand(1);
+      ConstantInt *Index = cast<ConstantInt>(IElt->getOperand(2));
+
+      if (Index->getValue() == 0 &&
+          std::all_of(Mask.begin(), Mask.end(), [](int I) { return I == 0; }))
+        return SplatVal;
+    }
+  }
+
   return nullptr;
 }
 
@@ -1551,9 +1572,8 @@
 const APInt &Constant::getUniqueInteger() const {
   if (const ConstantInt *CI = dyn_cast<ConstantInt>(this))
     return CI->getValue();
-  assert(this->getSplatValue() && "Doesn't contain a unique integer!");
-  const Constant *C = this->getAggregateElement(0U);
-  assert(C && isa<ConstantInt>(C) && "Not a vector of numbers!");
+  Constant *C = this->getSplatValue();
+  assert(C && isa<ConstantInt>(C) && "Doesn't contain a unique integer!");
   return cast<ConstantInt>(C)->getValue();
 }
 
diff --git a/llvm/lib/IR/DataLayout.cpp b/llvm/lib/IR/DataLayout.cpp
--- a/llvm/lib/IR/DataLayout.cpp
+++ b/llvm/lib/IR/DataLayout.cpp
@@ -814,7 +814,7 @@
   unsigned NumBits = getIndexTypeSizeInBits(Ty);
   IntegerType *IntTy = IntegerType::get(Ty->getContext(), NumBits);
   if (VectorType *VecTy = dyn_cast<VectorType>(Ty))
-    return FixedVectorType::get(IntTy, VecTy->getNumElements());
+    return VectorType::get(IntTy, VecTy);
   return IntTy;
 }
 
diff --git a/llvm/lib/IR/Instructions.cpp b/llvm/lib/IR/Instructions.cpp
--- a/llvm/lib/IR/Instructions.cpp
+++ b/llvm/lib/IR/Instructions.cpp
@@ -3220,7 +3220,7 @@
   // FIXME: Check address space sizes here
   if (VectorType *SrcVecTy = dyn_cast<VectorType>(SrcTy))
     if (VectorType *DestVecTy = dyn_cast<VectorType>(DestTy))
-      if (SrcVecTy->getNumElements() == DestVecTy->getNumElements()) {
+      if (SrcVecTy->getElementCount() == DestVecTy->getElementCount()) {
         // An element by element cast.  Find the appropriate opcode based on the
         // element types.
         SrcTy = SrcVecTy->getElementType();
diff --git a/llvm/test/Transforms/InstSimplify/gep.ll b/llvm/test/Transforms/InstSimplify/gep.ll
--- a/llvm/test/Transforms/InstSimplify/gep.ll
+++ b/llvm/test/Transforms/InstSimplify/gep.ll
@@ -168,4 +168,12 @@
   ret <vscale x 4 x i32*> %gep
 }
 
+define <vscale x 4 x float*> @scalable_vector_idx_mix_scalar_vector() {
+; CHECK-LABEL: @scalable_vector_idx_mix_scalar_vector(
+; CHECK-NEXT:    ret <vscale x 4 x float*> getelementptr (%struct, <vscale x 4 x %struct*> zeroinitializer, <vscale x 4 x i64> zeroinitializer, <vscale x 4 x i32> shufflevector (<vscale x 4 x i32> insertelement (<vscale x 4 x i32> undef, i32 1, i32 0), <vscale x 4 x i32> undef, <vscale x 4 x i32> zeroinitializer))
+;
+  %gep = getelementptr %struct, <vscale x 4 x %struct*> zeroinitializer, i32 0, <vscale x 4 x i32> shufflevector (<vscale x 4 x i32> insertelement (<vscale x 4 x i32> undef, i32 1, i32 0), <vscale x 4 x i32> undef, <vscale x 4 x i32> zeroinitializer)
+  ret <vscale x 4 x float*> %gep
+}
+
 ; Check ConstantExpr::getGetElementPtr() using ElementCount for size queries - end.