https://llvm.org/bugs/show_bug.cgi?id=27262
Bug ID: 27262
Summary: wrong code at -O3 on x86_64-linux-gnu in 32-bit and
64-bit modes
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 on
x86_64-linux-gnu at -O3 in both the 32-bit and 64-bit modes.
This is a regression from 3.8.x.
This one has been very tough to reduce.
$ clang-trunk -v
clang version 3.9.0 (trunk 265520)
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/5.3.0
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/4.9.3
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/5.3.0
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-trunk -O2 small.c; ./a.out
0
$ clang-3.8 -O3 small.c; ./a.out
0
$
$ clang-trunk -O3 small.c; ./a.out
3
$
-----------------------------------------------------
int printf (const char *, ...);
int a[6], e, k, p, r;
unsigned c;
short d, f, l, q;
long g, h;
char j, m, n, o;
void
fn1 (int p1)
{
c = c >> 8 ^ a[c ^ (p1 & 5)];
}
void
fn2 (long long p1)
{
int b = p1;
c = c >> 8 ^ a[c ^ (b & 5)] >> 8 ^ a[(c ^ 5) & 5];
c = c >> 8 ^ a[(c ^ 5) & 5];
fn1 (p1 >> 4);
fn1 (p1 >> 2);
fn1 (p1 >> 40);
c = c >> 8 ^ a[(c ^ 6) & 5];
}
void
fn3 (long long p1, int p3)
{
fn2 (p1);
if (p3)
printf ("%d\n", 5);
}
static void
fn4 ()
{
int s, i = 0, u = 1;
char t[3];
lbl:
for (; i < 3; i++)
t[i] = 1;
int v;
i = 0;
for (; u < 20; ++u)
{
if (m)
goto lbl;
if (j)
{
s = 0;
for (; s < 9; s++)
fn3 (g, v);
}
h = 0;
for (; h < 3; h++)
{
o ^= k &= d-- + (n && f == (n = l));
e = 0;
for (; e < 3; e++)
{
if (t[h])
break;
p = q;
}
}
}
v = r;
}
int
main ()
{
fn4 ();
printf ("%d\n", e);
return 0;
}
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