On 8/28/25 5:49 AM, alfie.richa...@arm.com wrote:
From: Alfie Richards <alfie.richa...@arm.com>

This patch introduces the TARGET_CHECK_TARGET_CLONE_VERSION hook
which is used to determine if a target_clones version string parses.

The hook has a flag to enable emitting diagnostics.

This is as specified in the Arm C Language Extension. The purpose of this
is to be able to ignore invalid versions to allow some portability of code
using target_clones attributes.

Currently this is only properly implemented for the Aarch64 backend.

For riscv which is the only other backend which uses target_version
semantics a partial implementation is present, where this hook is used
to check parsing, in which errors will be emitted on a failed parse
rather than warnings. A refactor of the riscv parsing logic would be
required to enable this functionality fully.

This fixes PR 118339 where parse failures could cause ICE in Aarch64.

gcc/ChangeLog:

        PR target/118339
        * target.def: Add check_target_clone_version hook.
        * tree.cc (get_clone_attr_versions): Add filter argument.
        (get_clone_versions): Add filter argument.
        * tree.h (get_clone_attr_versions): Add filter.
        (get_clone_versions): Add filter argument.
        * config/aarch64/aarch64.cc (aarch64_check_target_clone_version):
        New function
        (TARGET_CHECK_TARGET_CLONE_VERSION): New define.
        * config/riscv/riscv.cc (riscv_check_target_clone_version):
        New function.
        (TARGET_CHECK_TARGET_CLONE_VERSION): New define.
        * doc/tm.texi: Regenerated.
        * doc/tm.texi.in: Add documentation for new hook.
        * hooks.h (hook_stringslice_locationtptr_true): New function.
        * hooks.cc (hook_stringslice_locationtptr_true): New function.

gcc/c-family/ChangeLog:

        * c-attribs.cc (handle_target_clones_attribute): Update to use new hook.

The c-family change looks fine.

---
  gcc/c-family/c-attribs.cc     | 23 +++++++++++----
  gcc/config/aarch64/aarch64.cc | 53 +++++++++++++++++++++++++++++++++++
  gcc/config/riscv/riscv.cc     | 22 +++++++++++++++
  gcc/doc/tm.texi               |  9 ++++++
  gcc/doc/tm.texi.in            |  2 ++
  gcc/hooks.cc                  |  8 ++++++
  gcc/hooks.h                   |  3 ++
  gcc/target.def                | 13 +++++++++
  gcc/tree.cc                   | 17 +++++++----
  gcc/tree.h                    | 13 ++++++---
  10 files changed, 149 insertions(+), 14 deletions(-)

