[clang][fmv] Drop .ifunc from target_version's entrypoint's mangling (#81194)

jroelofs · web-flow · commit 99d743320c5d · 2024-02-09T08:13:15.000-08:00
Fixes: #81043
diff --git a/clang/include/clang/AST/Decl.h b/clang/include/clang/AST/Decl.h
@@ -2619,6 +2619,10 @@ class FunctionDecl : public DeclaratorDecl,
   /// the target-clones functionality.
   bool isTargetClonesMultiVersion() const;
 
+  /// True if this function is a multiversioned dispatch function as a part of
+  /// the target-version functionality.
+  bool isTargetVersionMultiVersion() const;
+
   /// \brief Get the associated-constraints of this function declaration.
   /// Currently, this will either be a vector of size 1 containing the
   /// trailing-requires-clause or an empty vector.
diff --git a/clang/include/clang/Basic/AttrDocs.td b/clang/include/clang/Basic/AttrDocs.td
@@ -2517,6 +2517,14 @@ function it instructs compiler to emit multiple function versions based on
 priority and target features availability. One of the versions is always
 ( implicitly or explicitly ) the ``default`` (fallback). Attribute strings can
 contain dependent features names joined by the "+" sign.
+
+For targets that support the GNU indirect function (IFUNC) feature, dispatch
+is performed by emitting an indirect function that is resolved to the appropriate
+target clone at load time. The indirect function is given the name the
+multiversioned function would have if it had been declared without the attribute.
+For backward compatibility with earlier Clang releases, a function alias with an
+``.ifunc`` suffix is also emitted. The  ``.ifunc`` suffixed symbol is a deprecated
+feature and support for it may be removed in the future.
 }];
 }
 
diff --git a/clang/lib/AST/Decl.cpp b/clang/lib/AST/Decl.cpp
@@ -3541,6 +3541,10 @@ bool FunctionDecl::isTargetClonesMultiVersion() const {
   return isMultiVersion() && hasAttr<TargetClonesAttr>();
 }
 
+bool FunctionDecl::isTargetVersionMultiVersion() const {
+  return isMultiVersion() && hasAttr<TargetVersionAttr>();
+}
+
 void
 FunctionDecl::setPreviousDeclaration(FunctionDecl *PrevDecl) {
   redeclarable_base::setPreviousDecl(PrevDecl);
diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp
@@ -30,6 +30,7 @@
 #include "clang/AST/ASTContext.h"
 #include "clang/AST/ASTLambda.h"
 #include "clang/AST/CharUnits.h"
+#include "clang/AST/Decl.h"
 #include "clang/AST/DeclCXX.h"
 #include "clang/AST/DeclObjC.h"
 #include "clang/AST/DeclTemplate.h"
@@ -4212,7 +4213,8 @@ void CodeGenModule::emitMultiVersionFunctions() {
     llvm::Constant *ResolverConstant = GetOrCreateMultiVersionResolver(GD);
     if (auto *IFunc = dyn_cast<llvm::GlobalIFunc>(ResolverConstant)) {
       ResolverConstant = IFunc->getResolver();
-      if (FD->isTargetClonesMultiVersion()) {
+      if (FD->isTargetClonesMultiVersion() ||
+          FD->isTargetVersionMultiVersion()) {
         const CGFunctionInfo &FI = getTypes().arrangeGlobalDeclaration(GD);
         llvm::FunctionType *DeclTy = getTypes().GetFunctionType(FI);
         std::string MangledName = getMangledNameImpl(
@@ -4393,8 +4395,18 @@ llvm::Constant *CodeGenModule::GetOrCreateMultiVersionResolver(GlobalDecl GD) {
   // a separate resolver).
   std::string ResolverName = MangledName;
   if (getTarget().supportsIFunc()) {
-    if (!FD->isTargetClonesMultiVersion())
+    switch (FD->getMultiVersionKind()) {
+    case MultiVersionKind::None:
+      llvm_unreachable("unexpected MultiVersionKind::None for resolver");
+    case MultiVersionKind::Target:
+    case MultiVersionKind::CPUSpecific:
+    case MultiVersionKind::CPUDispatch:
       ResolverName += ".ifunc";
+      break;
+    case MultiVersionKind::TargetClones:
+    case MultiVersionKind::TargetVersion:
+      break;
+    }
   } else if (FD->isTargetMultiVersion()) {
     ResolverName += ".resolver";
   }
diff --git a/clang/test/CodeGen/attr-target-version.c b/clang/test/CodeGen/attr-target-version.c
@@ -90,13 +90,20 @@ int hoo(void) {
 
 //.
