[LLVMbugs] [Bug 3119] New: maybe a loop miscompilation

[bugzilla-daemon at cs.uiuc.edu]

http://llvm.org/bugs/show_bug.cgi?id=3119

           Summary: maybe a loop miscompilation
           Product: new-bugs
           Version: unspecified
          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


This bug is in 2.4 but not 2.3 and is still in r59914.  This is seen on Ubuntu
Hardy on x86.

regehr at john-home:~/volatile/tmp63$ llvm-gcc -O0 small.c -o small
regehr at john-home:~/volatile/tmp63$ ./small
-1
regehr at john-home:~/volatile/tmp63$ llvm-gcc -O1 small.c -o small
regehr at john-home:~/volatile/tmp63$ ./small
0
regehr at john-home:~/volatile/tmp63$ cat small.c
#include <stdint.h>
#include <stdio.h>

static inline uint64_t
safe_mod_uint64_t_u_u (uint64_t ui1, uint64_t ui2)
{
        if (ui2 == 0) return ui1;
        return ui1 % ui2;
}

static inline int8_t
safe_sub_int8_t_s_s (int8_t si1, int8_t si2)
{
        if (((si1^si2)
                 & (((si1 ^ ((si1^si2)
                 & (1 << (sizeof(int8_t)*8-1))))-si2)^si2)) < 0) {
                return si1;
        }
        return si1 - si2;
}

uint32_t g_61;
uint32_t g_123;
uint32_t g_147 = 1;

int32_t func_19 (void);
int32_t func_37 (uint8_t p_39);
int32_t func_64 (uint32_t p_65, uint32_t p_66);
int32_t func_90 (uint8_t p_92, int16_t p_93, uint8_t p_95);
int32_t func_105 (int32_t p_107, int32_t p_108);

int32_t
func_19 (void)
{
  func_37 (1);
  return g_147;
}

int32_t
func_37 (uint8_t p_39)
{
  int32_t l_243 = -1L;
  if (func_90 (1, (safe_mod_uint64_t_u_u (l_243, -1L)), 1))
    {
      func_64 (1, 1);
    }
  return 1;
}

int32_t
func_64 (uint32_t p_65, uint32_t p_66)
{
  for (g_147 = 0; 0; 1)
    return 1;
  return 1;
}

int32_t
func_90 (uint8_t p_92, int16_t p_93, uint8_t p_95)
{
  return p_93;
}

int32_t
func_105 (int32_t p_107, int32_t p_108)
{
  return 1;
}

int
main (void)
{
  printf ("%d\n", safe_sub_int8_t_s_s ((func_19 ()), 1));
  return 0;
}


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