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From: "jakub at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/52979] [4.7/4.8 Regression] likely wrong code bug w/packed bitfields
Date: Tue, 24 Apr 2012 10:48:00 -0000
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52979

--- Comment #4 from Jakub Jelinek <jakub at gcc dot gnu.org> 2012-04-24 10:47:04 UTC ---
Doesn't apparently need a loop, the following fails on 4.7 branch and older
trunk with -O2 -ftree-vectorize as well.  The dummy foo function is important
to reproduce it, apparently otherwise notice_global_symbol is called on a and
creates DECL_RTL for it while it still has DECL_ALIGN 8.  Later on
vect_compute_data_ref_alignment increases the alignment of a to 128 and sets
DECL_USER_ALIGN.

extern void abort (void);
int c, d, e;

void
foo (void)
{
}

struct __attribute__((packed)) S { int g : 31; int h : 6; };
struct S a = { 1 };
static struct S b = { 1 };

void
bar (void)
{
  a.h = 1;
  struct S f = { };
  b = f;
  e = 0;
  if (d)
    c = a.g;
}

void
baz (void)
{
  bar ();
  a = b;
}

int
main ()
{
  baz ();
  if (a.g)
    abort ();
  return 0;
}