[LLVMbugs] [Bug 21160] New: Wrong code

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=21160

            Bug ID: 21160
           Summary: Wrong code
           Product: clang
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: LLVM Codegen
          Assignee: unassignedclangbugs at nondot.org
          Reporter: ishiura-compiler at ml.kwansei.ac.jp
                CC: llvmbugs at cs.uiuc.edu
    Classification: Unclassified

LLVM + clang 3.6 for x86_64 miscompiles the following code with optimize option
"-O1".

We have tried hard to minimize the code, but this is the best result we have
obtained so far.  

$ cat test.c
int a = 0;
int b = 0;
int c = 0;
int d = 0;
int e = 0;
int f = 0;
int g = 0;
int h = 0;
int i = 0;
int j = 0;
int k = 0;
int l = 0;
int m = 0;
int n = 0;
int o = 0;
int p = 0;

int main (void)
{
    volatile int q = 0;
    volatile int r = 0;
    volatile int s = 0;
    volatile int t = 0;
    volatile int u = 0;

    for (i = 0; i < 1; i++) {
        volatile int v = 1;
        a = m + 1;
        b = n;
        c = 1 / v;
        d = r + o;
        e = t;
        f = p + t;
        g = a + 1;
        h = g + q;
        j = s;
        k = r + l;
    }
    int w = g | (int)(16777219.0L + u);

    if (w != 16777219) {
        __builtin_abort();
    }

    return 0;
}

$ clang test.c -O1
$ ./a.out
Aborted (core dumped)

$ clang -v
clang version 3.6.0
Target: x86_64-unknown-linux-gnu
Thread model: posix

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