Patchwork [google] Add attributes: always_patch_for_instrumentation and never_patch_for_instrumentation (issue6821051)

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Submitter Harshit Chopra
Date Oct. 31, 2012, 12:15 a.m.
Message ID <20121031001531.5D197121AAA@hchopra.mtv.corp.google.com>
Download mbox | patch
Permalink /patch/195667/
State New
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Comments

Harshit Chopra - Oct. 31, 2012, 12:15 a.m.
Adding function attributes: 'always_patch_for_instrumentation' and 'never_patch_for_instrumentation' to always patch a function or to never patch a function, respectively, when given the option -mpatch-functions-for-instrumentation. Additionally, the attribute always_patch_for_instrumentation disables inlining of that function.

Tested:
  Tested by 'crosstool-validate.py --crosstool_ver=16 --testers=crosstool'

ChangeLog:

2012-10-30  Harshit Chopra <harshit@google.com>

	* gcc/c-family/c-common.c (handle_always_patch_for_instrumentation_attribute): Handle
  always_patch_for_instrumentation attribute and turn inlining off for the function.
	(handle_never_patch_for_instrumentation_attribute): Handle never_patch_for_instrumentation
  attribute of a function.
	* gcc/config/i386/i386.c (check_should_patch_current_function): Takes into account
  always_patch_for_instrumentation or never_patch_for_instrumentation attribute when
  deciding that a function should be patched.
	* gcc/testsuite/gcc.target/i386/patch-functions-force-no-patching.c: Test case
  to test for never_patch_for_instrumentation attribute.
	* gcc/testsuite/gcc.target/i386/patch-functions-force-patching.c: Test case to
  test for always_patch_for_instrumentation attribute.
	* gcc/tree.h (struct GTY): Add fields for the two attributes and macros to access
  the fields.

--
This patch is available for review at http://codereview.appspot.com/6821051
Xinliang David Li - Nov. 3, 2012, 7:38 p.m.
Harshit, Nov 5 is the gcc48 cutoff date. If you want to have the x-ray
instrumentation feature into this release, you will need to port your
patch and submit for trunk review now.


On Tue, Oct 30, 2012 at 5:15 PM, Harshit Chopra <harshit@google.com> wrote:
> Adding function attributes: 'always_patch_for_instrumentation' and 'never_patch_for_instrumentation' to always patch a function or to never patch a function, respectively, when given the option -mpatch-functions-for-instrumentation. Additionally, the attribute always_patch_for_instrumentation disables inlining of that function.
>
> Tested:
>   Tested by 'crosstool-validate.py --crosstool_ver=16 --testers=crosstool'
>
> ChangeLog:
>
> 2012-10-30  Harshit Chopra <harshit@google.com>
>
>         * gcc/c-family/c-common.c (handle_always_patch_for_instrumentation_attribute): Handle
>   always_patch_for_instrumentation attribute and turn inlining off for the function.
>         (handle_never_patch_for_instrumentation_attribute): Handle never_patch_for_instrumentation
>   attribute of a function.
>         * gcc/config/i386/i386.c (check_should_patch_current_function): Takes into account
>   always_patch_for_instrumentation or never_patch_for_instrumentation attribute when
>   deciding that a function should be patched.
>         * gcc/testsuite/gcc.target/i386/patch-functions-force-no-patching.c: Test case
>   to test for never_patch_for_instrumentation attribute.
>         * gcc/testsuite/gcc.target/i386/patch-functions-force-patching.c: Test case to
>   test for always_patch_for_instrumentation attribute.
>         * gcc/tree.h (struct GTY): Add fields for the two attributes and macros to access
>   the fields.
> diff --git a/gcc/c-family/c-common.c b/gcc/c-family/c-common.c
> index ab416ff..998645d 100644
> --- a/gcc/c-family/c-common.c
> +++ b/gcc/c-family/c-common.c
> @@ -396,6 +396,13 @@ static tree ignore_attribute (tree *, tree, tree, int, bool *);
>  static tree handle_no_split_stack_attribute (tree *, tree, tree, int, bool *);
>  static tree handle_fnspec_attribute (tree *, tree, tree, int, bool *);
>
> +static tree handle_always_patch_for_instrumentation_attribute (tree *, tree,
> +                                                               tree, int,
> +                                                               bool *);

Move bool * to the previous line.

> +static tree handle_never_patch_for_instrumentation_attribute (tree *, tree,
> +                                                              tree, int,
> +                                                              bool *);
> +

Same here.

>  static void check_function_nonnull (tree, int, tree *);
>  static void check_nonnull_arg (void *, tree, unsigned HOST_WIDE_INT);
>  static bool nonnull_check_p (tree, unsigned HOST_WIDE_INT);
> @@ -804,6 +811,13 @@ const struct attribute_spec c_common_attribute_table[] =
>       The name contains space to prevent its usage in source code.  */
>    { "fn spec",               1, 1, false, true, true,
>                               handle_fnspec_attribute, false },
> +  { "always_patch_for_instrumentation", 0, 0, true,  false, false,
> +                              handle_always_patch_for_instrumentation_attribute,
> +                              false },
> +  { "never_patch_for_instrumentation", 0, 0, true,  false, false,
> +                              handle_never_patch_for_instrumentation_attribute,
> +                              false },
> +
>    { NULL,                     0, 0, false, false, false, NULL, false }
>  };
>
> @@ -9158,6 +9172,48 @@ handle_no_thread_safety_analysis_attribute (tree *node, tree name,
>    return NULL_TREE;
>  }
>
> +/* Handle a "always_patch_for_instrumentation" attribute; arguments as in
> +   struct attribute_spec.handler.  */

Add new line here

> +static tree
> +handle_always_patch_for_instrumentation_attribute (tree *node, tree name,
> +                                                   tree ARG_UNUSED (args),
> +                                                   int ARG_UNUSED (flags),
> +                                                   bool *no_add_attrs)
> +{
> +  if (TREE_CODE (*node) == FUNCTION_DECL)
> +    {
> +      DECL_FORCE_PATCHING_FOR_INSTRUMENTATION (*node) = 1;
> +      DECL_UNINLINABLE (*node) = 1;
> +    }
> +  else
> +    {
> +      warning (OPT_Wattributes, "%qE attribute ignored", name);
> +      *no_add_attrs = true;
> +    }
> +  return NULL_TREE;
> +}
> +
> +
> +/* Handle a "never_patch_for_instrumentation" attribute; arguments as in
> +   struct attribute_spec.handler.  */

A new line here.

> +static tree
> +handle_never_patch_for_instrumentation_attribute (tree *node, tree name,
> +                                                  tree ARG_UNUSED (args),
> +                                                  int ARG_UNUSED (flags),
> +                                                  bool *no_add_attrs)
> +{
> +  if (TREE_CODE (*node) == FUNCTION_DECL)
> +    DECL_FORCE_NO_PATCHING_FOR_INSTRUMENTATION (*node) = 1;

Probably no need for this. The attribute will be attached to the decl
node -- can be queried using lookup_attribute method.

