Enable ICF and LTO (#33560)

Summary:
X-link: facebook/react-native#33560
Pull Request resolved: facebook#720

Turn on ICF for the build whenever it is available. This requires us to
link with LLD, which is only the default starting in NDK r23, so
manually specify LLD for the Android build.

Also turn on LTO for the CircleCI build, so we generate highly
optimised binaries for distribution.

Changelog: [Internal]

Reviewed By: jpporto

Differential Revision: D35344254

fbshipit-source-id: 64b37e6a7817a7b7826cc7480468367b95d63c61

.circleci/config.yml

@@ -143,7 +143,7 @@ jobs:
           name: Build Hermes for Linux
           command: |
             cd "$HERMES_WS_DIR"
-            cmake -S hermes -B build_release -G Ninja -DHERMES_STATIC_LINK=ON -DCMAKE_BUILD_TYPE=Release -DCMAKE_CXX_FLAGS=-s -DCMAKE_C_FLAGS=-s
+            cmake -S hermes -B build_release -G Ninja -DHERMES_STATIC_LINK=ON -DCMAKE_BUILD_TYPE=Release -DCMAKE_INTERPROCEDURAL_OPTIMIZATION=True -DCMAKE_CXX_FLAGS=-s -DCMAKE_C_FLAGS=-s
             cd build_release
             ninja github-cli-release
       - run:
@@ -399,7 +399,7 @@ jobs:
             $Env:PATH += ";$Env:CMAKE_DIR;$Env:MSBUILD_DIR"
             $Env:ICU_ROOT = "$Env:HERMES_WS_DIR\icu"
             cd $Env:HERMES_WS_DIR
-            cmake -S hermes -B build_release -G 'Visual Studio 16 2019' -Ax64 -DCMAKE_BUILD_TYPE=Release -DHERMES_ENABLE_WIN10_ICU_FALLBACK=OFF -DHERMES_GITHUB_RESOURCE_DIR="$Env:HERMES_WS_DIR\deps"
+            cmake -S hermes -B build_release -G 'Visual Studio 16 2019' -Ax64 -DCMAKE_BUILD_TYPE=Release -DCMAKE_INTERPROCEDURAL_OPTIMIZATION=True -DHERMES_ENABLE_WIN10_ICU_FALLBACK=OFF -DHERMES_GITHUB_RESOURCE_DIR="$Env:HERMES_WS_DIR\deps"
             if (-not $?) { throw "Failed to configure Hermes" }
             cd build_release
             cmake --build . --target github-cli-release --config Release

CMakeLists.txt

@@ -292,12 +292,15 @@ if (HERMES_STATIC_LINK)
   set(CMAKE_FIND_LIBRARY_SUFFIXES "${CMAKE_STATIC_LIBRARY_SUFFIX}")
 endif()
 
-# Check if the linker supports --gc-sections
+# Check if the linker supports --gc-sections and ICF.
 # We can't simply CHECK_CXX_COMPILER_FLAG("-Wl,--gc-sections" ..) because CMake
 # will compile and link separately and only passes the flag during compilation.
+# TODO: Use check_linker_flag once we have CMake 3.18.
 set(OLD_CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS}")
-set(CMAKE_EXE_LINKER_FLAGS "-Wl,--gc-sections")
+set(CMAKE_EXE_LINKER_FLAGS "${OLD_CMAKE_EXE_LINKER_FLAGS} -Wl,--gc-sections")
 CHECK_CXX_COMPILER_FLAG("" HAVE_GC_SECTIONS)
+set(CMAKE_EXE_LINKER_FLAGS "${OLD_CMAKE_EXE_LINKER_FLAGS} -Wl,--icf=safe")
+CHECK_CXX_COMPILER_FLAG("" HAVE_ICF)
 set(CMAKE_EXE_LINKER_FLAGS "${OLD_CMAKE_EXE_LINKER_FLAGS}")
 
 if(HAVE_GC_SECTIONS)
@@ -306,6 +309,11 @@ if(HAVE_GC_SECTIONS)
   list(APPEND HERMES_EXTRA_LINKER_FLAGS "LINKER:--gc-sections")
 endif()
 
+if(HAVE_ICF)
+  add_flag_if_supported("-faddrsig" ADDRSIG)
+  list(APPEND HERMES_EXTRA_LINKER_FLAGS "LINKER:--icf=safe")
+endif()
+
 # Make the HERMES_RELEASE_VERSION accessible for version printing in C++.
 add_definitions(-DHERMES_RELEASE_VERSION="${HERMES_RELEASE_VERSION}")
 
@@ -423,13 +431,6 @@ else()
     set(HERMES_ASSUMED_BUILD_MODE_IN_LIT_TEST "opt")
 endif()
 
-if (NOT (GENERATOR_IS_MULTI_CONFIG OR CMAKE_BUILD_TYPE STREQUAL Debug OR CMAKE_COMPILER_IS_GNUCXX))
-    # Enable LTO if we are not multi config generator and not a DEBUG build
-    # and not GCC
-    # GCC currently fails to link Hermes with LTO (see t16557748)
-    option(HERMES_ENABLE_LTO "Build Hermes with LTO" ON)
-endif()
-
 if (GCC_COMPATIBLE)
   # Don't export symbols unless we explicitly say so
   set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fvisibility=hidden")

android/hermes/build.gradle

@@ -22,6 +22,7 @@ android {
         arguments "-DHERMES_FACEBOOK_BUILD=${rootProject.ext.facebookBuild}"
         arguments "-DANDROID_STL=c++_shared"
         arguments "-DANDROID_PIE=True"
+        arguments "-DANDROID_LD=lld"
         arguments "-DIMPORT_HERMESC=${rootProject.ext.hermesC}"
         arguments "-DFBSOURCE_DIR=${rootProject.ext.fbsource}"
         arguments "-DHERMES_SLOW_DEBUG=False"