 // CHECK: @__aarch64_cpu_features = external dso_local global { i64 }
-// CHECK: @fmv.ifunc = weak_odr ifunc i32 (), ptr @fmv.resolver
-// CHECK: @fmv_one.ifunc = weak_odr ifunc i32 (), ptr @fmv_one.resolver
-// CHECK: @fmv_two.ifunc = weak_odr ifunc i32 (), ptr @fmv_two.resolver
-// CHECK: @fmv_e.ifunc = weak_odr ifunc i32 (), ptr @fmv_e.resolver
-// CHECK: @fmv_c.ifunc = weak_odr ifunc void (), ptr @fmv_c.resolver
-// CHECK: @fmv_inline.ifunc = weak_odr ifunc i32 (), ptr @fmv_inline.resolver
-// CHECK: @fmv_d.ifunc = internal ifunc i32 (), ptr @fmv_d.resolver
+// CHECK: @fmv.ifunc = weak_odr alias i32 (), ptr @fmv
+// CHECK: @fmv_one.ifunc = weak_odr alias i32 (), ptr @fmv_one
+// CHECK: @fmv_two.ifunc = weak_odr alias i32 (), ptr @fmv_two
+// CHECK: @fmv_e.ifunc = weak_odr alias i32 (), ptr @fmv_e
+// CHECK: @fmv_inline.ifunc = weak_odr alias i32 (), ptr @fmv_inline
+// CHECK: @fmv_d.ifunc = internal alias i32 (), ptr @fmv_d
+// CHECK: @fmv_c.ifunc = weak_odr alias void (), ptr @fmv_c
+// CHECK: @fmv = weak_odr ifunc i32 (), ptr @fmv.resolver
+// CHECK: @fmv_one = weak_odr ifunc i32 (), ptr @fmv_one.resolver
+// CHECK: @fmv_two = weak_odr ifunc i32 (), ptr @fmv_two.resolver
+// CHECK: @fmv_e = weak_odr ifunc i32 (), ptr @fmv_e.resolver
+// CHECK: @fmv_inline = weak_odr ifunc i32 (), ptr @fmv_inline.resolver
+// CHECK: @fmv_d = internal ifunc i32 (), ptr @fmv_d.resolver
+// CHECK: @fmv_c = weak_odr ifunc void (), ptr @fmv_c.resolver
 //.
 // CHECK: Function Attrs: noinline nounwind optnone
 // CHECK-LABEL: define {{[^@]+}}@fmv._MrngMflagmMfp16fml
@@ -105,6 +112,32 @@ int hoo(void) {
 // CHECK-NEXT:    ret i32 1
 //
 //
+// CHECK: Function Attrs: noinline nounwind optnone
+// CHECK-LABEL: define {{[^@]+}}@fmv_one._MsimdMls64
+// CHECK-SAME: () #[[ATTR1:[0-9]+]] {
+// CHECK-NEXT:  entry:
+// CHECK-NEXT:    ret i32 1
+//
+//
+// CHECK: Function Attrs: noinline nounwind optnone
+// CHECK-LABEL: define {{[^@]+}}@fmv_two._Mfp
+// CHECK-SAME: () #[[ATTR1]] {
+// CHECK-NEXT:  entry:
+// CHECK-NEXT:    ret i32 1
+//
+//
+// CHECK: Function Attrs: noinline nounwind optnone
+// CHECK-LABEL: define {{[^@]+}}@foo
+// CHECK-SAME: () #[[ATTR2:[0-9]+]] {
+// CHECK-NEXT:  entry:
+// CHECK-NEXT:    [[CALL:%.*]] = call i32 @fmv()
+// CHECK-NEXT:    [[CALL1:%.*]] = call i32 @fmv_one()
+// CHECK-NEXT:    [[ADD:%.*]] = add nsw i32 [[CALL]], [[CALL1]]
+// CHECK-NEXT:    [[CALL2:%.*]] = call i32 @fmv_two()
+// CHECK-NEXT:    [[ADD3:%.*]] = add nsw i32 [[ADD]], [[CALL2]]
+// CHECK-NEXT:    ret i32 [[ADD3]]
+//
+//
 // CHECK-LABEL: define {{[^@]+}}@fmv.resolver() comdat {
 // CHECK-NEXT:  resolver_entry:
 // CHECK-NEXT:    call void @__init_cpu_features_resolver()
