[llvm-bugs] [Bug 25225] New: wrong code at -Os and above on x86_64-linux-gnu

[via llvm-bugs]

https://llvm.org/bugs/show_bug.cgi?id=25225

            Bug ID: 25225
           Summary: wrong code at -Os and above on x86_64-linux-gnu
           Product: clang
           Version: trunk
          Hardware: PC
                OS: All
            Status: NEW
          Severity: normal
          Priority: P
         Component: -New Bugs
          Assignee: unassignedclangbugs at nondot.org
          Reporter: su at cs.ucdavis.edu
                CC: llvm-bugs at lists.llvm.org
    Classification: Unclassified

The following code is miscompiled by the current clang trunk on
x86_64-linux-gnu at -Os and above in both 32-bit and 64-bit modes.

This is a regression from 3.7.x.

The reduced test is still quite large, but it seems difficult to reduce it
further. 


$ clang-trunk -v
clang version 3.8.0 (trunk 250539)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /usr/local/tools/bin
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/4.9
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/4.9.2
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/5.1.0
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.4
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.4.7
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.6
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.6.4
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.7
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.7.3
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.8
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.8.4
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.9
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.9.2
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/5.1.0
Selected GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.9
Candidate multilib: .;@m64
Candidate multilib: 32;@m32
Candidate multilib: x32;@mx32
Selected multilib: .;@m64
$ 
$ clang-trunk -O1 small.c; ./a.out
$ clang-3.7.0 -Os small.c; ./a.out
$ 
$ clang-trunk -Os small.c
$ ./a.out
Aborted (core dumped)
$ 


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


int a = -1, *b = &a, f, l;
static short c, d, *e = &d;
static char g;

void fn1 () { }

void fn2 () { }

void fn3 () { }

void fn4 () { }

void fn5 () { }

void fn6 () { }

void fn7 () { }

void fn8 () { }

void fn9 () { }

void fn10 () { }

void fn11 () { }

void fn12 () { }

void fn13 () { }

void fn14 () { }

void fn15 () { }

void fn16 () { }

void fn17 () { }

void fn18 () { }

void fn19 () { }

void fn20 () { }

int fn21 (int p1) { return p1; }

void fn22 () { }

void fn23 () { }

void fn24 () { }

void fn25 () { }

void fn26 () { }

void fn27 () { }

void fn28 () { }

void fn29 () { }

void fn30 () { }

void fn31 () { }

void fn32 () { }

void fn33 () { }

void fn34 () { }

void fn35 () { }

void fn36 () { }

void fn37 () { }

void fn38 () { }

static int
fn39 ()
{
  if (d)
    {
      int h;
    }
  return 0;
}

static int
fn40 ()
{
  short *i = &c;
  *i = *e = 1;
  if (a < 0)
    __builtin_abort (); 
  return 0;
}

static int *fn41 (short);

void fn42 () { }

static int
fn43 ()
{
  char *j = &g;
  *j = 1;
  return 0;
}

static int 
fn44 ()
{
  if (f)
    fn41 (0);
  l = 0;
  return 0;
}

void fn45 () { }

static int
fn46 ()
{
  fn41 (a);
  fn40 ();
  fn39 ();
  fn21 (g);
  return 0;
}

static int *
fn41 (short p1)
{
  fn44 ();
  fn43 ();
  *b = p1 < 0;
  return 0;
}

void fn47 () { }

int
main ()
{
  if (c)
    fn35 ();
  fn46 ();
  return 0;
}

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