[Bug rtl-optimization/58726] New: wrong code at -Os on x86_64-linux-gnu (affecting trunk/4.7/4.6, but not 4.8)
su at cs dot ucdavis.edu
gcc-bugzilla@gcc.gnu.org
Mon Oct 14 18:38:00 GMT 2013
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58726
Bug ID: 58726
Summary: wrong code at -Os on x86_64-linux-gnu (affecting
trunk/4.7/4.6, but not 4.8)
Product: gcc
Version: 4.8.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: rtl-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: su at cs dot ucdavis.edu
The current gcc trunk miscompiles the following code on x86_64-linux at -Os in
both 32-bit and 64-bit modes.
This is a regression from 4.8.x.
It also affects 4.6.x and 4.7.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 20131014 (experimental) [trunk revision 203511] (GCC)
$
$ gcc-trunk -O1 small.c; a.out
-9162
$ gcc-trunk -Os small.c; a.out
-32768
$
$ gcc-4.8 -Os small.c; a.out
-9162
$
$ gcc-4.7 -Os small.c; a.out
-32768
$ gcc-4.6 -Os small.c; a.out
-32768
$
------------------------------------
int printf (const char *, ...);
int a, c;
union
{
int f1;
int f2:1;
} b;
short
foo (short p)
{
return p < 0 ? p : a;
}
int
main ()
{
b.f1 = 56374;
unsigned short d;
int e = b.f2;
d = e == 0 ? b.f1 : 0;
c = foo (d);
printf ("%d\n", c);
return 0;
}
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