[llvm-bugs] [Bug 31260] New: wrong code at -Os and above on x86_64-linux-gnu (in both 32-bit and 64-bit modes)

[via llvm-bugs]

https://llvm.org/bugs/show_bug.cgi?id=31260

            Bug ID: 31260
           Summary: wrong code at -Os and above on x86_64-linux-gnu (in
                    both 32-bit and 64-bit modes)
           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

This seems to be a recent regression.  The test case is difficult to reduce and
still quite large (1285 bytes), but it should be valid. 


$ clang -v
clang version 4.0.0 (trunk 288581)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /usr/local/clang-trunk/bin
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/4.9
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/4.9.4
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/5
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/4.9.4
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/5
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/5.3.0
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/6
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/6.2.0
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 -O1 -w small.c; ./a.out
4
$
$ clang -Os -w small.c
$ ./a.out
$
$


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


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

unsigned a = 294967288;
int b, e, g, h, i, j, k, l, m, n, o;
char c, d, f;
short p = 5344;

static int fn1 (int r)
{ 
  for (;; 1)
    { 
      int s;
      while (0)
        for (;; 0)
          for (;; 1)
            for (;; 1)
              while (1)
                for (;; j)
                  for (;; k)
                    for (;; 1)
                      while (0)
                        for (;; e)
                          for (;; l)
                            for (;; m)
                              while (0)
                                goto L4;
    L1:
    L2:
    L3:
      if (c)
        for (;; 1)
          goto L5;
      while (0)
        while (0)
          for (;; h)
            for (;; g)
              while (0)
                for (;; 0)
                  while (0)
                    for (;; j)
                      for (;; k)
                        for (;; 0)
                          for (;; i)
                            for (;; g)
                              for (;; 1)
                                goto L6;
      while (!b)
        { 
          for (; 0; 0)
            while (0)
              for (;; 3)
                for (;; c)
                  for (;; 0)
                    ;
        L7:
          d = r = 1;
          for (; 0; r)
            ;
        }
      for (; 1; 1)
        { 
          while (0)
            for (;; n)
              for (;; o)
                for (;; 1)
                  for (;; e)
                    for (;; s)
                      for (;; 1)
                        for (;; f)
                          ;
          for (;; 1)
            { 
              unsigned b = a = p * a;
              if (a > 94967288)
                { 
                  printf ("%d\n", 4);
                  goto L6;
                }
              if (r)
                { 
                  if (c < 0)
                    continue;
                  break;
                }
            }
        L4:
          for (; 0;)
          L5:
          L6:
            return 0;
        }
    }
}

int main ()
{ 
  b = 1;
  fn1 (4);
  return 0;
}

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