Re: [PATCH v12] add -fpatchable-function-entry=N,M option

[Maxim Kuvyrkov <maxim.kuvyrkov@linaro.org>]

> On Jul 17, 2017, at 3:10 PM, Torsten Duwe <duwe@suse.de> wrote:
> 
> What is the next step now? Is anybody going to commit that patch?
> 
> 	Torsten
> 
> On Fri, Jul 07, 2017 at 02:57:55PM +0100, Richard Earnshaw (lists) wrote:
>> On 06/07/17 15:03, Torsten Duwe wrote:
>> +#if TARGET_HAVE_NAMED_SECTIONS
> 
> No, this is a hook.  You need to test targetm_common.have_named_sections.
> 
> OK with that change.

Torsten, if you prefer I can commit your patch (after bootstrap and a regtest on aarch64-linux-gnu and x86_64-linux-gnu).

There is one last hurdle to sort out with the FSF copyright assignment.  Looking at FSF's list I don't see SuSe's copyright assignment for your contributions to FSF projects, of which GCC is one.  You can either request SuSe to file a copyright assignment for you, or, probably simpler, ask one of your SuSe colleagues (Richard B., Jan H.) to commit under their assignment.

--
Maxim Kuvyrkov
www.linaro.org


> 
> R.
> 
> On Fri, Jul 07, 2017 at 09:30:28PM +0200, Torsten Duwe wrote:
>> Change since v11:
>> 
>> < +#if TARGET_HAVE_NAMED_SECTIONS
>> 
>>> +  if (record_p && targetm_common.have_named_sections)
>> 
>> (plus > +#include "common/common-target.h" )
>> 
>> 	Torsten
>> 
>> 
>> gcc/c-family/ChangeLog
>> 2017-07-07  Torsten Duwe  <duwe@suse.de>
>> 
>> 	* c-attribs.c (c_common_attribute_table): Add entry for
>> 	"patchable_function_entry".
>> 
>> gcc/lto/ChangeLog
>> 2017-07-07  Torsten Duwe  <duwe@suse.de>
>> 
>> 	* lto-lang.c (lto_attribute_table): Add entry for
>> 	"patchable_function_entry".
>> 
>> gcc/ChangeLog
>> 2017-07-07  Torsten Duwe  <duwe@suse.de>
>> 
>> 	* common.opt: Introduce -fpatchable-function-entry
>> 	command line option, and its variables function_entry_patch_area_size
>> 	and function_entry_patch_area_start.
>> 	* opts.c (common_handle_option): Add -fpatchable_function_entry_ case,
>> 	including a two-value parser.
>> 	* target.def (print_patchable_function_entry): New target hook.
>> 	* targhooks.h (default_print_patchable_function_entry): New function.
>> 	* targhooks.c (default_print_patchable_function_entry): Likewise.
>> 	* toplev.c (process_options): Switch off IPA-RA if
>> 	patchable function entries are being generated.
>> 	* varasm.c (assemble_start_function): Look at the
>> 	patchable-function-entry command line switch and current
>> 	function attributes and maybe generate NOP instructions by
>> 	calling the print_patchable_function_entry hook.
>> 	* doc/extend.texi: Document patchable_function_entry attribute.
>> 	* doc/invoke.texi: Document -fpatchable_function_entry
>> 	command line option.
>> 	* doc/tm.texi.in (TARGET_ASM_PRINT_PATCHABLE_FUNCTION_ENTRY):
>> 	New target hook.
>> 	* doc/tm.texi: Likewise.
>> 
>> gcc/testsuite/ChangeLog
>> 2017-07-07  Torsten Duwe  <duwe@suse.de>
>> 
>> 	* c-c++-common/patchable_function_entry-default.c: New test.
>> 	* c-c++-common/patchable_function_entry-decl.c: Likewise.
>> 	* c-c++-common/patchable_function_entry-definition.c: Likewise.
