From 5cb17728d19408725d4ced928ff3276dd4ffd1c9 Mon Sep 17 00:00:00 2001
From: Leonard Chan <leonardchan@google.com>
Date: Thu, 6 May 2021 15:54:28 -0700
Subject: [PATCH] [clang][Fuchsia] Introduce compat multilibs

These are GCC-compatible multilibs that use the generic Itanium C++ ABI
instead of the Fuchsia C++ ABI.

Differential Revision: https://reviews.llvm.org/D102030
---
 clang/lib/Driver/ToolChains/Fuchsia.cpp        |  4 ++++
 .../x86_64-unknown-fuchsia/compat/libc++.so    |  0
 clang/test/Driver/fuchsia.cpp                  | 18 ++++++++++++++++++
 3 files changed, 22 insertions(+)
 create mode 100644 clang/test/Driver/Inputs/basic_fuchsia_tree/lib/x86_64-unknown-fuchsia/compat/libc++.so

diff --git a/clang/lib/Driver/ToolChains/Fuchsia.cpp b/clang/lib/Driver/ToolChains/Fuchsia.cpp
index cf562335e18e..502afdc1e30c 100644
--- a/clang/lib/Driver/ToolChains/Fuchsia.cpp
+++ b/clang/lib/Driver/ToolChains/Fuchsia.cpp
@@ -242,6 +242,8 @@ Fuchsia::Fuchsia(const Driver &D, const llvm::Triple &Triple,
                           .flag("+fsanitize=hwaddress")
                           .flag("-fexceptions")
                           .flag("+fno-exceptions"));
+  // Use Itanium C++ ABI for the compat multilib.
+  Multilibs.push_back(Multilib("compat", {}, {}, 12).flag("+fc++-abi=itanium"));
 
   Multilibs.FilterOut([&](const Multilib &M) {
     std::vector<std::string> RD = FilePaths(M);
@@ -263,6 +265,8 @@ Fuchsia::Fuchsia(const Driver &D, const llvm::Triple &Triple,
                    options::OPT_fno_experimental_relative_cxx_abi_vtables,
                    /*default=*/false),
       "fexperimental-relative-c++-abi-vtables", Flags);
+  addMultilibFlag(Args.getLastArgValue(options::OPT_fcxx_abi_EQ) == "itanium",
+                  "fc++-abi=itanium", Flags);
 
   Multilibs.setFilePathsCallback(FilePaths);
 
diff --git a/clang/test/Driver/Inputs/basic_fuchsia_tree/lib/x86_64-unknown-fuchsia/compat/libc++.so b/clang/test/Driver/Inputs/basic_fuchsia_tree/lib/x86_64-unknown-fuchsia/compat/libc++.so
new file mode 100644
index 000000000000..e69de29bb2d1
diff --git a/clang/test/Driver/fuchsia.cpp b/clang/test/Driver/fuchsia.cpp
index 86a0acebc084..bd4c7ebeb560 100644
--- a/clang/test/Driver/fuchsia.cpp
+++ b/clang/test/Driver/fuchsia.cpp
@@ -144,6 +144,23 @@
 // 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
+
+// Test compat multilibs.
+// RUN: %clangxx %s -### --target=x86_64-unknown-fuchsia -fc++-abi=itanium \
+// 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-COMPAT-X86
+// RUN: %clangxx %s -### --target=x86_64-unknown-fuchsia -fc++-abi=itanium -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 -fc++-abi=itanium \
+// 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-COMPAT-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"
@@ -156,4 +173,5 @@
 // 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-COMPAT-X86: "-L{{.*}}{{/|\\\\}}..{{/|\\\\}}lib{{/|\\\\}}x86_64-unknown-fuchsia{{/|\\\\}}compat"
 // CHECK-MULTILIB-X86: "-L{{.*}}{{/|\\\\}}..{{/|\\\\}}lib{{/|\\\\}}x86_64-unknown-fuchsia"