[Bug ipa/111873] [12/13/14 Regression] runtime Segmentation fault with '-O3 -fno-code-hoisting -fno-early-inlining -fno-tree-fre -fno-tree-pre'

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111873

--- Comment #8 from Eric Botcazou <ebotcazou at gcc dot gnu.org> ---
The bug is in the (early) SRA pass though;

void h (const struct a i)
{
  const short int i$b;
  int _1;
  short int _2;
  int _3;
  short int _4;
  int _5;

  <bb 2> :
  i$b_10 = i.b;
  i.b = i$b_10;
  _1 = g (i);
  d = _1;
  _2 = i$b_10;
  _3 = (int) _2;
  f (_3);
  _4 = i$b_10;
  _5 = (int) _4;
  e (_5);
  return;

}

which creates a store to the read-only parameter i:

(gdb) p debug_gimple_stmt(stmt)
# .MEM = VDEF <.MEM>
i.b = i$b;
$2 = void
(gdb) p debug_tree(gimple_get_lhs (stmt))
 <component_ref 0x7ffff71dee10
    type <integer_type 0x7ffff71b6930 short int readonly sizes-gimplified HI
        size <integer_cst 0x7ffff702c0f0 constant 16>
        unit-size <integer_cst 0x7ffff702c108 constant 2>
        align:16 warn_if_not_align:0 symtab:0 alias-set -1 canonical-type
0x7ffff71b6930 precision:16 min <integer_cst 0x7ffff702c090 -32768> max
<integer_cst 0x7ffff702c0c0 32767>>
    readonly
    arg:0 <parm_decl 0x7ffff7fc8300 i
        type <record_type 0x7ffff71b6540 a readonly sizes-gimplified type_0 HI
size <integer_cst 0x7ffff702c0f0 16> unit-size <integer_cst 0x7ffff702c108 2>
            align:16 warn_if_not_align:0 symtab:0 alias-set -1 canonical-type
0x7ffff71b6540 fields <field_decl 0x7ffff7039688 b>>
        readonly used read HI pr111873.c:18:24 size <integer_cst 0x7ffff702c0f0
16> unit-size <integer_cst 0x7ffff702c108 2>
        align:16 warn_if_not_align:0 context <function_decl 0x7ffff71e2300 h>
arg-type <record_type 0x7ffff71b6540 a>>
    arg:1 <field_decl 0x7ffff7039688 b
        type <integer_type 0x7ffff702a498 short int sizes-gimplified HI size
<integer_cst 0x7ffff702c0f0 16> unit-size <integer_cst 0x7ffff702c108 2>
            align:16 warn_if_not_align:0 symtab:0 alias-set -1 canonical-type
0x7ffff702a498 precision:16 min <integer_cst 0x7ffff702c090 -32768> max
<integer_cst 0x7ffff702c0c0 32767>>
        HI pr111873.c:5:9 size <integer_cst 0x7ffff702c0f0 16> unit-size
<integer_cst 0x7ffff702c108 2>
        align:16 warn_if_not_align:0 offset_align 128 decl_not_flexarray: 1
        offset <integer_cst 0x7ffff700bf60 constant 0>
        bit-offset <integer_cst 0x7ffff700bfa8 constant 0> context <record_type
0x7ffff71b6f18 a>>
    pr111873.c:21:7 start: pr111873.c:21:6 finish: pr111873.c:21:8>

/* In a VAR_DECL, PARM_DECL or FIELD_DECL, or any kind of ..._REF node,
   nonzero means it may not be the lhs of an assignment.
   Nonzero in a FUNCTION_DECL means this function should be treated
   as "const" function (can only read its arguments).  */
#define TREE_READONLY(NODE) (NON_TYPE_CHECK (NODE)->base.readonly_flag)