diff --git a/gcc/c-family/c-attribs.cc b/gcc/c-family/c-attribs.cc
index 1e3a94ed949..6e11f74de22 100644
--- a/gcc/c-family/c-attribs.cc
+++ b/gcc/c-family/c-attribs.cc
@@ -6282,12 +6282,25 @@ handle_target_clones_attribute (tree *node, tree name, 
tree ARG_UNUSED (args),
            }
        }
- auto_vec<string_slice> versions = get_clone_attr_versions (args, NULL);
-
-      if (versions.length () == 1)
+      int num_defaults = 0;
+      auto_vec<string_slice> versions = get_clone_attr_versions
+                                         (args,
+                                          &num_defaults,
+                                          false);
+
+      for (auto v : versions)
+       targetm.check_target_clone_version
+         (v, &DECL_SOURCE_LOCATION (*node));
+
+      /* Lone target_clones version is always ignored for target attr 
semantics.
+        Only ignore under target_version semantics if it is a default
+        version.  */
+      if (versions.length () == 1
+         && (TARGET_HAS_FMV_TARGET_ATTRIBUTE || num_defaults == 1))
        {
-         warning (OPT_Wattributes,
-                  "single %<target_clones%> attribute is ignored");
+         if (TARGET_HAS_FMV_TARGET_ATTRIBUTE)
+           warning (OPT_Wattributes,
+                    "single %<target_clones%> attribute is ignored");
          *no_add_attrs = true;
        }
        else
diff --git a/gcc/config/aarch64/aarch64.cc b/gcc/config/aarch64/aarch64.cc
index 4c4ec2d25f3..df3f5b2ea18 100644
--- a/gcc/config/aarch64/aarch64.cc
+++ b/gcc/config/aarch64/aarch64.cc
@@ -31946,6 +31946,56 @@ aarch64_expand_fp_spaceship (rtx dest, rtx op0, rtx 
op1, rtx hint)
      }
  }
+/* Implement TARGET_CHECK_TARGET_CLONE_VERSION. */
+
+bool
+aarch64_check_target_clone_version (string_slice str, location_t *loc)
+{
+  str = str.strip ();
+
+  if (str == "default")
+    return true;
+
+  enum aarch_parse_opt_result parse_res;
+  auto isa_flags = aarch64_asm_isa_flags;
+  std::string invalid_extension;
+
+  parse_res
+    = aarch64_parse_fmv_features (str, &isa_flags, NULL, &invalid_extension);
+
+  if (loc == NULL)
+    return parse_res == AARCH_PARSE_OK;
+
+  switch (parse_res)
+    {
+    case AARCH_PARSE_OK:
+      return true;
+    case AARCH_PARSE_MISSING_ARG:
+      warning_at (*loc, OPT_Wattributes,
+                 "empty string not valid for a %<target_clones%> version");
+      return false;
+    case AARCH_PARSE_INVALID_FEATURE:
+      warning_at (*loc, OPT_Wattributes,
+                 "invalid feature modifier %qs in version %qB for "
+                 "%<target_clones%> attribute",
+                 invalid_extension.c_str (), &str);
+      return false;
+    case AARCH_PARSE_DUPLICATE_FEATURE:
+      warning_at (*loc, OPT_Wattributes,
+                 "duplicate feature modifier %qs in version %qB for "
+                 "%<target_clones%> attribute",
+                 invalid_extension.c_str (), &str);
+      return false;
+    case AARCH_PARSE_INVALID_ARG:
+      warning_at (*loc, OPT_Wattributes,
+                 "invalid feature %qs in version %qB for "
+                 "%<target_clones%> attribute",
+                 invalid_extension.c_str (), &str);
+      return false;
+    }
+  gcc_unreachable ();
+}
+
  /* Target-specific selftests.  */
#if CHECKING_P
@@ -32803,6 +32853,9 @@ aarch64_libgcc_floating_mode_supported_p
  #undef TARGET_OPTION_FUNCTION_VERSIONS
  #define TARGET_OPTION_FUNCTION_VERSIONS aarch64_common_function_versions
+#undef TARGET_CHECK_TARGET_CLONE_VERSION
+#define TARGET_CHECK_TARGET_CLONE_VERSION aarch64_check_target_clone_version
+
  #undef TARGET_COMPARE_VERSION_PRIORITY
  #define TARGET_COMPARE_VERSION_PRIORITY aarch64_compare_version_priority
diff --git a/gcc/config/riscv/riscv.cc b/gcc/config/riscv/riscv.cc
index c5574453cf8..185c66c6b2c 100644
--- a/gcc/config/riscv/riscv.cc
+++ b/gcc/config/riscv/riscv.cc
@@ -14082,6 +14082,25 @@ riscv_common_function_versions (tree fn1, tree fn2)