@@ -183,42 +216,16 @@ int hoo(void) {
 // CHECK-NEXT:    ret ptr @fmv.default
 //
 //
-// CHECK: Function Attrs: noinline nounwind optnone
-// CHECK-LABEL: define {{[^@]+}}@fmv_one._MsimdMls64
-// CHECK-SAME: () #[[ATTR1:[0-9]+]] {
-// CHECK-NEXT:  entry:
-// CHECK-NEXT:    ret i32 1
-//
-//
 // CHECK-LABEL: define {{[^@]+}}@fmv_one.resolver() comdat {
 // CHECK-NEXT:  resolver_entry:
 // CHECK-NEXT:    ret ptr @fmv_one._MsimdMls64
 //
 //
-// CHECK: Function Attrs: noinline nounwind optnone
-// CHECK-LABEL: define {{[^@]+}}@fmv_two._Mfp
-// CHECK-SAME: () #[[ATTR1]] {
-// CHECK-NEXT:  entry:
-// CHECK-NEXT:    ret i32 1
-//
-//
 // CHECK-LABEL: define {{[^@]+}}@fmv_two.resolver() comdat {
 // CHECK-NEXT:  resolver_entry:
 // CHECK-NEXT:    ret ptr @fmv_two._MsimdMfp16
 //
 //
-// CHECK: Function Attrs: noinline nounwind optnone
-// CHECK-LABEL: define {{[^@]+}}@foo
-// CHECK-SAME: () #[[ATTR2:[0-9]+]] {
-// CHECK-NEXT:  entry:
-// CHECK-NEXT:    [[CALL:%.*]] = call i32 @fmv.ifunc()
-// CHECK-NEXT:    [[CALL1:%.*]] = call i32 @fmv_one.ifunc()
-// CHECK-NEXT:    [[ADD:%.*]] = add nsw i32 [[CALL]], [[CALL1]]
-// CHECK-NEXT:    [[CALL2:%.*]] = call i32 @fmv_two.ifunc()
-// CHECK-NEXT:    [[ADD3:%.*]] = add nsw i32 [[ADD]], [[CALL2]]
-// CHECK-NEXT:    ret i32 [[ADD3]]
-//
-//
 // CHECK-LABEL: define {{[^@]+}}@fmv_e.resolver() comdat {
 // CHECK-NEXT:  resolver_entry:
 // CHECK-NEXT:    ret ptr @fmv_e._Mls64
@@ -238,28 +245,14 @@ int hoo(void) {
 // CHECK-NEXT:    ret void
 //
 //
-// CHECK-LABEL: define {{[^@]+}}@fmv_c.resolver() comdat {
-// CHECK-NEXT:  resolver_entry:
-// CHECK-NEXT:    call void @__init_cpu_features_resolver()
-// CHECK-NEXT:    [[TMP0:%.*]] = load i64, ptr @__aarch64_cpu_features, align 8
-// CHECK-NEXT:    [[TMP1:%.*]] = and i64 [[TMP0]], 281474976710656
-// CHECK-NEXT:    [[TMP2:%.*]] = icmp eq i64 [[TMP1]], 281474976710656
-// CHECK-NEXT:    [[TMP3:%.*]] = and i1 true, [[TMP2]]
-// CHECK-NEXT:    br i1 [[TMP3]], label [[RESOLVER_RETURN:%.*]], label [[RESOLVER_ELSE:%.*]]
-// CHECK:       resolver_return:
-// CHECK-NEXT:    ret ptr @fmv_c._Mssbs
-// CHECK:       resolver_else:
-// CHECK-NEXT:    ret ptr @fmv_c.default
-//
-//
 // CHECK: Function Attrs: noinline nounwind optnone
 // CHECK-LABEL: define {{[^@]+}}@goo
 // CHECK-SAME: () #[[ATTR2]] {
 // CHECK-NEXT:  entry:
-// CHECK-NEXT:    [[CALL:%.*]] = call i32 @fmv_inline.ifunc()
-// CHECK-NEXT:    [[CALL1:%.*]] = call i32 @fmv_e.ifunc()
-// CHECK-NEXT:    [[CALL2:%.*]] = call i32 @fmv_d.ifunc()
-// CHECK-NEXT:    call void @fmv_c.ifunc()
+// CHECK-NEXT:    [[CALL:%.*]] = call i32 @fmv_inline()
+// CHECK-NEXT:    [[CALL1:%.*]] = call i32 @fmv_e()
+// CHECK-NEXT:    [[CALL2:%.*]] = call i32 @fmv_d()
