http://llvm.org/bugs/show_bug.cgi?id=20059
Bug ID: 20059
Summary: wrong code (FP exception) at -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 at -O3 on
x86_64-linux-gnu (in both 32-bit and 64-bit modes).
This is a regression from 3.4.
$ clang-trunk -v
clang version 3.5.0 (trunk 211006)
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 -O2 small.c; a.out
$ clang-3.4 -O3 small.c; a.out
$
$ clang-trunk -O3 small.c
$ a.out
Floating point exception (core dumped)
$
---------------------
int a, b, c, d = 1;
char e = 1;
void
fn1 ()
{
int h;
for (; e; e++)
{
for (; b;)
d--;
h = (d ? a % d : 0);
c &= h;
}
}
int
main ()
{
fn1 ();
return 0;
}
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