From: Sriraman Tallam <tmsriram@google.com>
To: "H.J. Lu" <hjl.tools@gmail.com>
Cc: Pedro Alves <palves@redhat.com>, Michael Matz <matz@suse.de>,
David Li <davidxl@google.com>,
GCC Patches <gcc-patches@gcc.gnu.org>,
Jan Hubicka <hubicka@ucw.cz>
Subject: Re: [RFC][PATCH][X86_64] Eliminate PLT stubs for specified external functions via -fno-plt=
Date: Thu, 28 May 2015 21:27:00 -0000 [thread overview]
Message-ID: <CAAs8Hmy0ymq=396N9i5=Z6u8B4+9d5u07nk=D14MwJMXNxCuCA@mail.gmail.com> (raw)
In-Reply-To: <CAMe9rOpcWnZv7yqyG6TeL_RtDochw6_ar_=7RKoAqv1ZzkTwLA@mail.gmail.com>
[-- Attachment #1: Type: text/plain, Size: 2171 bytes --]
On Thu, May 28, 2015 at 12:05 PM, H.J. Lu <hjl.tools@gmail.com> wrote:
> On Thu, May 28, 2015 at 11:50 AM, Sriraman Tallam <tmsriram@google.com> wrote:
>> On Thu, May 28, 2015 at 11:42 AM, H.J. Lu <hjl.tools@gmail.com> wrote:
>>> On Thu, May 28, 2015 at 11:34 AM, Sriraman Tallam <tmsriram@google.com> wrote:
>>>> I have attached a patch that adds the new attribute "noplt". Please review.
>>>>
>>>> * config/i386/i386.c (avoid_plt_to_call): New function.
>>>> (ix86_output_call_insn): Generate indirect call for functions
>>>> marked with "noplt" attribute.
>>>> (attribute_spec ix86_attribute_): Define new attribute "noplt".
>>>> * doc/extend.texi: Document new attribute "noplt".
>>>> * gcc.target/i386/noplt-1.c: New testcase.
>>>> * gcc.target/i386/noplt-2.c: New testcase.
>>>>
>>>
>>> 2 comments:
>>>
>>> 1. Don't remove "%!" prefix before call/jmp. It is needed for MPX.
>>> 2. Don't you need to check
>>>
>>> && !TARGET_MACHO
>>> && !TARGET_SEH
>>> && !TARGET_PECOFF
>>>
>>> since it only works for ELF.
>>
>> Ok, I will make this change. OTOH, is it just better to piggy-back on
>> existing -fno-plt change by Alex in calls.c
>> and do this:
>>
>> Index: calls.c
>> ===================================================================
>> --- calls.c (revision 223720)
>> +++ calls.c (working copy)
>> @@ -226,9 +226,11 @@ prepare_call_address (tree fndecl_or_type, rtx fun
>> && targetm.small_register_classes_for_mode_p (FUNCTION_MODE))
>> ? force_not_mem (memory_address (FUNCTION_MODE, funexp))
>> : memory_address (FUNCTION_MODE, funexp));
>> - else if (flag_pic && !flag_plt && fndecl_or_type
>> + else if (fndecl_or_type
>> && TREE_CODE (fndecl_or_type) == FUNCTION_DECL
>> - && !targetm.binds_local_p (fndecl_or_type))
>> + && !targetm.binds_local_p (fndecl_or_type)
>> + && ((flag_pic && !flag_plt)
>> + || (lookup_attribute ("noplt", DECL_ATTRIBUTES(fndecl_or_type)))))
>> {
>> funexp = force_reg (Pmode, funexp);
>> }
>>
>
> Does it work on non-PIC calls?
You are right, it doesnt work. I have attached the patch with the
changes you mentioned.
Thanks
Sri
>
> --
> H.J.
[-- Attachment #2: noplt_attrib_patch.txt --]
[-- Type: text/plain, Size: 4218 bytes --]
* config/i386/i386.c (avoid_plt_to_call): New function.
(ix86_output_call_insn): Generate indirect call for functions
marked with "noplt" attribute.
(attribute_spec ix86_attribute_): Define new attribute "noplt".
* doc/extend.texi: Document new attribute "noplt".
* gcc.target/i386/noplt-1.c: New testcase.
* gcc.target/i386/noplt-2.c: New testcase.
