[runtimes][VE] Change to compile crtbegin/end before compiler-rt

[kaz7]

Summary

VE doesn't distribute crtbegin/end, so compilation of LLVM for VE
requires to compile crtbegin/end first similar to builtin.

[kaz7]

This patch add mechanism to compile crtbegin/end before other libraries which is similar to a mechanism to compile builtins before compile-rt.

The crtbegin/end files are not available for VE freely. Those are distributed as a part of propariatary libraries. Therefore, we need to compile crtbegin/end before other libraries. This patch modifies building mechanism to compile crtbegin/end similar to builtins without other libraries. Then, compile compiler-rt again in the middle of compilation. This patch is useful for not only for SX-Aurora VE, but also other architectures which has no crtbegin/end freely.

However, I'm not sure what kind of mechanism is good for other architectures. For example, I can define LLVM_BUILTIN_CRTBEGIN_TARGETS variable to enable this feature. However, I'm not sure what is the best. So, this time, I send this patch for only crtbegin/end before other libraies for only VE at the moment. I appreciate any comments and requests for changes. Thanks!!

[phosek]

In D115038#3169582, @kaz7 wrote:

This patch add mechanism to compile crtbegin/end before other libraries which is similar to a mechanism to compile builtins before compile-rt.

The crtbegin/end files are not available for VE freely. Those are distributed as a part of propariatary libraries. Therefore, we need to compile crtbegin/end before other libraries. This patch modifies building mechanism to compile crtbegin/end similar to builtins without other libraries. Then, compile compiler-rt again in the middle of compilation. This patch is useful for not only for SX-Aurora VE, but also other architectures which has no crtbegin/end freely.

However, I'm not sure what kind of mechanism is good for other architectures. For example, I can define LLVM_BUILTIN_CRTBEGIN_TARGETS variable to enable this feature. However, I'm not sure what is the best. So, this time, I send this patch for only crtbegin/end before other libraies for only VE at the moment. I appreciate any comments and requests for changes. Thanks!!

Thank you for this change. We've discussed this before with other contributors. The main concern over adding another sub-build is the increased overhead since every CMake run takes considerable time. To address that, I have implemented D89492 which makes it possible to build builtins and crtbegin/crtend in a single CMake build without requiring another sub-build. That change is ready to land but it's been waiting for someone to review it, do you want to take a look if it addresses your use case?

[kaz7]

In D115038#3170172, @phosek wrote:

In D115038#3169582, @kaz7 wrote:

This patch add mechanism to compile crtbegin/end before other libraries which is similar to a mechanism to compile builtins before compile-rt.

Thank you for this change. We've discussed this before with other contributors. The main concern over adding another sub-build is the increased overhead since every CMake run takes considerable time. To address that, I have implemented D89492 which makes it possible to build builtins and crtbegin/crtend in a single CMake build without requiring another sub-build. That change is ready to land but it's been waiting for someone to review it, do you want to take a look if it addresses your use case?

Thank you for trying to achieve pre-compiling of crtbegin/crtend and builtins. I'll join D89492 and review it.

llvm/runtimes/CMakeLists.txt

llvm_ExternalProject_Add(builtins-${target}
                                       -DCOMPILER_RT_DEFAULT_TARGET_ONLY=ON
                                       ${COMMON_CMAKE_ARGS}
                                       ${${target}_extra_args}
                            USE_TOOLCHAIN
                            TARGET_TRIPLE ${target}
                            ${EXTRA_ARGS})
 endfunction()
 
