http://llvm.org/bugs/show_bug.cgi?id=18101
Bug ID: 18101
Summary: wrong code at -Os and above on x86_64-linux-gnu
(affecting 3.1 till trunk)
Product: clang
Version: trunk
Hardware: PC
OS: All
Status: NEW
Severity: normal
Priority: P
Component: -New Bugs
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected]
Classification: Unclassified
The following code is miscompiled by the current clang trunk (and earlier
versions starting from 3.1) on x86_64-linux-gnu at -Os and above in both 32-bit
and 64-bit modes.
$ clang-trunk -v
clang version 3.5 (trunk 195973)
Target: x86_64-unknown-linux-gnu
Thread model: posix
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.4
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.4.6
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/4.6.3
Selected GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.6
$
$ clang-trunk -O1 small.c; a.out
0
$ clang-3.0 -Os small.c; a.out
0
$ gcc-trunk -Os small.c; a.out
0
$ icc -Os small.c; a.out
0
$
$ clang-trunk -Os small.c; a.out
1
$ clang-3.3 -Os small.c; a.out
1
$ clang-3.2 -Os small.c; a.out
1
$ clang-3.1 -Os small.c; a.out
1
$
----------------------------------
int printf (const char *, ...);
struct S
{
int f0;
int f1:25;
};
int a, b, *c = &b, d;
struct S
fn1 ()
{
struct S e = {0, 0};
if (!d)
{
struct S f = {0, -1};
return f;
}
return e;
}
int
main ()
{
struct S g = fn1 (), h = g;
for (a = 0; a < 1; a++)
{
*c = 0;
*c = 1 <= ((h.f0 >= *c) ^ (h.f1 |= 1));
}
printf ("%d\n", b);
return 0;
}
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