Index: config/i386/i386.c
===================================================================
--- config/i386/i386.c (revision 223720)
+++ config/i386/i386.c (working copy)
@@ -25599,6 +25599,25 @@ ix86_expand_call (rtx retval, rtx fnaddr, rtx call
return call;
}
+/* Return true if the function being called was marked with attribute
+ "noplt". If this function is defined, this should return false. */
+static bool
+avoid_plt_to_call (rtx call_op)
+{
+ if (GET_CODE (call_op) != SYMBOL_REF
+ || SYMBOL_REF_LOCAL_P (call_op))
+ return false;
+
+ tree symbol_decl = SYMBOL_REF_DECL (call_op);
+
+ if (symbol_decl != NULL_TREE
+ && TREE_CODE (symbol_decl) == FUNCTION_DECL
+ && lookup_attribute ("noplt", DECL_ATTRIBUTES (symbol_decl)))
+ return true;
+
+ return false;
+}
+
/* Output the assembly for a call instruction. */
const char *
@@ -25611,7 +25630,13 @@ ix86_output_call_insn (rtx_insn *insn, rtx call_op
if (SIBLING_CALL_P (insn))
{
if (direct_p)
- xasm = "%!jmp\t%P0";
+ {
+ if (!TARGET_MACHO && !TARGET_SEH && !TARGET_PECOFF
+ && TARGET_64BIT && avoid_plt_to_call (call_op))
+ xasm = "%!jmp\t*%p0@GOTPCREL(%%rip)";
+ else
+ xasm = "%!jmp\t%P0";
+ }
/* SEH epilogue detection requires the indirect branch case
to include REX.W. */
else if (TARGET_SEH)
@@ -25654,7 +25679,13 @@ ix86_output_call_insn (rtx_insn *insn, rtx call_op
}
if (direct_p)
- xasm = "%!call\t%P0";
+ {
+ if (!TARGET_MACHO && !TARGET_SEH && !TARGET_PECOFF
+ && TARGET_64BIT && avoid_plt_to_call (call_op))
+ xasm = "%!call\t*%p0@GOTPCREL(%%rip)";
+ else
+ xasm = "%!call\t%P0";
+ }
else
xasm = "%!call\t%A0";
@@ -46628,6 +46659,9 @@ static const struct attribute_spec ix86_attribute_
false },
{ "callee_pop_aggregate_return", 1, 1, false, true, true,
ix86_handle_callee_pop_aggregate_return, true },
+ /* Attribute to avoid calling function via PLT. */
+ { "noplt", 0, 0, true, false, false, ix86_handle_fndecl_attribute,
+ false },
/* End element. */
{ NULL, 0, 0, false, false, false, NULL, false }
};
Index: doc/extend.texi
===================================================================
--- doc/extend.texi (revision 223720)
+++ doc/extend.texi (working copy)
@@ -4858,6 +4858,13 @@ On x86-32 targets, the @code{stdcall} attribute ca
assume that the called function pops off the stack space used to
pass arguments, unless it takes a variable number of arguments.
+@item noplt
+@cindex @code{noplt} function attribute, x86-64
+@cindex functions whose calls do not go via PLT
+On x86-64 targets. the @code{noplt} attribute causes the compiler to
+call this external function indirectly using a GOT entry and avoid the
+PLT.
+
@item target (@var{options})
@cindex @code{target} function attribute
As discussed in @ref{Common Function Attributes}, this attribute
Index: testsuite/gcc.target/i386/noplt-1.c
===================================================================
--- testsuite/gcc.target/i386/noplt-1.c (revision 0)
+++ testsuite/gcc.target/i386/noplt-1.c (working copy)
@@ -0,0 +1,13 @@
+/* { dg-do compile { target x86_64-*-* } } */
+
+
+__attribute__ ((noplt))
+void foo();
+
+int main()
+{
+ foo();
+ return 0;
+}
+
+/* { dg-final { scan-assembler "call\[ \t\]\\*.*foo.*@GOTPCREL\\(%rip\\)" } } */
Index: testsuite/gcc.target/i386/noplt-2.c
===================================================================
