[Bug middle-end/58677] New: wrong code at -O1 on x86_64-linux-gnu

[Bug middle-end/58677] New: wrong code at -O1 on x86_64-linux-gnu

[su at cs dot ucdavis.edu]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58677

            Bug ID: 58677
           Summary: wrong code at -O1 on x86_64-linux-gnu
           Product: gcc
           Version: 4.9.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: middle-end
          Assignee: unassigned at gcc dot gnu.org
          Reporter: su at cs dot ucdavis.edu

The current gcc trunk miscompiles the attached testcase on x86_64-linux at
(only) -O1 in 64-bit mode. 

This is a regression from 4.8.x.

This one was quite tough to reduce. The attached testcase is the best I was
able to get so far. 


$ gcc-trunk -v
Using built-in specs.
COLLECT_GCC=gcc-trunk
COLLECT_LTO_WRAPPER=/usr/local/gcc-trunk/libexec/gcc/x86_64-unknown-linux-gnu/4.9.0/lto-wrapper
Target: x86_64-unknown-linux-gnu
Configured with: ../gcc-trunk/configure
--enable-languages=c,c++,objc,obj-c++,fortran,lto --disable-werror
--enable-checking=release --with-gmp=/usr/local/gcc-trunk
--with-mpfr=/usr/local/gcc-trunk --with-mpc=/usr/local/gcc-trunk
--with-cloog=/usr/local/gcc-trunk --prefix=/usr/local/gcc-trunk
Thread model: posix
gcc version 4.9.0 20131009 (experimental) [trunk revision 203302] (GCC) 
$ 
$ gcc-trunk -O0 small.c; a.out
0
0
1
$ gcc-4.8 -O1 small.c; a.out
0
0
1
$ gcc-trunk -m32 -O1 small.c; a.out
0
0
1
$ clang-trunk -O1 small.c; a.out
0
0
1
$ gcc-trunk -O1 small.c; a.out
0
0
0
$ 


-------------------------------------


int printf (const char *, ...);

#pragma pack(1)
struct S
{
  unsigned int f0:7;
  int f1:19;
  unsigned int f2:22;
  int f3:25;
} k[6][8];

int a, b, c, e, h, l, m, n, o, *p = &h, **q = &p, r, s;
unsigned int d[256];

static void
fn1 ()
{
  for (a = 0; a < 256; a++)
    d[a] = a;
}

static void
fn2 (unsigned int p1, char *p2, int p3)
{
  e = d[e ^ p1];
  printf ("%s%X\n", p2, e);
}

static int *
fn3 (int p1, int p2)
{
  for (s = 10; s > 2; s = -6)
    for (r = 0; r < 6; r++)
      for (n = 0; n < 8; n++)
    {
      struct S t = { 1, -195, 321, 4857 };
      k[r][n] = t;
    }
  return *q;
}

static int
fn4 ()
{
  *q = fn3 (l, b);
  return c;
}

int
main (int argc, char *argv[])
{
  int v = 0;
  if (argc == 2)
    v = 1;
  fn1 ();
  fn4 ();
  fn2 (m, "", v);
  fn2 (o, "", v);
  fn2 (k[0][0].f0, "", v);
  return 0;
}

[Bug middle-end/58677] wrong code at -O1 on x86_64-linux-gnu

[mikpelinux at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58677

--- Comment #1 from Mikael Pettersson <mikpelinux at gmail dot com> ---
Started with r202525 (PR58404 missed-optimization fix), stopped with r203315
(PR58570 wrong-code fix).  The cause of PR58570 was not r202525.

Can you check if the original testcase works on current trunk?

[Bug middle-end/58677] wrong code at -O1 on x86_64-linux-gnu

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58677

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|---                         |DUPLICATE

--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> ---
(In reply to Mikael Pettersson from comment #1)
> Started with r202525 (PR58404 missed-optimization fix), stopped with r203315
> (PR58570 wrong-code fix).  The cause of PR58570 was not r202525.
> 
> Can you check if the original testcase works on current trunk?

But r202525 will expose more opportunities for the code with the bug
that was fixed by r203315 so it makes sense.

*** This bug has been marked as a duplicate of bug 58570 ***

[Bug middle-end/58677] wrong code at -O1 on x86_64-linux-gnu

[su at cs dot ucdavis.edu]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58677

--- Comment #3 from Zhendong Su <su at cs dot ucdavis.edu> ---
(In reply to Mikael Pettersson from comment #1)
> Started with r202525 (PR58404 missed-optimization fix), stopped with r203315
> (PR58570 wrong-code fix).  The cause of PR58570 was not r202525.
> 
> Can you check if the original testcase works on current trunk?

Just checked; it works. Thanks.