http://llvm.org/bugs/show_bug.cgi?id=17780
Bug ID: 17780
Summary: wrong code at -O2 and -Os on x86_64-linux-gnu in
32-bit mode
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 on
x86_64-linux-gnu at -O2 and -Os in both 32-bit mode.
This is a regression from clang 3.3.
$ clang-trunk -v
clang version 3.4 (trunk 193897)
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 -m32 -O1 small.c; a.out
0
$ clang-trunk -m32 -O2 small.c; a.out
1
$ clang-trunk -m32 -Os small.c; a.out
1
$ clang-3.3 -m32 -O2 small.c; a.out
0
$ clang-3.3 -m32 -Os small.c; a.out
0
$ gcc-4.8.2 -m32 -O2 small.c; a.out
0
$ icc -m32 -O2 small.c; a.out
0
$
---------------------------------
int printf (const char *, ...);
union U
{
int f1;
int f2;
} a = {1};
static int
foo (union U p)
{
for (a.f2 = 0; a.f2 < 1; a.f2++)
if (p.f2)
break;
return 0;
}
int
main ()
{
foo (a);
printf ("%d\n", a.f1);
return 0;
}
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