> +  else
> +    {
> +      warning (OPT_Wattributes, "%qE attribute ignored", name);
> +      *no_add_attrs = true;
> +    }
> +  return NULL_TREE;
> +}
> +
> +
> +
>  /* Check for valid arguments being passed to a function with FNTYPE.
>     There are NARGS arguments in the array ARGARRAY.  */
>  void
> diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
> index 6972ae6..b1475bf 100644
> --- a/gcc/config/i386/i386.c
> +++ b/gcc/config/i386/i386.c
> @@ -10983,6 +10983,13 @@ check_should_patch_current_function (void)
>    int num_loops = 0;
>    int min_functions_instructions;
>
> +  /* If a function has an attribute forcing patching on or off, do as it
> +     indicates.  */
> +  if (DECL_FORCE_PATCHING_FOR_INSTRUMENTATION (current_function_decl))
> +    return true;
> +  else if (DECL_FORCE_NO_PATCHING_FOR_INSTRUMENTATION (current_function_decl))
> +    return false;
> +
>    /* Patch the function if it has at least a loop.  */
>    if (!patch_functions_ignore_loops)
>      {
> diff --git a/gcc/testsuite/gcc.target/i386/patch-functions-force-no-patching.c b/gcc/testsuite/gcc.target/i386/patch-functions-force-no-patching.c
> new file mode 100644
> index 0000000..cad6f2d
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/i386/patch-functions-force-no-patching.c
> @@ -0,0 +1,27 @@
> +/* { dg-do compile } */
> +/* { dg-require-effective-target lp64 } */
> +/* { dg-options "-mpatch-functions-for-instrumentation -mno-patch-functions-main-always" } */

>  /* Nonzero if a FUNCTION_CODE is a TM load/store.  */
>  #define BUILTIN_TM_LOAD_STORE_P(FN) \
>    ((FN) >= BUILT_IN_TM_STORE_1 && (FN) <= BUILT_IN_TM_LOAD_RFW_LDOUBLE)
> @@ -3586,7 +3596,8 @@ struct GTY(()) tree_function_decl {
>    unsigned has_debug_args_flag : 1;
>    unsigned tm_clone_flag : 1;
>
> -  /* 1 bit left */
> +  unsigned force_patching_for_instrumentation : 1;
> +  unsigned force_no_patching_for_instrumentation : 1;


I don't think you should use precious bits here -- directly query the
attributes.

thanks,

David

>  };
>
>  /* The source language of the translation-unit.  */
>
> --
> This patch is available for review at http://codereview.appspot.com/6821051
Harshit Chopra - Nov. 5, 2012, 8:20 p.m.
Thanks David for the review. My comments are inline.


On Sat, Nov 3, 2012 at 12:38 PM, Xinliang David Li <davidxl@google.com> wrote:
>
> Harshit, Nov 5 is the gcc48 cutoff date. If you want to have the x-ray
> instrumentation feature into this release, you will need to port your
> patch and submit for trunk review now.


I am a bit too late now, I guess. If I target for the next release,
will it create any issues for the gcc48 release?

>
>
>
> On Tue, Oct 30, 2012 at 5:15 PM, Harshit Chopra <harshit@google.com> wrote:
> > Adding function attributes: 'always_patch_for_instrumentation' and 'never_patch_for_instrumentation' to always patch a function or to never patch a function, respectively, when given the option -mpatch-functions-for-instrumentation. Additionally, the attribute always_patch_for_instrumentation disables inlining of that function.
> >
> > Tested:
> >   Tested by 'crosstool-validate.py --crosstool_ver=16 --testers=crosstool'
> >
> > ChangeLog:
> >
> > 2012-10-30  Harshit Chopra <harshit@google.com>
> >
> >         * gcc/c-family/c-common.c (handle_always_patch_for_instrumentation_attribute): Handle
> >   always_patch_for_instrumentation attribute and turn inlining off for the function.
> >         (handle_never_patch_for_instrumentation_attribute): Handle never_patch_for_instrumentation
> >   attribute of a function.
> >         * gcc/config/i386/i386.c (check_should_patch_current_function): Takes into account
> >   always_patch_for_instrumentation or never_patch_for_instrumentation attribute when
> >   deciding that a function should be patched.
> >         * gcc/testsuite/gcc.target/i386/patch-functions-force-no-patching.c: Test case
> >   to test for never_patch_for_instrumentation attribute.
> >         * gcc/testsuite/gcc.target/i386/patch-functions-force-patching.c: Test case to
> >   test for always_patch_for_instrumentation attribute.
> >         * gcc/tree.h (struct GTY): Add fields for the two attributes and macros to access
> >   the fields.
> > diff --git a/gcc/c-family/c-common.c b/gcc/c-family/c-common.c
> > index ab416ff..998645d 100644
> > --- a/gcc/c-family/c-common.c
> > +++ b/gcc/c-family/c-common.c
> > @@ -396,6 +396,13 @@ static tree ignore_attribute (tree *, tree, tree, int, bool *);
> >  static tree handle_no_split_stack_attribute (tree *, tree, tree, int, bool *);
> >  static tree handle_fnspec_attribute (tree *, tree, tree, int, bool *);
> >
> > +static tree handle_always_patch_for_instrumentation_attribute (tree *, tree,
> > +                                                               tree, int,
> > +                                                               bool *);
>
> Move bool * to the previous line.


If I do that, it goes beyond the 80 char boundary.

>
>
> > +static tree handle_never_patch_for_instrumentation_attribute (tree *, tree,
> > +                                                              tree, int,
> > +                                                              bool *);
> > +
>
> Same here.


As above.

>
>
> >  static void check_function_nonnull (tree, int, tree *);
> >  static void check_nonnull_arg (void *, tree, unsigned HOST_WIDE_INT);
> >  static bool nonnull_check_p (tree, unsigned HOST_WIDE_INT);
> > @@ -804,6 +811,13 @@ const struct attribute_spec c_common_attribute_table[] =
> >       The name contains space to prevent its usage in source code.  */
> >    { "fn spec",               1, 1, false, true, true,
> >                               handle_fnspec_attribute, false },
> > +  { "always_patch_for_instrumentation", 0, 0, true,  false, false,
> > +                              handle_always_patch_for_instrumentation_attribute,
> > +                              false },
> > +  { "never_patch_for_instrumentation", 0, 0, true,  false, false,
> > +                              handle_never_patch_for_instrumentation_attribute,
> > +                              false },
> > +
> >    { NULL,                     0, 0, false, false, false, NULL, false }
> >  };
> >
> > @@ -9158,6 +9172,48 @@ handle_no_thread_safety_analysis_attribute (tree *node, tree name,
> >    return NULL_TREE;
> >  }
> >
> > +/* Handle a "always_patch_for_instrumentation" attribute; arguments as in
> > +   struct attribute_spec.handler.  */
>
> Add new line here


Done.

>
>
> > +static tree
> > +handle_always_patch_for_instrumentation_attribute (tree *node, tree name,
> > +                                                   tree ARG_UNUSED (args),
> > +                                                   int ARG_UNUSED (flags),
> > +                                                   bool *no_add_attrs)
> > +{
> > +  if (TREE_CODE (*node) == FUNCTION_DECL)
> > +    {
> > +      DECL_FORCE_PATCHING_FOR_INSTRUMENTATION (*node) = 1;
> > +      DECL_UNINLINABLE (*node) = 1;
> > +    }
> > +  else
> > +    {
> > +      warning (OPT_Wattributes, "%qE attribute ignored", name);
> > +      *no_add_attrs = true;
> > +    }
> > +  return NULL_TREE;
> > +}
> > +
> > +
> > +/* Handle a "never_patch_for_instrumentation" attribute; arguments as in
> > +   struct attribute_spec.handler.  */
>
> A new line here.


