https://llvm.org/bugs/show_bug.cgi?id=26046
Bug ID: 26046
Summary: wrong code at -O1 and above on x86_64-linux-gnu
Product: clang
Version: trunk
Hardware: PC
OS: All
Status: NEW
Severity: normal
Priority: P
Component: -New Bugs
Assignee: unassignedclangb...@nondot.org
Reporter: s...@cs.ucdavis.edu
CC: llvm-bugs@lists.llvm.org
Classification: Unclassified
The following code is miscompiled by the current clang trunk at -O1 and above
in both the 32-bit and 64-bit modes on x86_64-linux-gnu.
This is a regression from 3.7.x.
$ clang-trunk -v
clang version 3.8.0 (trunk 256854)
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/5.2.1
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/4.8.4
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/5.2.1
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 -O0 small.c; ./a.out
6
$ clang-3.7.0 -O1 small.c; ./a.out
6
$
$ clang-trunk -O1 small.c; ./a.out
0
$
------------------------------------------
int printf (const char *, ...);
char a, b, g, l, m;
int c, d, e, h, k, p;
static int f;
unsigned char i, *j = &i;
void
fn1 (int *p1)
{
int *o;
char n;
if (d)
h = p == 1;
o = &f;
n = a - 5;
for (; g > -1; g = n)
{
*j = m;
i = -k | 4;
e ^= d && *o;
l = b || (b > (7 >> b)) < c;
d = *o ^= l;
*p1 = 6;
*p1 = *o;
}
}
int
main ()
{
fn1 (&f);
printf ("%d\n", f);
return 0;
}
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