On Wed, 18 Oct 2023, Andrew Carlotti wrote:
> This patch adds support for the "target_version" attribute to the middle
> end and the C++ frontend, which will be used to implement function
> multiversioning in the aarch64 backend.
>
> Note that C++ is currently the only frontend which supports
> multiversioning using the "target" attribute, whereas the
> "target_clones" attribute is additionally supported in C, D and Ada.
> Support for the target_version attribute will be extended to C at a
> later date.
>
> Targets that currently use the "target" attribute for function
> multiversioning (i.e. i386 and rs6000) are not affected by this patch.
>
>
> I could have implemented the target hooks slightly differently, by reusing the
> valid_attribute_p hook and adding attribute name checks to each backend
> implementation (c.f. the aarch64 implementation in patch 2/3). Would this be
> preferable?
>
> Otherwise, is this ok for master?
This lacks user-level documentation in doc/extend.texi (where
target_clones is documented).
Was there any discussion/description of why target_clones cannot
be made work for aarch64?
Richard.
>
> gcc/c-family/ChangeLog:
>
> * c-attribs.cc (handle_target_version_attribute): New.
> (c_common_attribute_table): Add target_version.
> (handle_target_clones_attribute): Add conflict with
> target_version attribute.
>
> gcc/ChangeLog:
>
> * attribs.cc (is_function_default_version): Update comment to
> specify incompatibility with target_version attributes.
> * cgraphclones.cc (cgraph_node::create_version_clone_with_body):
> Call valid_version_attribute_p for target_version attributes.
> * target.def (valid_version_attribute_p): New hook.
> (expanded_clones_attribute): New hook.
> * doc/tm.texi.in: Add new hooks.
> * doc/tm.texi: Regenerate.
> * multiple_target.cc (create_dispatcher_calls): Remove redundant
> is_function_default_version check.
> (expand_target_clones): Use target hook for attribute name.
> * targhooks.cc (default_target_option_valid_version_attribute_p):
> New.
> * targhooks.h (default_target_option_valid_version_attribute_p):
> New.
> * tree.h (DECL_FUNCTION_VERSIONED): Update comment to include
> target_version attributes.
>
> gcc/cp/ChangeLog:
>
> * decl2.cc (check_classfn): Update comment to include
> target_version attributes.
>
>
> diff --git a/gcc/attribs.cc b/gcc/attribs.cc
> index
> b1300018d1e8ed8e02ded1ea721dc192a6d32a49..a3c4a81e8582ea4fd06b9518bf51fad7c998ddd6
> 100644
> --- a/gcc/attribs.cc
> +++ b/gcc/attribs.cc
> @@ -1233,8 +1233,9 @@ make_dispatcher_decl (const tree decl)
> return func_decl;
> }
>
> -/* Returns true if decl is multi-versioned and DECL is the default function,
> - that is it is not tagged with target specific optimization. */
> +/* Returns true if DECL is multi-versioned using the target attribute, and
> this
> + is the default version. This function can only be used for targets that
> do
> + not support the "target_version" attribute. */
>
> bool
> is_function_default_version (const tree decl)
> diff --git a/gcc/c-family/c-attribs.cc b/gcc/c-family/c-attribs.cc
> index
> 072cfb69147bd6b314459c0bd48a0c1fb92d3e4d..1a224c036277d51ab4dc0d33a403177bd226e48a
> 100644
> --- a/gcc/c-family/c-attribs.cc
> +++ b/gcc/c-family/c-attribs.cc
> @@ -148,6 +148,7 @@ static tree handle_alloc_align_attribute (tree *, tree,
> tree, int, bool *);
> static tree handle_assume_aligned_attribute (tree *, tree, tree, int, bool
> *);
> static tree handle_assume_attribute (tree *, tree, tree, int, bool *);
> static tree handle_target_attribute (tree *, tree, tree, int, bool *);
> +static tree handle_target_version_attribute (tree *, tree, tree, int, bool
> *);
> static tree handle_target_clones_attribute (tree *, tree, tree, int, bool *);
> static tree handle_optimize_attribute (tree *, tree, tree, int, bool *);
> static tree ignore_attribute (tree *, tree, tree, int, bool *);
> @@ -480,6 +481,8 @@ const struct attribute_spec c_common_attribute_table[] =
> handle_error_attribute, NULL },
> { "target", 1, -1, true, false, false, false,
> handle_target_attribute, NULL },
> + { "target_version", 1, -1, true, false, false, false,
> + handle_target_version_attribute, NULL },
> { "target_clones", 1, -1, true, false, false, false,