    return riscv_compare_version_priority (fn1, fn2) != 0;
  }
+/* Checks if the function version specifying string STR parses correctly.
+   If it is an invalid string, currently emits a diagnostic at LOC.
+   Always returns true.  */
+
+bool
+riscv_check_target_clone_version (string_slice str, location_t *loc_p)
+{
+  struct riscv_feature_bits mask;
+  int prio;
+
+  /* Currently it is not possible to parse without emitting errors on failure
+     so do not reject on a failed parse, as this would then emit two
+     diagnostics.  Instead let errors be emitted which will halt
+     compilation.  */
+  parse_features_for_version (str, loc_p, mask, prio);
+
+  return true;
+}
+
  /* Implement TARGET_MANGLE_DECL_ASSEMBLER_NAME, to add function 
multiversioning
     suffixes.  */
@@ -15845,6 +15864,9 @@ riscv_prefetch_offset_address_p (rtx x, machine_mode mode)
  #undef TARGET_COMPARE_VERSION_PRIORITY
  #define TARGET_COMPARE_VERSION_PRIORITY riscv_compare_version_priority
+#undef TARGET_CHECK_TARGET_CLONE_VERSION
+#define TARGET_CHECK_TARGET_CLONE_VERSION riscv_check_target_clone_version
+
  #undef TARGET_OPTION_FUNCTION_VERSIONS
  #define TARGET_OPTION_FUNCTION_VERSIONS riscv_common_function_versions
diff --git a/gcc/doc/tm.texi b/gcc/doc/tm.texi
index 37642680f42..4650e805846 100644
--- a/gcc/doc/tm.texi
+++ b/gcc/doc/tm.texi
@@ -12289,6 +12289,15 @@ function version at run-time for a given set of 
function versions.
  body must be generated.
  @end deftypefn
+@deftypefn {Target Hook} bool TARGET_CHECK_TARGET_CLONE_VERSION (string_slice @var{str}, location_t *@var{loc})
+This hook is used to check if a version specified in a @code{target_clones}
+annotation is valid. @var{str} is the version to be considered.
+If @var{loc} is not @code{NULL} then emit warnings for invalid versions at
+that location.  Otherwise emit no diagnostics.
+Returns @code{true} if @var{str} is a valid version string, and @code{false}
+otherwise
+@end deftypefn
+
  @deftypefn {Target Hook} bool TARGET_PREDICT_DOLOOP_P (class loop *@var{loop})
  Return true if we can predict it is possible to use a low-overhead loop
  for a particular loop.  The parameter @var{loop} is a pointer to the loop.
diff --git a/gcc/doc/tm.texi.in b/gcc/doc/tm.texi.in
index c3ed9a9fd7c..30a9400f0f9 100644
--- a/gcc/doc/tm.texi.in
+++ b/gcc/doc/tm.texi.in
@@ -7897,6 +7897,8 @@ to by @var{ce_info}.
@hook TARGET_GENERATE_VERSION_DISPATCHER_BODY +@hook TARGET_CHECK_TARGET_CLONE_VERSION
+
  @hook TARGET_PREDICT_DOLOOP_P
@hook TARGET_HAVE_COUNT_REG_DECR_P
diff --git a/gcc/hooks.cc b/gcc/hooks.cc
index 76cb593103d..865820d80b1 100644
--- a/gcc/hooks.cc
+++ b/gcc/hooks.cc
@@ -585,3 +585,11 @@ hook_optmode_mode_uhwi_none (machine_mode, unsigned 
HOST_WIDE_INT)
  {
    return opt_machine_mode ();
  }
+
+/* Generic hook that takes a string_slice and a locations and returns false.  
*/
+
+bool
+hook_stringslice_locationtptr_true (string_slice, location_t *)
+{
+  return true;
+}
diff --git a/gcc/hooks.h b/gcc/hooks.h
index e95bd11aca8..08542d7a24e 100644
--- a/gcc/hooks.h
+++ b/gcc/hooks.h
@@ -137,4 +137,7 @@ extern const char 
*hook_constcharptr_int_const_tree_const_tree_null (int, const_
extern opt_machine_mode hook_optmode_mode_uhwi_none (machine_mode,
                                                     unsigned HOST_WIDE_INT);
+
+extern bool hook_stringslice_locationtptr_true (string_slice, location_t *);
+
  #endif
diff --git a/gcc/target.def b/gcc/target.def
index 8e491d83864..adb8edc7353 100644
--- a/gcc/target.def
+++ b/gcc/target.def
@@ -2606,6 +2606,19 @@ version at run-time. @var{decl} is one version from a 
set of semantically\n\
  identical versions.",
   tree, (void *decl), NULL)
+/* Target hook is used to ignore certain versions specified in a target_clones
+   annoration.  STR is the version to be considered.  */
+DEFHOOK
+(check_target_clone_version ,
+ "This hook is used to check if a version specified in a 
@code{target_clones}\n\
