http://llvm.org/bugs/show_bug.cgi?id=17544
Bug ID: 17544
Summary: wrong code at -Os and above on x86_64-linux-gnu
(affecting trunk, 3.3, and 3.2)
Product: clang
Version: trunk
Hardware: PC
OS: All
Status: NEW
Severity: normal
Priority: P
Component: LLVM Codegen
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected]
Classification: Unclassified
The following code is miscompiled by the current clang trunk (as well as clang
3.3 and 3.2) on x86_64-linux-gnu at -Os and above in both 32-bit and 64-bit
modes.
This is a regression from 3.1.
$ clang-trunk -v
clang version 3.4 (trunk 192380)
Target: x86_64-pc-linux-gnu
Thread model: posix
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/4.6.3
Selected GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.6
$
$ clang-trunk -O1 small.c; a.out
0
$ clang-trunk -Os small.c; a.out
1
$ clang-3.3 -Os small.c; a.out
1
$ clang-3.2 -Os small.c; a.out
1
$ clang-3.1 -Os small.c; a.out
0
$
------------------------------------
int printf (const char *, ...);
int a = 1, c;
struct S
{
char f0;
int:31;
char f1;
int f2;
} b;
int
foo ()
{
struct S d = { 0, 0, 0 };
c = d.f0;
b = d;
return b.f1;
}
int
main ()
{
c = foo ();
if (!c)
a = 0;
printf ("%d\n", a);
return 0;
}
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