>> 
>> diff --git a/gcc/c-family/c-attribs.c b/gcc/c-family/c-attribs.c
>> index 626ffa1cde7..ecb00c1d5b9 100644
>> --- a/gcc/c-family/c-attribs.c
>> +++ b/gcc/c-family/c-attribs.c
>> @@ -142,6 +142,8 @@ static tree handle_bnd_variable_size_attribute (tree *, tree, tree, int, bool *)
>> static tree handle_bnd_legacy (tree *, tree, tree, int, bool *);
>> static tree handle_bnd_instrument (tree *, tree, tree, int, bool *);
>> static tree handle_fallthrough_attribute (tree *, tree, tree, int, bool *);
>> +static tree handle_patchable_function_entry_attribute (tree *, tree, tree,
>> +						       int, bool *);
>> 
>> /* Table of machine-independent attributes common to all C-like languages.
>> 
>> @@ -351,6 +353,9 @@ const struct attribute_spec c_common_attribute_table[] =
>> 			      handle_bnd_instrument, false },
>>   { "fallthrough",	      0, 0, false, false, false,
>> 			      handle_fallthrough_attribute, false },
>> +  { "patchable_function_entry",	1, 2, true, false, false,
>> +			      handle_patchable_function_entry_attribute,
>> +			      false },
>>   { NULL,                     0, 0, false, false, false, NULL, false }
>> };
>> 
>> @@ -3260,3 +3265,10 @@ handle_fallthrough_attribute (tree *, tree name, tree, int,
>>   *no_add_attrs = true;
>>   return NULL_TREE;
>> }
>> +
>> +static tree
>> +handle_patchable_function_entry_attribute (tree *, tree, tree, int, bool *)
>> +{
>> +  /* Nothing to be done here.  */
>> +  return NULL_TREE;
>> +}
>> diff --git a/gcc/common.opt b/gcc/common.opt
>> index e81165c488b..78cfa568a95 100644
>> --- a/gcc/common.opt
>> +++ b/gcc/common.opt
>> @@ -163,6 +163,13 @@ bool flag_stack_usage_info = false
>> Variable
>> int flag_debug_asm
>> 
>> +; How many NOP insns to place at each function entry by default
>> +Variable
>> +HOST_WIDE_INT function_entry_patch_area_size
>> +
>> +; And how far the real asm entry point is into this area
>> +Variable
>> +HOST_WIDE_INT function_entry_patch_area_start
>> 
>> ; Balance between GNAT encodings and standard DWARF to emit.
>> Variable
>> @@ -2030,6 +2037,10 @@ fprofile-reorder-functions
>> Common Report Var(flag_profile_reorder_functions)
>> Enable function reordering that improves code placement.
>> 
>> +fpatchable-function-entry=
>> +Common Joined Optimization
>> +Insert NOP instructions at each function entry.
>> +
>> frandom-seed
>> Common Var(common_deferred_options) Defer
>> 
>> diff --git a/gcc/doc/extend.texi b/gcc/doc/extend.texi
>> index 5cb512fe575..9c171abc121 100644
>> --- a/gcc/doc/extend.texi
>> +++ b/gcc/doc/extend.texi
>> @@ -3105,6 +3105,27 @@ that affect more than one function.
>> This attribute should be used for debugging purposes only.  It is not
>> suitable in production code.
>> 
>> +@item patchable_function_entry
>> +@cindex @code{patchable_function_entry} function attribute
>> +@cindex extra NOP instructions at the function entry point
>> +In case the target's text segment can be made writable at run time by
>> +any means, padding the function entry with a number of NOPs can be
>> +used to provide a universal tool for instrumentation.
>> +
>> +The @code{patchable_function_entry} function attribute can be used to
>> +change the number of NOPs to any desired value.  The two-value syntax
>> +is the same as for the command-line switch
>> +@option{-fpatchable-function-entry=N,M}, generating @var{N} NOPs, with
>> +the function entry point before the @var{M}th NOP instruction.
