http://llvm.org/bugs/show_bug.cgi?id=22173
Bug ID: 22173
Summary: wrong code at -Os and above 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 at -Os and above on
x86_64-linux-gnu in both 32-bit and 64-bit modes.
This is a regression from 3.5.0.
$ clang-trunk -v
clang version 3.6.0 (trunk 225511)
Target: x86_64-unknown-linux-gnu
Thread model: posix
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 -O1 small.c; a.out
$ clang-3.5.0 -Os small.c; a.out
$
$ clang-trunk -Os small.c
$ a.out
Aborted (core dumped)
$
------------------------------
int a, b = 1;
char c;
void
fn1 ()
{
c = a - b;
if (c)
b = 0;
}
int
main ()
{
for (a = 0; a < 1; a++)
fn1 ();
if (b != 0)
__builtin_abort ();
return 0;
}
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