http://llvm.org/bugs/show_bug.cgi?id=21309
Bug ID: 21309
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 following code is miscompiled by the current clang trunk on
x86_64-linux-gnu at -Os and above 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 220084)
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 -O1 small.c; a.out
0
$ clang-3.5.0 -Os small.c; a.out
0
$
$ clang-trunk -Os small.c; a.out
-85
$
--------------------------------
int printf (const char *, ...);
struct
{
char f1;
} a;
char
fn1 (int p1, int p2)
{
return p1 * p2;
}
int
main ()
{
char *b = &a.f1;
while (fn1(--*b, 3))
;
printf ("%d\n", a.f1);
return 0;
}
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