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Message #08904
[Bug 1263806] Re: gccgo fails to compile tomb.go on arm64
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------------------------------------------------------------------------
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 <stdlib.h>
#include <stdio.h>
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):
0000000000400608 <is_bigger>:
400608: b0000082 adrp x2, 411000 <_GLOBAL_OFFSET_TABLE_+0x28>
40060c: 91010042 add x2, x2, #0x40
400610: a9bf7bfd stp x29, x30, [sp,#-16]!
400614: 52800003 mov w3, #0x0 // #0
400618: 910003fd mov x29, sp
40061c: b8a1d841 ldrsw x1, [x2,w1,sxtw #2]
400620: ab00003f cmn x1, x0
400624: 540000a2 b.cs 400638 <is_bigger+0x30>
400628: 90000000 adrp x0, 400000 <_init-0x3f8>
40062c: 911b6000 add x0, x0, #0x6d8
400630: 97ffff90 bl 400470 <puts@plt>
400634: 52800023 mov w3, #0x1 // #1
400638: 2a0303e0 mov w0, w3
40063c: a8c17bfd ldp x29, x30, [sp],#16
400640: d65f03c0 ret
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/ubuntu/+source/gcc-4.8/+bug/1263806/comments/2
------------------------------------------------------------------------
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/ubuntu/+source/gcc-4.8/+bug/1263806/comments/4
------------------------------------------------------------------------
On 2014-01-10T15:21:53+00:00 Rearnsha wrote:
Author: rearnsha
Date: Fri Jan 10 15:21:21 2014
New Revision: 206530
URL: http://gcc.gnu.org/viewcvs?rev=206530&root=gcc&view=rev
Log:
PR target/59744
Fix ChangeLog typos in previous commit (r206529).
Modified:
trunk/gcc/ChangeLog
Reply at:
https://bugs.launchpad.net/ubuntu/+source/gcc-4.8/+bug/1263806/comments/5
------------------------------------------------------------------------
On 2014-01-10T15:23:36+00:00 Rearnsha wrote:
Fixed on trunk
Reply at:
https://bugs.launchpad.net/ubuntu/+source/gcc-4.8/+bug/1263806/comments/6
------------------------------------------------------------------------
On 2014-01-13T01:00:43+00:00 Michael Hudson-Doyle wrote:
Hi, thanks for the super fast fix. Could it be backported to 4.8? git
cherry-pick gives a conflict in aarch64.md which is probably easy to fix
if you know how this code works:
(define_insn "*compare_neg<mode>"
<<<<<<< HEAD
[(set (reg:CC CC_REGNUM)
(compare:CC
(match_operand:GPI 0 "register_operand" "r")
(neg:GPI (match_operand:GPI 1 "register_operand" "r"))))]
||||||| parent of 46b590a... PR target/9744
[(set (reg:CC_SWP CC_REGNUM)
(compare:CC_SWP
(neg:GPI (match_operand:GPI 0 "register_operand" "r"))
(match_operand:GPI 1 "register_operand" "r")))]
=======
[(set (reg:CC_Z CC_REGNUM)
(compare:CC_Z
(neg:GPI (match_operand:GPI 0 "register_operand" "r"))
(match_operand:GPI 1 "register_operand" "r")))]
>>>>>>> 46b590a... PR target/9744
""
"cmn\\t%<w>0, %<w>1"
[(set_attr "v8type" "alus")
(set_attr "mode" "<MODE>")]
)
Reply at:
https://bugs.launchpad.net/ubuntu/+source/gcc-4.8/+bug/1263806/comments/7
------------------------------------------------------------------------
On 2014-01-13T09:34:19+00:00 Rearnsha wrote:
I don't expect that pattern to match on 4.8 (the pattern is not
canonical form), which is why this wasn't seen before.
If you can find a test-case that triggers on that branch, I'll do a
back-port; otherwise, there's no point.