Done

>
>
> > +static tree
> > +handle_never_patch_for_instrumentation_attribute (tree *node, tree name,
> > +                                                  tree ARG_UNUSED (args),
> > +                                                  int ARG_UNUSED (flags),
> > +                                                  bool *no_add_attrs)
> > +{
> > +  if (TREE_CODE (*node) == FUNCTION_DECL)
> > +    DECL_FORCE_NO_PATCHING_FOR_INSTRUMENTATION (*node) = 1;
>
> Probably no need for this. The attribute will be attached to the decl
> node -- can be queried using lookup_attribute method.


Done.

>
>
> > +  else
> > +    {
> > +      warning (OPT_Wattributes, "%qE attribute ignored", name);
> > +      *no_add_attrs = true;
> > +    }
> > +  return NULL_TREE;
> > +}
> > +
> > +
> > +
> >  /* Check for valid arguments being passed to a function with FNTYPE.
> >     There are NARGS arguments in the array ARGARRAY.  */
> >  void
> > diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
> > index 6972ae6..b1475bf 100644
> > --- a/gcc/config/i386/i386.c
> > +++ b/gcc/config/i386/i386.c
> > @@ -10983,6 +10983,13 @@ check_should_patch_current_function (void)
> >    int num_loops = 0;
> >    int min_functions_instructions;
> >
> > +  /* If a function has an attribute forcing patching on or off, do as it
> > +     indicates.  */
> > +  if (DECL_FORCE_PATCHING_FOR_INSTRUMENTATION (current_function_decl))
> > +    return true;
> > +  else if (DECL_FORCE_NO_PATCHING_FOR_INSTRUMENTATION (current_function_decl))
> > +    return false;
> > +
> >    /* Patch the function if it has at least a loop.  */
> >    if (!patch_functions_ignore_loops)
> >      {
> > diff --git a/gcc/testsuite/gcc.target/i386/patch-functions-force-no-patching.c b/gcc/testsuite/gcc.target/i386/patch-functions-force-no-patching.c
> > new file mode 100644
> > index 0000000..cad6f2d
> > --- /dev/null
> > +++ b/gcc/testsuite/gcc.target/i386/patch-functions-force-no-patching.c
> > @@ -0,0 +1,27 @@
> > +/* { dg-do compile } */
> > +/* { dg-require-effective-target lp64 } */
> > +/* { dg-options "-mpatch-functions-for-instrumentation -mno-patch-functions-main-always" } */
>
> >  /* Nonzero if a FUNCTION_CODE is a TM load/store.  */
> >  #define BUILTIN_TM_LOAD_STORE_P(FN) \
> >    ((FN) >= BUILT_IN_TM_STORE_1 && (FN) <= BUILT_IN_TM_LOAD_RFW_LDOUBLE)
> > @@ -3586,7 +3596,8 @@ struct GTY(()) tree_function_decl {
> >    unsigned has_debug_args_flag : 1;
> >    unsigned tm_clone_flag : 1;
> >
> > -  /* 1 bit left */
> > +  unsigned force_patching_for_instrumentation : 1;
> > +  unsigned force_no_patching_for_instrumentation : 1;
>
>
> I don't think you should use precious bits here -- directly query the
> attributes.


Done.

>
>
> thanks,
>
> David
>
> >  };
> >
> >  /* The source language of the translation-unit.  */
> >
> > --
> > This patch is available for review at http://codereview.appspot.com/6821051
Xinliang David Li - Nov. 5, 2012, 8:29 p.m.
It does not hurt to submit the patch for review -- you need to provide
more background and motivation for this work
1) comparison with -finstrument-functions (runtime overhead etc)
2) use model difference (production binary ..)
3) Interesting examples of use cases (with graphs).

