[Bug 1267761] Re: miscompilation of unsigned comparison on aarch64
** Changed in: gcc-linaro Status: New => Fix Released -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1267761 Title: miscompilation of unsigned comparison on aarch64 To manage notifications about this bug go to: https://bugs.launchpad.net/gcc/+bug/1267761/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
[Bug 1267761] Re: miscompilation of unsigned comparison on aarch64
** Changed in: gcc-linaro Assignee: (unassigned) => Michael Collison (michael-collison) -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1267761 Title: miscompilation of unsigned comparison on aarch64 To manage notifications about this bug go to: https://bugs.launchpad.net/gcc/+bug/1267761/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
[Bug 1267761] Re: miscompilation of unsigned comparison on aarch64
** Branch linked: lp:debian/gnat-4.8 -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1267761 Title: miscompilation of unsigned comparison on aarch64 To manage notifications about this bug go to: https://bugs.launchpad.net/gcc/+bug/1267761/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
[Bug 1267761] Re: miscompilation of unsigned comparison on aarch64
This bug was fixed in the package gcc-4.8 - 4.8.2-13ubuntu1 --- gcc-4.8 (4.8.2-13ubuntu1) trusty; urgency=medium * Merge with Debian; remaining changes: - Build from the upstream source. gcc-4.8 (4.8.2-13) unstable; urgency=medium * Update to SVN 20140112 (r206564) from the gcc-4_8-branch. - Fix miscompilation due to wrong RTL-optimization (see PR rtl-optimization/59137). Closes: #716635. [ Aurelien Jarno ] * Reenable the testsuite on mips. [ Matthias Klose ] * Add libgcc, libstdc++, libgfortran symbols files for ppc64el. * Update libitm symbols for non-default multilibs. * Add libgcc, libstdc++, libgfortran symbols files for arm64. * Fix PR target/59588 (AArch64), backport proposed patch. LP: #1263576. * Fix PR target/59744 (AArch64), taken from the trunk. LP: #1267761. -- Matthias KloseSun, 12 Jan 2014 14:16:19 +0100 ** Changed in: gcc-4.8 (Ubuntu Trusty) Status: Confirmed => Fix Released -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1267761 Title: miscompilation of unsigned comparison on aarch64 To manage notifications about this bug go to: https://bugs.launchpad.net/gcc/+bug/1267761/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
[Bug 1267761] Re: miscompilation of unsigned comparison on aarch64
** Branch linked: lp:debian/gcc-4.8 -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1267761 Title: miscompilation of unsigned comparison on aarch64 To manage notifications about this bug go to: https://bugs.launchpad.net/gcc/+bug/1267761/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
[Bug 1267761] Re: miscompilation of unsigned comparison on aarch64
** Changed in: gcc Status: Confirmed => Fix Released -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1267761 Title: miscompilation of unsigned comparison on aarch64 To manage notifications about this bug go to: https://bugs.launchpad.net/gcc/+bug/1267761/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
[Bug 1267761] Re: miscompilation of unsigned comparison on aarch64
Launchpad has imported 2 comments from the remote bug at
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59744.
If you reply to an imported comment from within Launchpad, your comment
will be sent to the remote bug automatically. Read more about
Launchpad's inter-bugtracker facilities at
https://help.launchpad.net/InterBugTracking.
