[llvm-bugs] [Bug 27611] New: wrong code at -O3 in 32-bit mode on x86_64-linux-gnu

[via llvm-bugs]

https://llvm.org/bugs/show_bug.cgi?id=27611

            Bug ID: 27611
           Summary: wrong code at -O3 in 32-bit mode 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 trunk at -O3 in the 32-bit mode (but
not in the 64-bit mode) on x86_64-linux-gnu.

This is a regression from 3.8.x. 


$ clang-trunk -v
clang version 3.9.0 (trunk 268212)
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/4.9.3
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/5.3.0
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/4.8.5
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.9
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.9.3
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/5.3.0
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 -m32 -O2 small.c; ./a.out
$ clang-3.8 -m32 -O3 small.c; ./a.out
$ clang-trunk -m64 -O3 small.c; ./a.out
$
$ clang-trunk -m32 -O3 small.c
$ ./a.out
Floating point exception (core dumped)
$


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


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

unsigned a;
int h, e, g, i;
static int c = 7, f;
char j = 6, d;

struct S1
{ 
  char f1;
  char f2;
  int f3;
} b;

void
fn1 ()
{ 
  int k = 6, o = 248, l = 0;
  struct S1 n = { 4, 0, 0 };
  if (j)
    { 
      int q = g;
    lbl:
      l = l << h / (q || c << 0) << n.f2;
      if (k)
        n.f3 = ~(-e | (o - 94967289));
      if (!n.f3)
        { 
          printf ("\n");
          goto lbl;
        }
      if (!c)
        { 
          n = b;
          goto lbl;
        }
      if (b.f2)
        { 
          n.f2 = f;
          for (; k > 5; k = 8)
            ;
        }
    }
  o = a;
  char s = i / n.f1;
  d = s;
  if (!n.f1)
    goto lbl;
  if (l)
    c = 0;
}

int
main ()
{ 
  fn1 ();
  return 0;
}

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