From: Sriraman Tallam <tmsriram@google.com>
To: "H.J. Lu" <hjl.tools@gmail.com>
Cc: Richard Henderson <rth@redhat.com>,
Bernhard Reutner-Fischer <rep.dot.nop@gmail.com>,
Jakub Jelinek <jakub@redhat.com>,
Uros Bizjak <ubizjak@gmail.com>,
"gcc-patches@gcc.gnu.org" <gcc-patches@gcc.gnu.org>,
David Li <davidxl@google.com>,
Cary Coutant <ccoutant@google.com>
Subject: Re: [PATCH x86_64] Optimize access to globals in "-fpie -pie" builds with copy relocations
Date: Thu, 05 Feb 2015 22:48:00 -0000 [thread overview]
Message-ID: <CAAs8Hmze9Db41kt=g1GA2to5KFMh28CWe=B3Mpp-g4aOhk7SAw@mail.gmail.com> (raw)
In-Reply-To: <CAMe9rOo8+ou8mkRJ950vQO-rZ=PrqX1JWCHAjgp2pAfOO96hXg@mail.gmail.com>
On Thu, Feb 5, 2015 at 2:23 PM, H.J. Lu <hjl.tools@gmail.com> wrote:
> On Thu, Feb 5, 2015 at 2:05 PM, Sriraman Tallam <tmsriram@google.com> wrote:
>> On Thu, Feb 5, 2015 at 11:59 AM, Richard Henderson <rth@redhat.com> wrote:
>>> On 02/05/2015 11:01 AM, H.J. Lu wrote:
>>>> Can you elaborate why it depends on COPY relocation? There
>>>> is no COPY relocation on x86-64.
>>>
>>> Ho hum, we appear to have switched topics mid-thread.
>>>
>>> I agree that we cannot override a weak symbol in the executable with even a
>>> non-weak symbol in a shared library.
>>
>> Hi HJ,
>>
>> Is your patch supposed to fix weak symbols too? Will
>> SYMBOL_REF_LOCAL_P evaluate to true for weak defined symbols with this
>> patch? I tested this in gcc-4_9 and it didnt seem to do that.
>
> I am working on a comprehensive patch. I will post it
> after testing is finished.
Thanks!
Sri
>
> --
> H.J.
> --
> [hjl@gnu-6 copyreloc-3]$ cat initweak.i
> __attribute__((weak))
> int xxxxxxxxxxxx = -1;
>
> int
> foo ()
> {
> return xxxxxxxxxxxx;
> }
> [hjl@gnu-6 copyreloc-3]$ cat commonweak.i
> __attribute__((weak))
> int xxxxxxxxxxxx;
>
> int
> foo ()
> {
> return xxxxxxxxxxxx;
> }
> [hjl@gnu-6 copyreloc-3]$ make initweak.s commonweak.s
> /export/build/gnu/gcc-x32/build-x86_64-linux/gcc/xgcc
> -B/export/build/gnu/gcc-x32/build-x86_64-linux/gcc/ -pie -fpie -O3
> -fuse-ld=gold -S initweak.i
> /export/build/gnu/gcc-x32/build-x86_64-linux/gcc/xgcc
> -B/export/build/gnu/gcc-x32/build-x86_64-linux/gcc/ -pie -fpie -O3
> -fuse-ld=gold -S commonweak.i
> [hjl@gnu-6 copyreloc-3]$ cat commonweak.s initweak.s
> .file "commonweak.i"
> .section .text.unlikely,"ax",@progbits
> .LCOLDB0:
> .text
> .LHOTB0:
> .p2align 4,,15
> .globl foo
> .type foo, @function
> foo:
> .LFB0:
> .cfi_startproc
> movl xxxxxxxxxxxx(%rip), %eax
> ret
> .cfi_endproc
> .LFE0:
> .size foo, .-foo
> .section .text.unlikely
> .LCOLDE0:
> .text
> .LHOTE0:
> .weak xxxxxxxxxxxx
> .bss
> .align 4
> .type xxxxxxxxxxxx, @object
> .size xxxxxxxxxxxx, 4
> xxxxxxxxxxxx:
> .zero 4
> .ident "GCC: (GNU) 5.0.0 20150205 (experimental)"
> .section .note.GNU-stack,"",@progbits
> .file "initweak.i"