+// CHECK-NEXT:    call void @fmv_c()
 // CHECK-NEXT:    [[CALL3:%.*]] = call i32 @fmv_default()
 // CHECK-NEXT:    ret i32 [[CALL3]]
 //
@@ -412,6 +405,20 @@ int hoo(void) {
 // CHECK-NEXT:    ret ptr @fmv_d.default
 //
 //
+// CHECK-LABEL: define {{[^@]+}}@fmv_c.resolver() comdat {
+// CHECK-NEXT:  resolver_entry:
+// CHECK-NEXT:    call void @__init_cpu_features_resolver()
+// CHECK-NEXT:    [[TMP0:%.*]] = load i64, ptr @__aarch64_cpu_features, align 8
+// CHECK-NEXT:    [[TMP1:%.*]] = and i64 [[TMP0]], 281474976710656
+// CHECK-NEXT:    [[TMP2:%.*]] = icmp eq i64 [[TMP1]], 281474976710656
+// CHECK-NEXT:    [[TMP3:%.*]] = and i1 true, [[TMP2]]
+// CHECK-NEXT:    br i1 [[TMP3]], label [[RESOLVER_RETURN:%.*]], label [[RESOLVER_ELSE:%.*]]
+// CHECK:       resolver_return:
+// CHECK-NEXT:    ret ptr @fmv_c._Mssbs
+// CHECK:       resolver_else:
+// CHECK-NEXT:    ret ptr @fmv_c.default
+//
+//
 // CHECK: Function Attrs: noinline nounwind optnone
 // CHECK-LABEL: define {{[^@]+}}@recur
 // CHECK-SAME: () #[[ATTR2]] {
@@ -437,9 +444,9 @@ int hoo(void) {
 // CHECK-NEXT:  entry:
 // CHECK-NEXT:    [[FP1:%.*]] = alloca ptr, align 8
 // CHECK-NEXT:    [[FP2:%.*]] = alloca ptr, align 8
-// CHECK-NEXT:    call void @f(ptr noundef @fmv.ifunc)
-// CHECK-NEXT:    store ptr @fmv.ifunc, ptr [[FP1]], align 8
-// CHECK-NEXT:    store ptr @fmv.ifunc, ptr [[FP2]], align 8
+// CHECK-NEXT:    call void @f(ptr noundef @fmv)
+// CHECK-NEXT:    store ptr @fmv, ptr [[FP1]], align 8
+// CHECK-NEXT:    store ptr @fmv, ptr [[FP2]], align 8
 // CHECK-NEXT:    [[TMP0:%.*]] = load ptr, ptr [[FP1]], align 8
 // CHECK-NEXT:    [[CALL:%.*]] = call i32 [[TMP0]]()
 // CHECK-NEXT:    [[TMP1:%.*]] = load ptr, ptr [[FP2]], align 8
@@ -561,13 +568,6 @@ int hoo(void) {
 //
 //
 // CHECK: Function Attrs: noinline nounwind optnone
-// CHECK-LABEL: define {{[^@]+}}@fmv_c.default
-// CHECK-SAME: () #[[ATTR2]] {
-// CHECK-NEXT:  entry:
-// CHECK-NEXT:    ret void
-//
-//
-// CHECK: Function Attrs: noinline nounwind optnone
 // CHECK-LABEL: define {{[^@]+}}@fmv_inline._Msha1MpmullMf64mm
 // CHECK-SAME: () #[[ATTR12:[0-9]+]] {
 // CHECK-NEXT:  entry:
@@ -700,6 +700,13 @@ int hoo(void) {
 // CHECK-NEXT:    ret i32 1
 //
 //
+// CHECK: Function Attrs: noinline nounwind optnone
+// CHECK-LABEL: define {{[^@]+}}@fmv_c.default
+// CHECK-SAME: () #[[ATTR2]] {
+// CHECK-NEXT:  entry:
+// CHECK-NEXT:    ret void
+//
+//
 // CHECK-NOFMV: Function Attrs: noinline nounwind optnone
 // CHECK-NOFMV-LABEL: define {{[^@]+}}@fmv
 // CHECK-NOFMV-SAME: () #[[ATTR0:[0-9]+]] {
diff --git a/clang/test/CodeGenCXX/attr-target-version.cpp b/clang/test/CodeGenCXX/attr-target-version.cpp
