http://llvm.org/bugs/show_bug.cgi?id=19958
Bug ID: 19958
Summary: wrong code at -O1 and above on x86_64-linux-gnu
Product: clang
Version: unspecified
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 -O1 and above 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 210239)
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-3.4 -O1 small.c; a.out; echo $?
0
$ clang-trunk -O0 small.c; a.out; echo $?
0
$
$ clang-trunk -O1 small.c; a.out; echo $?
1
$
---------------------
int a, c, d;
unsigned int b;
char e;
int
main ()
{
for (; c < 1; c++)
{
for (b = 0; b < 2; b++)
a = (d != 0);
e = a - 8;
if ((unsigned int) e >= b)
break;
}
return c;
}
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