https://llvm.org/bugs/show_bug.cgi?id=24516
Bug ID: 24516
Summary: wrong code at -Os and above on x86_64-linux-gnu
(affecting all clang versions)
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 on
x86_64-linux-gnu at -Os and above in both 32-bit and 64-bit modes. It also
affects all earlier clang versions since at least 3.0.
The generated code in the 64-bit mode also seems to behave
nondeterministically.
$ clang-trunk -v
clang version 3.8.0 (trunk 245480)
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/4.9.2
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/5.1.0
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/4.8.2
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.9
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.9.2
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/5.1.0
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 -m32 -O1 small.c; ./a.out
4
$ clang-trunk -m32 -Os small.c; ./a.out
3
$ clang-3.0 -m32 -Os small.c; ./a.out
3
$
$ clang-trunk -m64 -Os small.c
$ ./a.out
3
$ ./a.out
3
$ ./a.out
4
$ ./a.out
3
$
--------------------------------
int printf(const char *, ...);
int a;
short
fn1 (short p1)
{
return p1 + 1;
}
short
fn2 (int p1, int p2)
{
return p1 + p2;
}
int
main ()
{
int c;
char e;
c = fn2 (-1, a && 1);
e = fn1 ((unsigned) c > 33000) + 2;
printf("%d\n", e);
return 0;
}
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