From: Sriraman Tallam <tmsriram@google.com>
To: Bernhard Reutner-Fischer <rep.dot.nop@gmail.com>
Cc: ramrad01@arm.com,
Ramana Radhakrishnan <ramana.radhakrishnan@arm.com>,
Jan Hubicka <hubicka@ucw.cz>, "H.J. Lu" <hjl.tools@gmail.com>,
Pedro Alves <palves@redhat.com>, Michael Matz <matz@suse.de>,
David Li <davidxl@google.com>,
GCC Patches <gcc-patches@gcc.gnu.org>
Subject: Re: [RFC][PATCH][X86_64] Eliminate PLT stubs for specified external functions via -fno-plt=
Date: Tue, 02 Jun 2015 20:09:00 -0000 [thread overview]
Message-ID: <CAAs8HmwVab+rgGYbzCWSzTfJ36Cs9fYpQMPn8NfzZcu9eaOayA@mail.gmail.com> (raw)
In-Reply-To: <E7B625BD-C42E-4D36-B243-B49DA1F31FB1@gmail.com>
[-- Attachment #1: Type: text/plain, Size: 1887 bytes --]
On Tue, Jun 2, 2015 at 12:32 PM, Bernhard Reutner-Fischer
<rep.dot.nop@gmail.com> wrote:
> On June 2, 2015 8:15:42 PM GMT+02:00, Sriraman Tallam <tmsriram@google.com> wrote:
> []
>
>>I have now modified this patch.
>>
>>This patch does two things:
>>
>>1) Adds new generic function attribute "no_plt" that is similar in
>>functionality to -fno-plt except that it applies only to calls to
>>functions that are marked with this attribute.
>>2) For x86_64, it makes -fno-plt(and the attribute) also work for
>>non-PIC code by directly generating an indirect call via a GOT entry.
>>
>>For PIC code, no_plt merely shadows the implementation of -fno-plt, no
>>surprises here.
>>
>>* c-family/c-common.c (no_plt): New attribute.
>>(handle_no_plt_attribute): New handler.
>>* calls.c (prepare_call_address): Check for no_plt
>>attribute.
>>* config/i386/i386.c (ix86_function_ok_for_sibcall): Check
>>for no_plt attribute.
>>(ix86_expand_call): Ditto.
>>(nopic_no_plt_attribute): New function.
>>(ix86_output_call_insn): Output indirect call for non-pic
>>no plt calls.
>>* doc/extend.texi (no_plt): Document new attribute.
>>* testsuite/gcc.target/i386/noplt-1.c: New test.
>>* testsuite/gcc.target/i386/noplt-2.c: New test.
>>* testsuite/gcc.target/i386/noplt-3.c: New test.
>>* testsuite/gcc.target/i386/noplt-4.c: New test.
>>
>>
>>Please review.
>
> --- config/i386/i386.c (revision 223720)
> +++ config/i386/i386.c (working copy)
> @@ -5479,6 +5479,8 @@ ix86_function_ok_for_sibcall (tree decl, tree exp)
> && !TARGET_64BIT
> && flag_pic
> && flag_plt
> + && (TREE_CODE (decl) != FUNCTION_DECL
> + || !lookup_attribute ("no_plt", DECL_ATTRIBUTES (decl)))
> && decl && !targetm.binds_local_p (decl))
> return false;
>
> Wrong order or && decl is redundant. Stopped reading here.
Fixed and new patch attached.
Thanks
Sri
>
> Thanks,
>
[-- Attachment #2: noplt_attrib_patch_new.txt --]
[-- Type: text/plain, Size: 9785 bytes --]
* c-family/c-common.c (no_plt): New attribute.
(handle_no_plt_attribute): New handler.
* calls.c (prepare_call_address): Check for no_plt
attribute.
* config/i386/i386.c (ix86_function_ok_for_sibcall): Check
for no_plt attribute.
(ix86_expand_call): Ditto.
(nopic_no_plt_attribute): New function.
(ix86_output_call_insn): Output indirect call for non-pic
no plt calls.
* doc/extend.texi (no_plt): Document new attribute.
* testsuite/gcc.target/i386/noplt-1.c: New test.
* testsuite/gcc.target/i386/noplt-2.c: New test.
* testsuite/gcc.target/i386/noplt-3.c: New test.
* testsuite/gcc.target/i386/noplt-4.c: New test.
This patch does two things:
* Adds new generic function attribute "no_plt" that is similar in functionality
to -fno-plt except that it applies only to calls to functions that are marked
with this attribute.
* For x86_64, it makes -fno-plt(and the attribute) also work for non-PIC code by
directly generating an indirect call via a GOT entry.
