[BOLT] Add BOLT_TARGETS_TO_BUILD

[urnathan]

Summary

Currently BOLT enables X86 and/or AArch64, if those are targets in LLVM_TARGETS_TO_BUILD. It can support both of them concurrently because they happen to also be ELF64LE exec formats, and the way RewriteInstance is structured makes it hard to support multiple ELF formats. As more targets are added to BOLT, it will become more likely that a multi-target build would have multiple ELF formats. To allow greater control, this adds BOLT_TARGETS_TO_BUILD, which defaults to the intersection of X86;AArch64 and LLVM_TARGETS_TO_BUILD, but allows configuration to alter that -- for instance omitting one of those two targets even if llvm supports both.

If you enable bolt you have to end up with at least one BOLT_TARGETS_TO_BUILD -- unlike right now, when I think you can end up with a no-target BOLT.

It also allows some rather nice refactoring of the CMake files, by iterating over BOLT_TARGETS_TO_BUILD rather than individually check specific arches in LLVM_TARGETS_TO_BUILD.

i've tested this in a few different configs, most notably LLVM_TARGETS_TO_BUILD='X86;AArch64;PowerPC' BOLT_TARGETS_TO_BUILD=X86, where we end up with an X86 only BOLT

[rafauler]

LGTM

bolt/CMakeLists.txt

 include(ExternalProject)
 
 set(BOLT_SOURCE_DIR ${CMAKE_CURRENT_SOURCE_DIR})
 set(BOLT_BINARY_DIR ${CMAKE_CURRENT_BINARY_DIR})
 set(CMAKE_CXX_STANDARD 17)
 
+# Determine default set of targets to build -- the intersection of
+# those BOLT supports and those LLVM is targeting.
+set(BOLT_TARGETS_TO_BUILD_all "AArch64;X86")
+set(BOLT_TARGETS_TO_BUILD_default)
+foreach (tgt ${BOLT_TARGETS_TO_BUILD_all})
+  if (tgt IN_LIST LLVM_TARGETS_TO_BUILD)
+    list(APPEND BOLT_TARGETS_TO_BUILD_default ${tgt})
+  endif()
+endforeach()
+
+# Allow the user to specify the BOLT targets, and then check that LLVM
+# is indeed targeting those.
+set(BOLT_TARGETS_TO_BUILD "${BOLT_TARGETS_TO_BUILD_default}"
+  CACHE STRING "Targets for BOLT to support.")
+if (NOT BOLT_TARGETS_TO_BUILD)
+  message(FATAL_ERROR "BOLT enabled but BOLT_TARGETS_TO_BUILD is empty")
+endif()
+foreach (tgt ${BOLT_TARGETS_TO_BUILD})
+  if (NOT tgt IN_LIST LLVM_TARGETS_TO_BUILD)
+    message(FATAL_ERROR "BOLT target '${tgt}' is not in LLVM_TARGETS_TO_BUILD")
+  endif()
+  message(STATUS "Targeting ${tgt} in llvm-bolt")
+endforeach()
+
 set(BOLT_ENABLE_RUNTIME_default OFF)
 if (CMAKE_SYSTEM_PROCESSOR STREQUAL "x86_64"
     AND (CMAKE_SYSTEM_NAME STREQUAL "Linux"
       OR CMAKE_SYSTEM_NAME STREQUAL "Darwin")
-    AND "X86" IN_LIST LLVM_TARGETS_TO_BUILD)
+    AND "X86" IN_LIST BOLT_TARGETS_TO_BUILD)
   set(BOLT_ENABLE_RUNTIME_default ON)
 endif()
 option(BOLT_ENABLE_RUNTIME "Enable BOLT runtime" ${BOLT_ENABLE_RUNTIME_default})
 if (BOLT_ENABLE_RUNTIME)
   # Some systems prevent reading /proc/self/map_files
   execute_process(COMMAND ls /proc/self/map_files
     RESULT_VARIABLE LS OUTPUT_QUIET ERROR_QUIET)
   if (LS)

bolt/lib/Rewrite/CMakeLists.txt

 set(LLVM_LINK_COMPONENTS
   DebugInfoDWARF
   DWP
   ExecutionEngine
   MC
   Object
   Support
   TargetParser
   )
 
-set(TARGET_LINK_LIBRARIES
-  LLVMBOLTCore
-  LLVMBOLTPasses
-  LLVMBOLTProfile
-  LLVMBOLTRuntimeLibs
-  LLVMBOLTUtils
-  )
-
-if ("AArch64" IN_LIST LLVM_TARGETS_TO_BUILD)
-  list(APPEND TARGET_LINK_LIBRARIES LLVMBOLTTargetAArch64)
-  set(BOLT_AArch64 On)
-endif()
-
-if ("X86" IN_LIST LLVM_TARGETS_TO_BUILD)
-  list(APPEND TARGET_LINK_LIBRARIES LLVMBOLTTargetX86)
-  set(BOLT_X64 On)
-endif()
-
 add_llvm_library(LLVMBOLTRewrite
   BinaryPassManager.cpp
   BoltDiff.cpp
   DWARFRewriter.cpp
   ExecutableFileMemoryManager.cpp
   MachORewriteInstance.cpp
   RewriteInstance.cpp
 
