http://llvm.org/bugs/show_bug.cgi?id=19109
Bug ID: 19109
Summary: wrong code (that segfaults) by LTO at -O2 and -O3 on
x86_64-linux-gnu
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 current clang trunk miscompiles the following code when using LTO at -O2
and -O3 on x86_64-linux-gnu (in both 32-bit and 64-bit modes).
This is likely related to http://llvm.org/bugs/show_bug.cgi?id=19062.
$ clang-trunk -v
clang version 3.5.0 (trunk 203564)
Target: x86_64-unknown-linux-gnu
Thread model: posix
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/4.8
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/4.8.1
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.4
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.4.6
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/4.6.4
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/4.8.1
Selected GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.8
Candidate multilib: .;@m64
Candidate multilib: 32;@m32
Selected multilib: .;@m64
$
$ clang-trunk -O2 small.c; a.out
$ clang-trunk -flto -Os small.c; a.out
$
$ clang-trunk -flto -O2 small.c
$ a.out
a.out: small.c:13: void foo(): Assertion `a == 0' failed.
Aborted (core dumped)
$
-------------------------------
#include <assert.h>
int *a, **volatile b = &a, c, *d = &c, *e = &c, **f = &a, g;
void
foo ()
{
for (;;)
{
assert (a == 0);
*f = &g;
*b = 0;
assert (a == 0);
*f = 0;
if (*e)
break;
}
}
int
main ()
{
*d = 1;
assert (a == 0);
foo ();
return 0;
}
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