[clang][Fuchsia] Also use -fc++-abi=fuchsia for selecting relative-vtables multilibs

clang/lib/Driver/ToolChains/Fuchsia.cpp

Fuchsia::Fuchsia(const Driver &D, const llvm::Triple &Triple,
   Multilib::flags_list Flags;
   addMultilibFlag(
       Args.hasFlag(options::OPT_fexceptions, options::OPT_fno_exceptions, true),
       "fexceptions", Flags);
   addMultilibFlag(getSanitizerArgs().needsAsanRt(), "fsanitize=address", Flags);
   addMultilibFlag(getSanitizerArgs().needsHwasanRt(), "fsanitize=hwaddress",
                   Flags);
 
-  addMultilibFlag(
-      Args.hasFlag(options::OPT_fexperimental_relative_cxx_abi_vtables,
-                   options::OPT_fno_experimental_relative_cxx_abi_vtables,
-                   /*default=*/false),
-      "fexperimental-relative-c++-abi-vtables", Flags);
+  // If `-fexperimental-relative-c++-abi-vtables` or `-fc++-abi=fuchsia` is
+  // passed to the driver, and `-fno-experimental-relative-c++-abi-vtables` is
+  // not passed, then use the RV multilib.
+  bool UseFuchsiaCXXABI =
+      Args.getLastArgValue(options::OPT_fcxx_abi_EQ) == "fuchsia";
+  bool UseCXXRelVTables = Args.hasFlag(
+      options::OPT_fexperimental_relative_cxx_abi_vtables,
+      options::OPT_fno_experimental_relative_cxx_abi_vtables, UseFuchsiaCXXABI);
+  addMultilibFlag(UseCXXRelVTables, "fexperimental-relative-c++-abi-vtables",
+                  Flags);
 
   Multilibs.setFilePathsCallback(FilePaths);
 
   if (Multilibs.select(Flags, SelectedMultilib))
     if (!SelectedMultilib.isDefault())
       if (const auto &PathsCallback = Multilibs.filePathsCallback())
         for (const auto &Path : PathsCallback(SelectedMultilib))
           // Prepend the multilib path to ensure it takes the precedence.

clang/test/Driver/fuchsia.cpp

 // RUN:     -resource-dir=%S/Inputs/resource_dir_with_per_target_subdir \
 // RUN:     -fuse-ld=lld 2>&1\
 // RUN:     | FileCheck %s -check-prefixes=CHECK-MULTILIB-X86,CHECK-MULTILIB-NOEXCEPT-X86
 // RUN: %clangxx %s -### --target=x86_64-unknown-fuchsia -fsanitize=address -fno-exceptions \
 // RUN:     -ccc-install-dir %S/Inputs/basic_fuchsia_tree/bin \
 // RUN:     -resource-dir=%S/Inputs/resource_dir_with_per_target_subdir \
 // RUN:     -fuse-ld=lld 2>&1\
 // RUN:     | FileCheck %s -check-prefixes=CHECK-MULTILIB-X86,CHECK-MULTILIB-ASAN-NOEXCEPT-X86
+
 // RUN: %clangxx %s -### --target=x86_64-unknown-fuchsia -fexperimental-relative-c++-abi-vtables \
 // RUN:     -ccc-install-dir %S/Inputs/basic_fuchsia_tree/bin \
 // RUN:     -resource-dir=%S/Inputs/resource_dir_with_per_target_subdir \
 // RUN:     -fuse-ld=lld 2>&1\
 // RUN:     | FileCheck %s -check-prefixes=CHECK-MULTILIB-X86,CHECK-MULTILIB-RELATIVE-VTABLES-X86
 // RUN: %clangxx %s -### --target=x86_64-unknown-fuchsia -fexperimental-relative-c++-abi-vtables -fno-exceptions \
 // RUN:     -ccc-install-dir %S/Inputs/basic_fuchsia_tree/bin \
 // RUN:     -resource-dir=%S/Inputs/resource_dir_with_per_target_subdir \