thanks,

David

On Mon, Nov 5, 2012 at 12:20 PM, Harshit Chopra <harshit@google.com> wrote:
> Thanks David for the review. My comments are inline.
>
>
> On Sat, Nov 3, 2012 at 12:38 PM, Xinliang David Li <davidxl@google.com> wrote:
>>
>> Harshit, Nov 5 is the gcc48 cutoff date. If you want to have the x-ray
>> instrumentation feature into this release, you will need to port your
>> patch and submit for trunk review now.
>
>
> I am a bit too late now, I guess. If I target for the next release,
> will it create any issues for the gcc48 release?
>
>>
>>
>>
>> On Tue, Oct 30, 2012 at 5:15 PM, Harshit Chopra <harshit@google.com> wrote:
>> > Adding function attributes: 'always_patch_for_instrumentation' and 'never_patch_for_instrumentation' to always patch a function or to never patch a function, respectively, when given the option -mpatch-functions-for-instrumentation. Additionally, the attribute always_patch_for_instrumentation disables inlining of that function.
>> >
>> > Tested:
>> >   Tested by 'crosstool-validate.py --crosstool_ver=16 --testers=crosstool'
>> >
>> > ChangeLog:
>> >
>> > 2012-10-30  Harshit Chopra <harshit@google.com>
>> >
>> >         * gcc/c-family/c-common.c (handle_always_patch_for_instrumentation_attribute): Handle
>> >   always_patch_for_instrumentation attribute and turn inlining off for the function.
>> >         (handle_never_patch_for_instrumentation_attribute): Handle never_patch_for_instrumentation
>> >   attribute of a function.
>> >         * gcc/config/i386/i386.c (check_should_patch_current_function): Takes into account
>> >   always_patch_for_instrumentation or never_patch_for_instrumentation attribute when
>> >   deciding that a function should be patched.
>> >         * gcc/testsuite/gcc.target/i386/patch-functions-force-no-patching.c: Test case
>> >   to test for never_patch_for_instrumentation attribute.
>> >         * gcc/testsuite/gcc.target/i386/patch-functions-force-patching.c: Test case to
>> >   test for always_patch_for_instrumentation attribute.
>> >         * gcc/tree.h (struct GTY): Add fields for the two attributes and macros to access
>> >   the fields.
>> > diff --git a/gcc/c-family/c-common.c b/gcc/c-family/c-common.c
>> > index ab416ff..998645d 100644
>> > --- a/gcc/c-family/c-common.c
>> > +++ b/gcc/c-family/c-common.c
>> > @@ -396,6 +396,13 @@ static tree ignore_attribute (tree *, tree, tree, int, bool *);
>> >  static tree handle_no_split_stack_attribute (tree *, tree, tree, int, bool *);
>> >  static tree handle_fnspec_attribute (tree *, tree, tree, int, bool *);
>> >
>> > +static tree handle_always_patch_for_instrumentation_attribute (tree *, tree,
>> > +                                                               tree, int,
>> > +                                                               bool *);
>>
>> Move bool * to the previous line.
>
>
> If I do that, it goes beyond the 80 char boundary.
>
>>
>>
>> > +static tree handle_never_patch_for_instrumentation_attribute (tree *, tree,
>> > +                                                              tree, int,
>> > +                                                              bool *);
>> > +
>>
>> Same here.
>
>
> As above.
>
>>
>>
>> >  static void check_function_nonnull (tree, int, tree *);
>> >  static void check_nonnull_arg (void *, tree, unsigned HOST_WIDE_INT);
>> >  static bool nonnull_check_p (tree, unsigned HOST_WIDE_INT);
>> > @@ -804,6 +811,13 @@ const struct attribute_spec c_common_attribute_table[] =
>> >       The name contains space to prevent its usage in source code.  */
>> >    { "fn spec",               1, 1, false, true, true,
>> >                               handle_fnspec_attribute, false },
>> > +  { "always_patch_for_instrumentation", 0, 0, true,  false, false,
>> > +                              handle_always_patch_for_instrumentation_attribute,
>> > +                              false },
>> > +  { "never_patch_for_instrumentation", 0, 0, true,  false, false,
>> > +                              handle_never_patch_for_instrumentation_attribute,
>> > +                              false },
>> > +
>> >    { NULL,                     0, 0, false, false, false, NULL, false }
>> >  };
>> >
>> > @@ -9158,6 +9172,48 @@ handle_no_thread_safety_analysis_attribute (tree *node, tree name,
>> >    return NULL_TREE;
>> >  }
>> >
>> > +/* Handle a "always_patch_for_instrumentation" attribute; arguments as in
>> > +   struct attribute_spec.handler.  */
>>
>> Add new line here
>
>
> Done.
>
>>
>>
>> > +static tree
>> > +handle_always_patch_for_instrumentation_attribute (tree *node, tree name,
>> > +                                                   tree ARG_UNUSED (args),
>> > +                                                   int ARG_UNUSED (flags),
>> > +                                                   bool *no_add_attrs)
>> > +{
>> > +  if (TREE_CODE (*node) == FUNCTION_DECL)
>> > +    {
>> > +      DECL_FORCE_PATCHING_FOR_INSTRUMENTATION (*node) = 1;
>> > +      DECL_UNINLINABLE (*node) = 1;
>> > +    }
>> > +  else
>> > +    {
>> > +      warning (OPT_Wattributes, "%qE attribute ignored", name);
>> > +      *no_add_attrs = true;
>> > +    }
>> > +  return NULL_TREE;
>> > +}
>> > +
>> > +
>> > +/* Handle a "never_patch_for_instrumentation" attribute; arguments as in
>> > +   struct attribute_spec.handler.  */
>>
>> A new line here.
>
>
> Done
>
>>
>>
>> > +static tree
>> > +handle_never_patch_for_instrumentation_attribute (tree *node, tree name,
>> > +                                                  tree ARG_UNUSED (args),
>> > +                                                  int ARG_UNUSED (flags),
>> > +                                                  bool *no_add_attrs)
>> > +{
>> > +  if (TREE_CODE (*node) == FUNCTION_DECL)
>> > +    DECL_FORCE_NO_PATCHING_FOR_INSTRUMENTATION (*node) = 1;
>>
>> Probably no need for this. The attribute will be attached to the decl
>> node -- can be queried using lookup_attribute method.
>
>
> Done.
>
>>
>>
>> > +  else
>> > +    {
>> > +      warning (OPT_Wattributes, "%qE attribute ignored", name);
>> > +      *no_add_attrs = true;
>> > +    }
>> > +  return NULL_TREE;
>> > +}
>> > +
>> > +
>> > +
>> >  /* Check for valid arguments being passed to a function with FNTYPE.
>> >     There are NARGS arguments in the array ARGARRAY.  */
>> >  void
>> > diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
>> > index 6972ae6..b1475bf 100644
>> > --- a/gcc/config/i386/i386.c
>> > +++ b/gcc/config/i386/i386.c
>> > @@ -10983,6 +10983,13 @@ check_should_patch_current_function (void)
>> >    int num_loops = 0;
>> >    int min_functions_instructions;
>> >
>> > +  /* If a function has an attribute forcing patching on or off, do as it
>> > +     indicates.  */
>> > +  if (DECL_FORCE_PATCHING_FOR_INSTRUMENTATION (current_function_decl))
>> > +    return true;
>> > +  else if (DECL_FORCE_NO_PATCHING_FOR_INSTRUMENTATION (current_function_decl))
>> > +    return false;
>> > +
>> >    /* Patch the function if it has at least a loop.  */
>> >    if (!patch_functions_ignore_loops)
>> >      {
>> > diff --git a/gcc/testsuite/gcc.target/i386/patch-functions-force-no-patching.c b/gcc/testsuite/gcc.target/i386/patch-functions-force-no-patching.c
>> > new file mode 100644
>> > index 0000000..cad6f2d
>> > --- /dev/null
>> > +++ b/gcc/testsuite/gcc.target/i386/patch-functions-force-no-patching.c
>> > @@ -0,0 +1,27 @@
>> > +/* { dg-do compile } */
>> > +/* { dg-require-effective-target lp64 } */
>> > +/* { dg-options "-mpatch-functions-for-instrumentation -mno-patch-functions-main-always" } */
>>
>> >  /* Nonzero if a FUNCTION_CODE is a TM load/store.  */
>> >  #define BUILTIN_TM_LOAD_STORE_P(FN) \
>> >    ((FN) >= BUILT_IN_TM_STORE_1 && (FN) <= BUILT_IN_TM_LOAD_RFW_LDOUBLE)
>> > @@ -3586,7 +3596,8 @@ struct GTY(()) tree_function_decl {
>> >    unsigned has_debug_args_flag : 1;
>> >    unsigned tm_clone_flag : 1;
>> >
>> > -  /* 1 bit left */
>> > +  unsigned force_patching_for_instrumentation : 1;
>> > +  unsigned force_no_patching_for_instrumentation : 1;
>>
>>
>> I don't think you should use precious bits here -- directly query the
>> attributes.
>
>
> Done.
>
>>
>>
>> thanks,
>>
>> David
>>
>> >  };
>> >
>> >  /* The source language of the translation-unit.  */
>> >
>> > --
>> > This patch is available for review at http://codereview.appspot.com/6821051
Harshit Chopra - Nov. 7, 2012, 1:17 a.m.
Yes, will do, but probably not so soon. Once I have some spare time to
prepare my case for this being useful to public.

Meanwhile, this patch is just for google-main and then I will port it
to google_4-7 and adds to the already existing functionality of
-mpatch-function-for-instrumentation.