Index: c-family/c-common.c
===================================================================
--- c-family/c-common.c (revision 223720)
+++ c-family/c-common.c (working copy)
@@ -357,6 +357,7 @@ static tree handle_mode_attribute (tree *, tree, t
static tree handle_section_attribute (tree *, tree, tree, int, bool *);
static tree handle_aligned_attribute (tree *, tree, tree, int, bool *);
static tree handle_weak_attribute (tree *, tree, tree, int, bool *) ;
+static tree handle_no_plt_attribute (tree *, tree, tree, int, bool *) ;
static tree handle_alias_ifunc_attribute (bool, tree *, tree, tree, bool *);
static tree handle_ifunc_attribute (tree *, tree, tree, int, bool *);
static tree handle_alias_attribute (tree *, tree, tree, int, bool *);
@@ -706,6 +707,8 @@ const struct attribute_spec c_common_attribute_tab
handle_aligned_attribute, false },
{ "weak", 0, 0, true, false, false,
handle_weak_attribute, false },
+ { "no_plt", 0, 0, true, false, false,
+ handle_no_plt_attribute, false },
{ "ifunc", 1, 1, true, false, false,
handle_ifunc_attribute, false },
{ "alias", 1, 1, true, false, false,
@@ -8185,6 +8188,25 @@ handle_weak_attribute (tree *node, tree name,
return NULL_TREE;
}
+/* Handle a "no_plt" attribute; arguments as in
+ struct attribute_spec.handler. */
+
+static tree
+handle_no_plt_attribute (tree *node, tree name,
+ tree ARG_UNUSED (args),
+ int ARG_UNUSED (flags),
+ bool * ARG_UNUSED (no_add_attrs))
+{
+ if (TREE_CODE (*node) != FUNCTION_DECL)
+ {
+ warning (OPT_Wattributes,
+ "%qE attribute is only applicable on functions", name);
+ *no_add_attrs = true;
+ return NULL_TREE;
+ }
+ return NULL_TREE;
+}
+
/* Handle an "alias" or "ifunc" attribute; arguments as in
struct attribute_spec.handler, except that IS_ALIAS tells us
whether this is an alias as opposed to ifunc attribute. */
Index: calls.c
===================================================================
--- calls.c (revision 223720)
+++ calls.c (working copy)
@@ -226,8 +226,10 @@ 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 (flag_pic && fndecl_or_type
&& TREE_CODE (fndecl_or_type) == FUNCTION_DECL
+ && (!flag_plt
+ || lookup_attribute ("no_plt", DECL_ATTRIBUTES (fndecl_or_type)))
&& !targetm.binds_local_p (fndecl_or_type))
{
funexp = force_reg (Pmode, funexp);
Index: config/i386/i386.c
===================================================================
--- config/i386/i386.c (revision 223720)
+++ config/i386/i386.c (working copy)
@@ -5479,7 +5479,10 @@ ix86_function_ok_for_sibcall (tree decl, tree exp)
&& !TARGET_64BIT
&& flag_pic
&& flag_plt
- && decl && !targetm.binds_local_p (decl))
+ && decl
+ && (TREE_CODE (decl) != FUNCTION_DECL
+ || !lookup_attribute ("no_plt", DECL_ATTRIBUTES (decl)))
+ && !targetm.binds_local_p (decl))
return false;
/* If we need to align the outgoing stack, then sibcalling would
@@ -25497,13 +25500,19 @@ ix86_expand_call (rtx retval, rtx fnaddr, rtx call
}
else
{
- /* Static functions and indirect calls don't need the pic register. */
+ /* Static functions and indirect calls don't need the pic register. Also,
+ check if PLT was explicitly avoided via no-plt or "no_plt" attribute, making
+ it an indirect call. */
if (flag_pic
&& (!TARGET_64BIT
|| (ix86_cmodel == CM_LARGE_PIC
&& DEFAULT_ABI != MS_ABI))
&& GET_CODE (XEXP (fnaddr, 0)) == SYMBOL_REF
- && ! SYMBOL_REF_LOCAL_P (XEXP (fnaddr, 0)))
+ && ! SYMBOL_REF_LOCAL_P (XEXP (fnaddr, 0))
+ && flag_plt
+ && (TREE_CODE (SYMBOL_REF_DECL (XEXP(fnaddr, 0))) != FUNCTION_DECL
+ || !lookup_attribute ("no_plt",
+ DECL_ATTRIBUTES (SYMBOL_REF_DECL (XEXP(fnaddr, 0))))))
{
use_reg (&use, gen_rtx_REG (Pmode, REAL_PIC_OFFSET_TABLE_REGNUM));
if (ix86_use_pseudo_pic_reg ())
@@ -25599,6 +25608,34 @@ ix86_expand_call (rtx retval, rtx fnaddr, rtx call
return call;
}
+/* Return true if the function being called was marked with attribute
+ "no_plt" or using -fno-plt and we are compiling for no-PIC and x86_64.