 // RUN:     -resource-dir=%S/Inputs/resource_dir_with_per_target_subdir \
 // RUN:     -fuse-ld=lld 2>&1\
 // RUN:     | FileCheck %s -check-prefixes=CHECK-MULTILIB-X86,CHECK-MULTILIB-RELATIVE-VTABLES-ASAN-NOEXCEPT-X86
 // RUN: %clangxx %s -### --target=x86_64-unknown-fuchsia -fno-experimental-relative-c++-abi-vtables \
 // RUN:     -ccc-install-dir %S/Inputs/basic_fuchsia_tree/bin \
 // RUN:     -resource-dir=%S/Inputs/resource_dir_with_per_target_subdir \
 // RUN:     -fuse-ld=lld 2>&1\
 // RUN:     | FileCheck %s -check-prefixes=CHECK-MULTILIB-X86
-// RUN: %clangxx %s -### --target=x86_64-unknown-fuchsia -fno-experimental-relative-c++-abi-vtables \
-// RUN:     -ccc-install-dir %S/Inputs/basic_fuchsia_tree/bin \
-// RUN:     -resource-dir=%S/Inputs/resource_dir_with_per_target_subdir \
-// RUN:     -fuse-ld=lld 2>&1\
-// RUN:     | FileCheck %s -check-prefixes=CHECK-MULTILIB-X86
 // RUN: %clangxx %s -### --target=x86_64-unknown-fuchsia -fno-experimental-relative-c++-abi-vtables -fexperimental-relative-c++-abi-vtables \
 // RUN:     -ccc-install-dir %S/Inputs/basic_fuchsia_tree/bin \
 // RUN:     -resource-dir=%S/Inputs/resource_dir_with_per_target_subdir \
 // RUN:     -fuse-ld=lld 2>&1\
 // RUN:     | FileCheck %s -check-prefixes=CHECK-MULTILIB-X86
 // RUN: %clangxx %s -### --target=x86_64-unknown-fuchsia -fsanitize=hwaddress \
 // RUN:     -ccc-install-dir %S/Inputs/basic_fuchsia_tree/bin \
 // RUN:     -resource-dir=%S/Inputs/resource_dir_with_per_target_subdir \

