Index: lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
===================================================================
--- lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
+++ lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
@@ -1330,6 +1330,15 @@
       return &I;
     }
 
+  // ((X % Z) + (Y % Z)) % Z -> (X + Y) % Z
+  Value *X, *Y, *Z;
+  if (match(Op1, m_Value(Z)) &&
+      match(Op0, m_Add(m_SRem(m_Value(X), m_Specific(Z)),
+                       m_SRem(m_Value(Y), m_Specific(Z))))) {
+    return ReplaceInstUsesWith(
+        I, Builder->CreateSRem(Builder->CreateAdd(X, Y), Z));
+  }
+
   // If the sign bits of both operands are zero (i.e. we can prove they are
   // unsigned inputs), turn this into a urem.
   if (I.getType()->isIntegerTy()) {
Index: test/Transforms/InstCombine/rem.ll
===================================================================
--- test/Transforms/InstCombine/rem.ll
+++ test/Transforms/InstCombine/rem.ll
@@ -213,3 +213,15 @@
 	%R = urem <2 x i64> %V, <i64 2, i64 3>
 	ret <2 x i64> %R
 }
+
+define i32 @test21(i32 %x, i32 %y, i32 %n) {
+; CHECK-LABEL: @test21(
+; CHECK-NEXT: %1 = add i32 %x, %y
+; CHECK-NEXT: %2 = srem i32 %1, %n
+; CHECK-NEXT: ret i32 %2
+  %mod = srem i32 %x, %n
+  %mod1 = srem i32 %y, %n
+  %add = add i32 %mod, %mod1
+  %mod2 = srem i32 %add, %n
+  ret i32 %mod2
+}