>> +@var{M} defaults to 0 if omitted e.g. function entry point is before
>> +the first NOP.
>> +
>> +If patchable function entries are enabled globally using the command-line
>> +option @option{-fpatchable-function-entry=N,M}, then you must disable
>> +instrumentation on all functions that are part of the instrumentation
>> +framework with the attribute @code{patchable_function_entry (0)}
>> +to prevent recursion.
>> +
>> @item pure
>> @cindex @code{pure} function attribute
>> @cindex functions that have no side effects
>> diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
>> index d0b90503ced..dc93f0ccd50 100644
>> --- a/gcc/doc/invoke.texi
>> +++ b/gcc/doc/invoke.texi
>> @@ -11520,6 +11520,34 @@ of the function name, it is considered to be a match.  For C99 and C++
>> extended identifiers, the function name must be given in UTF-8, not
>> using universal character names.
>> 
>> +@item -fpatchable-function-entry=@var{N}[,@var{M}]
>> +@opindex fpatchable-function-entry
>> +Generate @var{N} NOPs right at the beginning
>> +of each function, with the function entry point before the @var{M}th NOP.
>> +If @var{M} is omitted, it defaults to @code{0} so the
>> +function entry points to the address just at the first NOP.
>> +The NOP instructions reserve extra space which can be used to patch in
>> +any desired instrumentation at run time, provided that the code segment
>> +is writable.  The amount of space is controllable indirectly via
>> +the number of NOPs; the NOP instruction used corresponds to the instruction
>> +emitted by the internal GCC back-end interface @code{gen_nop}.  This behavior
>> +is target-specific and may also depend on the architecture variant and/or
>> +other compilation options.
>> +
>> +For run-time identification, the starting addresses of these areas,
>> +which correspond to their respective function entries minus @var{M},
>> +are additionally collected in the @code{__patchable_function_entries}
>> +section of the resulting binary.
>> +
>> +Note that the value of @code{__attribute__ ((patchable_function_entry
>> +(N,M)))} takes precedence over command-line option
>> +@option{-fpatchable-function-entry=N,M}.  This can be used to increase
>> +the area size or to remove it completely on a single function.
>> +If @code{N=0}, no pad location is recorded.
>> +
>> +The NOP instructions are inserted at---and maybe before, depending on
>> +@var{M}---the function entry address, even before the prologue.
>> +
>> @end table
>> 
>> 
>> diff --git a/gcc/doc/tm.texi b/gcc/doc/tm.texi
>> index 795e49246af..23e85c7afea 100644
>> --- a/gcc/doc/tm.texi
>> +++ b/gcc/doc/tm.texi
>> @@ -4573,6 +4573,15 @@ will select the smallest suitable mode.
>> This section describes the macros that output function entry
>> (@dfn{prologue}) and exit (@dfn{epilogue}) code.
>> 
>> +@deftypefn {Target Hook} void TARGET_ASM_PRINT_PATCHABLE_FUNCTION_ENTRY (FILE *@var{file}, unsigned HOST_WIDE_INT @var{patch_area_size}, bool @var{record_p})
>> +Generate a patchable area at the function start, consisting of
>> +@var{patch_area_size} NOP instructions.  If the target supports named
>> +sections and if @var{record_p} is true, insert a pointer to the current
>> +location in the table of patchable functions.  The default implementation
>> +of the hook places the table of pointers in the special section named
>> +@code{__patchable_function_entries}.
>> +@end deftypefn
>> +
>> @deftypefn {Target Hook} void TARGET_ASM_FUNCTION_PROLOGUE (FILE *@var{file}, HOST_WIDE_INT @var{size})
>> If defined, a function that outputs the assembler code for entry to a
>> function.  The prologue is responsible for setting up the stack frame,
>> diff --git a/gcc/doc/tm.texi.in b/gcc/doc/tm.texi.in
>> index 98f2e6bce5f..6df08a2c477 100644
>> --- a/gcc/doc/tm.texi.in
>> +++ b/gcc/doc/tm.texi.in
>> @@ -3650,6 +3650,8 @@ will select the smallest suitable mode.