+annotation is valid. @var{str} is the version to be considered.\n\
+If @var{loc} is not @code{NULL} then emit warnings for invalid versions at\n\
+that location.  Otherwise emit no diagnostics.\n\
+Returns @code{true} if @var{str} is a valid version string, and @code{false}\n\
+otherwise",
+ bool, (string_slice str, location_t *loc),
+ hook_stringslice_locationtptr_true)
+
  /* Returns a code for a target-specific builtin that implements
     reciprocal of a target-specific function, or NULL_TREE if not available.  
*/
  DEFHOOK
diff --git a/gcc/tree.cc b/gcc/tree.cc
index d351e9e253c..05fd3d097e0 100644
--- a/gcc/tree.cc
+++ b/gcc/tree.cc
@@ -15421,10 +15421,13 @@ get_attr_nonstring_decl (tree expr, tree *ref)
  }
/* Returns an auto_vec of string_slices containing the version strings from
-   ARGLIST.  DEFAULT_COUNT is incremented for each default version found.  */
+   ARGLIST.  DEFAULT_COUNT is incremented for each default version found.
+   If FILTER is true then any invalid versions strings are not included.  */
auto_vec<string_slice>
-get_clone_attr_versions (const tree arglist, int *default_count)
+get_clone_attr_versions (const tree arglist,
+                        int *default_count,
+                        bool filter)
  {
    gcc_assert (TREE_CODE (arglist) == TREE_LIST);
    auto_vec<string_slice> versions;
@@ -15440,6 +15443,9 @@ get_clone_attr_versions (const tree arglist, int 
*default_count)
          string_slice attr = string_slice::tokenize (&str, separators);
          attr = attr.strip ();
+ if (filter && !targetm.check_target_clone_version (attr, NULL))
+           continue;
+
          if (attr == "default" && default_count)
            (*default_count)++;
          versions.safe_push (attr);
@@ -15450,15 +15456,16 @@ get_clone_attr_versions (const tree arglist, int 
*default_count)
/* Returns an auto_vec of string_slices containing the version strings from
     the target_clone attribute from DECL.  DEFAULT_COUNT is incremented for 
each
-   default version found.  */
+   default version found.  If FILTER is true then any invalid versions strings
+   are not included.  */
  auto_vec<string_slice>
-get_clone_versions (const tree decl, int *default_count)
+get_clone_versions (const tree decl, int *default_count, bool filter)
  {
    tree attr = lookup_attribute ("target_clones", DECL_ATTRIBUTES (decl));
    if (!attr)
      return auto_vec<string_slice> ();
    tree arglist = TREE_VALUE (attr);
-  return get_clone_attr_versions (arglist, default_count);
+  return get_clone_attr_versions (arglist, default_count, filter);
  }
/* If DECL has a target_version attribute, returns a string_slice containing the
diff --git a/gcc/tree.h b/gcc/tree.h
index 6d28f2dddd8..b22dce5214a 100644
--- a/gcc/tree.h
+++ b/gcc/tree.h
@@ -7105,10 +7105,15 @@ extern tree get_attr_nonstring_decl (tree, tree * = 
NULL);
     Returns an invalid string_slice if no attribute is present.  */
  extern string_slice get_target_version (const tree);
  /* Returns a vector of the version strings from a target_clones attribute on
-   a decl.  Can also record the number of default versions found.  */
-extern auto_vec<string_slice> get_clone_versions (const tree, int * = NULL);
+   a decl.  Can also record the number of default versions found.
+   Use bool to control whether or not the results should
+   be filtered with TARGET_CHECK_TARGET_CLONE_VERSION.  */
+extern auto_vec<string_slice> get_clone_versions
+  (const tree,int * = NULL, bool = true);
  /* Returns a vector of the version strings from a target_clones attribute
-   directly.  */
-extern auto_vec<string_slice> get_clone_attr_versions (const tree, int *);
+   directly.  Additionally takes a bool to control whether or not the results
+   should be filtered with TARGET_CHECK_TARGET_CLONE_VERSION.  */
+extern auto_vec<string_slice> get_clone_attr_versions
+  (const tree, int *, bool = true);
#endif /* GCC_TREE_H */

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