Index: lib/Transforms/Scalar/LoopDataPrefetch.cpp
===================================================================
--- lib/Transforms/Scalar/LoopDataPrefetch.cpp
+++ lib/Transforms/Scalar/LoopDataPrefetch.cpp
@@ -313,6 +313,14 @@
               if (DomBB != PrefetchBB)
                 Pref.first->moveBefore(DomBB->getTerminator());
             }
+            /// If MemI is a store but the already emitted prefetch is for a
+            /// 'read', update the prefetch argument to 'write'.
+            bool HasLoadPrefetch =
+              cast<ConstantInt>(Pref.first->getOperand(1))->getZExtValue() == 0;
+            if (PD == 0 && HasLoadPrefetch && MemI->mayWriteToMemory()) {
+              Type *I32 = Type::getInt32Ty(BB->getContext());
+              Pref.first->setOperand(1, ConstantInt::get(I32, 1));
+            }
             DupPref = true;
             break;
           }
Index: test/CodeGen/SystemZ/prefetch-04.ll
===================================================================
--- /dev/null
+++ test/CodeGen/SystemZ/prefetch-04.ll
@@ -0,0 +1,28 @@
+; RUN: llc < %s -mtriple=s390x-linux-gnu -mcpu=z14 -prefetch-distance=50 \
+; RUN:   -loop-prefetch-writes -stop-after=loop-data-prefetch | FileCheck %s
+;
+; Check that for a load followed by a store to the same address gets a single
+; write prefetch.
+;
+; CHECK-LABEL: for.body
+; CHECK: call void @llvm.prefetch.p0i8(i8* %scevgep{{.*}}, i32 1, i32 3, i32 1
+; CHECK-not: call void @llvm.prefetch
+
+define void @fun(i32* nocapture %Src, i32* nocapture readonly %Dst) {
+entry:
+  br label %for.body
+
+for.body:
+  %indvars.iv = phi i64 [ 0, %entry ], [ %indvars.iv.next.9, %for.body ]
+  %arrayidx = getelementptr inbounds i32, i32* %Dst, i64 %indvars.iv
+  %0 = load i32, i32* %arrayidx, align 4
+  %a = add i32 %0, 128
+  store i32 %a, i32* %arrayidx, align 4
+  %indvars.iv.next.9 = add nuw nsw i64 %indvars.iv, 1600
+  %cmp.9 = icmp ult i64 %indvars.iv.next.9, 11200
+  br i1 %cmp.9, label %for.body, label %for.cond.cleanup
+
+for.cond.cleanup:
+  ret void
+}
+