https://llvm.org/bugs/show_bug.cgi?id=30838
Bug ID: 30838
Summary: wrong code at -O3 on x86_64-linux-gnu (in both 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
Interestingly, although fn2 isn't invoked, removing it seems to hide the bug.
$ clang -v
clang version 4.0.0 (trunk 285491)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /usr/local/clang-trunk/bin
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/4.7.4
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
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/5.4.0
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/6
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/6.0.0
Selected GCC installation: /usr/lib/gcc/x86_64-linux-gnu/5.4.0
Candidate multilib: .;@m64
Candidate multilib: 32;@m32
Candidate multilib: x32;@mx32
Selected multilib: .;@m64
$
$ clang -O2 small.c; ./a.out
10
$ clang-3.8 -O3 small.c; ./a.out
10
$
$ clang -O3 small.c; ./a.out
0
$
------------------------------------------
int printf (const char *, ...);
short a, b, *c = &a;
static char d, e = 5;
int f, *g = &f, h, i, j = 6, k;
int fn1 (int p1)
{
for (; j < 7; j++)
if (b || d < 2)
for (; e; e++)
{
*g = 10;
h = *c;
}
return p1;
}
void fn2 ()
{
d++;
}
int main ()
{
int l[1];
for (; k < 1; k++)
if (j)
l[0] = 1;
fn1 (l[0]);
l[i] = 0;
printf ("%d\n", f);
return 0;
}
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