[Bug middle-end/85880] Different code generation for uninitialized variables

[fredrik.hederstie...@securitas-direct.com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85880

--- Comment #2 from Fredrik Hederstierna 
<fredrik.hederstie...@securitas-direct.com> ---
All old GCC < 8
---------------

Disassembly of section .text:

00000000 <get_undef_stack_var>:
   0:   2000            movs    r0, #0
   2:   4770            bx      lr

00000004 <test_1>:
   4:   b500            push    {lr}
   6:   2000            movs    r0, #0
   8:   bd00            pop     {pc}

0000000a <test_2>:
   a:   b500            push    {lr}
   c:   2000            movs    r0, #0
   e:   bd00            pop     {pc}

------------------------------------------------------

From GCC 8.1.0
---------------

Disassembly of section .text:

00000000 <get_undef_stack_var>:
   0:   2000            movs    r0, #0
   2:   4770            bx      lr

00000004 <test_1>:
   4:   b500            push    {lr}
   6:   2000            movs    r0, #0
   8:   bd00            pop     {pc}

0000000a <test_2>:
   a:   2380            movs    r3, #128        ; 0x80
   c:   b510            push    {r4, lr}
   e:   005b            lsls    r3, r3, #1
  10:   2000            movs    r0, #0
  12:   2b00            cmp     r3, #0
  14:   d101            bne.n   1a <test_2+0x10>
  16:   f7ff fffe       bl      0 <call_external_func>
  1a:   bd10            pop     {r4, pc}