diff --git a/llvm/lib/Target/AArch64/AArch64ISelLowering.h b/llvm/lib/Target/AArch64/AArch64ISelLowering.h
--- a/llvm/lib/Target/AArch64/AArch64ISelLowering.h
+++ b/llvm/lib/Target/AArch64/AArch64ISelLowering.h
@@ -432,6 +432,12 @@
 // FIXME: X86 also checks for CMOV here. Do we need something similar?
 static inline bool isDef32(const SDNode &N) {
   unsigned Opc = N.getOpcode();
+
+  if (Opc == ISD::SIGN_EXTEND_INREG) {
+    SDValue Opr = N.getOperand(0);
+    return Opr->getOpcode() != ISD::TRUNCATE;
+  }
+
   return Opc != ISD::TRUNCATE && Opc != TargetOpcode::EXTRACT_SUBREG &&
          Opc != ISD::CopyFromReg && Opc != ISD::AssertSext &&
          Opc != ISD::AssertZext;
diff --git a/llvm/test/CodeGen/AArch64/aarch64-avoid-implicit-zext-for-SIGN_EXTEND_INREG.ll b/llvm/test/CodeGen/AArch64/aarch64-avoid-implicit-zext-for-SIGN_EXTEND_INREG.ll
new file mode 100644
--- /dev/null
+++ b/llvm/test/CodeGen/AArch64/aarch64-avoid-implicit-zext-for-SIGN_EXTEND_INREG.ll
@@ -0,0 +1,28 @@
+; RUN: llc -O3 -mtriple=aarch64-unknown-linux-gnu < %s | FileCheck %s
+@b = dso_local local_unnamed_addr global { [3 x i8], i8, i8, i8, i8, i8 } { [3 x i8] undef, i8 -64, i8 74, i8 -9, i8 -1, i8 7 }, align 8
+@c = common dso_local local_unnamed_addr global i64 0, align 8
+@.str = private unnamed_addr constant [9 x i8] c"c = %ld\0A\00", align 1
+
+define dso_local i8 @d(i64 %h) local_unnamed_addr {
+entry:
+  ret i8 undef
+}
+
+declare dso_local i32 @printf(i8* nocapture readonly, ...) local_unnamed_addr
+
+define dso_local i32 @main() local_unnamed_addr {
+entry:
+  %bf.load = load i64, i64* bitcast ({ [3 x i8], i8, i8, i8, i8, i8 }* @b to i64*), align 8
+  %0 = lshr i64 %bf.load, 30
+  %sext3 = shl nuw nsw i64 %0, 16
+  %sext = trunc i64 %sext3 to i32
+  %conv.i = ashr exact i32 %sext, 16
+  %conv.i.i = zext i32 %conv.i to i64
+; CHECK:        // %bb.0:
+; CHECK:        sbfx    x{{[0-9]+}}, x{{[0-9]+}}, #{{[0-9]+}}, #{{[0-9]+}}
+; CHECK-NEXT:   mov     w{{[0-9]+}}, w{{[0-9]+}}
+  store i64 %conv.i.i, i64* @c, align 8
+  %call.i.i = tail call i32 (i8*, ...) @printf(i8* nonnull dereferenceable(1) getelementptr inbounds ([9 x i8], [9 x i8]* @.str, i64 0, i64 0), i64 %conv.i.i)
+  %call4.i = tail call i8 bitcast (i8 (i64)* @d to i8 (i32, i32)*)(i32 0, i32 %conv.i)
+  ret i32 0
+}