>> This section describes the macros that output function entry
>> (@dfn{prologue}) and exit (@dfn{epilogue}) code.
>> 
>> +@hook TARGET_ASM_PRINT_PATCHABLE_FUNCTION_ENTRY
>> +
>> @hook TARGET_ASM_FUNCTION_PROLOGUE
>> 
>> @hook TARGET_ASM_FUNCTION_END_PROLOGUE
>> diff --git a/gcc/lto/lto-lang.c b/gcc/lto/lto-lang.c
>> index 58935172b2c..6e9a138fa3b 100644
>> --- a/gcc/lto/lto-lang.c
>> +++ b/gcc/lto/lto-lang.c
>> @@ -48,6 +48,8 @@ static tree handle_sentinel_attribute (tree *, tree, tree, int, bool *);
>> static tree handle_type_generic_attribute (tree *, tree, tree, int, bool *);
>> static tree handle_transaction_pure_attribute (tree *, tree, tree, int, bool *);
>> static tree handle_returns_twice_attribute (tree *, tree, tree, int, bool *);
>> +static tree handle_patchable_function_entry_attribute (tree *, tree, tree,
>> +						       int, bool *);
>> static tree ignore_attribute (tree *, tree, tree, int, bool *);
>> 
>> static tree handle_format_attribute (tree *, tree, tree, int, bool *);
>> @@ -76,6 +78,9 @@ const struct attribute_spec lto_attribute_table[] =
>> 			      handle_nonnull_attribute, false },
>>   { "nothrow",                0, 0, true,  false, false,
>> 			      handle_nothrow_attribute, false },
>> +  { "patchable_function_entry", 1, 2, true, false, false,
>> +			      handle_patchable_function_entry_attribute,
>> +			      false },
>>   { "returns_twice",          0, 0, true,  false, false,
>> 			      handle_returns_twice_attribute, false },
>>   { "sentinel",               0, 1, false, true, true,
>> @@ -473,6 +478,13 @@ handle_returns_twice_attribute (tree *node, tree ARG_UNUSED (name),
>>   return NULL_TREE;
>> }
>> 
>> +static tree
>> +handle_patchable_function_entry_attribute (tree *, tree, tree, int, bool *)
>> +{
>> +  /* Nothing to be done here.  */
>> +  return NULL_TREE;
>> +}
>> +
>> /* Ignore the given attribute.  Used when this attribute may be usefully
>>    overridden by the target, but is not used generically.  */
>> 
>> diff --git a/gcc/opts.c b/gcc/opts.c
>> index 7555ed55434..fecf97978fc 100644
>> --- a/gcc/opts.c
>> +++ b/gcc/opts.c
>> @@ -2199,6 +2199,33 @@ common_handle_option (struct gcc_options *opts,
>>         opts->x_flag_ipa_reference = false;
>>       break;
>> 
>> +    case OPT_fpatchable_function_entry_:
>> +      {
>> +	char *patch_area_arg = xstrdup (arg);
>> +	char *comma = strchr (patch_area_arg, ',');
>> +	if (comma)
>> +	  {
>> +	    *comma = '\0';
>> +	    function_entry_patch_area_size = 
>> +	      integral_argument (patch_area_arg);
>> +	    function_entry_patch_area_start =
>> +	      integral_argument (comma + 1);
>> +	  }
>> +	else
>> +	  {
>> +	    function_entry_patch_area_size =
>> +	      integral_argument (patch_area_arg);
>> +	    function_entry_patch_area_start = 0;
>> +	  }
>> +	if (function_entry_patch_area_size < 0
>> +	    || function_entry_patch_area_start < 0
>> +	    || function_entry_patch_area_size 
>> +		< function_entry_patch_area_start)
>> +	  error ("invalid arguments for %<-fpatchable_function_entry%>");
>> +	free (patch_area_arg);
>> +      }
>> +      break;
>> +