> handle_target_clones_attribute, NULL },
> { "optimize", 1, -1, true, false, false, false,
> @@ -5569,6 +5572,45 @@ handle_target_attribute (tree *node, tree name, tree
> args, int flags,
> return NULL_TREE;
> }
>
> +/* Handle a "target_version" attribute. */
> +
> +static tree
> +handle_target_version_attribute (tree *node, tree name, tree args, int flags,
> + bool *no_add_attrs)
> +{
> + /* Ensure we have a function type. */
> + if (TREE_CODE (*node) != FUNCTION_DECL)
> + {
> + warning (OPT_Wattributes, "%qE attribute ignored", name);
> + *no_add_attrs = true;
> + }
> + else if (lookup_attribute ("target_clones", DECL_ATTRIBUTES (*node)))
> + {
> + warning (OPT_Wattributes, "%qE attribute ignored due to conflict "
> + "with %qs attribute", name, "target_clones");
> + *no_add_attrs = true;
> + }
> + else if (!targetm.target_option.valid_version_attribute_p (*node, name,
> args,
> + flags))
> + *no_add_attrs = true;
> +
> + /* Check that there's no empty string in values of the attribute. */
> + for (tree t = args; t != NULL_TREE; t = TREE_CHAIN (t))
> + {
> + tree value = TREE_VALUE (t);
> + if (TREE_CODE (value) == STRING_CST
> + && TREE_STRING_LENGTH (value) == 1
> + && TREE_STRING_POINTER (value)[0] == '\0')
> + {
> + warning (OPT_Wattributes,
> + "empty string in attribute %<target_version%>");
> + *no_add_attrs = true;
> + }
> + }
> +
> + return NULL_TREE;
> +}
> +
> /* Handle a "target_clones" attribute. */
>
> static tree
> @@ -5601,6 +5643,12 @@ handle_target_clones_attribute (tree *node, tree name,
> tree ARG_UNUSED (args),
> "with %qs attribute", name, "target");
> *no_add_attrs = true;
> }
> + else if (lookup_attribute ("target_version", DECL_ATTRIBUTES (*node)))
> + {
> + warning (OPT_Wattributes, "%qE attribute ignored due to conflict "
> + "with %qs attribute", name, "target_version");
> + *no_add_attrs = true;
> + }
> else if (get_target_clone_attr_len (args) == -1)
> {
> warning (OPT_Wattributes,
> diff --git a/gcc/cgraphclones.cc b/gcc/cgraphclones.cc
> index
> 29d28ef895a73a223695cbb86aafbc845bbe7688..8af6b23d8c0306920e0fdcb3559ef047a16689f4
> 100644
> --- a/gcc/cgraphclones.cc
> +++ b/gcc/cgraphclones.cc
> @@ -78,6 +78,7 @@ along with GCC; see the file COPYING3. If not see
> #include "tree-eh.h"
> #include "tree-cfg.h"
> #include "tree-inline.h"
> +#include "attribs.h"
> #include "dumpfile.h"
> #include "gimple-pretty-print.h"
> #include "alloc-pool.h"
> @@ -1048,7 +1049,17 @@ cgraph_node::create_version_clone_with_body
> location_t saved_loc = input_location;
> tree v = TREE_VALUE (target_attributes);
> input_location = DECL_SOURCE_LOCATION (new_decl);
> - bool r = targetm.target_option.valid_attribute_p (new_decl, NULL, v,
> 1);
> + bool r;
> + tree name_id = get_attribute_name (target_attributes);
> + const char* name_str = IDENTIFIER_POINTER (name_id);
> + if (strcmp (name_str, "target") == 0)
> + r = targetm.target_option.valid_attribute_p (new_decl, name_id, v, 1);
> + else if (strcmp (name_str, "target_version") == 0)
> + r = targetm.target_option.valid_version_attribute_p (new_decl, name_id,
> + v, 1);
> + else
> + gcc_assert(false);
> +
> input_location = saved_loc;
> if (!r)
> return NULL;
> diff --git a/gcc/cp/decl2.cc b/gcc/cp/decl2.cc
> index
> 9594be4092c3c00fddc9d4c6da5931ea3b7e8792..ec78d5a5440bedd360ac8e5bc44e164da3dab410
> 100644
> --- a/gcc/cp/decl2.cc
> +++ b/gcc/cp/decl2.cc
> @@ -829,8 +829,8 @@ check_classfn (tree ctype, tree function, tree
> template_parms)
> tree c2 = get_constraints (fndecl);
>
> /* While finding a match, same types and params are not enough
> - if the function is versioned. Also check version ("target")
> - attributes. */
> + if the function is versioned. Also check for different target
> + specific attributes. */
> if (same_type_p (TREE_TYPE (TREE_TYPE (function)),
> TREE_TYPE (TREE_TYPE (fndecl)))
> && compparms (p1, p2)
> diff --git a/gcc/doc/tm.texi b/gcc/doc/tm.texi
> index
> 33e7ffc8af5a9d48430145ef9b8e7924613b7dd7..97b3e9c31631a943d95f1cf7739716a574afcfb7
> 100644
> --- a/gcc/doc/tm.texi
> +++ b/gcc/doc/tm.texi
> @@ -10507,6 +10507,23 @@ the function declaration to hold a pointer to a
> target-specific
> @code{struct cl_target_option} structure.
