[LLVMbugs] [Bug 19093] New: wrong code by LTO at -Os and above on x86_64-linux-gnu (both 32-bit and 64-bit modes)
bugzilla-daemon at llvm.org
bugzilla-daemon at llvm.org
Sun Mar 9 20:34:48 PDT 2014
http://llvm.org/bugs/show_bug.cgi?id=19093
Bug ID: 19093
Summary: wrong code by LTO at -Os and above on x86_64-linux-gnu
(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: unassignedclangbugs at nondot.org
Reporter: su at cs.ucdavis.edu
CC: llvmbugs at cs.uiuc.edu
Classification: Unclassified
The current clang trunk miscompiles the following code when using LTO at -Os
and above on x86_64-linux-gnu (in both 32-bit and 64-bit modes).
$ clang-trunk -v
clang version 3.5.0 (trunk 203396)
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 -Os small.c; a.out
1
$ clang-trunk -flto -O1 small.c; a.out
1
$
$ clang-trunk -flto -Os small.c; a.out
0
$
---------------------------------
int printf (const char *, ...);
int a[2], b = 2, c, *d = &c, **e = &d, ***f = &e, *g = &b, *h = &b, i;
static int
fn1 ()
{
for (c = 2; c; c--)
for (;;)
{
*g &= **e;
for (; i; i++)
;
if (*h)
break;
return 0;
}
return 0;
}
int
main ()
{
a[1] = 1;
fn1 ();
printf ("%d\n", a[c]);
return 0;
}
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