The current gcc trunk miscompiles the following code on x86_64-linux at -O2 and -O3 in 64-bit mode. 

This is a regression from 4.8.x and may be related to 58831, which also affects gcc 4.8.x though. 

$ 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 20131021 (experimental) [trunk revision 203907] (GCC) 
$ 
$ gcc-trunk -m64 -O1 small.c; a.out
$ gcc-trunk -m32 -O2 small.c; a.out
$ gcc-4.8.2 -m64 -O2 small.c; a.out
$ gcc-4.7.3 -m64 -O2 small.c; a.out
$ 
$ gcc-trunk -m64 -O2 small.c; a.out
a.out: small.c:9: fn1: Assertion `d || (1 & e)' failed.
Aborted (core dumped)
$ gcc-trunk -m64 -O3 small.c; a.out
a.out: small.c:9: fn1: Assertion `d || (1 & e)' failed.
Aborted (core dumped)
$ 
$ 


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


#include<assert.h>

int a, b, c, *d, e, g;

void
fn1 (int *p1, int **p2)
{
  *p2 = &g;
  assert (d || (1 & e));
}

static int **
fn2 ()
{
  int *f = &b;
  for (; c; c--)
    f = 0;
  assert(a || f);
  return 0;
}

static unsigned short
fn3 ()
{
  fn2 ();
  fn1 (0, &d);
  return 0;
}


int
main ()
{
  fn2 ();
  fn3 ();
  return 0;
}