[ARM] Add a regression test for D154281

This is a reduced version of one of the tests that was broken by the
original commit of D154281 "[CodeGen] Store SP adjustment in
MachineBasicBlock. NFCI.".

Differential Revision: https://reviews.llvm.org/D155471

llvm/test/CodeGen/ARM/struct-byval-loop.ll

@@ -0,0 +1,39 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 3
+; RUN: llc -mtriple=arm--none-eabi < %s | FileCheck %s
+
+%t = type [20 x i32]
+
+declare void @func(ptr, ptr byval(%t))
+
+define void @main() {
+; CHECK-LABEL: main:
+; CHECK:       @ %bb.0:
+; CHECK-NEXT:    .save {r11, lr}
+; CHECK-NEXT:    push {r11, lr}
+; CHECK-NEXT:    .pad #152
+; CHECK-NEXT:    sub sp, sp, #152
+; CHECK-NEXT:    add r0, sp, #72
+; CHECK-NEXT:    ldr r1, .LCPI0_0
+; CHECK-NEXT:    add r0, r0, #12
+; CHECK-NEXT:    mov r2, sp
+; CHECK-NEXT:  .LBB0_1: @ =>This Inner Loop Header: Depth=1
+; CHECK-NEXT:    ldr r3, [r0], #4
+; CHECK-NEXT:    subs r1, r1, #4
+; CHECK-NEXT:    str r3, [r2], #4
+; CHECK-NEXT:    bne .LBB0_1
+; CHECK-NEXT:  @ %bb.2:
+; CHECK-NEXT:    add r3, sp, #72
+; CHECK-NEXT:    mov r0, #0
+; CHECK-NEXT:    ldm r3, {r1, r2, r3}
+; CHECK-NEXT:    bl func
+; CHECK-NEXT:    add sp, sp, #152
+; CHECK-NEXT:    pop {r11, lr}
+; CHECK-NEXT:    mov pc, lr
+; CHECK-NEXT:    .p2align 2
+; CHECK-NEXT:  @ %bb.3:
+; CHECK-NEXT:  .LCPI0_0:
+; CHECK-NEXT:    .long 68 @ 0x44
+  %a = alloca %t
+  call void @func(ptr null, ptr %a)
+  ret void
+}