Index: InstCombineCasts.cpp
===================================================================
--- InstCombineCasts.cpp
+++ InstCombineCasts.cpp
@@ -1254,6 +1254,20 @@
     return BinaryOperator::CreateAShr(A, ShAmtV);
   }
 
+  // Transform:
+  //   %shr26 = lshr i32 %0, 16                        ; [#uses=1 type=i32]
+  //   %conv4 = trunc i32 %shr26 to i16                ; [#uses=1 type=i16]
+  //   %3 = sext i16 %conv4 to i32                     ; [#uses=N type=i32]
+  // To:
+  //   %3 = ashr i32 %0, 16
+  if (match(Src, m_OneUse(m_Trunc( m_OneUse(m_LShr(m_Value(A), m_ConstantInt(BA)))))) &&
+      A->getType() == CI.getType()) {
+    unsigned SextSize = CI.getType()->getScalarSizeInBits();
+    unsigned TruncSize = Src->getType()->getScalarSizeInBits();
+    if (BA->getZExtValue() == SextSize - TruncSize)
+      return BinaryOperator::CreateAShr(A, BA);
+  }
+
   return nullptr;
 }