diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp
index 9ca8194b44f8f..3d407464ffec6 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp
@@ -1528,7 +1528,15 @@ Instruction *InstCombinerImpl::visitSExt(SExtInst &Sext) {
   }
 
   // Try to extend the entire expression tree to the wide destination type.
-  if (shouldChangeType(SrcTy, DestTy) && canEvaluateSExtd(Src, DestTy)) {
+  bool shouldExtendExpression = true;
+  Value *TruncSrc = nullptr;
+  // It is not desirable to extend expression in the trunc + sext pattern when
+  // destination type is narrower than original (pre-trunc) type.
+  if (match(Src, m_Trunc(m_Value(TruncSrc))))
+    if (TruncSrc->getType()->getScalarSizeInBits() > DestBitSize)
+      shouldExtendExpression = false;
+  if (shouldExtendExpression && shouldChangeType(SrcTy, DestTy) &&
+      canEvaluateSExtd(Src, DestTy)) {
     // Okay, we can transform this!  Insert the new expression now.
     LLVM_DEBUG(
         dbgs() << "ICE: EvaluateInDifferentType converting expression type"
@@ -1548,8 +1556,8 @@ Instruction *InstCombinerImpl::visitSExt(SExtInst &Sext) {
                                       ShAmt);
   }
 
-  Value *X;
-  if (match(Src, m_Trunc(m_Value(X)))) {
+  Value *X = TruncSrc;
+  if (X) {
     // If the input has more sign bits than bits truncated, then convert
     // directly to final type.
     unsigned XBitSize = X->getType()->getScalarSizeInBits();
diff --git a/llvm/test/Transforms/InstCombine/trunc-sext.ll b/llvm/test/Transforms/InstCombine/trunc-sext.ll
new file mode 100644
index 0000000000000..ac1438405e171
--- /dev/null
+++ b/llvm/test/Transforms/InstCombine/trunc-sext.ll
@@ -0,0 +1,16 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 6
+; RUN: opt < %s -passes=instcombine -S | FileCheck %s
+
+target datalayout = "i16:16:16-i32:32:32-i64:64:64-n16:32:64"
+
+define i32 @test(i64 %i) {
+; CHECK-LABEL: define i32 @test(
+; CHECK-SAME: i64 [[I:%.*]]) {
+; CHECK-NEXT:    [[A:%.*]] = trunc i64 [[I]] to i16
+; CHECK-NEXT:    [[B:%.*]] = sext i16 [[A]] to i32
+; CHECK-NEXT:    ret i32 [[B]]
+;
+  %a = trunc i64 %i to i16
+  %b = sext i16 %a to i32
+  ret i32 %b
+}