[CMake] Replace clang binary if using clang-bolt target

Instead of creating an extra clang-bolt binary and clang++-bolt symlink,
replace the original clang binary with BOLT-optimized one.

This fixes the issue with installing optimized binary as `install-clang`
target now copies the new version.

Reviewed By: phosek

Differential Revision: https://reviews.llvm.org/D139454

clang/CMakeLists.txt

@@ -856,8 +856,6 @@ if (CLANG_BOLT_INSTRUMENT AND NOT LLVM_BUILD_INSTRUMENTED)
   set(CLANGXX_PATH ${CLANG_PATH}++)
   set(CLANG_INSTRUMENTED ${CLANG_PATH}-bolt.inst)
   set(CLANGXX_INSTRUMENTED ${CLANGXX_PATH}-bolt.inst)
-  set(CLANG_OPTIMIZED ${CLANG_PATH}-bolt)
-  set(CLANGXX_OPTIMIZED ${CLANGXX_PATH}-bolt)
 
   # Instrument clang with BOLT
   add_custom_target(clang-instrumented
@@ -935,6 +933,7 @@ if (CLANG_BOLT_INSTRUMENT AND NOT LLVM_BUILD_INSTRUMENTED)
   )
 
   # Optimize original (pre-bolt) Clang using the collected profile
+  set(CLANG_OPTIMIZED ${CMAKE_CURRENT_BINARY_DIR}/clang.bolt)
   add_custom_target(clang-bolt
     DEPENDS ${CLANG_OPTIMIZED}
   )
@@ -945,22 +944,10 @@ if (CLANG_BOLT_INSTRUMENT AND NOT LLVM_BUILD_INSTRUMENTED)
       -data ${CMAKE_CURRENT_BINARY_DIR}/prof.fdata
       -reorder-blocks=ext-tsp -reorder-functions=hfsort+ -split-functions
       -split-all-cold -split-eh -dyno-stats -icf=1 -use-gnu-stack
+    COMMAND ${CMAKE_COMMAND} -E rename ${CLANG_OPTIMIZED} $<TARGET_FILE:clang>
     COMMENT "Optimizing Clang with BOLT"
     VERBATIM
   )
-
-  # Make a symlink from clang-bolt to clang++-bolt
-  add_custom_target(clang++-bolt
-    DEPENDS ${CLANGXX_OPTIMIZED}
-  )
-  add_custom_command(OUTPUT ${CLANGXX_OPTIMIZED}
-    DEPENDS clang-bolt
-    COMMAND ${CMAKE_COMMAND} -E create_symlink
-      ${CLANG_OPTIMIZED}
-      ${CLANGXX_OPTIMIZED}
-    COMMENT "Creating symlink from BOLT optimized clang to clang++"
-    VERBATIM
-  )
 endif()
 
 if (LLVM_ADD_NATIVE_VISUALIZERS_TO_SOLUTION)

clang/cmake/caches/BOLT-PGO.cmake

@@ -2,11 +2,9 @@ set(LLVM_ENABLE_PROJECTS "bolt;clang;lld" CACHE STRING "")
 
 set(CLANG_BOOTSTRAP_TARGETS
   stage2-clang-bolt
-  stage2-clang++-bolt
   CACHE STRING "")
 set(BOOTSTRAP_CLANG_BOOTSTRAP_TARGETS
   clang-bolt
-  clang++-bolt
   CACHE STRING "")
 
 set(PGO_BUILD_CONFIGURATION ${CMAKE_CURRENT_LIST_DIR}/BOLT.cmake CACHE STRING "")

llvm/docs/AdvancedBuilds.rst

@@ -224,7 +224,7 @@ Then, build the BOLT-optimized binary by running the following ninja command:
 
 .. code-block:: console
 
-  $ ninja clang++-bolt
+  $ ninja clang-bolt
 
 If you're seeing errors in the build process, try building with a recent
 version of Clang/LLVM by setting the CMAKE_C_COMPILER and
@@ -243,12 +243,11 @@ configuration command:
       -DBOOTSTRAP_BOOTSTRAP_LLVM_ENABLE_LLD=ON \
       -DPGO_INSTRUMENT_LTO=Thin
 
-Then, to build the final optimized binary, build the stage2-clang++-bolt
-target:
+Then, to build the final optimized binary, build the stage2-clang-bolt target:
 
 .. code-block:: console
 
-  $ ninja stage2-clang++-bolt
+  $ ninja stage2-clang-bolt
 
 3-Stage Non-Determinism
 =======================