> .section .text.unlikely,"ax",@progbits
> .LCOLDB0:
> .text
> .LHOTB0:
> .p2align 4,,15
> .globl foo
> .type foo, @function
> foo:
> .LFB0:
> .cfi_startproc
> movl xxxxxxxxxxxx(%rip), %eax
> ret
> .cfi_endproc
> .LFE0:
> .size foo, .-foo
> .section .text.unlikely
> .LCOLDE0:
> .text
> .LHOTE0:
> .weak xxxxxxxxxxxx
> .data
> .align 4
> .type xxxxxxxxxxxx, @object
> .size xxxxxxxxxxxx, 4
> xxxxxxxxxxxx:
> .long -1
> .ident "GCC: (GNU) 5.0.0 20150205 (experimental)"
> .section .note.GNU-stack,"",@progbits
> [hjl@gnu-6 copyreloc-3]$
next prev parent reply other threads:[~2015-02-05 22:48 UTC|newest]
Thread overview: 63+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-12-02 19:19 Uros Bizjak
2014-12-02 19:39 ` H.J. Lu
2014-12-02 19:40 ` H.J. Lu
2014-12-02 20:01 ` Uros Bizjak
2014-12-02 20:43 ` H.J. Lu
2014-12-02 20:19 ` Jakub Jelinek
2014-12-02 22:14 ` H.J. Lu
2014-12-02 23:21 ` H.J. Lu
2014-12-03 13:47 ` H.J. Lu
2014-12-03 15:01 ` H.J. Lu
2014-12-03 21:35 ` H.J. Lu
2014-12-04 12:44 ` Uros Bizjak
2014-12-04 16:46 ` H.J. Lu
2014-12-04 19:32 ` Uros Bizjak
2015-02-03 19:25 ` Sriraman Tallam
2015-02-03 19:26 ` Sriraman Tallam
2015-02-03 19:36 ` Jakub Jelinek
2015-02-03 21:20 ` Sriraman Tallam
2015-02-03 21:29 ` H.J. Lu
2015-02-03 21:36 ` Sriraman Tallam
2015-02-03 22:03 ` H.J. Lu
2015-02-03 22:19 ` Jakub Jelinek
2015-02-04 1:16 ` H.J. Lu
2015-02-04 18:27 ` Sriraman Tallam
2015-02-04 18:31 ` Jakub Jelinek
2015-02-04 18:38 ` H.J. Lu
2015-02-04 18:42 ` Jakub Jelinek
2015-02-04 18:45 ` H.J. Lu
2015-02-04 18:51 ` Sriraman Tallam
2015-02-04 18:57 ` H.J. Lu
2015-02-04 21:53 ` Sriraman Tallam
2015-02-04 22:37 ` H.J. Lu
2015-02-04 22:47 ` Bernhard Reutner-Fischer
2015-02-04 23:10 ` H.J. Lu
2015-02-04 23:29 ` H.J. Lu
2015-02-05 16:57 ` Bernhard Reutner-Fischer
2015-02-05 18:54 ` Richard Henderson
2015-02-05 19:01 ` H.J. Lu
2015-02-05 19:59 ` Richard Henderson
2015-02-05 22:05 ` Sriraman Tallam
2015-02-05 22:47 ` H.J. Lu
2015-02-05 22:48 ` Sriraman Tallam [this message]
2015-02-06 16:25 ` H.J. Lu
2015-02-27 23:39 ` H.J. Lu
2015-02-27 23:46 ` H.J. Lu
-- strict thread matches above, loose matches on Subject: below --
2014-12-04 22:19 Dominique Dhumieres
2014-12-04 23:54 ` H.J. Lu
2014-05-15 18:34 Sriraman Tallam
2014-05-19 18:11 ` Sriraman Tallam
2014-06-09 22:55 ` Sriraman Tallam
2014-06-21 0:17 ` Sriraman Tallam
2014-06-26 17:55 ` Sriraman Tallam
2014-07-11 17:42 ` Sriraman Tallam
2014-09-02 18:15 ` Sriraman Tallam
2014-09-02 20:40 ` Richard Henderson
2014-09-03 7:25 ` Bernhard Reutner-Fischer
2014-09-08 22:19 ` Sriraman Tallam
2014-09-19 21:11 ` Sriraman Tallam
2014-09-29 17:57 ` Sriraman Tallam
2014-10-06 20:43 ` Sriraman Tallam
2014-11-10 23:35 ` Sriraman Tallam
2014-12-02 18:01 ` Sriraman Tallam
2014-12-02 19:06 ` H.J. Lu
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