> @end deftypefn
>
> +@deftypefn {Target Hook} bool TARGET_OPTION_VALID_VERSION_ATTRIBUTE_P (tree
> @var{fndecl}, tree @var{name}, tree @var{args}, int @var{flags})
> +This hook is called to parse @code{attribute(target_version("..."))},
> +which allows setting target-specific options on individual function versions.
> +These function-specific options may differ
> +from the options specified on the command line. The hook should return
> +@code{true} if the options are valid.
> +
> +The hook should set the @code{DECL_FUNCTION_SPECIFIC_TARGET} field in
> +the function declaration to hold a pointer to a target-specific
> +@code{struct cl_target_option} structure.
> +@end deftypefn
> +
> +@deftypevr {Target Hook} {const char *}
> TARGET_OPTION_EXPANDED_CLONES_ATTRIBUTE
> +Contains the name of the attribute used for the version description string
> +when expanding clones for a function with the target_clones attribute.
> +@end deftypevr
> +
> @deftypefn {Target Hook} void TARGET_OPTION_SAVE (struct cl_target_option
> *@var{ptr}, struct gcc_options *@var{opts}, struct gcc_options
> *@var{opts_set})
> This hook is called to save any additional target-specific information
> in the @code{struct cl_target_option} structure for function-specific
> diff --git a/gcc/doc/tm.texi.in b/gcc/doc/tm.texi.in
> index
> c98b2447e28aa17996b1cbf8af7ed02d70db54f2..56fa3de6bba06bc0ac124bb3a41324be1997e209
> 100644
> --- a/gcc/doc/tm.texi.in
> +++ b/gcc/doc/tm.texi.in
> @@ -6979,6 +6979,10 @@ on this implementation detail.
>
> @hook TARGET_OPTION_VALID_ATTRIBUTE_P
>
> +@hook TARGET_OPTION_VALID_VERSION_ATTRIBUTE_P
> +
> +@hook TARGET_OPTION_EXPANDED_CLONES_ATTRIBUTE
> +
> @hook TARGET_OPTION_SAVE
>
> @hook TARGET_OPTION_RESTORE
> diff --git a/gcc/multiple_target.cc b/gcc/multiple_target.cc
> index
> a2ed048d7dd28ec470953fcd8a0dc86817e4b7dc..3db57c2b13d612a37240d9dcf58ad21b2286633c
> 100644
> --- a/gcc/multiple_target.cc
> +++ b/gcc/multiple_target.cc
> @@ -66,10 +66,6 @@ create_dispatcher_calls (struct cgraph_node *node)
> {
> ipa_ref *ref;
>
> - if (!DECL_FUNCTION_VERSIONED (node->decl)
> - || !is_function_default_version (node->decl))
> - return;
> -
> if (!targetm.has_ifunc_p ())
> {
> error_at (DECL_SOURCE_LOCATION (node->decl),
> @@ -377,6 +373,7 @@ expand_target_clones (struct cgraph_node *node, bool
> definition)
> return false;
> }
>
> + const char *new_attr_name =
> targetm.target_option.expanded_clones_attribute;
> cgraph_function_version_info *decl1_v = NULL;
> cgraph_function_version_info *decl2_v = NULL;
> cgraph_function_version_info *before = NULL;
> @@ -392,7 +389,7 @@ expand_target_clones (struct cgraph_node *node, bool
> definition)
> char *attr = attrs[i];
>
> /* Create new target clone. */
> - tree attributes = make_attribute ("target", attr,
> + tree attributes = make_attribute (new_attr_name, attr,
> DECL_ATTRIBUTES (node->decl));
>
> char *suffix = XNEWVEC (char, strlen (attr) + 1);
> @@ -430,7 +427,7 @@ expand_target_clones (struct cgraph_node *node, bool
> definition)
> XDELETEVEC (attr_str);
>
> /* Setting new attribute to initial function. */
> - tree attributes = make_attribute ("target", "default",
> + tree attributes = make_attribute (new_attr_name, "default",
> DECL_ATTRIBUTES (node->decl));
> DECL_ATTRIBUTES (node->decl) = attributes;
> node->local = false;
> diff --git a/gcc/target.def b/gcc/target.def
> index
> cda6c51e5167f85625168c7c26b777d6c8ccad82..39acea04db01ebaf918910b7dd73d397de6a84ec
> 100644
> --- a/gcc/target.def
> +++ b/gcc/target.def
> @@ -6492,6 +6492,31 @@ the function declaration to hold a pointer to a
> target-specific\n\
> bool, (tree fndecl, tree name, tree args, int flags),
> default_target_option_valid_attribute_p)
>
> +/* Function to validate the attribute((target_version(...))) strings. If
