From: Sriraman Tallam <tmsriram@google.com>
To: Richard Henderson <rth@redhat.com>
Cc: 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: Thu, 04 Jun 2015 16:56:00 -0000 [thread overview]
Message-ID: <CAAs8HmxAmAZQ2hJnV0WiKFJq7o9OAG8BEikUr-JcX71J9+xkoA@mail.gmail.com> (raw)
In-Reply-To: <CAAs8HmyQ+emX+kzq+ciCyE-03C_aNXRF==Y21Y6nGBYEogfjzw@mail.gmail.com>
[-- Attachment #1: Type: text/plain, Size: 748 bytes --]
> Patch attached with those changes.
Is this patch alright to commit?
* c-family/c-common.c (noplt): New attribute.
(handle_noplt_attribute): New handler.
* calls.c (prepare_call_address): Check for noplt attribute.
* config/i386/i386.c (ix86_function_ok_for_sibcall): Check
for noplt attribute.
(ix86_expand_call): Ditto.
(ix86_nopic_noplt_attribute_p): New function.
(ix86_output_call_insn): Output indirect call for non-pic no plt calls.
* doc/extend.texi (noplt): Document new attribute.
* doc/invoke.texi: 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.
Thanks
Sri
[-- Attachment #2: noplt_attrib_patch_new.txt --]
[-- Type: text/plain, Size: 10794 bytes --]
* c-family/c-common.c (noplt): New attribute.
(handle_noplt_attribute): New handler.
* calls.c (prepare_call_address): Check for noplt
attribute.
* config/i386/i386.c (ix86_function_ok_for_sibcall): Check
for noplt attribute.
(ix86_expand_call): Ditto.
(ix86_nopic_noplt_attribute_p): New function.
(ix86_output_call_insn): Output indirect call for non-pic
no plt calls.
* doc/extend.texi (noplt): Document new attribute.
* doc/invoke.texi: 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 "noplt" 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_noplt_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 },
+ { "noplt", 0, 0, true, false, false,
+ handle_noplt_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 "noplt" attribute; arguments as in
+ struct attribute_spec.handler. */
+
+static tree
+handle_noplt_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)
@@ -226,10 +226,16 @@ 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 ("noplt", DECL_ATTRIBUTES (fndecl_or_type)))
&& !targetm.binds_local_p (fndecl_or_type))
{
+ /* This is done only for PIC code. There is no easy interface to force the
+ function address into GOT for non-PIC case. non-PIC case needs to be
+ handled specially by the backend. */
funexp = force_reg (Pmode, funexp);
}
else if (! sibcallp)
Index: config/i386/i386.c
===================================================================
--- config/i386/i386.c (revision 223720)
+++ config/i386/i386.c (working copy)
@@ -25497,13 +25497,18 @@ 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 "noplt" 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
+ && !lookup_attribute ("noplt",
+ 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 ())
@@ -25598,7 +25603,31 @@ ix86_expand_call (rtx retval, rtx fnaddr, rtx call
return call;
}
+/* Return true if the function being called was marked with attribute "noplt"
+ or using -fno-plt and we are compiling for non-PIC and x86_64. We need to
+ handle the non-PIC case in the backend because there is no easy interface
+ for the front-end to force non-PLT calls to use the GOT. This is currently
+ used only with 64-bit ELF targets to call the function marked "noplt"
+ indirectly. */
+static bool
+ix86_nopic_noplt_attribute_p (rtx call_op)
+{
+ if (flag_pic || ix86_cmodel == CM_LARGE
+ || !TARGET_64BIT || TARGET_MACHO|| TARGET_SEH || TARGET_PECOFF
+ || SYMBOL_REF_LOCAL_P (call_op))
+ return false;
+
+ tree symbol_decl = SYMBOL_REF_DECL (call_op);
+
+ if (!flag_plt
+ || (symbol_decl != NULL_TREE
+ && lookup_attribute ("noplt", DECL_ATTRIBUTES (symbol_decl))))
+ return true;
+
+ return false;
+}
+
/* Output the assembly for a call instruction. */
const char *
@@ -25610,7 +25639,9 @@ ix86_output_call_insn (rtx_insn *insn, rtx call_op
if (SIBLING_CALL_P (insn))
{
- if (direct_p)
+ if (direct_p && ix86_nopic_noplt_attribute_p (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 +25684,9 @@ ix86_output_call_insn (rtx_insn *insn, rtx call_op
seh_nop_p = true;
}
- if (direct_p)
+ if (direct_p && ix86_nopic_noplt_attribute_p (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 +2916,35 @@ 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 noplt
+@cindex @code{noplt} function attribute
+The @code{noplt} attribute is the counterpart to option @option{-fno-plt} and
+does not use PLT for calls to functions marked with this attribute in position
+independent code.
+
+@smallexample
+@group
+/* Externally defined function foo. */
+int foo () __attribute__ ((noplt));
+
+int
+main (/* @r{@dots{}} */)
+@{
+ /* @r{@dots{}} */
+ foo ();
+ /* @r{@dots{}} */
+@}
+@end group
+@end smallexample
+
+The @code{noplt} attribute on function foo tells the compiler to assume that
+the function foo is externally defined and the call to foo must avoid the PLT
+in position independent code.
+
+Additionally, a few targets also convert calls to those functions that are
+marked to not use the PLT to use the GOT instead for non-position independent
+code.
+
@item optimize
@cindex @code{optimize} function attribute
The @code{optimize} attribute is used to specify that a function is to
Index: doc/invoke.texi
===================================================================
--- doc/invoke.texi (revision 223720)
+++ doc/invoke.texi (working copy)
@@ -23868,6 +23868,14 @@ PLT stubs expect GOT pointer in a specific registe
register allocation freedom to the compiler. Lazy binding requires PLT:
with @option{-fno-plt} all external symbols are resolved at load time.
+Alternatively, function attribute @code{noplt} can be used to avoid PLT
+for calls to specific external functions by marking those functions with
+this attribute.
+
+Additionally, a few targets also convert calls to those functions that are
+marked to not use the PLT to use the GOT instead for non-position independent
+code.
+
@item -fno-jump-tables
@opindex fno-jump-tables
Do not use jump tables for switch statements even where it would be
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__ ((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-*-linux* } } */
+/* { dg-options "-O2 -fno-pic" } */
+
+
+__attribute__ ((noplt))
+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:[~2015-06-04 16:54 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
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 [this message]
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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