[Bug target/63234] arm used label is removed

[Bug target/63234] arm used label is removed

[rearnsha at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63234

Richard Earnshaw <rearnsha at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |WAITING
   Last reconfirmed|                            |2014-09-15
     Ever confirmed|0                           |1

--- Comment #1 from Richard Earnshaw <rearnsha at gcc dot gnu.org> ---
Incomplete.  Please fill in details of how to reproduce.

[Bug target/63234] arm used label is removed

[pangbw at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63234

baoshan <pangbw at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Version|4.9.1                       |4.9.0

--- Comment #2 from baoshan <pangbw at gmail dot com> ---
1. configure & build gcc
$ PATH_TO_SRC/configure --enable-languages=c --target=arm-linux-eabi
--enable-tls
$ make
2. cat m.c
typedef struct _GHashTable GHashTable;
typedef struct _DNSCacheEntry DNSCacheEntry;
typedef struct _DNSCacheKey DNSCacheKey;
struct _DNSCacheKey
{
};
struct _DNSCacheEntry
{
  DNSCacheEntry *prev, *next;
  DNSCacheKey key;
};
struct __tls_variables
{
  GHashTable *cache;
  DNSCacheEntry persist_first;
  DNSCacheEntry persist_last;
}
 ;
static __thread struct __tls_variables __tls;
dns_cache_cleanup_persistent_hosts (void)
{
  while ((__tls.persist_first).next != &(__tls.persist_last))
    {
      g_hash_table_remove ((__tls.cache), &(__tls.persist_first).next->key);
    }
}

3. cc1 -O1 -fPIC m.c -o m.s
4. cat m.s
In the output you can see there is one line at the end of file:
       .word   .LANCHOR0(tlsldm) + (. - .LPIC3 - 8)
But the lable .LPIC3 is not existed in the file.

[Bug target/63234] arm used label is removed

[mikpelinux at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63234

Mikael Pettersson <mikpelinux at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |mikpelinux at gmail dot com

--- Comment #3 from Mikael Pettersson <mikpelinux at gmail dot com> ---
I can reproduce with gcc 4.7, 4.8, and 4.9 on armv5tel-linux-gnueabi, but not
with 4.6 or 5.0.  4.9 says:

> /mnt/scratch/objdir49/gcc/xgcc -B/mnt/scratch/objdir49/gcc/ -O1 -fPIC -c pr63234.c
/tmp/ccG9Y32i.s: Assembler messages:
/tmp/ccG9Y32i.s:64: Error: invalid operands (.text and *UND* sections) for `-'

Line 64 contains
.word   .LANCHOR0(tlsldm) + (. - .LPIC3 - 8)

[Bug target/63234] arm used label is removed

[mikpelinux at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63234

--- Comment #4 from Mikael Pettersson <mikpelinux at gmail dot com> ---
(apparently TAB became "save changes", how weird...)

... but .LPIC3 is not defined at all.  .LPIC[0124] are all defined and used.

[Bug target/63234] arm used label is removed

[pangbw at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63234

--- Comment #5 from baoshan <pangbw at gmail dot com> ---
I dig it deeper yesterday, and I believe this change makes the 5.0 works fine:

https://github.com/gcc-mirror/gcc/commit/9b59e2174ee59dd3aa55c7c3342daa2a6bc23fba

[Bug target/63234] arm used label is removed

[rearnsha at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63234

Richard Earnshaw <rearnsha at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|WAITING                     |UNCONFIRMED
     Ever confirmed|1                           |0

[Bug target/63234] arm used label is removed

[ramana at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63234

Ramana Radhakrishnan <ramana at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|2014-09-15 00:00:00         |2015-01-15
                 CC|                            |ramana at gcc dot gnu.org
      Known to work|                            |5.0
     Ever confirmed|0                           |1
      Known to fail|                            |4.9.2

--- Comment #6 from Ramana Radhakrishnan <ramana at gcc dot gnu.org> ---
Not sure if this is target or what in this particular case. But sure, confirmed
on 4.9 but works on 5.0.

[Bug target/63234] arm used label is removed

[mikpelinux at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63234

--- Comment #7 from Mikael Pettersson <mikpelinux at gmail dot com> ---
The wrong-code started in the 4.7 dev cycle with r183328, a fix for a similar
bug (PR50313) in 4.6.  That fix was backported to 4.6 but doesn't trigger this
PR there (I just re-checked with 4.6.4).

The bug is masked on trunk by r211885, a generic missed-optimization tweak, and
even earlier for Cortex-A9 by a costing tweak in r203828, but I doubt either of
those actually fixes the underlying problem.

[Bug target/63234] arm used label is removed

[mikpelinux at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63234

--- Comment #8 from Mikael Pettersson <mikpelinux at gmail dot com> ---
The failures on 4.7+ seem to be triggered by r177855, yet another ARM costing
tweak.

I'm not going to investigate this any further.