>>     case OPT_ftree_vectorize:
>>       if (!opts_set->x_flag_tree_loop_vectorize)
>>         opts->x_flag_tree_loop_vectorize = value;
>> diff --git a/gcc/target.def b/gcc/target.def
>> index bbd9c015189..6d67b1fe8ba 100644
>> --- a/gcc/target.def
>> +++ b/gcc/target.def
>> @@ -288,6 +288,17 @@ hidden, protected or internal visibility as specified by @var{visibility}.",
>>  void, (tree decl, int visibility),
>>  default_assemble_visibility)
>> 
>> +DEFHOOK
>> +(print_patchable_function_entry,
>> + "Generate a patchable area at the function start, consisting of\n\
>> +@var{patch_area_size} NOP instructions.  If the target supports named\n\
>> +sections and if @var{record_p} is true, insert a pointer to the current\n\
>> +location in the table of patchable functions.  The default implementation\n\
>> +of the hook places the table of pointers in the special section named\n\
>> +@code{__patchable_function_entries}.",
>> + void, (FILE *file, unsigned HOST_WIDE_INT patch_area_size, bool record_p),
>> + default_print_patchable_function_entry)
>> +
>> /* Output the assembler code for entry to a function.  */
>> DEFHOOK
>> (function_prologue,
>> diff --git a/gcc/targhooks.c b/gcc/targhooks.c
>> index 940deec67f9..6a8fae656d0 100644
>> --- a/gcc/targhooks.c
>> +++ b/gcc/targhooks.c
>> @@ -73,6 +73,7 @@ along with GCC; see the file COPYING3.  If not see
>> #include "calls.h"
>> #include "expr.h"
>> #include "output.h"
>> +#include "common/common-target.h"
>> #include "reload.h"
>> #include "intl.h"
>> #include "opts.h"
>> @@ -1610,6 +1611,51 @@ default_compare_by_pieces_branch_ratio (machine_mode)
>>   return 1;
>> }
>> 
>> +/* Write PATCH_AREA_SIZE NOPs into the asm outfile FILE around a function
>> +   entry.  If RECORD_P is true and the target supports named sections,
>> +   the location of the NOPs will be recorded in a special object section
>> +   called "__patchable_function_entries".  This routine may be called
>> +   twice per function to put NOPs before and after the function
>> +   entry.  */
>> +
>> +void
>> +default_print_patchable_function_entry (FILE *file,
>> +					unsigned HOST_WIDE_INT patch_area_size,
>> +					bool record_p)
>> +{
>> +  const char *nop_templ = 0;
>> +  int code_num;
>> +  rtx_insn *my_nop = make_insn_raw (gen_nop ());
>> +
>> +  /* We use the template alone, relying on the (currently sane) assumption
>> +     that the NOP template does not have variable operands.  */
>> +  code_num = recog_memoized (my_nop);
>> +  nop_templ = get_insn_template (code_num, my_nop);
>> +
>> +  if (record_p && targetm_common.have_named_sections)
>> +    {
>> +      char buf[256];
>> +      static int patch_area_number;
>> +      section *previous_section = in_section;
>> +
>> +      patch_area_number++;
>> +      ASM_GENERATE_INTERNAL_LABEL (buf, "LPFE", patch_area_number);
>> +
>> +      switch_to_section (get_section ("__patchable_function_entries",
>> +				      0, NULL));
>> +      fputs (integer_asm_op (POINTER_SIZE_UNITS, false), file);
>> +      assemble_name_raw (file, buf);
>> +      fputc ('\n', file);
>> +
>> +      switch_to_section (previous_section);