On 2014-01-10T00:30:27+00:00 Michael Hudson-Doyle wrote:
Hi,
This slightly strangely written program (it's distilled down from
frame_offset_overflow in the gcc source itself) should print "bigger" if
the first argument is bigger than 10 (or negative, but let's ignore that
please):
#include
#include
int a[2] = { 10, 20 };
int
is_bigger (long offset, int index)
{
unsigned long size = -offset;
if (size > a[index])
{
printf("bigger\n");
return 1;
}
return 0;
}
int
main (int argc, char** argv)
{
long v;
v = atol(argv[1]);
is_bigger(-v, 0);
return 0;
}
When compiled at -O1 or above (and with inlining disabled at -O2 and
above), though, it bungles the 0 case:
(t-doko)mwhudson@arm64:~$ gcc-4.9 -O3 test.c -o test -fno-inline -Wall
(t-doko)mwhudson@arm64:~$ ./test 1
(t-doko)mwhudson@arm64:~$ ./test 11
bigger
(t-doko)mwhudson@arm64:~$ ./test 0
bigger
(t-doko)mwhudson@arm64:~$ gcc-4.9 -O0 test.c -o test -Wall
(t-doko)mwhudson@arm64:~$ ./test 1
(t-doko)mwhudson@arm64:~$ ./test 11
bigger
(t-doko)mwhudson@arm64:~$ ./test 0
(t-doko)mwhudson@arm64:~$
What's going on? Here's the disassembly of is_bigger (at O3):
00400608 :
400608: b082adrpx2, 411000 <_GLOBAL_OFFSET_TABLE_+0x28>
40060c: 91010042add x2, x2, #0x40
400610: a9bf7bfdstp x29, x30, [sp,#-16]!
400614: 5283mov w3, #0x0// #0
400618: 910003fdmov x29, sp
40061c: b8a1d841ldrsw x1, [x2,w1,sxtw #2]
400620: ab3fcmn x1, x0
400624: 54a2b.cs400638
400628: 9000adrpx0, 40 <_init-0x3f8>
40062c: 911b6000add x0, x0, #0x6d8
400630: 9790bl 400470
400634: 52800023mov w3, #0x1// #1
400638: 2a0303e0mov w0, w3
40063c: a8c17bfdldp x29, x30, [sp],#16
400640: d65f03c0ret
Basically it seems that the condition "-offset > val" is being compiled
as "val + offset does not overflow", which is not valid for offset == 0.
Reply at: https://bugs.launchpad.net/gcc-linaro/+bug/1267761/comments/0
On 2014-01-10T01:00:19+00:00 Pinskia wrote:
(insn 14 13 15 2 (set (reg:CC_SWP 66 cc)
(compare:CC_SWP (neg:DI (reg:DI 0 x0 [ offset ]))
(reg:DI 1 x1 [orig:85 D.3895 ] [85]))) t7.c:11 114 {*compare_negdi}
(expr_list:REG_DEAD (reg:DI 1 x1 [orig:85 D.3895 ] [85])
(expr_list:REG_DEAD (reg:DI 0 x0 [ offset ])
(nil
--- CUT ---
Here is a testcase that fails at -O1 and above without any arguments.
int a[2] = { 10, 20 };
int
is_bigger (long, int) __attribute__((noinline,noclone));
int
is_bigger (long offset, int index)
{
unsigned long size = -offset;
if (size > a[index])
return 1;
return 0;
}
int
main (int argc, char** argv)
{
long v;
if (is_bigger(0, 0))
__builtin_abort ();
if (!is_bigger(1, 0))
__builtin_abort ();
if (is_bigger(-10, 0))
__builtin_abort ();
if (!is_bigger(10, 0))
__builtin_abort ();
return 0;
}
Reply at: https://bugs.launchpad.net/gcc-linaro/+bug/1267761/comments/1
** Changed in: gcc
Status: Unknown => Confirmed
** Changed in: gcc
Importance: Unknown => Medium
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Title:
miscompilation of unsigned comparison on aarch64
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[Bug 1267761] Re: miscompilation of unsigned comparison on aarch64
** Also affects: gcc-4.8 (Ubuntu) Importance: Undecided Status: New ** Also affects: gcc-4.8 (Ubuntu Trusty) Importance: Undecided Status: New ** Changed in: gcc-4.8 (Ubuntu Trusty) Importance: Undecided => High ** Changed in: gcc-4.8 (Ubuntu Trusty) Status: New => Confirmed ** Changed in: gcc-4.8 (Ubuntu Trusty) Milestone: None => ubuntu-14.01 -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1267761 Title: miscompilation of unsigned comparison on aarch64 To manage notifications about this bug go to: https://bugs.launchpad.net/gcc/+bug/1267761/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