Reply at:
https://bugs.launchpad.net/ubuntu/+source/gcc-4.8/+bug/1263806/comments/8
------------------------------------------------------------------------
On 2014-01-13T09:35:41+00:00 Ktkachov wrote:
I couldn't reproduce the failure using 4.8.
Reply at:
https://bugs.launchpad.net/ubuntu/+source/gcc-4.8/+bug/1263806/comments/9
------------------------------------------------------------------------
On 2014-01-14T00:30:04+00:00 Michael Hudson-Doyle wrote:
I saw the problem with Linaro GCC 4.8, but haven't tried the vanilla 4.8
branch. If the committed test case doesn't fail, I'll believe that it
is not a problem. Sorry for the noise.
Reply at:
https://bugs.launchpad.net/ubuntu/+source/gcc-4.8/+bug/1263806/comments/10
------------------------------------------------------------------------
On 2014-08-11T22:08:36+00:00 Yroux wrote:
Author: yroux
Date: Mon Aug 11 22:08:03 2014
New Revision: 213842
URL: https://gcc.gnu.org/viewcvs?rev=213842&root=gcc&view=rev
Log:
gcc/
2014-08-11 Michael Collison <michael.collison@xxxxxxxxxx>
Backport from trunk r206529, r206530
2014-01-10 Richard Earnshaw <rearnsha@xxxxxxx>
PR target/59744
* aarch64-modes.def (CC_Zmode): New flags mode.
* aarch64.c (aarch64_select_cc_mode): Only allow NEG when the condition
represents an equality.
(aarch64_get_condition_code): Handle CC_Zmode.
* aarch64.md (compare_neg<mode>): Restrict to equality operations.
gcc/testsuite/
2014-08-11 Michael Collison <michael.collison@xxxxxxxxxx>
Backport from trunk r206529
2014-01-10 Richard Earnshaw <rearnsha@xxxxxxx>
PR target/59744
* gcc.target/aarch64/cmn-neg.c: Use equality comparisons.
* gcc.target/aarch64/cmn-neg2.c: New test.
Added:
branches/linaro/gcc-4_8-branch/gcc/testsuite/gcc.target/aarch64/cmn-neg2.c
Modified:
branches/linaro/gcc-4_8-branch/gcc/ChangeLog.linaro
branches/linaro/gcc-4_8-branch/gcc/config/aarch64/aarch64-modes.def
branches/linaro/gcc-4_8-branch/gcc/config/aarch64/aarch64.c
branches/linaro/gcc-4_8-branch/gcc/config/aarch64/aarch64.md
branches/linaro/gcc-4_8-branch/gcc/testsuite/ChangeLog.linaro
branches/linaro/gcc-4_8-branch/gcc/testsuite/gcc.target/aarch64/cmn-neg.c
Reply at:
https://bugs.launchpad.net/ubuntu/+source/gcc-4.8/+bug/1263806/comments/12
** Changed in: gcc
Status: Unknown => Fix Released
** Changed in: gcc
Importance: Unknown => Medium
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https://bugs.launchpad.net/bugs/1263806
Title:
gccgo fails to compile tomb.go on arm64
Status in The GNU Compiler Collection:
Fix Released
Status in “gcc-4.8” package in Ubuntu:
Fix Released
Bug description:
Hi, on am2:
ubuntu@arm64:~/gopath/src/launchpad.net/tomb$ gccgo -g -c -o tomb.o tomb.go
tomb.go: In function 'tomb.Wait.pN12_go.tomb.Tomb':
tomb.go:108:1: error: total size of local objects too large
func (t *Tomb) Wait() error {
^
tomb.go: In function 'tomb.Kill.pN12_go.tomb.Tomb':
tomb.go:134:1: error: total size of local objects too large
func (t *Tomb) Kill(reason error) {
^
This is the first error line:
http://bazaar.launchpad.net/~niemeyer/tomb/trunk/view/head:/tomb.go#L108
which seems pretty innocuous.
Will dig (and probably kick upstream) in January.
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