 // RUN:     -resource-dir=%S/Inputs/resource_dir_with_per_target_subdir \
 // RUN:     -fuse-ld=lld 2>&1\
 // RUN:     | FileCheck %s -check-prefixes=CHECK-MULTILIB-X86,CHECK-MULTILIB-RELATIVE-VTABLES-HWASAN-X86
 // RUN: %clangxx %s -### --target=x86_64-unknown-fuchsia -fexperimental-relative-c++-abi-vtables -fno-exceptions -fsanitize=hwaddress \
 // RUN:     -ccc-install-dir %S/Inputs/basic_fuchsia_tree/bin \
 // RUN:     -resource-dir=%S/Inputs/resource_dir_with_per_target_subdir \
 // RUN:     -fuse-ld=lld 2>&1\
 // RUN:     | FileCheck %s -check-prefixes=CHECK-MULTILIB-X86,CHECK-MULTILIB-RELATIVE-VTABLES-HWASAN-NOEXCEPT-X86
+
+// RUN: %clangxx %s -### --target=x86_64-unknown-fuchsia -fc++-abi=fuchsia \
+// RUN:     -ccc-install-dir %S/Inputs/basic_fuchsia_tree/bin \
+// RUN:     -resource-dir=%S/Inputs/resource_dir_with_per_target_subdir \
+// RUN:     -fuse-ld=lld 2>&1\
+// RUN:     | FileCheck %s -check-prefixes=CHECK-MULTILIB-X86,CHECK-MULTILIB-RELATIVE-VTABLES-X86
+// RUN: %clangxx %s -### --target=x86_64-unknown-fuchsia -fc++-abi=fuchsia -fno-exceptions \
+// RUN:     -ccc-install-dir %S/Inputs/basic_fuchsia_tree/bin \
+// RUN:     -resource-dir=%S/Inputs/resource_dir_with_per_target_subdir \
+// RUN:     -fuse-ld=lld 2>&1\
+// RUN:     | FileCheck %s -check-prefixes=CHECK-MULTILIB-X86,CHECK-MULTILIB-RELATIVE-VTABLES-NOEXCEPT-X86
+// RUN: %clangxx %s -### --target=x86_64-unknown-fuchsia -fc++-abi=fuchsia -fsanitize=address \
+// RUN:     -ccc-install-dir %S/Inputs/basic_fuchsia_tree/bin \
+// RUN:     -resource-dir=%S/Inputs/resource_dir_with_per_target_subdir \
+// RUN:     -fuse-ld=lld 2>&1\
+// RUN:     | FileCheck %s -check-prefixes=CHECK-MULTILIB-X86,CHECK-MULTILIB-RELATIVE-VTABLES-ASAN-X86
+// RUN: %clangxx %s -### --target=x86_64-unknown-fuchsia -fc++-abi=fuchsia -fno-exceptions -fsanitize=address \
+// RUN:     -ccc-install-dir %S/Inputs/basic_fuchsia_tree/bin \
+// RUN:     -resource-dir=%S/Inputs/resource_dir_with_per_target_subdir \
+// RUN:     -fuse-ld=lld 2>&1\
+// RUN:     | FileCheck %s -check-prefixes=CHECK-MULTILIB-X86,CHECK-MULTILIB-RELATIVE-VTABLES-ASAN-NOEXCEPT-X86
+// RUN: %clangxx %s -### --target=x86_64-unknown-fuchsia -fno-experimental-relative-c++-abi-vtables -fc++-abi=fuchsia \
+// RUN:     -ccc-install-dir %S/Inputs/basic_fuchsia_tree/bin \
+// RUN:     -resource-dir=%S/Inputs/resource_dir_with_per_target_subdir \
+// RUN:     -fuse-ld=lld 2>&1\
+// RUN:     | FileCheck %s -check-prefixes=CHECK-MULTILIB-X86
+// RUN: %clangxx %s -### --target=x86_64-unknown-fuchsia -fc++-abi=fuchsia -fsanitize=hwaddress \
+// RUN:     -ccc-install-dir %S/Inputs/basic_fuchsia_tree/bin \
+// RUN:     -resource-dir=%S/Inputs/resource_dir_with_per_target_subdir \
+// RUN:     -fuse-ld=lld 2>&1\
+// RUN:     | FileCheck %s -check-prefixes=CHECK-MULTILIB-X86,CHECK-MULTILIB-RELATIVE-VTABLES-HWASAN-X86
+// RUN: %clangxx %s -### --target=x86_64-unknown-fuchsia -fc++-abi=fuchsia -fno-exceptions -fsanitize=hwaddress \
+// RUN:     -ccc-install-dir %S/Inputs/basic_fuchsia_tree/bin \
