diff --git a/clang/cmake/caches/Fuchsia-stage2.cmake b/clang/cmake/caches/Fuchsia-stage2.cmake
index ef67b518497a..7b2f2213d3ef 100644
--- a/clang/cmake/caches/Fuchsia-stage2.cmake
+++ b/clang/cmake/caches/Fuchsia-stage2.cmake
@@ -1,105 +1,105 @@
 # This file sets up a CMakeCache for the second stage of a Fuchsia toolchain
 # build.
 
 set(LLVM_TARGETS_TO_BUILD X86;ARM;AArch64 CACHE STRING "")
 
 set(PACKAGE_VENDOR Fuchsia CACHE STRING "")
 
 set(LLVM_INCLUDE_EXAMPLES OFF CACHE BOOL "")
 set(LLVM_INCLUDE_DOCS OFF CACHE BOOL "")
 set(LLVM_ENABLE_ZLIB ON CACHE BOOL "")
 set(LLVM_ENABLE_BACKTRACES OFF CACHE BOOL "")
 set(LLVM_EXTERNALIZE_DEBUGINFO ON CACHE BOOL "")
 set(CLANG_PLUGIN_SUPPORT OFF CACHE BOOL "")
 
 set(LLVM_ENABLE_LTO ON CACHE BOOL "")
 if(NOT APPLE)
   set(LLVM_ENABLE_LLD ON CACHE BOOL "")
   set(CLANG_DEFAULT_LINKER lld CACHE STRING "")
 endif()
 
 # This is a "Does your linker support it?" option that only applies
 # to x86-64 ELF targets.  All Fuchsia target linkers do support it.
 # For x86-64 Linux, it's supported by LLD and by GNU linkers since
 # binutils 2.27, so one can hope that all Linux hosts in use handle it.
 # Ideally this would be settable as a per-target option.
 set(ENABLE_X86_RELAX_RELOCATIONS ON CACHE BOOL "")
 
 if(APPLE)
   set(LLDB_CODESIGN_IDENTITY "" CACHE STRING "")
 endif()
 
 set(CMAKE_BUILD_TYPE RelWithDebInfo CACHE STRING "")
-set(CMAKE_C_FLAGS_RELWITHDEBINFO "-O2 -gline-tables-only -DNDEBUG" CACHE STRING "")
-set(CMAKE_CXX_FLAGS_RELWITHDEBINFO "-O2 -gline-tables-only -DNDEBUG" CACHE STRING "")
+set(CMAKE_C_FLAGS_RELWITHDEBINFO "-O3 -gline-tables-only -DNDEBUG" CACHE STRING "")
+set(CMAKE_CXX_FLAGS_RELWITHDEBINFO "-O3 -gline-tables-only -DNDEBUG" CACHE STRING "")
 
 set(LLVM_BUILTIN_TARGETS "x86_64-fuchsia;aarch64-fuchsia" CACHE STRING "")
 foreach(target x86_64;aarch64)
   set(BUILTINS_${target}-fuchsia_CMAKE_SYSROOT ${FUCHSIA_${target}_SYSROOT} CACHE PATH "")
   set(BUILTINS_${target}-fuchsia_CMAKE_SYSTEM_NAME Fuchsia CACHE STRING "")
 endforeach()
 
 if(NOT APPLE)
   set(LLVM_BUILTIN_TARGETS "default;${LLVM_BUILTIN_TARGETS}" CACHE STRING "" FORCE)
 endif()
 
 set(LLVM_RUNTIME_TARGETS "default;x86_64-fuchsia;aarch64-fuchsia;x86_64-fuchsia-asan:x86_64-fuchsia;aarch64-fuchsia-asan:aarch64-fuchsia" CACHE STRING "")
 foreach(target x86_64;aarch64)
   set(RUNTIMES_${target}-fuchsia_CMAKE_BUILD_WITH_INSTALL_RPATH ON CACHE BOOL "")
   set(RUNTIMES_${target}-fuchsia_CMAKE_SYSROOT ${FUCHSIA_${target}_SYSROOT} CACHE PATH "")
   set(RUNTIMES_${target}-fuchsia_CMAKE_SYSTEM_NAME Fuchsia CACHE STRING "")
   set(RUNTIMES_${target}-fuchsia_UNIX 1 CACHE BOOL "")
   set(RUNTIMES_${target}-fuchsia_LLVM_ENABLE_LIBCXX ON CACHE BOOL "")
   set(RUNTIMES_${target}-fuchsia_LIBUNWIND_USE_COMPILER_RT ON CACHE BOOL "")
   set(RUNTIMES_${target}-fuchsia_LIBUNWIND_ENABLE_STATIC OFF CACHE BOOL "")
   set(RUNTIMES_${target}-fuchsia_LIBCXXABI_USE_COMPILER_RT ON CACHE BOOL "")
   set(RUNTIMES_${target}-fuchsia_LIBCXXABI_USE_LLVM_UNWINDER ON CACHE BOOL "")
   set(RUNTIMES_${target}-fuchsia_LIBCXXABI_ENABLE_STATIC OFF CACHE BOOL "")
   set(RUNTIMES_${target}-fuchsia_LIBCXX_USE_COMPILER_RT ON CACHE BOOL "")
   set(RUNTIMES_${target}-fuchsia_LIBCXX_ABI_VERSION 2 CACHE STRING "")
   set(RUNTIMES_${target}-fuchsia_LIBCXX_ENABLE_STATIC OFF CACHE BOOL "")
   set(RUNTIMES_${target}-fuchsia_SANITIZER_USE_COMPILER_RT ON CACHE BOOL "")
 
   set(RUNTIMES_${target}-fuchsia-asan_LLVM_USE_SANITIZER Address CACHE STRING "")
   set(RUNTIMES_${target}-fuchsia-asan_LLVM_RUNTIMES_PREFIX "${target}-fuchsia/" CACHE STRING "")
   set(RUNTIMES_${target}-fuchsia-asan_LLVM_RUNTIMES_LIBDIR_SUFFIX "/asan" CACHE STRING "")
   set(RUNTIMES_${target}-fuchsia-asan_LIBCXX_INSTALL_HEADERS OFF CACHE BOOL "")
 endforeach()
 
 # Setup toolchain.
 set(LLVM_INSTALL_TOOLCHAIN_ONLY ON CACHE BOOL "")
 set(LLVM_TOOLCHAIN_TOOLS
   llc
   llvm-ar
   llvm-cov
   llvm-cxxfilt
   llvm-dwarfdump
   llvm-dsymutil
   llvm-lib
   llvm-nm
   llvm-objcopy
   llvm-objdump
   llvm-profdata
   llvm-ranlib
   llvm-readelf
   llvm-readobj
   llvm-size
   llvm-symbolizer
   opt
   sancov
   CACHE STRING "")
 
 set(LLVM_DISTRIBUTION_COMPONENTS
   clang
   lld
   lldb
   liblldb
   LTO
   clang-format
   clang-headers
   clang-tidy
   clangd
   builtins
   runtimes
   ${LLVM_TOOLCHAIN_TOOLS}
   CACHE STRING "")