+function(builtin_crt_register_target compiler_rt_path target)
+  cmake_parse_arguments(ARG "" "" "DEPENDS" ${ARGN})
+
+  check_apple_target(${target} builtin)
+
+  set(${target}_extra_args ${ARG_CMAKE_ARGS})
+  get_cmake_property(variableNames VARIABLES)
+  foreach(variableName ${variableNames})
+    string(FIND "${variableName}" "BUILTINS_${target}" out)
+    if("${out}" EQUAL 0)
+      string(REPLACE "BUILTINS_${target}_" "" new_name ${variableName})
+      string(REPLACE ";" "|" new_value "${${variableName}}")
+      list(APPEND ${target}_extra_args "-D${new_name}=${new_value}")
+    endif()
+  endforeach()
+
+  llvm_ExternalProject_Add(builtins-crt-${target}
+                           ${compiler_rt_path}
+                           DEPENDS ${ARG_DEPENDS}
+                           CMAKE_ARGS -DLLVM_LIBRARY_OUTPUT_INTDIR=${LLVM_LIBRARY_DIR}
+                                      -DLLVM_RUNTIME_OUTPUT_INTDIR=${LLVM_TOOLS_BINARY_DIR}
+                                      -DLLVM_DEFAULT_TARGET_TRIPLE=${target}
+                                      -DLLVM_ENABLE_PER_TARGET_RUNTIME_DIR=ON
+                                      -DCMAKE_C_COMPILER_WORKS=ON
+                                      -DCMAKE_ASM_COMPILER_WORKS=ON
+                                      -DCOMPILER_RT_DEFAULT_TARGET_ONLY=ON
+                                      -DCOMPILER_RT_BUILD_BUILTINS=OFF
+                                      -DCOMPILER_RT_BUILD_CRT=ON
+                                      -DCOMPILER_RT_BUILD_SANITIZERS=OFF
+                                      -DCOMPILER_RT_BUILD_XRAY=OFF
+                                      -DCOMPILER_RT_BUILD_LIBFUZZER=OFF
+                                      -DCOMPILER_RT_BUILD_PROFILE=OFF
+                                      -DCOMPILER_RT_BUILD_MEMPROF=OFF
+                                      -DCOMPILER_RT_BUILD_ORC=OFF
+                                      -DCOMPILER_RT_BUILD_GWP_ASAN=OFF
+                                      -DTEST_COMPILE_ONLY=ON
+                                      -DCMAKE_C_FLAGS=-nostdlib
+                                      -DCMAKE_CXX_FLAGS=-nostdlib
+                                      ${COMMON_CMAKE_ARGS}
+                                      ${${target}_extra_args}
+                           USE_TOOLCHAIN
+                           TARGET_TRIPLE ${target}
+                           ${EXTRA_ARGS})
+endfunction()
+
 # If compiler-rt is present we need to build the builtin libraries first. This
 # is required because the other runtimes need the builtin libraries present
 # before the just-built compiler can pass the configuration tests.
 get_compiler_rt_path(compiler_rt_path)
 if(compiler_rt_path)
   if(NOT LLVM_BUILTIN_TARGETS)
     builtin_default_target(${compiler_rt_path}
       DEPENDS clang-resource-headers)
else()
 
     foreach(target ${LLVM_BUILTIN_TARGETS})
       builtin_register_target(${compiler_rt_path} ${target}
         DEPENDS clang-resource-headers)
 
       add_dependencies(builtins builtins-${target})
       add_dependencies(install-builtins install-builtins-${target})
       add_dependencies(install-builtins-stripped install-builtins-${target}-stripped)
+      # If compiler-rt is present and compiling for VE, we need to build not
+      # only the builtin libraries but also crtbegin/end object files first.
+      # This is required because the other runtimes need the builtin libraries
+      # and crtbegin/end object files present before the just-built compiler
+      # can pass the configuration tests.  And those crtbegin/end object files
+      # for VE are a part of NEC SDK and not distributed freely.
+      if(${target} MATCHES "^ve-")
+        builtin_crt_register_target(${compiler_rt_path} ${target}
+          DEPENDS clang-resource-headers)
+        add_dependencies(builtins builtins-crt-${target})
+        add_dependencies(install-builtins install-builtins-crt-${target})
+        add_dependencies(install-builtins-stripped install-builtins-crt-${target}-stripped)
+      endif()
     endforeach()
   endif()
   set(deps builtins)
   # We don't need to depend on the builtins if we're building instrumented
   # because the next stage will use the same compiler used to build this stage.
   if(NOT LLVM_BUILD_INSTRUMENTED AND CLANG_ENABLE_BOOTSTRAP)
     add_dependencies(clang-bootstrap-deps builtins)
   endif()