[Bug middle-end/81445] Dynamic stack allocation not optimized into static allocation

[wilco at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81445

--- Comment #2 from Wilco <wilco at gcc dot gnu.org> ---
(In reply to Marc Glisse from comment #1)
> Note that we already do it for VLA (aka BUILT_IN_ALLOCA_WITH_ALIGN) in CCP.

I don't see it happen for the simplest case in current trunk:

void t(int *);
void vla(void)
{
  int x = 100;
  int arr[x];
  t (arr);
}

void no_vla(void)
{
  int arr[100];
  t (arr);
}

vla:
        stp     x29, x30, [sp, -16]!
        add     x29, sp, 0
        sub     sp, sp, #416   // alloca
        mov     x0, sp
        bl      t
        add     sp, x29, 0
        ldp     x29, x30, [sp], 16
        ret

no_vla:
        stp     x29, x30, [sp, -416]!
        add     x29, sp, 0
        add     x0, sp, 16
        bl      t
        ldp     x29, x30, [sp], 416
        ret