[Bug tree-optimization/102162] Byte-wise access optimized away at -O1 and above

[danglin at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102162

--- Comment #1 from John David Anglin <danglin at gcc dot gnu.org> ---
Created attachment 51395
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=51395&action=edit
Second test case

Changing the optimization of get_unaligned_le32 to 0 results in correct
code generation.  We have the following in test-unaligned.c.235t.optimized:

ave@atlas:~/linux/misc$ cat test-unaligned.c.235t.optimized

;; Function get_unaligned_le32 (get_unaligned_le32, funcdef_no=0,
decl_uid=1506, cgraph_uid=1, symbol_order=1)

__attribute__((optimize (0)))
get_unaligned_le32 (const void * p)
{
  const struct
  {
    u32 x;
  } * __pptr;
  u32 D.1517;
  u32 _4;

  <bb 2> :
  __pptr_2 = p_1(D);
  _4 = __pptr_2->x;

  <bb 3> :
<L0>:
  return _4;

}



;; Function test (test, funcdef_no=1, decl_uid=1512, cgraph_uid=2,
symbol_order=2)

test ()
{
  unsigned int _1;
  int _4;

  <bb 2> [local count: 1073741824]:
  _1 = get_unaligned_le32 (&output_len); [tail call]
  _4 = (int) _1;
  return _4;

}