http://llvm.org/bugs/show_bug.cgi?id=19132
Bug ID: 19132
Summary: wrong code (that hangs) by LTO on x86_64-linux-gnu
(affecting 3.4 and trunk)
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 and 3.4 miscompile the following code when using LTO on
x86_64-linux-gnu in both 32-bit and 64-bit modes.
This is a regression from clang 3.3.
This should be different from http://llvm.org/bugs/show_bug.cgi?id=19111 as
19111 also fails for 3.2 and 3.3.
$ clang-trunk -v
clang version 3.5.0 (trunk 203791)
Target: x86_64-unknown-linux-gnu
Thread model: posix
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/4.8
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/4.8.1
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.4
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.4.6
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/4.8.1
Selected GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.8
Candidate multilib: .;@m64
Candidate multilib: 32;@m32
Selected multilib: .;@m64
$
$ clang-trunk -O0 foo.c main.c
$ a.out
$
$ clang-3.3 -flto -O0 -c foo.c
$ clang-3.3 -flto -O1 -c main.c
$ clang-3.3 -flto -O1 foo.o main.o
$ a.out
$
$ clang-trunk -flto -O0 -c foo.c
$ clang-trunk -flto -O1 -c main.c
$ clang-trunk -flto -O1 foo.o main.o
$ a.out
^C
$
$ clang-3.4 -flto -O0 -c foo.c
$ clang-3.4 -flto -O1 -c main.c
$ clang-3.4 -flto -O1 foo.o main.o
$ a.out
^C
$
$
$ cat foo.c
extern int a, c;
static int
bar (int p1, int p2)
{
return p2 + 1;
}
void
foo (void)
{
int e = 0, g = 0, b = 1;
a = (b == 0 ? 0 : b);
if (bar (a || 0, g) & 1)
a = e && 0;
}
$ cat main.c
extern int foo (void);
int a, c;
int
main ()
{
for (; c < 2; c++)
foo ();
return 0;
}
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