https://llvm.org/bugs/show_bug.cgi?id=24356
Bug ID: 24356
Summary: wrong code at -O1 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 following code is miscompiled by the current clang trunk on
x86_64-linux-gnu at -O1 and above in both 32-bit and 64-bit modes.
This is a regression from 3.6.x.
$ clang-trunk -v
clang version 3.8.0 (trunk 243961)
Target: x86_64-unknown-linux-gnu
Thread model: posix
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 -O0 small.c; ./a.out
$ clang-3.6 -O1 small.c; ./a.out
$
$ clang-trunk -O1 small.c
$ ./a.out
Aborted (core dumped)
$
---------------------------------
int a;
void
fn1 ()
{
char b = 0;
for (; b != -2; b--)
for (a = 0 ; a < 1; a++)
if ((unsigned int) b > 1)
return;
}
int
main ()
{
fn1 ();
if (a != 0)
__builtin_abort ();
return 0;
}
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