[LLVMbugs] [Bug 4814] New: possible integer wrong code bug

[bugzilla-daemon at cs.uiuc.edu]

http://llvm.org/bugs/show_bug.cgi?id=4814

           Summary: possible integer wrong code bug
           Product: new-bugs
           Version: trunk
          Platform: PC
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P2
         Component: new bugs
        AssignedTo: unassignedbugs at nondot.org
        ReportedBy: regehr at cs.utah.edu
                CC: llvmbugs at cs.uiuc.edu


Seen on Ubuntu Hardy.  

g_96 is initialized to 1 and perhaps at -O3 we're forgetting to zero it in the
loop?

regehr at john-home:~/volatile/tmp190$ llvm-gcc -O2 small.c -o small -w
regehr at john-home:~/volatile/tmp190$ ./small
checksum = 0
regehr at john-home:~/volatile/tmp190$ llvm-gcc -O3 small.c -o small -w
regehr at john-home:~/volatile/tmp190$ ./small
checksum = 1
regehr at john-home:~/volatile/tmp190$ llvm-gcc -v
Using built-in specs.
Target: i686-pc-linux-gnu
Configured with: ../configure
--prefix=/home/regehr/z/tmp/llvm-gcc-r80328-install
--program-prefix=llvm-r80328- --enable-languages=c,c++
--enable-llvm=/home/regehr/z/tmp/llvm-r80328 --enable-checking=release
Thread model: posix
gcc version 4.2.1 (Based on Apple Inc. build 5649) (LLVM build)
regehr at john-home:~/volatile/tmp190$ cat small.c
#include <stdint.h>
#include <limits.h>
#include <stdio.h>

#define safe_rshift_macro_int8_t_s_u(left,right) \
  (((((int8_t)(left)) < ((int8_t)0)) \
                         || (((unsigned int)(right)) >=
sizeof(int8_t)*CHAR_BIT)) \
                        ? ((int8_t)(left)) \
                        : (((int8_t)(left)) >> ((unsigned int)(right))))

static int8_t
safe_rshift_func_int8_t_s_u(int8_t _left, unsigned int _right)
{
  return safe_rshift_macro_int8_t_s_u(_left,_right);
}

struct S0
{
  uint8_t f0;
  uint8_t f1;
  uint8_t f2;
};

uint8_t g_3 = 0xB4E1265AL;
uint8_t g_96 = 1;
volatile uint8_t g_100;

struct S0 func_47 (void);
struct S0 func_47 (void)
{
  struct S0 l_74 = {
    0xB9CEB518L, 0x4A9CL, 1
  };
  return l_74;
}

int32_t func_18 (struct S0 p_19);
int32_t func_18 (struct S0 p_19)
{
  if (g_96 >= (1 || p_19.f1))
    g_100;
  return 1;
}

int32_t func_4 (int64_t p_5, uint32_t p_6);
int32_t func_4 (int64_t p_5, uint32_t p_6)
{
  struct S0 l_116 = {
    0xA76FC585L, 7L, 1
  };
  func_18 (l_116);
  return l_116.f2;
}

void func_1 (void);
void func_1 (void)
{
  uint8_t l_2;
  uint8_t l_120 = 0;
  for (l_2 = 0; l_2 <= 0; l_2++)
    if (safe_rshift_func_int8_t_s_u (g_3, func_4 (0, 1)))
      for (g_96 = 0; 0; 1)
        {
        }
    else if (func_18 (func_47 ()))
      for (1; l_120; l_120 = 1)
        {
        }
}

int main (void)
{
  func_1 ();
  printf ("checksum = %d\n", g_96);
  return 0;
}


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