[PATCH] D64140: [CMake][Fuchsia] Define asan+noexcept multilib

[Petr Hosek via Phabricator via cfe-commits]

phosek created this revision.
phosek added a reviewer: mcgrathr.
Herald added subscribers: cfe-commits, mgorny.
Herald added a project: clang.

Using noexcept multilib with -fno-exceptions can lead to significant
space savings when statically linking libc++abi because we don't need
all the unwinding and demangling code.

When compiling with ASan, we already get a lot of overhead from the
instrumentation itself, when statically linking libc++abi, that overhead
is even larger.

Having the noexcept variant for ASan can help significantly, we've seen
more than 50% size reduction in our system image, which offsets the cost
of having to build another multilib.


Repository:
  rC Clang

https://reviews.llvm.org/D64140

Files:
  clang/cmake/caches/Fuchsia-stage2.cmake
  clang/lib/Driver/ToolChains/Fuchsia.cpp


Index: clang/lib/Driver/ToolChains/Fuchsia.cpp
===================================================================
--- clang/lib/Driver/ToolChains/Fuchsia.cpp
+++ clang/lib/Driver/ToolChains/Fuchsia.cpp
@@ -192,6 +192,11 @@
   // ASan has higher priority because we always want the instrumentated version.
   Multilibs.push_back(Multilib("asan", {}, {}, 2)
                           .flag("+fsanitize=address"));
+  // Use the asan+noexcept variant with ASan and -fno-exceptions.
+  Multilibs.push_back(Multilib("asan+noexcept", {}, {}, 3)
+                          .flag("+fsanitize=address")
+                          .flag("-fexceptions")
+                          .flag("+fno-exceptions"));
   Multilibs.FilterOut([&](const Multilib &M) {
     std::vector<std::string> RD = FilePaths(M);
     return std::all_of(RD.begin(), RD.end(), [&](std::string P) {
Index: clang/cmake/caches/Fuchsia-stage2.cmake
===================================================================
--- clang/cmake/caches/Fuchsia-stage2.cmake
+++ clang/cmake/caches/Fuchsia-stage2.cmake
@@ -153,13 +153,21 @@
     set(RUNTIMES_${target}-unknown-fuchsia+noexcept_LIBCXXABI_ENABLE_EXCEPTIONS OFF CACHE BOOL "")
     set(RUNTIMES_${target}-unknown-fuchsia+noexcept_LIBCXX_ENABLE_EXCEPTIONS OFF CACHE BOOL "")
 
+    set(RUNTIMES_${target}-unknown-fuchsia+asan+noexcept_LLVM_BUILD_COMPILER_RT OFF CACHE BOOL "")
+    set(RUNTIMES_${target}-unknown-fuchsia+asan+noexcept_LLVM_USE_SANITIZER "Address" CACHE STRING "")
+    set(RUNTIMES_${target}-unknown-fuchsia+asan+noexcept_LIBCXXABI_ENABLE_NEW_DELETE_DEFINITIONS OFF CACHE BOOL "")
+    set(RUNTIMES_${target}-unknown-fuchsia+asan+noexcept_LIBCXX_ENABLE_NEW_DELETE_DEFINITIONS OFF CACHE BOOL "")
+    set(RUNTIMES_${target}-unknown-fuchsia+asan+noexcept_LIBCXXABI_ENABLE_EXCEPTIONS OFF CACHE BOOL "")
+    set(RUNTIMES_${target}-unknown-fuchsia+asan+noexcept_LIBCXX_ENABLE_EXCEPTIONS OFF CACHE BOOL "")
+
     # Use .build-id link.
     list(APPEND RUNTIME_BUILD_ID_LINK "${target}-unknown-fuchsia")
   endforeach()
 
-  set(LLVM_RUNTIME_MULTILIBS "asan;noexcept" CACHE STRING "")
+  set(LLVM_RUNTIME_MULTILIBS "asan;noexcept;asan+noexcept" CACHE STRING "")
   set(LLVM_RUNTIME_MULTILIB_asan_TARGETS "x86_64-unknown-fuchsia;aarch64-unknown-fuchsia" CACHE STRING "")
   set(LLVM_RUNTIME_MULTILIB_noexcept_TARGETS "x86_64-unknown-fuchsia;aarch64-unknown-fuchsia" CACHE STRING "")
+  set(LLVM_RUNTIME_MULTILIB_asan+noexcept_TARGETS "x86_64-unknown-fuchsia;aarch64-unknown-fuchsia" CACHE STRING "")
 endif()
 
 set(LLVM_BUILTIN_TARGETS "${BUILTIN_TARGETS}" CACHE STRING "")


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