[NFC] Add one test to verify the sign_extend of vector type.

llvm/test/CodeGen/ARM/signext-inreg.ll

@@ -0,0 +1,17 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; RUN: llc < %s -mtriple=armv8 -mattr=+mve | FileCheck %s
+define <4 x i32> @test(<4 x i32> %m) {
+; CHECK-LABEL: test:
+; CHECK:       @ %bb.0: @ %entry
+; CHECK-NEXT:    vmov d1, r2, r3
+; CHECK-NEXT:    vmov d0, r0, r1
+; CHECK-NEXT:    vshl.i32 q0, q0, #24
+; CHECK-NEXT:    vshr.s32 q0, q0, #24
+; CHECK-NEXT:    vmov r0, r1, d0
+; CHECK-NEXT:    vmov r2, r3, d1
+; CHECK-NEXT:    bx lr
+entry:
+  %shl = shl <4 x i32> %m, <i32 24, i32 24, i32 24, i32 24>
+  %shr = ashr exact <4 x i32> %shl, <i32 24, i32 24, i32 24, i32 24>
+  ret <4 x i32> %shr
+}