>> +      ASM_OUTPUT_LABEL (file, buf);
>> +    }
>> +
>> +  unsigned i;
>> +  for (i = 0; i < patch_area_size; ++i)
>> +    fprintf (file, "\t%s\n", nop_templ);
>> +}
>> +
>> bool
>> default_profile_before_prologue (void)
>> {
>> diff --git a/gcc/targhooks.h b/gcc/targhooks.h
>> index 1ddb8891fe4..c73ea0bda20 100644
>> --- a/gcc/targhooks.h
>> +++ b/gcc/targhooks.h
>> @@ -203,6 +203,9 @@ extern bool default_use_by_pieces_infrastructure_p (unsigned HOST_WIDE_INT,
>> 						    bool);
>> extern int default_compare_by_pieces_branch_ratio (machine_mode);
>> 
>> +extern void default_print_patchable_function_entry (FILE *,
>> +						    unsigned HOST_WIDE_INT,
>> +						    bool);
>> extern bool default_profile_before_prologue (void);
>> extern reg_class_t default_preferred_reload_class (rtx, reg_class_t);
>> extern reg_class_t default_preferred_output_reload_class (rtx, reg_class_t);
>> diff --git a/gcc/testsuite/c-c++-common/patchable_function_entry-decl.c b/gcc/testsuite/c-c++-common/patchable_function_entry-decl.c
>> new file mode 100644
>> index 00000000000..8514b10e820
>> --- /dev/null
>> +++ b/gcc/testsuite/c-c++-common/patchable_function_entry-decl.c
>> @@ -0,0 +1,16 @@
>> +/* { dg-do compile } */
>> +/* { dg-options "-O2 -fpatchable-function-entry=3,1" } */
>> +/* { dg-final { scan-assembler-times "nop" 2 } } */
>> +
>> +extern int a;
>> +
>> +/* Respect overriding attributes in the declaration.  */
>> +int f3 (void) __attribute__((patchable_function_entry(2)));
>> +
>> +/* F3 should now get 2 NOPs.  */
>> +int
>> +__attribute__((noinline))
>> +f3 (void)
>> +{
>> +  return 5*a;
>> +}
>> diff --git a/gcc/testsuite/c-c++-common/patchable_function_entry-default.c b/gcc/testsuite/c-c++-common/patchable_function_entry-default.c
>> new file mode 100644
>> index 00000000000..0dcf1181dde
>> --- /dev/null
>> +++ b/gcc/testsuite/c-c++-common/patchable_function_entry-default.c
>> @@ -0,0 +1,16 @@
>> +/* { dg-do compile } */
>> +/* { dg-options "-O2 -fpatchable-function-entry=3,1" } */
>> +/* { dg-final { scan-assembler-times "nop" 3 } } */
>> +
>> +extern int a;
>> +
>> +/* Nothing declared must not mean anything.  */
>> +int f3 (void);
>> +
>> +/* F3 should get a default-sized NOP area.  */
>> +int
>> +__attribute__((noinline))
>> +f3 (void)
>> +{
>> +  return 5*a;
>> +}
>> diff --git a/gcc/testsuite/c-c++-common/patchable_function_entry-definition.c b/gcc/testsuite/c-c++-common/patchable_function_entry-definition.c
>> new file mode 100644
>> index 00000000000..a007867dcb0
>> --- /dev/null
>> +++ b/gcc/testsuite/c-c++-common/patchable_function_entry-definition.c
>> @@ -0,0 +1,16 @@
>> +/* { dg-do compile } */
>> +/* { dg-options "-O2 -fpatchable-function-entry=3,1" } */
>> +/* { dg-final { scan-assembler-times "nop" 1 } } */
>> +
>> +extern int a;
>> +
>> +int f3 (void);
>> +
>> +/* F3 should now get 1 NOP.  */
>> +int
>> +__attribute__((noinline))
>> +__attribute__((patchable_function_entry(1)))
>> +f3 (void)
>> +{
>> +  return 5*a;
>> +}
>> diff --git a/gcc/toplev.c b/gcc/toplev.c
>> index e6c69a4ba93..b28f1847c83 100644
>> --- a/gcc/toplev.c
>> +++ b/gcc/toplev.c
