[Bug rtl-optimization/38245] [4.4 Regression] apparent improper segfault in compiler output

[jakub at gcc dot gnu dot org]

------- Comment #1 from jakub at gcc dot gnu dot org  2008-11-24 09:01 -------
Smaller testcase:
static inline int
f1 (int si1, int si2)
{
  return si2 == 0 ? si1 : si1 / si2;
}

static inline unsigned long long
f2 (unsigned long long ui1, unsigned long long ui2)
{
  return ui1 % ui2;
}

unsigned char g;
volatile unsigned int h;

void
f3 (void)
{
  if (!((signed char) f1 (0, f2 (g, 2123)) - 1))
    h;
}

int
main (void)
{
  f3 ();
  return 0;
}

The problem seems to be that RTL DCE pass removes umoddi3 call:
(insn 8 6 34 2 u2.c:19 (set (mem:DI (plus:SI (reg/f:SI 7 sp)
                (const_int 8 [0x8])) [0 S8 A32])
        (const_int 2123 [0x84b])) 88 {*movdi_2} (nil))

(insn 34 8 35 2 u2.c:19 (set (mem:SI (reg/f:SI 7 sp) [0 S4 A32])
        (reg:SI 61 [ g ])) 47 {*movsi_1} (expr_list:REG_DEAD (reg:SI 61 [ g ])
        (nil)))

(insn 35 34 10 2 u2.c:19 (set (mem:SI (plus:SI (reg/f:SI 7 sp)
                (const_int 4 [0x4])) [0 S4 A32])
        (const_int 0 [0x0])) 47 {*movsi_1} (nil))

(call_insn/u 10 35 0 2 u2.c:19 (set (reg:DI 0 ax)
        (call (mem:QI (symbol_ref:SI ("__umoddi3") [flags 0x41]) [0 S1 A8])
            (const_int 16 [0x10]))) 902 {*call_value_0} (expr_list:REG_UNUSED
(reg:SI 1 dx)
        (expr_list:REG_EH_REGION (const_int -1 [0xffffffffffffffff])
            (nil)))
    (expr_list:REG_DEP_TRUE (use (mem:DI (reg/f:SI 7 sp) [0 S8 A8]))
        (expr_list:REG_DEP_TRUE (use (mem:DI (plus:SI (reg/f:SI 7 sp)
                        (const_int 8 [0x8])) [0 S8 A8]))
            (nil))))

but doesn't remove the pushes of its arguments, and then
ix86_compute_frame_layout doesn't allocate space for the outgoing arguments
as the function is leaf.

  /* Add outgoing arguments area.  Can be skipped if we eliminated
     all the function calls as dead code.
     Skipping is however impossible when function calls alloca.  Alloca
     expander assumes that last crtl->outgoing_args_size
     of stack frame are unused.  */
  if (ACCUMULATE_OUTGOING_ARGS
      && (!current_function_is_leaf || cfun->calls_alloca
          || ix86_current_function_calls_tls_descriptor))
    {
      offset += crtl->outgoing_args_size;
      frame->outgoing_arguments_size = crtl->outgoing_args_size;
    }
  else
    frame->outgoing_arguments_size = 0;

I guess this was caused by the removal of REG_LIBCALL notes.


-- 

jakub at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |steven at gcc dot gnu dot
                   |                            |org
          Component|c                           |rtl-optimization
      Known to fail|                            |4.4.0
      Known to work|                            |4.3.2
            Summary|apparent improper segfault  |[4.4 Regression] apparent
                   |in compiler output          |improper segfault in
                   |                            |compiler output
   Target Milestone|---                         |4.4.0
            Version|unknown                     |4.4.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38245