Thanks,
Harshit


On Mon, Nov 5, 2012 at 12:29 PM, Xinliang David Li <davidxl@google.com> wrote:
> It does not hurt to submit the patch for review -- you need to provide
> more background and motivation for this work
> 1) comparison with -finstrument-functions (runtime overhead etc)
> 2) use model difference (production binary ..)
> 3) Interesting examples of use cases (with graphs).
>
> thanks,
>
> David
>
> On Mon, Nov 5, 2012 at 12:20 PM, Harshit Chopra <harshit@google.com> wrote:
>> Thanks David for the review. My comments are inline.
>>
>>
>> On Sat, Nov 3, 2012 at 12:38 PM, Xinliang David Li <davidxl@google.com> wrote:
>>>
>>> Harshit, Nov 5 is the gcc48 cutoff date. If you want to have the x-ray
>>> instrumentation feature into this release, you will need to port your
>>> patch and submit for trunk review now.
>>
>>
>> I am a bit too late now, I guess. If I target for the next release,
>> will it create any issues for the gcc48 release?
>>
>>>
>>>
>>>
>>> On Tue, Oct 30, 2012 at 5:15 PM, Harshit Chopra <harshit@google.com> wrote:
>>> > Adding function attributes: 'always_patch_for_instrumentation' and 'never_patch_for_instrumentation' to always patch a function or to never patch a function, respectively, when given the option -mpatch-functions-for-instrumentation. Additionally, the attribute always_patch_for_instrumentation disables inlining of that function.
>>> >
>>> > Tested:
>>> >   Tested by 'crosstool-validate.py --crosstool_ver=16 --testers=crosstool'
>>> >
>>> > ChangeLog:
>>> >
>>> > 2012-10-30  Harshit Chopra <harshit@google.com>
>>> >
>>> >         * gcc/c-family/c-common.c (handle_always_patch_for_instrumentation_attribute): Handle
>>> >   always_patch_for_instrumentation attribute and turn inlining off for the function.
>>> >         (handle_never_patch_for_instrumentation_attribute): Handle never_patch_for_instrumentation
>>> >   attribute of a function.
>>> >         * gcc/config/i386/i386.c (check_should_patch_current_function): Takes into account
>>> >   always_patch_for_instrumentation or never_patch_for_instrumentation attribute when
>>> >   deciding that a function should be patched.
>>> >         * gcc/testsuite/gcc.target/i386/patch-functions-force-no-patching.c: Test case
>>> >   to test for never_patch_for_instrumentation attribute.
>>> >         * gcc/testsuite/gcc.target/i386/patch-functions-force-patching.c: Test case to
>>> >   test for always_patch_for_instrumentation attribute.
>>> >         * gcc/tree.h (struct GTY): Add fields for the two attributes and macros to access
>>> >   the fields.
>>> > diff --git a/gcc/c-family/c-common.c b/gcc/c-family/c-common.c
>>> > index ab416ff..998645d 100644
>>> > --- a/gcc/c-family/c-common.c
>>> > +++ b/gcc/c-family/c-common.c
>>> > @@ -396,6 +396,13 @@ static tree ignore_attribute (tree *, tree, tree, int, bool *);
>>> >  static tree handle_no_split_stack_attribute (tree *, tree, tree, int, bool *);
>>> >  static tree handle_fnspec_attribute (tree *, tree, tree, int, bool *);
>>> >
>>> > +static tree handle_always_patch_for_instrumentation_attribute (tree *, tree,
>>> > +                                                               tree, int,
>>> > +                                                               bool *);
>>>
>>> Move bool * to the previous line.
>>
>>
>> If I do that, it goes beyond the 80 char boundary.
>>
>>>
>>>
>>> > +static tree handle_never_patch_for_instrumentation_attribute (tree *, tree,
>>> > +                                                              tree, int,
>>> > +                                                              bool *);
>>> > +
>>>
>>> Same here.
>>
>>
>> As above.
>>
>>>
>>>
>>> >  static void check_function_nonnull (tree, int, tree *);
>>> >  static void check_nonnull_arg (void *, tree, unsigned HOST_WIDE_INT);
>>> >  static bool nonnull_check_p (tree, unsigned HOST_WIDE_INT);
>>> > @@ -804,6 +811,13 @@ const struct attribute_spec c_common_attribute_table[] =
>>> >       The name contains space to prevent its usage in source code.  */
>>> >    { "fn spec",               1, 1, false, true, true,
>>> >                               handle_fnspec_attribute, false },
>>> > +  { "always_patch_for_instrumentation", 0, 0, true,  false, false,
>>> > +                              handle_always_patch_for_instrumentation_attribute,
>>> > +                              false },
>>> > +  { "never_patch_for_instrumentation", 0, 0, true,  false, false,
>>> > +                              handle_never_patch_for_instrumentation_attribute,
>>> > +                              false },
>>> > +
>>> >    { NULL,                     0, 0, false, false, false, NULL, false }
>>> >  };
>>> >
>>> > @@ -9158,6 +9172,48 @@ handle_no_thread_safety_analysis_attribute (tree *node, tree name,
>>> >    return NULL_TREE;
>>> >  }
>>> >
>>> > +/* Handle a "always_patch_for_instrumentation" attribute; arguments as in
>>> > +   struct attribute_spec.handler.  */
>>>
>>> Add new line here
>>
>>
>> Done.
>>
>>>
>>>
>>> > +static tree
>>> > +handle_always_patch_for_instrumentation_attribute (tree *node, tree name,
>>> > +                                                   tree ARG_UNUSED (args),
>>> > +                                                   int ARG_UNUSED (flags),
>>> > +                                                   bool *no_add_attrs)
>>> > +{
>>> > +  if (TREE_CODE (*node) == FUNCTION_DECL)
>>> > +    {
>>> > +      DECL_FORCE_PATCHING_FOR_INSTRUMENTATION (*node) = 1;
>>> > +      DECL_UNINLINABLE (*node) = 1;
>>> > +    }
>>> > +  else
>>> > +    {
>>> > +      warning (OPT_Wattributes, "%qE attribute ignored", name);
>>> > +      *no_add_attrs = true;
>>> > +    }
>>> > +  return NULL_TREE;
>>> > +}
>>> > +
>>> > +
>>> > +/* Handle a "never_patch_for_instrumentation" attribute; arguments as in
>>> > +   struct attribute_spec.handler.  */
>>>
>>> A new line here.
>>
>>
>> Done
>>
>>>
>>>
>>> > +static tree
>>> > +handle_never_patch_for_instrumentation_attribute (tree *node, tree name,
>>> > +                                                  tree ARG_UNUSED (args),
>>> > +                                                  int ARG_UNUSED (flags),
>>> > +                                                  bool *no_add_attrs)
>>> > +{
>>> > +  if (TREE_CODE (*node) == FUNCTION_DECL)
>>> > +    DECL_FORCE_NO_PATCHING_FOR_INSTRUMENTATION (*node) = 1;
>>>
>>> Probably no need for this. The attribute will be attached to the decl
>>> node -- can be queried using lookup_attribute method.
>>
>>
>> Done.
>>
>>>
>>>
>>> > +  else
>>> > +    {
>>> > +      warning (OPT_Wattributes, "%qE attribute ignored", name);
>>> > +      *no_add_attrs = true;
>>> > +    }
>>> > +  return NULL_TREE;
>>> > +}
>>> > +
>>> > +
>>> > +
>>> >  /* Check for valid arguments being passed to a function with FNTYPE.
>>> >     There are NARGS arguments in the array ARGARRAY.  */
>>> >  void
>>> > diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
>>> > index 6972ae6..b1475bf 100644
>>> > --- a/gcc/config/i386/i386.c
>>> > +++ b/gcc/config/i386/i386.c
>>> > @@ -10983,6 +10983,13 @@ check_should_patch_current_function (void)
>>> >    int num_loops = 0;
>>> >    int min_functions_instructions;
>>> >
>>> > +  /* If a function has an attribute forcing patching on or off, do as it
>>> > +     indicates.  */
>>> > +  if (DECL_FORCE_PATCHING_FOR_INSTRUMENTATION (current_function_decl))
>>> > +    return true;
>>> > +  else if (DECL_FORCE_NO_PATCHING_FOR_INSTRUMENTATION (current_function_decl))
>>> > +    return false;
>>> > +
>>> >    /* Patch the function if it has at least a loop.  */
>>> >    if (!patch_functions_ignore_loops)
>>> >      {
>>> > diff --git a/gcc/testsuite/gcc.target/i386/patch-functions-force-no-patching.c b/gcc/testsuite/gcc.target/i386/patch-functions-force-no-patching.c
>>> > new file mode 100644
>>> > index 0000000..cad6f2d
>>> > --- /dev/null
>>> > +++ b/gcc/testsuite/gcc.target/i386/patch-functions-force-no-patching.c
>>> > @@ -0,0 +1,27 @@
>>> > +/* { dg-do compile } */
>>> > +/* { dg-require-effective-target lp64 } */
>>> > +/* { dg-options "-mpatch-functions-for-instrumentation -mno-patch-functions-main-always" } */
>>>
>>> >  /* Nonzero if a FUNCTION_CODE is a TM load/store.  */
>>> >  #define BUILTIN_TM_LOAD_STORE_P(FN) \
>>> >    ((FN) >= BUILT_IN_TM_STORE_1 && (FN) <= BUILT_IN_TM_LOAD_RFW_LDOUBLE)
>>> > @@ -3586,7 +3596,8 @@ struct GTY(()) tree_function_decl {
>>> >    unsigned has_debug_args_flag : 1;
>>> >    unsigned tm_clone_flag : 1;
>>> >
>>> > -  /* 1 bit left */
>>> > +  unsigned force_patching_for_instrumentation : 1;
>>> > +  unsigned force_no_patching_for_instrumentation : 1;
>>>
>>>
>>> I don't think you should use precious bits here -- directly query the
>>> attributes.
>>
>>
>> Done.
>>
>>>
>>>
>>> thanks,
>>>
>>> David
>>>
>>> >  };
>>> >
>>> >  /* The source language of the translation-unit.  */
>>> >
>>> > --
>>> > This patch is available for review at http://codereview.appspot.com/6821051
Xinliang David Li - Nov. 7, 2012, 4:44 p.m.
ok for google branches.

