diff --git a/llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp b/llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp
--- a/llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp
+++ b/llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp
@@ -2361,6 +2361,45 @@
     return false;
   }
 
+  /// Eliminates writes to locations where the value that is being written
+  /// is already stored at the same location.
+  bool eliminateRedundantStoresOfExisitingValues() {
+    bool MadeChange = false;
+    LLVM_DEBUG(dbgs() << "Trying to eliminate MemoryDefs that write the "
+                         "already exisiting value\n");
+    for (MemoryDef *Def : reverse(MemDefs)) {
+      if (SkipStores.find(Def) != SkipStores.end() ||
+          !isRemovable(Def->getMemoryInst()))
+        continue;
+
+      Instruction *DefI = Def->getMemoryInst();
+      Optional<MemoryLocation> MaybeDefLoc = getLocForWriteEx(DefI);
+      if (!MaybeDefLoc)
+        continue;
+
+      // Remove any uses of Def, that are MemoryDefs that write the same value
+      // to the same location as Def.
+      for (Use &U : make_early_inc_range(Def->uses())) {
+        MemoryAccess *UseAccess = cast<MemoryAccess>(U.getUser());
+        MemoryDef *UseDef = dyn_cast_or_null<MemoryDef>(UseAccess);
+        if (!UseDef)
+          continue;
+        Instruction *UseI = UseDef->getMemoryInst();
+
+        // Skip self-reads.
+        if (isReadClobber(*MaybeDefLoc, UseI))
+          continue;
+
+        if (UseI->isIdenticalTo(DefI)) {
+          deleteDeadInstruction(UseI);
+          NumRedundantStores++;
+          MadeChange = true;
+        }
+      }
+    }
+    return MadeChange;
+  }
+
   /// Eliminate writes to objects that are not visible in the caller and are not
   /// accessed before returning from the function.
   bool eliminateDeadWritesAtEndOfFunction() {
@@ -2630,6 +2669,8 @@
     }
   }
 
+  MadeChange |= State.eliminateRedundantStoresOfExisitingValues();
+
   if (EnablePartialOverwriteTracking)
     for (auto &KV : State.IOLs)
       MadeChange |= removePartiallyOverlappedStores(State.DL, KV.second, TLI);
diff --git a/llvm/test/Transforms/DeadStoreElimination/MSSA/stores-of-existing-values.ll b/llvm/test/Transforms/DeadStoreElimination/MSSA/stores-of-existing-values.ll
--- a/llvm/test/Transforms/DeadStoreElimination/MSSA/stores-of-existing-values.ll
+++ b/llvm/test/Transforms/DeadStoreElimination/MSSA/stores-of-existing-values.ll
@@ -11,7 +11,6 @@
 ; CHECK-NEXT:    store i8 1, i8* [[R:%.*]], align 1
 ; CHECK-NEXT:    br i1 [[B:%.*]], label [[IF_THEN:%.*]], label [[IF_ELSE:%.*]]
 ; CHECK:       if.then:
-; CHECK-NEXT:    store i8 1, i8* [[R]], align 1
 ; CHECK-NEXT:    tail call void @fn_mayread_or_clobber()
 ; CHECK-NEXT:    br label [[IF_END:%.*]]
 ; CHECK:       if.else:
@@ -54,7 +53,6 @@
 ; CHECK-NEXT:    tail call void @fn_readonly()
 ; CHECK-NEXT:    br label [[IF_END]]
 ; CHECK:       if.end:
-; CHECK-NEXT:    store i8 1, i8* [[R]], align 1
 ; CHECK-NEXT:    ret void
 ;
 entry:
@@ -74,6 +72,39 @@
   ret void
 }
 
+; Make sure volatile stores are not removed.
+define void @test2_volatile(i1 %b, i8* nocapture %r) {
+; CHECK-LABEL: @test2_volatile(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    store volatile i8 1, i8* [[R:%.*]], align 1
+; CHECK-NEXT:    br i1 [[B:%.*]], label [[IF_THEN:%.*]], label [[IF_ELSE:%.*]]
+; CHECK:       if.then:
+; CHECK-NEXT:    tail call void @fn_readonly()
+; CHECK-NEXT:    br label [[IF_END:%.*]]
+; CHECK:       if.else:
+; CHECK-NEXT:    tail call void @fn_readonly()
+; CHECK-NEXT:    br label [[IF_END]]
+; CHECK:       if.end:
+; CHECK-NEXT:    store volatile i8 1, i8* [[R]], align 1
+; CHECK-NEXT:    ret void
+;
+entry:
+  store volatile i8 1, i8* %r, align 1
+  br i1 %b, label %if.then, label %if.else
+
+if.then:                                          ; preds = %entry
+  tail call void @fn_readonly()
+  br label %if.end
+
+if.else:                                          ; preds = %entry
+  tail call void @fn_readonly()
+  br label %if.end
+
+if.end:                                           ; preds = %if.else, %if.then
+  store volatile i8 1, i8* %r, align 1
+  ret void
+}
+
 define void @test3(i1 %b, i8* nocapture %r) {
 ; CHECK-LABEL: @test3(
 ; CHECK-NEXT:  entry:
@@ -181,7 +212,6 @@
 ; CHECK-NEXT:    [[C1:%.*]] = call i1 @cond()
 ; CHECK-NEXT:    br i1 [[C1]], label [[FOR_BODY:%.*]], label [[END:%.*]]
 ; CHECK:       for.body:
-; CHECK-NEXT:    store i32 1, i32* [[P]], align 4
 ; CHECK-NEXT:    [[LV:%.*]] = load i32, i32* [[P]], align 4
 ; CHECK-NEXT:    br label [[FOR_HEADER]]
 ; CHECK:       end:
@@ -216,7 +246,6 @@
 ; CHECK:       bb2:
 ; CHECK-NEXT:    ret void
 ; CHECK:       bb3:
-; CHECK-NEXT:    store i32 0, i32* [[P]], align 4
 ; CHECK-NEXT:    ret void
 ;
   store i32 0, i32* %P
@@ -268,7 +297,6 @@
 ; CHECK-NEXT:    call void @fn_mayread_or_clobber()
 ; CHECK-NEXT:    ret void
 ; CHECK:       bb3:
-; CHECK-NEXT:    store i32 0, i32* [[P]], align 4
 ; CHECK-NEXT:    ret void
 ;
   store i32 0, i32* %P