On 6/12/25 11:00 AM, Alfie Richards wrote:
This patch changes the semantics of target_version and target_clones attributes
to match the behavior described in the Arm C Language extension.
The changes to behavior are:
- The scope and signature of an FMV function set is now that of the default
version.
- The FMV resolver is now created at the locations of the default version
implementation. Previously this was at the first call to an FMV function.
- When a TU has a single annotated function version, it gets mangled.
- This includes a lone annotated default version.
This only affects targets with TARRGET_HAS_FMV_TARGET_ATTRIBUTE set to false.
Currently that is aarch64 and riscv.
This is achieved by:
- Skipping the existing FMV dispatching code at C++ gimplification and instead
making use of the target_clones dispatching code in multiple_targets.cc.
(This fixes PR target/118313 for aarch64 and riscv).
- Splitting target_clones pass in two, an early and late pass, where the early
pass handles cases where multiple declarations are used to define a version,
and the late pass handling target semantics targets, and cases where a FMV
set is defined by a single target_clones decl.
- Changing the logic in add_candidates and resolve_address of overloaded
function to prevent resolution of any version except a default version.
(thus making the default version determine scope and signature of the
versioned function set).
- Adding logic for dispatching a lone annotated default version in
multiple_targets.cc
- As as annotated default version gets mangled an alias is created from the
dispatched symbol to the default version as no ifunc resolution is required
in this case. (ie. an alias from `_Z3foov` to `_Z3foov.default`)
- Adding logic to `symbol_table::remove_unreachable_nodes` and analyze_functions
that a reference to the default function version also implies a possible
reference to the other versions (so they shouldnt be deleted and do need to
be analyzed).
gcc/ChangeLog:
PR target/118313
* cgraphunit.cc (analyze_functions): Add logic for target version
dependencies.
* ipa.cc (symbol_table::remove_unreachable_nodes): Ditto.
* multiple_target.cc (create_dispatcher_calls): Change to support
target version semantics.
(ipa_target_clone): Change to dispatch all function sets in
target_version semantics, and to have early and late pass.
(is_simple_target_clones_case): New function.
* config/aarch64/aarch64.cc: (aarch64_get_function_versions_dispatcher):
Refactor with the assumption that the DECL node will be default.
* config/riscv/riscv.cc: (riscv_get_function_versions_dispatcher):
Refactor with the assumption that the DECL node will be default.
* passes.def: Split target_clones pass into early and late version.
gcc/cp/ChangeLog:
PR target/118313
* call.cc (add_candidates): Change to not resolve non-default versions
in
target_version semantics.
* class.cc (resolve_address_of_overloaded_function): Ditto.
* cp-gimplify.cc (cp_genericize_r): Change logic to not apply for
target_version semantics.
* decl.cc (start_decl): Change to mark and therefore mangle all
target_version decls.
(start_preparsed_function): Ditto.
* typeck.cc (cp_build_function_call_vec): Add error for calling
unresolvable
non-default node in target_version semantics.
gcc/testsuite/ChangeLog:
* g++.target/aarch64/mv-1.C: Change for target_version semantics.
* g++.target/aarch64/mv-symbols2.C: Ditto.
* g++.target/aarch64/mv-symbols3.C: Ditto.
* g++.target/aarch64/mv-symbols4.C: Ditto.
* g++.target/aarch64/mv-symbols5.C: Ditto.
* g++.target/aarch64/mvc-symbols3.C: Ditto.
* g++.target/riscv/mv-symbols2.C: Ditto.
* g++.target/riscv/mv-symbols3.C: Ditto.
* g++.target/riscv/mv-symbols4.C: Ditto.
* g++.target/riscv/mv-symbols5.C: Ditto.
* g++.target/riscv/mvc-symbols3.C: Ditto.
* g++.target/aarch64/mv-symbols10.C: New test.
* g++.target/aarch64/mv-symbols11.C: New test.
* g++.target/aarch64/mv-symbols12.C: New test.
* g++.target/aarch64/mv-symbols13.C: New test.
* g++.target/aarch64/mv-symbols6.C: New test.
* g++.target/aarch64/mv-symbols7.C: New test.
* g++.target/aarch64/mv-symbols8.C: New test.
* g++.target/aarch64/mv-symbols9.C: New test.
---
Just a few nits below, nothing function. So like the prior patch I
reviewed today, if this can go in independently now it probably should
after fixing the nits.
diff --git a/gcc/cp/typeck.cc b/gcc/cp/typeck.cc
index ac1eb397f01..702539a5512 100644
--- a/gcc/cp/typeck.cc
+++ b/gcc/cp/typeck.cc
@@ -4434,6 +4434,16 @@ cp_build_function_call_vec (tree function, vec<tree,
va_gc> **params,
return error_mark_node;
fndecl = function;
+ /* For target_version semantics, the funciton set cannot be called
s/funciton/function/
diff --git a/gcc/multiple_target.cc b/gcc/multiple_target.cc
index 44340cbc6a4..bb430bc4fbf 100644
--- a/gcc/multiple_target.cc
+++ b/gcc/multiple_target.cc
@@ -58,8 +58,15 @@ replace_function_decl (tree *op, int *walk_subtrees, void
*data)
return NULL;
}
-/* If the call in NODE has multiple target attribute with multiple fields,
- replace it with dispatcher call and create dispatcher (once). */
+/* In target FMV attributes, if the call in NODE has multiple target attribute
+ with multiple fields, replace it with calls to the dispatched symbol and
+ create the disptacher body (once).
Nit. s/disptacher/dispatcher.
+static bool is_simple_target_clones_case (cgraph_node *node)
Linkage & return type on separate line. Needs function comment.
+{
+ /* target attribute semantics doesnt support the complex case,
s/doesnt/doesn't/ Or if you don't want the single quote in the comment,
then s/doesnt/does not/.
