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[Bug tree-optimization/59047] New: wrong code for bitfields at -O3 on x86_64-linux-gnu
- From: "su at cs dot ucdavis.edu" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: Fri, 08 Nov 2013 09:21:05 +0000
- Subject: [Bug tree-optimization/59047] New: wrong code for bitfields at -O3 on x86_64-linux-gnu
- Auto-submitted: auto-generated
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59047
Bug ID: 59047
Summary: wrong code for bitfields at -O3 on x86_64-linux-gnu
Product: gcc
Version: 4.9.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: su at cs dot ucdavis.edu
The current gcc trunk miscompiles the following testcase on x86_64-linux-gnu at
-O3 (in both 32-bit and 64-bit modes).
This is a regression from 4.8.x.
$ gcc-trunk -v
Using built-in specs.
COLLECT_GCC=gcc-trunk
COLLECT_LTO_WRAPPER=/usr/local/gcc-trunk/libexec/gcc/x86_64-unknown-linux-gnu/4.9.0/lto-wrapper
Target: x86_64-unknown-linux-gnu
Configured with: ../gcc-trunk/configure
--enable-languages=c,c++,objc,obj-c++,fortran,lto --disable-werror
--enable-checking=release --with-gmp=/usr/local/gcc-trunk
--with-mpfr=/usr/local/gcc-trunk --with-mpc=/usr/local/gcc-trunk
--with-cloog=/usr/local/gcc-trunk --prefix=/usr/local/gcc-trunk
Thread model: posix
gcc version 4.9.0 20131108 (experimental) [trunk revision 204560] (GCC)
$
$ gcc-trunk -O2 small.c; a.out
1
$ gcc-4.8.2 -O3 small.c; a.out
1
$
$ gcc-trunk -O3 small.c; a.out
0
$
--------------------------------------
int printf (const char *, ...);
struct
{
int f0;
int f1:1;
int f2:2;
} a = {0, 0, 1};
int b, c, *d, e, f;
int
fn1 ()
{
for (; b < 1; ++b)
{
for (e = 0; e < 1; e = 1)
{
int **g = &d;
*g = &c;
}
*d = 0;
f = a.f1;
if (f)
return 0;
}
return 0;
}
int
main ()
{
fn1 ();
printf ("%d\n", b);
return 0;
}