   DISABLE_LLVM_LINK_LLVM_DYLIB
 
   LINK_LIBS
   ${LLVM_PTHREAD_LIB}
   )
 
 target_link_libraries(LLVMBOLTRewrite
   PRIVATE
-  ${TARGET_LINK_LIBRARIES}
+  LLVMBOLTCore
+  LLVMBOLTPasses
+  LLVMBOLTProfile
+  LLVMBOLTRuntimeLibs
+  LLVMBOLTUtils
   )
 
-if (DEFINED BOLT_AArch64)
-  target_compile_definitions(LLVMBOLTRewrite PRIVATE AARCH64_AVAILABLE)
-endif()
-
-if (DEFINED BOLT_X64)
-  target_compile_definitions(LLVMBOLTRewrite PRIVATE X86_AVAILABLE)
-endif()
+foreach (tgt ${BOLT_TARGETS_TO_BUILD})
+  target_link_libraries(LLVMBOLTRewrite PRIVATE LLVMBOLTTarget${tgt})
+  string(TOUPPER "${tgt}" upper)
+  target_compile_definitions(LLVMBOLTRewrite PRIVATE ${upper}_AVAILABLE)
+endforeach()

bolt/lib/Target/CMakeLists.txt

-if ("X86" IN_LIST LLVM_TARGETS_TO_BUILD)
-  message(STATUS "Targeting X86 in llvm-bolt")
-  add_subdirectory(X86)
-endif()
-
-if ("AArch64" IN_LIST LLVM_TARGETS_TO_BUILD)
-  message(STATUS "Targeting AArch64 in llvm-bolt")
-  add_subdirectory(AArch64)
-endif()
+foreach (tgt ${BOLT_TARGETS_TO_BUILD})
+  add_subdirectory(${tgt})
+endforeach()

bolt/test/lit.site.cfg.py.in

 config.lit_tools_dir = "@LLVM_LIT_TOOLS_DIR@"
 config.host_triple = "@LLVM_HOST_TRIPLE@"
 config.target_triple = "@LLVM_TARGET_TRIPLE@"
 config.llvm_use_sanitizer = "@LLVM_USE_SANITIZER@"
 config.host_arch = "@HOST_ARCH@"
 config.python_executable = "@Python3_EXECUTABLE@"
 config.bolt_clang = "@BOLT_CLANG_EXE@"
 config.bolt_lld = "@BOLT_LLD_EXE@"
-config.targets_to_build = "@TARGETS_TO_BUILD@"
+config.targets_to_build = "@BOLT_TARGETS_TO_BUILD@"
 config.gnu_ld = "@GNU_LD_EXECUTABLE@"
 
 import lit.llvm
 lit.llvm.initialize(lit_config, config)
 
 # Let the main config do the real work.
 lit_config.load_config(config, "@BOLT_SOURCE_DIR@/test/lit.cfg.py")

bolt/unittests/Core/CMakeLists.txt

add_bolt_unittest(CoreTests
   )
 
 target_link_libraries(CoreTests
   PRIVATE
   LLVMBOLTCore
   LLVMBOLTRewrite
   )
 
-if ("AArch64" IN_LIST LLVM_TARGETS_TO_BUILD)
+foreach (tgt ${BOLT_TARGETS_TO_BUILD})
   include_directories(
-    ${LLVM_MAIN_SRC_DIR}/lib/Target/AArch64
-    ${LLVM_BINARY_DIR}/lib/Target/AArch64
+    ${LLVM_MAIN_SRC_DIR}/lib/Target/${tgt}
+    ${LLVM_BINARY_DIR}/lib/Target/${tgt}
   )
-
-  target_compile_definitions(CoreTests PRIVATE AARCH64_AVAILABLE)
-endif()
-
-if ("X86" IN_LIST LLVM_TARGETS_TO_BUILD)
-  include_directories(
-    ${LLVM_MAIN_SRC_DIR}/lib/Target/X86
-    ${LLVM_BINARY_DIR}/lib/Target/X86
-  )
-
-  target_compile_definitions(CoreTests PRIVATE X86_AVAILABLE)
-endif()
+  string(TOUPPER "${tgt}" upper)
+  target_compile_definitions(CoreTests PRIVATE "${upper}_AVAILABLE")
+endforeach()