>> @@ -1630,8 +1630,10 @@ process_options (void)
>>     }
>> 
>>  /* Do not use IPA optimizations for register allocation if profiler is active
>> +    or patchable function entries are inserted for run-time instrumentation
>>     or port does not emit prologue and epilogue as RTL.  */
>> -  if (profile_flag || !targetm.have_prologue () || !targetm.have_epilogue ())
>> +  if (profile_flag || function_entry_patch_area_size
>> +      || !targetm.have_prologue () || !targetm.have_epilogue ())
>>     flag_ipa_ra = 0;
>> 
>>   /* Enable -Werror=coverage-mismatch when -Werror and -Wno-error
>> diff --git a/gcc/varasm.c b/gcc/varasm.c
>> index fbaebc1b5c0..ec1640ea378 100644
>> --- a/gcc/varasm.c
>> +++ b/gcc/varasm.c
>> @@ -1825,6 +1825,46 @@ assemble_start_function (tree decl, const char *fnname)
>>   if (DECL_PRESERVE_P (decl))
>>     targetm.asm_out.mark_decl_preserved (fnname);
>> 
>> +  unsigned HOST_WIDE_INT patch_area_size = function_entry_patch_area_size;
>> +  unsigned HOST_WIDE_INT patch_area_entry = function_entry_patch_area_start;
>> +
>> +  tree patchable_function_entry_attr
>> +    = lookup_attribute ("patchable_function_entry", DECL_ATTRIBUTES (decl));
>> +  if (patchable_function_entry_attr)
>> +    {
>> +      tree pp_val = TREE_VALUE (patchable_function_entry_attr);
>> +      tree patchable_function_entry_value1 = TREE_VALUE (pp_val);
>> +
>> +      if (tree_fits_uhwi_p (patchable_function_entry_value1))
>> +	patch_area_size = tree_to_uhwi (patchable_function_entry_value1);
>> +      else
>> +	gcc_unreachable ();
>> +
>> +      patch_area_entry = 0;
>> +      if (list_length (pp_val) > 1)
>> +	{
>> +	  tree patchable_function_entry_value2 =
>> +	    TREE_VALUE (TREE_CHAIN (pp_val));
>> +
>> +	  if (tree_fits_uhwi_p (patchable_function_entry_value2))
>> +	    patch_area_entry = tree_to_uhwi (patchable_function_entry_value2);
>> +	  else
>> +	    gcc_unreachable ();
>> +	}
>> +    }
>> +
>> +  if (patch_area_entry > patch_area_size)
>> +    {
>> +      if (patch_area_size > 0)
>> +	warning (OPT_Wattributes, "Patchable function entry > size");
>> +      patch_area_entry = 0;
>> +    }
>> +
>> +  /* Emit the patching area before the entry label, if any.  */
>> +  if (patch_area_entry > 0)
>> +    targetm.asm_out.print_patchable_function_entry (asm_out_file,
>> +						    patch_area_entry, true);
>> +
>>   /* Do any machine/system dependent processing of the function name.  */
>> #ifdef ASM_DECLARE_FUNCTION_NAME
>>   ASM_DECLARE_FUNCTION_NAME (asm_out_file, fnname, current_function_decl);
>> @@ -1833,6 +1873,12 @@ assemble_start_function (tree decl, const char *fnname)
>>   ASM_OUTPUT_FUNCTION_LABEL (asm_out_file, fnname, current_function_decl);
>> #endif /* ASM_DECLARE_FUNCTION_NAME */
>> 
>> +  /* And the area after the label.  Record it if we haven't done so yet.  */
>> +  if (patch_area_size > patch_area_entry)
>> +    targetm.asm_out.print_patchable_function_entry (asm_out_file,
>> +					     patch_area_size-patch_area_entry,
>> +						    patch_area_entry == 0);
>> +
>>   if (lookup_attribute ("no_split_stack", DECL_ATTRIBUTES (decl)))
>>     saw_no_split_stack = true;
>> }