David

On Tue, Nov 6, 2012 at 5:17 PM, Harshit Chopra <harshit@google.com> wrote:
> Yes, will do, but probably not so soon. Once I have some spare time to
> prepare my case for this being useful to public.
>
> Meanwhile, this patch is just for google-main and then I will port it
> to google_4-7 and adds to the already existing functionality of
> -mpatch-function-for-instrumentation.
>
> Thanks,
> Harshit
>
>
> On Mon, Nov 5, 2012 at 12:29 PM, Xinliang David Li <davidxl@google.com> wrote:
>> It does not hurt to submit the patch for review -- you need to provide
>> more background and motivation for this work
>> 1) comparison with -finstrument-functions (runtime overhead etc)
>> 2) use model difference (production binary ..)
>> 3) Interesting examples of use cases (with graphs).
>>
>> thanks,
>>
>> David
>>
>> On Mon, Nov 5, 2012 at 12:20 PM, Harshit Chopra <harshit@google.com> wrote:
>>> Thanks David for the review. My comments are inline.
>>>
>>>
>>> On Sat, Nov 3, 2012 at 12:38 PM, Xinliang David Li <davidxl@google.com> wrote:
>>>>
>>>> Harshit, Nov 5 is the gcc48 cutoff date. If you want to have the x-ray
>>>> instrumentation feature into this release, you will need to port your
>>>> patch and submit for trunk review now.
>>>
>>>
>>> I am a bit too late now, I guess. If I target for the next release,
>>> will it create any issues for the gcc48 release?
>>>
>>>>
>>>>
>>>>
>>>> On Tue, Oct 30, 2012 at 5:15 PM, Harshit Chopra <harshit@google.com> wrote:
>>>> > Adding function attributes: 'always_patch_for_instrumentation' and 'never_patch_for_instrumentation' to always patch a function or to never patch a function, respectively, when given the option -mpatch-functions-for-instrumentation. Additionally, the attribute always_patch_for_instrumentation disables inlining of that function.
>>>> >
>>>> > Tested:
>>>> >   Tested by 'crosstool-validate.py --crosstool_ver=16 --testers=crosstool'
>>>> >
>>>> > ChangeLog:
>>>> >
>>>> > 2012-10-30  Harshit Chopra <harshit@google.com>
>>>> >
>>>> >         * gcc/c-family/c-common.c (handle_always_patch_for_instrumentation_attribute): Handle
>>>> >   always_patch_for_instrumentation attribute and turn inlining off for the function.
>>>> >         (handle_never_patch_for_instrumentation_attribute): Handle never_patch_for_instrumentation
>>>> >   attribute of a function.
>>>> >         * gcc/config/i386/i386.c (check_should_patch_current_function): Takes into account
>>>> >   always_patch_for_instrumentation or never_patch_for_instrumentation attribute when
>>>> >   deciding that a function should be patched.
>>>> >         * gcc/testsuite/gcc.target/i386/patch-functions-force-no-patching.c: Test case
>>>> >   to test for never_patch_for_instrumentation attribute.
>>>> >         * gcc/testsuite/gcc.target/i386/patch-functions-force-patching.c: Test case to
>>>> >   test for always_patch_for_instrumentation attribute.
>>>> >         * gcc/tree.h (struct GTY): Add fields for the two attributes and macros to access
>>>> >   the fields.
>>>> > diff --git a/gcc/c-family/c-common.c b/gcc/c-family/c-common.c
>>>> > index ab416ff..998645d 100644
>>>> > --- a/gcc/c-family/c-common.c
>>>> > +++ b/gcc/c-family/c-common.c
>>>> > @@ -396,6 +396,13 @@ static tree ignore_attribute (tree *, tree, tree, int, bool *);
>>>> >  static tree handle_no_split_stack_attribute (tree *, tree, tree, int, bool *);
>>>> >  static tree handle_fnspec_attribute (tree *, tree, tree, int, bool *);
>>>> >
>>>> > +static tree handle_always_patch_for_instrumentation_attribute (tree *, tree,
>>>> > +                                                               tree, int,
>>>> > +                                                               bool *);
>>>>
>>>> Move bool * to the previous line.
>>>
>>>
>>> If I do that, it goes beyond the 80 char boundary.
>>>
>>>>
>>>>
>>>> > +static tree handle_never_patch_for_instrumentation_attribute (tree *, tree,
>>>> > +                                                              tree, int,
>>>> > +                                                              bool *);
>>>> > +
>>>>
>>>> Same here.
>>>
>>>
>>> As above.
>>>
>>>>
>>>>
>>>> >  static void check_function_nonnull (tree, int, tree *);
>>>> >  static void check_nonnull_arg (void *, tree, unsigned HOST_WIDE_INT);
>>>> >  static bool nonnull_check_p (tree, unsigned HOST_WIDE_INT);
>>>> > @@ -804,6 +811,13 @@ const struct attribute_spec c_common_attribute_table[] =
>>>> >       The name contains space to prevent its usage in source code.  */
>>>> >    { "fn spec",               1, 1, false, true, true,
>>>> >                               handle_fnspec_attribute, false },
>>>> > +  { "always_patch_for_instrumentation", 0, 0, true,  false, false,
>>>> > +                              handle_always_patch_for_instrumentation_attribute,
>>>> > +                              false },
>>>> > +  { "never_patch_for_instrumentation", 0, 0, true,  false, false,
>>>> > +                              handle_never_patch_for_instrumentation_attribute,