+ This is currently used only with 64-bit ELF targets to call the function
+ marked "no_plt" indirectly. */
+
+static bool
+nopic_no_plt_attribute (rtx call_op)
+{
+ if (flag_pic)
+ return false;
+
+ if (!TARGET_64BIT || TARGET_MACHO|| TARGET_SEH || TARGET_PECOFF)
+ return false;
+
+ if (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
+ && (!flag_plt
+ || lookup_attribute ("no_plt", DECL_ATTRIBUTES (symbol_decl))))
+ return true;
+
+ return false;
+}
+
/* Output the assembly for a call instruction. */
const char *
@@ -25610,7 +25647,9 @@ ix86_output_call_insn (rtx_insn *insn, rtx call_op
if (SIBLING_CALL_P (insn))
{
- if (direct_p)
+ if (direct_p && nopic_no_plt_attribute (call_op))
+ xasm = "%!jmp\t*%p0@GOTPCREL(%%rip)";
+ else if (direct_p)
xasm = "%!jmp\t%P0";
/* SEH epilogue detection requires the indirect branch case
to include REX.W. */
@@ -25653,7 +25692,9 @@ ix86_output_call_insn (rtx_insn *insn, rtx call_op
seh_nop_p = true;
}
- if (direct_p)
+ if (direct_p && nopic_no_plt_attribute (call_op))
+ xasm = "%!call\t*%p0@GOTPCREL(%%rip)";
+ else if (direct_p)
xasm = "%!call\t%P0";
else
xasm = "%!call\t%A0";
Index: doc/extend.texi
===================================================================
--- doc/extend.texi (revision 223720)
+++ doc/extend.texi (working copy)
@@ -2916,6 +2916,15 @@ the standard C library can be guaranteed not to th
with the notable exceptions of @code{qsort} and @code{bsearch} that
take function pointer arguments.
+@item no_plt
+@cindex @code{no_plt} function attribute
+The @code{no_plt} attribute is used to inform the compiler that a calls
+to the function should not use the PLT. For example, external functions
+defined in shared objects are called from the executable using the PLT.
+This attribute on the function declaration calls these functions indirectly
+rather than going via the PLT. This is similar to @option{-fno-plt} but
+is only applicable to calls to the function marked with this attribute.
+
@item optimize
@cindex @code{optimize} function attribute
The @code{optimize} attribute is used to specify that a function is to
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-*-linux* } } */
+/* { dg-options "-fno-pic" } */
+
+__attribute__ ((no_plt))
+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-*-linux* } } */
+/* { dg-options "-O2 -fno-pic" } */
+
+
+__attribute__ ((no_plt))
+int foo();
+
+int main()
+{
+ return foo();
+}
+
+/* { dg-final { scan-assembler "jmp\[ \t\]\\*.*foo.*@GOTPCREL\\(%rip\\)" } } */
Index: testsuite/gcc.target/i386/noplt-3.c
===================================================================
--- testsuite/gcc.target/i386/noplt-3.c (revision 0)
+++ testsuite/gcc.target/i386/noplt-3.c (working copy)
@@ -0,0 +1,12 @@
+/* { dg-do compile { target x86_64-*-linux* } } */
+/* { dg-options "-fno-pic -fno-plt" } */
+
+void foo();
+
+int main()
+{
+ foo();
+ return 0;
+}
+
+/* { dg-final { scan-assembler "call\[ \t\]\\*.*foo.*@GOTPCREL\\(%rip\\)" } } */
Index: testsuite/gcc.target/i386/noplt-4.c
===================================================================
--- testsuite/gcc.target/i386/noplt-4.c (revision 0)
+++ testsuite/gcc.target/i386/noplt-4.c (working copy)
@@ -0,0 +1,11 @@
+/* { dg-do compile { target x86_64-*-linux* } } */
+/* { dg-options "-O2 -fno-pic -fno-plt" } */
+
+int foo();
+
+int main()
+{
+ return foo();
+}
+
+/* { dg-final { scan-assembler "jmp\[ \t\]\\*.*foo.*@GOTPCREL\\(%rip\\)" } } */
next prev parent reply other threads:[~2015-06-02 19:59 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
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 [this message]
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
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