[Bug middle-end/102276] New: -ftrivial-auto-var-init fails to initialize a variable, causes a spurious warning

["amonakov at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102276

            Bug ID: 102276
           Summary: -ftrivial-auto-var-init fails to initialize a
                    variable, causes a spurious warning
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: middle-end
          Assignee: unassigned at gcc dot gnu.org
          Reporter: amonakov at gcc dot gnu.org
  Target Milestone: ---

int g(int *);
int f1()
{
    switch (0) {
        int x;
        default:
        return g(&x);
    }
}
int f2()
{
    goto L;
    {
        int x;
        L:
        return g(&x);
    }
}

Compiling with -O2 -ftrivial-auto-var-init=pattern causes spurious

warning: statement will never be executed [-Wswitch-unreachable]
    5 |         int x;
      |             ^


In both f1 and f2, resulting assembly does not in fact initialize 'x':

f1:
        subq    $24, %rsp
        leaq    12(%rsp), %rdi
        call    g
        addq    $24, %rsp
        ret
f2:
        subq    $24, %rsp
        leaq    12(%rsp), %rdi
        call    g
        addq    $24, %rsp
        ret