>>>> > +                              false },
>>>> > +
>>>> >    { NULL,                     0, 0, false, false, false, NULL, false }
>>>> >  };
>>>> >
>>>> > @@ -9158,6 +9172,48 @@ handle_no_thread_safety_analysis_attribute (tree *node, tree name,
>>>> >    return NULL_TREE;
>>>> >  }
>>>> >
>>>> > +/* Handle a "always_patch_for_instrumentation" attribute; arguments as in
>>>> > +   struct attribute_spec.handler.  */
>>>>
>>>> Add new line here
>>>
>>>
>>> Done.
>>>
>>>>
>>>>
>>>> > +static tree
>>>> > +handle_always_patch_for_instrumentation_attribute (tree *node, tree name,
>>>> > +                                                   tree ARG_UNUSED (args),
>>>> > +                                                   int ARG_UNUSED (flags),
>>>> > +                                                   bool *no_add_attrs)
>>>> > +{
>>>> > +  if (TREE_CODE (*node) == FUNCTION_DECL)
>>>> > +    {
>>>> > +      DECL_FORCE_PATCHING_FOR_INSTRUMENTATION (*node) = 1;
>>>> > +      DECL_UNINLINABLE (*node) = 1;
>>>> > +    }
>>>> > +  else
>>>> > +    {
>>>> > +      warning (OPT_Wattributes, "%qE attribute ignored", name);
>>>> > +      *no_add_attrs = true;
>>>> > +    }
>>>> > +  return NULL_TREE;
>>>> > +}
>>>> > +
>>>> > +
>>>> > +/* Handle a "never_patch_for_instrumentation" attribute; arguments as in
>>>> > +   struct attribute_spec.handler.  */
>>>>
>>>> A new line here.
>>>
>>>
>>> Done
>>>
>>>>
>>>>
>>>> > +static tree
>>>> > +handle_never_patch_for_instrumentation_attribute (tree *node, tree name,
>>>> > +                                                  tree ARG_UNUSED (args),
>>>> > +                                                  int ARG_UNUSED (flags),
>>>> > +                                                  bool *no_add_attrs)
>>>> > +{
>>>> > +  if (TREE_CODE (*node) == FUNCTION_DECL)
>>>> > +    DECL_FORCE_NO_PATCHING_FOR_INSTRUMENTATION (*node) = 1;
>>>>
>>>> Probably no need for this. The attribute will be attached to the decl
>>>> node -- can be queried using lookup_attribute method.
>>>
>>>
>>> Done.
>>>
>>>>
>>>>
>>>> > +  else
>>>> > +    {
>>>> > +      warning (OPT_Wattributes, "%qE attribute ignored", name);
>>>> > +      *no_add_attrs = true;
>>>> > +    }
>>>> > +  return NULL_TREE;
>>>> > +}
>>>> > +
>>>> > +
>>>> > +
>>>> >  /* Check for valid arguments being passed to a function with FNTYPE.
>>>> >     There are NARGS arguments in the array ARGARRAY.  */
>>>> >  void
>>>> > diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
>>>> > index 6972ae6..b1475bf 100644
>>>> > --- a/gcc/config/i386/i386.c
>>>> > +++ b/gcc/config/i386/i386.c
>>>> > @@ -10983,6 +10983,13 @@ check_should_patch_current_function (void)
>>>> >    int num_loops = 0;
>>>> >    int min_functions_instructions;
>>>> >
>>>> > +  /* If a function has an attribute forcing patching on or off, do as it
>>>> > +     indicates.  */
>>>> > +  if (DECL_FORCE_PATCHING_FOR_INSTRUMENTATION (current_function_decl))
>>>> > +    return true;
>>>> > +  else if (DECL_FORCE_NO_PATCHING_FOR_INSTRUMENTATION (current_function_decl))
>>>> > +    return false;
>>>> > +
>>>> >    /* Patch the function if it has at least a loop.  */
>>>> >    if (!patch_functions_ignore_loops)
>>>> >      {
>>>> > diff --git a/gcc/testsuite/gcc.target/i386/patch-functions-force-no-patching.c b/gcc/testsuite/gcc.target/i386/patch-functions-force-no-patching.c
>>>> > new file mode 100644
>>>> > index 0000000..cad6f2d
>>>> > --- /dev/null
>>>> > +++ b/gcc/testsuite/gcc.target/i386/patch-functions-force-no-patching.c
>>>> > @@ -0,0 +1,27 @@
>>>> > +/* { dg-do compile } */
>>>> > +/* { dg-require-effective-target lp64 } */
>>>> > +/* { dg-options "-mpatch-functions-for-instrumentation -mno-patch-functions-main-always" } */
>>>>
>>>> >  /* Nonzero if a FUNCTION_CODE is a TM load/store.  */
>>>> >  #define BUILTIN_TM_LOAD_STORE_P(FN) \
>>>> >    ((FN) >= BUILT_IN_TM_STORE_1 && (FN) <= BUILT_IN_TM_LOAD_RFW_LDOUBLE)
>>>> > @@ -3586,7 +3596,8 @@ struct GTY(()) tree_function_decl {
>>>> >    unsigned has_debug_args_flag : 1;
>>>> >    unsigned tm_clone_flag : 1;
>>>> >
>>>> > -  /* 1 bit left */
>>>> > +  unsigned force_patching_for_instrumentation : 1;
>>>> > +  unsigned force_no_patching_for_instrumentation : 1;
>>>>
>>>>
>>>> I don't think you should use precious bits here -- directly query the
>>>> attributes.
>>>
>>>
>>> Done.
>>>
>>>>
>>>>
>>>> thanks,
>>>>
>>>> David
>>>>
>>>> >  };
>>>> >
>>>> >  /* The source language of the translation-unit.  */
>>>> >
>>>> > --
>>>> > This patch is available for review at http://codereview.appspot.com/6821051

Patch

diff --git a/gcc/c-family/c-common.c b/gcc/c-family/c-common.c
index ab416ff..998645d 100644
--- a/gcc/c-family/c-common.c
+++ b/gcc/c-family/c-common.c
@@ -396,6 +396,13 @@  static tree ignore_attribute (tree *, tree, tree, int, bool *);
 static tree handle_no_split_stack_attribute (tree *, tree, tree, int, bool *);
 static tree handle_fnspec_attribute (tree *, tree, tree, int, bool *);
 
