https://llvm.org/bugs/show_bug.cgi?id=26256
Bug ID: 26256
Summary: wrong code 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: 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 (and 3.7.x) on
x86_64-linux-gnu at -O2 and -O3 in both 32-bit and 64-bit modes.
This is a regression from 3.6.x.
$ clang-trunk -v
clang version 3.9.0 (trunk 258416)
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/5.2.1
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.4
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.4.7
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/4.8.4
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/5.2.1
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 -Os small.c; ./a.out
$ clang-3.6 -O2 small.c; ./a.out
$
$ clang-trunk -O2 small.c
$ ./a.out
0
$ clang-3.7 -O2 small.c
$ ./a.out
0
$
------------------------------------
int printf (const char *, ...);
int a = 8, b, d, e, f;
short c;
void
fn1 ()
{
char g = c, h = c = c | 195;
if (d)
;
if ((!a && c > d) || c < d)
for (g = 0; g < 20; g++)
e ^= f;
a = 2 & g;
if (h >= c || g)
printf ("%d\n", b);
if (a)
{
fn1 ();
for (;;)
;
}
}
int
main ()
{
fn1 ();
return 0;
}
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