--- testsuite/gcc.target/i386/noplt-2.c (revision 0)
+++ testsuite/gcc.target/i386/noplt-2.c (working copy)
@@ -0,0 +1,13 @@
+/* { dg-do compile { target x86_64-*-* } } */
+/* { dg-options "-O2" } */
+
+
+__attribute__ ((noplt))
+int foo();
+
+int main()
+{
+ return foo();
+}
+
+/* { dg-final { scan-assembler "jmp\[ \t\]\\*.*foo.*@GOTPCREL\\(%rip\\)" } } */
next prev parent reply other threads:[~2015-05-28 20:54 UTC|newest]
Thread overview: 65+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-05-10 15:19 H.J. Lu
[not found] ` <CAAs8HmwWSDY+KjKcB4W=TiYV0Pz7NSvfL_8igp+hPT-LU1utTg@mail.gmail.com>
2015-05-21 21:31 ` Sriraman Tallam
2015-05-21 21:39 ` Sriraman Tallam
2015-05-21 22:02 ` Pedro Alves
2015-05-21 22:02 ` Jakub Jelinek
2015-05-22 1:47 ` H.J. Lu
2015-05-22 3:38 ` Xinliang David Li
2015-05-21 22:34 ` Sriraman Tallam
2015-05-22 9:22 ` Pedro Alves
2015-05-22 15:13 ` Sriraman Tallam
2015-05-28 18:53 ` Sriraman Tallam
2015-05-28 19:05 ` H.J. Lu
2015-05-28 19:48 ` Sriraman Tallam
2015-05-28 20:19 ` H.J. Lu
2015-05-28 21:27 ` Sriraman Tallam [this message]
2015-05-28 21:31 ` H.J. Lu
2015-05-28 21:52 ` Sriraman Tallam
2015-05-28 22:48 ` H.J. Lu
2015-05-29 3:51 ` Sriraman Tallam
2015-05-29 5:13 ` H.J. Lu
2015-05-29 7:13 ` Sriraman Tallam
2015-05-29 17:36 ` Sriraman Tallam
2015-05-29 17:52 ` H.J. Lu
2015-05-29 18:33 ` Sriraman Tallam
2015-05-29 20:50 ` Jan Hubicka
2015-05-29 22:56 ` Sriraman Tallam
2015-05-29 23:08 ` Sriraman Tallam
[not found] ` <CAJA7tRYsMiq7rx34c=z6KwRdwYxxaeP6Z6qzA4XEwnJSMT7z=Q@mail.gmail.com>
2015-05-30 4:44 ` Sriraman Tallam
2015-06-01 8:24 ` Ramana Radhakrishnan
2015-06-01 18:01 ` Sriraman Tallam
2015-06-01 18:41 ` Ramana Radhakrishnan
2015-06-01 18:55 ` Sriraman Tallam
2015-06-01 20:33 ` Ramana Radhakrishnan
2015-06-02 18:27 ` Sriraman Tallam
2015-06-02 19:59 ` Bernhard Reutner-Fischer
2015-06-02 20:09 ` Sriraman Tallam
2015-06-02 21:18 ` Bernhard Reutner-Fischer
2015-06-02 21:09 ` Ramana Radhakrishnan
2015-06-02 21:25 ` Xinliang David Li
2015-06-02 21:52 ` Bernhard Reutner-Fischer
2015-06-02 21:40 ` Sriraman Tallam
2015-06-03 14:37 ` Ramana Radhakrishnan
2015-06-03 18:53 ` Sriraman Tallam
2015-06-03 20:16 ` Richard Henderson
2015-06-03 20:59 ` Sriraman Tallam
2015-06-04 16:56 ` Sriraman Tallam
2015-06-04 17:30 ` Richard Henderson
2015-06-04 21:34 ` Sriraman Tallam
2015-07-24 19:02 ` H.J. Lu
2015-06-03 19:57 ` Richard Henderson
-- strict thread matches above, loose matches on Subject: below --
2015-05-01 0:31 Sriraman Tallam
2015-05-01 3:21 ` Alan Modra
2015-05-01 3:26 ` Sriraman Tallam
2015-05-01 15:01 ` Andi Kleen
2015-05-01 16:19 ` Xinliang David Li
2015-05-01 16:23 ` H.J. Lu
2015-05-01 16:26 ` Xinliang David Li
2015-05-01 18:06 ` Sriraman Tallam
2015-05-02 12:12 ` Andi Kleen
2015-05-01 17:50 ` Sriraman Tallam
2015-05-04 14:45 ` Michael Matz
2015-05-04 16:43 ` Xinliang David Li
2015-05-04 16:58 ` Michael Matz
2015-05-04 17:22 ` Xinliang David Li
2015-05-09 16:35 ` H.J. Lu
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to='CAAs8Hmy0ymq=396N9i5=Z6u8B4+9d5u07nk=D14MwJMXNxCuCA@mail.gmail.com' \
--to=tmsriram@google.com \
--cc=davidxl@google.com \
--cc=gcc-patches@gcc.gnu.org \
--cc=hjl.tools@gmail.com \
--cc=hubicka@ucw.cz \
--cc=matz@suse.de \
--cc=palves@redhat.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).