+static tree handle_always_patch_for_instrumentation_attribute (tree *, tree,
+                                                               tree, int,
+                                                               bool *);
+static tree handle_never_patch_for_instrumentation_attribute (tree *, tree,
+                                                              tree, int,
+                                                              bool *);
+
 static void check_function_nonnull (tree, int, tree *);
 static void check_nonnull_arg (void *, tree, unsigned HOST_WIDE_INT);
 static bool nonnull_check_p (tree, unsigned HOST_WIDE_INT);
@@ -804,6 +811,13 @@  const struct attribute_spec c_common_attribute_table[] =
      The name contains space to prevent its usage in source code.  */
   { "fn spec",	 	      1, 1, false, true, true,
 			      handle_fnspec_attribute, false },
+  { "always_patch_for_instrumentation", 0, 0, true,  false, false,
+                              handle_always_patch_for_instrumentation_attribute,
+                              false },
+  { "never_patch_for_instrumentation", 0, 0, true,  false, false,
+                              handle_never_patch_for_instrumentation_attribute,
+                              false },
+
   { NULL,                     0, 0, false, false, false, NULL, false }
 };
 
@@ -9158,6 +9172,48 @@  handle_no_thread_safety_analysis_attribute (tree *node, tree name,
   return NULL_TREE;
 }
 
+/* Handle a "always_patch_for_instrumentation" attribute; arguments as in
+   struct attribute_spec.handler.  */
+static tree
+handle_always_patch_for_instrumentation_attribute (tree *node, tree name,
+                                                   tree ARG_UNUSED (args),
+                                                   int ARG_UNUSED (flags),
+                                                   bool *no_add_attrs)
+{
+  if (TREE_CODE (*node) == FUNCTION_DECL)
+    {
+      DECL_FORCE_PATCHING_FOR_INSTRUMENTATION (*node) = 1;
+      DECL_UNINLINABLE (*node) = 1;
+    }
+  else
+    {
+      warning (OPT_Wattributes, "%qE attribute ignored", name);
+      *no_add_attrs = true;
+    }
+  return NULL_TREE;
+}
+
+
+/* Handle a "never_patch_for_instrumentation" attribute; arguments as in
+   struct attribute_spec.handler.  */
+static tree
+handle_never_patch_for_instrumentation_attribute (tree *node, tree name,
+                                                  tree ARG_UNUSED (args),
+                                                  int ARG_UNUSED (flags),
+                                                  bool *no_add_attrs)
+{
+  if (TREE_CODE (*node) == FUNCTION_DECL)
+    DECL_FORCE_NO_PATCHING_FOR_INSTRUMENTATION (*node) = 1;
+  else
+    {
+      warning (OPT_Wattributes, "%qE attribute ignored", name);
+      *no_add_attrs = true;
+    }
+  return NULL_TREE;
+}
+
+
+
 /* Check for valid arguments being passed to a function with FNTYPE.
    There are NARGS arguments in the array ARGARRAY.  */
 void
diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
index 6972ae6..b1475bf 100644
--- a/gcc/config/i386/i386.c
+++ b/gcc/config/i386/i386.c
@@ -10983,6 +10983,13 @@  check_should_patch_current_function (void)
   int num_loops = 0;
   int min_functions_instructions;
 
+  /* If a function has an attribute forcing patching on or off, do as it
+     indicates.  */
+  if (DECL_FORCE_PATCHING_FOR_INSTRUMENTATION (current_function_decl))
+    return true;
+  else if (DECL_FORCE_NO_PATCHING_FOR_INSTRUMENTATION (current_function_decl))
+    return false;
+
   /* Patch the function if it has at least a loop.  */
   if (!patch_functions_ignore_loops)
     {
diff --git a/gcc/testsuite/gcc.target/i386/patch-functions-force-no-patching.c b/gcc/testsuite/gcc.target/i386/patch-functions-force-no-patching.c
new file mode 100644
index 0000000..cad6f2d
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/patch-functions-force-no-patching.c
@@ -0,0 +1,27 @@ 
+/* { dg-do compile } */
+/* { dg-require-effective-target lp64 } */
+/* { dg-options "-mpatch-functions-for-instrumentation -mno-patch-functions-main-always" } */
+
+/* Even complicated functions shouldn't get patched if they have the
+   never_patch_for_instrumentation attribute. */
+
+/* { dg-final { scan-assembler-not ".byte\t0xeb,0x09(.*).byte\t0x90" } } */
+/* { dg-final { scan-assembler-not "ret(.*).byte\t0x90(.*).byte\t0x90" } } */
+
+__attribute__ ((never_patch_for_instrumentation))
+int foo () {
+  volatile unsigned x = 0;
+  volatile unsigned y = 1;
+  x += y;
+  x *= y;
+  while (++x)
+    foo ();
+  return y;
+}
+
+
+int main ()
+{
+  int x = 0;
+  return 0;
+}
diff --git a/gcc/testsuite/gcc.target/i386/patch-functions-force-patching.c b/gcc/testsuite/gcc.target/i386/patch-functions-force-patching.c
new file mode 100644
index 0000000..86ad159
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/patch-functions-force-patching.c
@@ -0,0 +1,20 @@ 
+/* { dg-do compile } */
+/* { dg-require-effective-target lp64 } */
+/* { dg-options "-O3 -mpatch-functions-for-instrumentation -mno-patch-functions-main-always" } */
+
+/* Functions which have the always_patch attribute should be patched no matter
+   what.  Check that there are nop-bytes at the beginning and end of the
+   function.  We add -O3 so that the compiler will try to inline foo (but it
+   will be blocked by the attribute).  */
+
+/* { dg-final { scan-assembler ".byte\t0xeb,0x09(.*).byte\t0x90" } } */
+/* { dg-final { scan-assembler "ret(.*).byte\t0x90(.*).byte\t0x90" } } */
+
+__attribute__ ((always_patch_for_instrumentation))
+static int foo () {
+  return 3;
+}
+
+int main () {
+  volatile int x = foo ();
+}
diff --git a/gcc/tree.h b/gcc/tree.h
index 1eafaa0..9d26a00 100644
--- a/gcc/tree.h
+++ b/gcc/tree.h
@@ -3474,6 +3474,16 @@  struct GTY(())
 #define DECL_NO_INLINE_WARNING_P(NODE) \
   (FUNCTION_DECL_CHECK (NODE)->function_decl.no_inline_warning_flag)
 
+/* In a FUNCTION_DECL, nonzero if patching is forced.  */
+#define DECL_FORCE_PATCHING_FOR_INSTRUMENTATION(NODE) \
+  (FUNCTION_DECL_CHECK (NODE)->function_decl.force_patching_for_instrumentation)
+
+/* In a FUNCTION_DECL, nonzero if not patching is forced.  */
+#define DECL_FORCE_NO_PATCHING_FOR_INSTRUMENTATION(NODE)\
+  (FUNCTION_DECL_CHECK (NODE)->function_decl.force_no_patching_for_instrumentation)
+
+
+
 /* Nonzero if a FUNCTION_CODE is a TM load/store.  */
 #define BUILTIN_TM_LOAD_STORE_P(FN) \
   ((FN) >= BUILT_IN_TM_STORE_1 && (FN) <= BUILT_IN_TM_LOAD_RFW_LDOUBLE)
@@ -3586,7 +3596,8 @@  struct GTY(()) tree_function_decl {
   unsigned has_debug_args_flag : 1;
   unsigned tm_clone_flag : 1;
 
-  /* 1 bit left */
+  unsigned force_patching_for_instrumentation : 1;
+  unsigned force_no_patching_for_instrumentation : 1;
 };
 
 /* The source language of the translation-unit.  */