From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Daniel Bertalan <dani@danielbertalan.dev>
Date: Fri, 8 Sep 2023 00:42:17 +0200
Subject: [PATCH] [clang] Add -fvisibility-inlines-hidden-function-templates

---
 clang/include/clang/Basic/LangOptions.def |  3 +++
 clang/include/clang/Driver/Options.td     |  6 ++++++
 clang/lib/AST/Decl.cpp                    | 18 ++++++++++++------
 clang/lib/Driver/ToolChains/Clang.cpp     |  2 ++
 4 files changed, 23 insertions(+), 6 deletions(-)

diff --git a/clang/include/clang/Basic/LangOptions.def b/clang/include/clang/Basic/LangOptions.def
index 4942dcaa086e..677ad6273e3a 100644
--- a/clang/include/clang/Basic/LangOptions.def
+++ b/clang/include/clang/Basic/LangOptions.def
@@ -310,6 +310,9 @@ BENIGN_LANGOPT(IgnoreXCOFFVisibility, 1, 0, "All the visibility attributes that
 BENIGN_LANGOPT(VisibilityInlinesHiddenStaticLocalVar, 1, 0,
                "hidden visibility for static local variables in inline C++ "
                "methods when -fvisibility-inlines hidden is enabled")
+BENIGN_LANGOPT(VisibilityInlinesHiddenFunctionTemplate, 1, 0,
+               "hidden visibility for implicitly instantiated C++ function "
+               "templates when -fvisibility-inlines-hidden is enabled")
 ENUM_LANGOPT(GlobalAllocationFunctionVisibility, VisibilityForcedKinds, 3, VisibilityForcedKinds::ForceDefault,
              "How to apply visibility to global operator new and delete declarations")
 LANGOPT(NewInfallible , 1, 0, "Treats throwing global C++ operator new as always returning valid memory (annotates with __attribute__((returns_nonnull)) and throw()). This is detectable in source.")
diff --git a/clang/include/clang/Driver/Options.td b/clang/include/clang/Driver/Options.td
index 175bedbfb4d0..7cc661956e3a 100644
--- a/clang/include/clang/Driver/Options.td
+++ b/clang/include/clang/Driver/Options.td
@@ -3918,6 +3918,12 @@ defm visibility_inlines_hidden_static_local_var : BoolFOption<"visibility-inline
   NegFlag<SetFalse, [], [ClangOption], "Disables -fvisibility-inlines-hidden-static-local-var"
          " (this is the default on non-darwin targets)">, BothFlags<
                  [], [ClangOption, CC1Option]>>;
+defm visibility_inlines_hidden_function_template : BoolFOption<"visibility-inlines-hidden-function-template",
+  LangOpts<"VisibilityInlinesHiddenFunctionTemplate">, DefaultFalse,
+  PosFlag<SetTrue, [], [ClangOption, CC1Option],
+          "When -fvisibility-inlines-hidden is enabled, all template functions will be given"
+          " hidden visibility by default, even if they are not declared ``inline``">,
+  NegFlag<SetFalse>>;
 def fvisibility_ms_compat : Flag<["-"], "fvisibility-ms-compat">, Group<f_Group>,
   HelpText<"Give global types 'default' visibility and global functions and "
            "variables 'hidden' visibility by default">;
diff --git a/clang/lib/AST/Decl.cpp b/clang/lib/AST/Decl.cpp
index 1ee33fd7576d..b8cb7e5a494b 100644
--- a/clang/lib/AST/Decl.cpp
+++ b/clang/lib/AST/Decl.cpp
@@ -562,13 +562,19 @@ static bool useInlineVisibilityHidden(const NamedDecl *D) {
     TSK = MSI->getTemplateSpecializationKind();
   }
 
+  if (TSK == TSK_ExplicitInstantiationDeclaration ||
+      TSK == TSK_ExplicitInstantiationDefinition)
+    return false;
+
   const FunctionDecl *Def = nullptr;
-  // InlineVisibilityHidden only applies to definitions, and
-  // isInlined() only gives meaningful answers on definitions
-  // anyway.
-  return TSK != TSK_ExplicitInstantiationDeclaration &&
-    TSK != TSK_ExplicitInstantiationDefinition &&
-    FD->hasBody(Def) && Def->isInlined() && !Def->hasAttr<GNUInlineAttr>();
+  if (!FD->hasBody(Def))
+    return false;
+
+  if (Def->hasAttr<GNUInlineAttr>())
+    return false;
+
+  return Def->isInlined() || (TSK == TSK_ImplicitInstantiation &&
+                              Opts.VisibilityInlinesHiddenFunctionTemplate);
 }
 
 template <typename T> static bool isFirstInExternCContext(T *D) {
diff --git a/clang/lib/Driver/ToolChains/Clang.cpp b/clang/lib/Driver/ToolChains/Clang.cpp
index aa344b3465ab..a9e2a4012fd1 100644
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -6350,6 +6350,8 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
 
   Args.AddLastArg(CmdArgs, options::OPT_fvisibility_inlines_hidden_static_local_var,
                            options::OPT_fno_visibility_inlines_hidden_static_local_var);
+  Args.AddLastArg(CmdArgs, options::OPT_fvisibility_inlines_hidden_function_template,
+                           options::OPT_fno_visibility_inlines_hidden_function_template);
 
   // -fvisibility-global-new-delete-hidden is a deprecated spelling of
   // -fvisibility-global-new-delete=force-hidden.
-- 
2.44.0