> + the option is validated, the hook should also fill in
> + DECL_FUNCTION_SPECIFIC_TARGET in the function decl node. */
> +DEFHOOK
> +(valid_version_attribute_p,
> + "This hook is called to parse @code{attribute(target_version(\"...\"))},\n\
> +which allows setting target-specific options on individual function
> versions.\n\
> +These function-specific options may differ\n\
> +from the options specified on the command line. The hook should return\n\
> +@code{true} if the options are valid.\n\
> +\n\
> +The hook should set the @code{DECL_FUNCTION_SPECIFIC_TARGET} field in\n\
> +the function declaration to hold a pointer to a target-specific\n\
> +@code{struct cl_target_option} structure.",
> + bool, (tree fndecl, tree name, tree args, int flags),
> + default_target_option_valid_version_attribute_p)
> +
> +/* Attribute to be used when expanding clones for functions with
> + target_clones attribute. */
> +DEFHOOKPOD
> +(expanded_clones_attribute,
> + "Contains the name of the attribute used for the version description
> string\n\
> +when expanding clones for a function with the target_clones attribute.",
> + const char *, "target")
> +
> /* Function to save any extra target state in the target options structure.
> */
> DEFHOOK
> (save,
> diff --git a/gcc/targhooks.h b/gcc/targhooks.h
> index
> 1a0db8dddd594d9b1fb04ae0d9a66ad6b7a396dc..0efc993d82ef59b581a1df74ee0de71135a28703
> 100644
> --- a/gcc/targhooks.h
> +++ b/gcc/targhooks.h
> @@ -192,6 +192,7 @@ extern bool default_hard_regno_scratch_ok (unsigned int);
> extern bool default_mode_dependent_address_p (const_rtx, addr_space_t);
> extern bool default_new_address_profitable_p (rtx, rtx_insn *, rtx);
> extern bool default_target_option_valid_attribute_p (tree, tree, tree, int);
> +extern bool default_target_option_valid_version_attribute_p (tree, tree,
> tree, int);
> extern bool default_target_option_pragma_parse (tree, tree);
> extern bool default_target_can_inline_p (tree, tree);
> extern bool default_update_ipa_fn_target_info (unsigned int &, const gimple
> *);
> diff --git a/gcc/targhooks.cc b/gcc/targhooks.cc
> index
> e190369f87a92e6a92372dc348d9374c3a965c0a..7fc7bf455e80c333cced1bac7085210c2b108f8d
> 100644
> --- a/gcc/targhooks.cc
> +++ b/gcc/targhooks.cc
> @@ -1787,7 +1787,19 @@ default_target_option_valid_attribute_p (tree
> ARG_UNUSED (fndecl),
> int ARG_UNUSED (flags))
> {
> warning (OPT_Wattributes,
> - "target attribute is not supported on this machine");
> + "%<target%> attribute is not supported on this machine");
> +
> + return false;
> +}
> +
> +bool
> +default_target_option_valid_version_attribute_p (tree ARG_UNUSED (fndecl),
> + tree ARG_UNUSED (name),
> + tree ARG_UNUSED (args),
> + int ARG_UNUSED (flags))
> +{
> + warning (OPT_Wattributes,
> + "%<target_version%> attribute is not supported on this machine");
>
> return false;
> }
> diff --git a/gcc/tree.h b/gcc/tree.h
> index
> 0b72663e6a1a94406127f6253460f498b7a3ea9c..ebd89ce79566c350eaaab210c0dca3cc1ac2048e
> 100644
> --- a/gcc/tree.h
> +++ b/gcc/tree.h
> @@ -3438,8 +3438,8 @@ extern vec<tree, va_gc> **decl_debug_args_insert (tree);
> (FUNCTION_DECL_CHECK (NODE)->function_decl.function_specific_optimization)
>
> /* In FUNCTION_DECL, this is set if this function has other versions
> generated
> - using "target" attributes. The default version is the one which does not
> - have any "target" attribute set. */
> + to support different architecture feature sets, e.g. using "target" or
> + "target_version" attributes. */
> #define DECL_FUNCTION_VERSIONED(NODE)\
> (FUNCTION_DECL_CHECK (NODE)->function_decl.versioned_function)
>
>
--
Richard Biener <rguent...@suse.de>
SUSE Software Solutions Germany GmbH,
Frankenstrasse 146, 90461 Nuernberg, Germany;
GF: Ivo Totev, Andrew McDonald, Werner Knoblich; (HRB 36809, AG Nuernberg)