+// RUN:     -resource-dir=%S/Inputs/resource_dir_with_per_target_subdir \
+// RUN:     -fuse-ld=lld 2>&1\
+// RUN:     | FileCheck %s -check-prefixes=CHECK-MULTILIB-X86,CHECK-MULTILIB-RELATIVE-VTABLES-HWASAN-NOEXCEPT-X86
+
+// RUN: %clangxx %s -### --target=x86_64-unknown-fuchsia -fc++-abi=itanium -fno-exceptions \
+// RUN:     -ccc-install-dir %S/Inputs/basic_fuchsia_tree/bin \
+// RUN:     -resource-dir=%S/Inputs/resource_dir_with_per_target_subdir \
+// RUN:     -fuse-ld=lld 2>&1\
+// RUN:     | FileCheck %s -check-prefixes=CHECK-MULTILIB-X86,CHECK-MULTILIB-NOEXCEPT-X86
+// RUN: %clangxx %s -### --target=x86_64-unknown-fuchsia -fc++-abi=itanium -fno-exceptions -fc++-abi=fuchsia \
+// RUN:     -ccc-install-dir %S/Inputs/basic_fuchsia_tree/bin \
+// RUN:     -resource-dir=%S/Inputs/resource_dir_with_per_target_subdir \
+// RUN:     -fuse-ld=lld 2>&1\
+// RUN:     | FileCheck %s -check-prefixes=CHECK-MULTILIB-X86,CHECK-MULTILIB-RELATIVE-VTABLES-NOEXCEPT-X86
+// RUN: %clangxx %s -### --target=x86_64-unknown-fuchsia -fc++-abi=itanium -fno-exceptions -fexperimental-relative-c++-abi-vtables \
+// RUN:     -ccc-install-dir %S/Inputs/basic_fuchsia_tree/bin \
+// RUN:     -resource-dir=%S/Inputs/resource_dir_with_per_target_subdir \
+// RUN:     -fuse-ld=lld 2>&1\
+// RUN:     | FileCheck %s -check-prefixes=CHECK-MULTILIB-X86,CHECK-MULTILIB-RELATIVE-VTABLES-NOEXCEPT-X86
+
 // CHECK-MULTILIB-X86: "-resource-dir" "[[RESOURCE_DIR:[^"]+]]"
 // CHECK-MULTILIB-ASAN-X86: "-L{{.*}}{{/|\\\\}}..{{/|\\\\}}lib{{/|\\\\}}x86_64-unknown-fuchsia{{/|\\\\}}asan"
 // CHECK-MULTILIB-NOEXCEPT-X86: "-L{{.*}}{{/|\\\\}}..{{/|\\\\}}lib{{/|\\\\}}x86_64-unknown-fuchsia{{/|\\\\}}noexcept"
 // CHECK-MULTILIB-ASAN-NOEXCEPT-X86: "-L{{.*}}{{/|\\\\}}..{{/|\\\\}}lib{{/|\\\\}}x86_64-unknown-fuchsia{{/|\\\\}}asan+noexcept"
 // CHECK-MULTILIB-RELATIVE-VTABLES-X86: "-L{{.*}}{{/|\\\\}}..{{/|\\\\}}lib{{/|\\\\}}x86_64-unknown-fuchsia{{/|\\\\}}relative-vtables"
 // CHECK-MULTILIB-RELATIVE-VTABLES-NOEXCEPT-X86: "-L{{.*}}{{/|\\\\}}..{{/|\\\\}}lib{{/|\\\\}}x86_64-unknown-fuchsia{{/|\\\\}}relative-vtables+noexcept"
 // CHECK-MULTILIB-RELATIVE-VTABLES-ASAN-X86: "-L{{.*}}{{/|\\\\}}..{{/|\\\\}}lib{{/|\\\\}}x86_64-unknown-fuchsia{{/|\\\\}}relative-vtables+asan"
 // CHECK-MULTILIB-RELATIVE-VTABLES-ASAN-NOEXCEPT-X86: "-L{{.*}}{{/|\\\\}}..{{/|\\\\}}lib{{/|\\\\}}x86_64-unknown-fuchsia{{/|\\\\}}relative-vtables+asan+noexcept"
 // CHECK-MULTILIB-HWASAN-X86: "-L{{.*}}{{/|\\\\}}..{{/|\\\\}}lib{{/|\\\\}}x86_64-unknown-fuchsia{{/|\\\\}}hwasan"
 // CHECK-MULTILIB-HWASAN-NOEXCEPT-X86: "-L{{.*}}{{/|\\\\}}..{{/|\\\\}}lib{{/|\\\\}}x86_64-unknown-fuchsia{{/|\\\\}}hwasan+noexcept"
 // CHECK-MULTILIB-RELATIVE-VTABLES-HWASAN-X86: "-L{{.*}}{{/|\\\\}}..{{/|\\\\}}lib{{/|\\\\}}x86_64-unknown-fuchsia{{/|\\\\}}relative-vtables+hwasan"
 // CHECK-MULTILIB-RELATIVE-VTABLES-HWASAN-NOEXCEPT-X86: "-L{{.*}}{{/|\\\\}}..{{/|\\\\}}lib{{/|\\\\}}x86_64-unknown-fuchsia{{/|\\\\}}relative-vtables+hwasan+noexcept"
 // CHECK-MULTILIB-X86: "-L{{.*}}{{/|\\\\}}..{{/|\\\\}}lib{{/|\\\\}}x86_64-unknown-fuchsia"