diff --git a/llvm/lib/Target/DirectX/DXILFlattenArrays.cpp b/llvm/lib/Target/DirectX/DXILFlattenArrays.cppindex ce43645d005b0..f0e2e786dfaf4 100644--- a/llvm/lib/Target/DirectX/DXILFlattenArrays.cpp+++ b/llvm/lib/Target/DirectX/DXILFlattenArrays.cpp@@ -343,6 +343,16 @@ bool DXILFlattenArraysVisitor::visitGetElementPtrInst(GetElementPtrInst &GEP) {         Info.RootFlattenedArrayType, Info.RootPointerOperand,         {ZeroIndex, FlattenedIndex}, GEP.getName(), GEP.getNoWrapFlags());+    // If the pointer operand is a global variable and all indices are 0,+    // IRBuilder::CreateGEP will return the global variable instead of creating+    // a GEP instruction or GEP ConstantExpr. In this case we have to create and+    // insert our own GEP instruction.+    if (!isa<GEPOperator>(NewGEP))+      NewGEP = GetElementPtrInst::Create(+          Info.RootFlattenedArrayType, Info.RootPointerOperand,+          {ZeroIndex, FlattenedIndex}, GEP.getNoWrapFlags(), GEP.getName(),+          Builder.GetInsertPoint());+     // Replace the current GEP with the new GEP. Store GEPInfo into the map     // for later use in case this GEP was not the end of the chain     GEPChainInfoMap.insert({cast<GEPOperator>(NewGEP), std::move(Info)});diff --git a/llvm/test/CodeGen/DirectX/flatten-array.ll b/llvm/test/CodeGen/DirectX/flatten-array.llindex 1376a1db25975..a2e105537ab88 100644--- a/llvm/test/CodeGen/DirectX/flatten-array.ll+++ b/llvm/test/CodeGen/DirectX/flatten-array.ll@@ -218,6 +218,28 @@ define void @two_index_gep_const() {   ret void }+define void @zero_index_global() {+  ; CHECK-LABEL: define void @zero_index_global(+  ; CHECK-NEXT: [[GEP:%.*]] = getelementptr inbounds nuw [4 x float], ptr addrspace(3) @g.1dim, i32 0, i32 0+  ; CHECK-NEXT: load float, ptr addrspace(3) [[GEP]], align 4+  ; CHECK-NEXT: ret void+  %1 = getelementptr inbounds nuw [2 x [2 x float]], ptr addrspace(3) @g, i32 0, i32 0, i32 0+  %2 = load float, ptr addrspace(3) %1, align 4+  ret void+}++; Note: A ConstantExpr GEP with all 0 indices is equivalent to the pointer+; operand of the GEP. Therefore the visitLoadInst will not see the pointer operand+; as a ConstantExpr GEP and will not create a GEP instruction to be visited.+; The later dxil-legalize pass will insert a GEP in this instance.+define void @zero_index_global_const() {+  ; CHECK-LABEL: define void @zero_index_global_const(+  ; CHECK-NEXT: load float, ptr addrspace(3) @g.1dim, align 4+  ; CHECK-NEXT: ret void+  %1 = load float, ptr addrspace(3) getelementptr inbounds nuw ([2 x [2 x float]], ptr addrspace(3) @g, i32 0, i32 0, i32 0), align 4+  ret void+}+ define void @gep_4d_index_test()  {     ; CHECK-LABEL: gep_4d_index_test     ; CHECK: [[a:%.*]] = alloca [16 x i32], align 4