Index: lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
===================================================================
--- lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
+++ lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
@@ -1330,6 +1330,12 @@
       return &I;
     }
 
+  // ((X % Y) % Y) -> (X % Y)
+  Value *X, *Y;
+  if (match(Op1, m_Value(Y)) && match(Op0, m_SRem(m_Value(X), m_Specific(Y)))) {
+    return ReplaceInstUsesWith(I, Op0);
+  }
+
   // 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 +213,12 @@
 	%R = urem <2 x i64> %V, <i64 2, i64 3>
 	ret <2 x i64> %R
 }
+
+define i32 @test21(i32 %x, i32 %n) {
+; CHECK-LABEL: @test21(
+; CHECK-NEXT: %mod = srem i32 %x, %n
+; CHECK-NEXT: ret i32 %mod
+  %mod = srem i32 %x, %n
+  %mod1 = srem i32 %mod, %n
+  ret i32 %mod1
+}