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
@@ -418,12 +418,14 @@
 // Any instruction that defines a 32-bit result zeros out the high half of the
 // register. Truncate can be lowered to EXTRACT_SUBREG. CopyFromReg may
 // be copying from a truncate. But any other 32-bit operation will zero-extend
-// up to 64 bits.
+// up to 64 bits. AssertSext/AssertZext aren't saying anything about the upper
+// 32 bits, they're probably just qualifying a CopyFromReg.
 // FIXME: X86 also checks for CMOV here. Do we need something similar?
 static inline bool isDef32(const SDNode &N) {
   unsigned Opc = N.getOpcode();
   return Opc != ISD::TRUNCATE && Opc != TargetOpcode::EXTRACT_SUBREG &&
-         Opc != ISD::CopyFromReg;
+         Opc != ISD::CopyFromReg && Opc != ISD::AssertSext &&
+         Opc != ISD::AssertZext;
 }
 
 } // end anonymous namespace
diff --git a/llvm/test/CodeGen/AArch64/shift_minsize.ll b/llvm/test/CodeGen/AArch64/shift_minsize.ll
--- a/llvm/test/CodeGen/AArch64/shift_minsize.ll
+++ b/llvm/test/CodeGen/AArch64/shift_minsize.ll
@@ -59,7 +59,7 @@
 ; CHECK-NEXT:    str x30, [sp, #-16]! // 8-byte Folded Spill
 ; CHECK-NEXT:    .cfi_def_cfa_offset 16
 ; CHECK-NEXT:    .cfi_offset w30, -16
-; CHECK-NEXT:    // kill: def $w2 killed $w2 def $x2
+; CHECK-NEXT:    mov w2, w2
 ; CHECK-NEXT:    bl __ashlti3
 ; CHECK-NEXT:    ldr x30, [sp], #16 // 8-byte Folded Reload
 ; CHECK-NEXT:    ret
@@ -86,7 +86,7 @@
 ; CHECK-NEXT:    str x30, [sp, #-16]! // 8-byte Folded Spill
 ; CHECK-NEXT:    .cfi_def_cfa_offset 16
 ; CHECK-NEXT:    .cfi_offset w30, -16
-; CHECK-NEXT:    // kill: def $w2 killed $w2 def $x2
+; CHECK-NEXT:    mov w2, w2
 ; CHECK-NEXT:    bl __ashrti3
 ; CHECK-NEXT:    ldr x30, [sp], #16 // 8-byte Folded Reload
 ; CHECK-NEXT:    ret
@@ -112,7 +112,7 @@
 ; CHECK-NEXT:    str x30, [sp, #-16]! // 8-byte Folded Spill
 ; CHECK-NEXT:    .cfi_def_cfa_offset 16
 ; CHECK-NEXT:    .cfi_offset w30, -16
-; CHECK-NEXT:    // kill: def $w2 killed $w2 def $x2
+; CHECK-NEXT:    mov w2, w2
 ; CHECK-NEXT:    bl __lshrti3
 ; CHECK-NEXT:    ldr x30, [sp], #16 // 8-byte Folded Reload
 ; CHECK-NEXT:    ret