[llvm/runtimes] Add runtimes as a dependency of clang-bootstrap-deps

[xinxinw1]

Summary

With the new LLVM_ENABLE_RUNTIMES option introduced in https://reviews.llvm.org/D40233, compiler-rt can now be included as a runtime. Since compiler-rt is needed for PGO, runtimes needs to be included as a dependency of clang-bootstrap-deps when building the stage1 compiler.

[smeenai]

This makes sense to me ... @beanz @phosek what do you think?

llvm/runtimes/CMakeLists.txt

566

I'd say "we need the profile runtime" instead of "we need it", just to be a bit more specific.

[phosek]

llvm/runtimes/CMakeLists.txt

567

I don't think we can add this dependency unconditionally. If LLVM_ENABLE_RUNTIMES isn't set, runtimes list would end up empty here https://github.com/llvm/llvm-project/blob/master/llvm/runtimes/CMakeLists.txt#L32, in which case we wouldn't define runtimes target at all here https://github.com/llvm/llvm-project/blob/master/llvm/runtimes/CMakeLists.txt#L497.

We also cannot just check whether LLVM_ENABLE_RUNTIMES is set because in theory we still support the nested layout where users can place runtimes directly into llvm/runtimes subdirectory; we probably don't need this now that we're in monorepo, but we shouldn't break it until we officially announce the deprecation of that feature.

[xinxinw1]

llvm/runtimes/CMakeLists.txt

567

We're not adding this dependency unconditionally. This line is under an if(runtimes) block, so at this point where we're adding runtimes to clang-bootstrap-deps, the runtimes list won't be empty and the runtimes target would be defined. Additionally, if the runtimes target wasn't defined, then the runtimes-configure target which is referenced in the line above also wouldn't be defined, but since that line works fine, adding an additional dependency on runtimes should be fine.

[xinxinw1]

Update comment text

[phosek]

LGTM

llvm/runtimes/CMakeLists.txt

else()
           add_dependencies(runtimes runtimes-${name}+${multilib})
           add_dependencies(runtimes-configure runtimes-${name}+${multilib}-configure)
           add_dependencies(install-runtimes install-runtimes-${name}+${multilib})
           add_dependencies(install-runtimes-stripped install-runtimes-${name}+${multilib}-stripped)
         endforeach()
       endforeach()
     endif()
 
+    if(NOT LLVM_BUILD_INSTRUMENTED AND CLANG_ENABLE_BOOTSTRAP)
       # TODO: This is a hack needed because the libcxx headers are copied into the
       # build directory during configuration. Without that step the clang in the
       # build directory cannot find the C++ headers in certain configurations.
       # I need to build a mechanism for runtime projects to provide CMake code
       # that executes at LLVM configuration time to handle this case.
-    if(NOT LLVM_BUILD_INSTRUMENTED AND CLANG_ENABLE_BOOTSTRAP)
       add_dependencies(clang-bootstrap-deps runtimes-configure)
+      # We need to add the runtimes as a dependency because compiler-rt can be
+      # built as part of runtimes and we need it for PGO
+      add_dependencies(clang-bootstrap-deps runtimes)
     endif()
 
     if(LLVM_INCLUDE_TESTS)
       set_property(GLOBAL APPEND PROPERTY LLVM_ADDITIONAL_TEST_DEPENDS runtimes-test-depends)
       set_property(GLOBAL APPEND PROPERTY LLVM_ADDITIONAL_TEST_TARGETS check-runtimes)
 
       set(RUNTIMES_TEST_DEPENDS
           FileCheck