Actually, the way we tag options recognized by GCC is wrong. We should use a more specific group instead of DriverOption.

In D83648#2146472, @pzheng wrote:

Actually, this patch won't change --help because it just reduced some duplication by extracting the common part (" the integrated assembler") of the help message into the "help" of "OptOutFFlag". Sorry for the confusion.

The real fix here is to restore "integrated_as" as a DriverOption. Without this, when we have -fintegrated-as on a link line, it will be passed to the linker and cause the linker to fail because it is not a valid linker flag.

At last!

Address review comments.

Address @jsji 's comments.

In D82702#2146536, @phosek wrote:

One more thing I've noticed is that both of those invocations include __config_site which is added by the cxx-headers interface library, so that library must be used, it's just as if target_include_directories(${CXX_HEADER_TARGET} INTERFACE ${output_dir}) was ignored when building the instrumented version.

In D83650#2146534, @mehdi_amini wrote:

I agree that I'd like to have more info inline and this is going in the right direction, but what seems missing is still the check line itself.

Have you looked into localizing it as well?

(renaming variables for readability)

%a = select i1 %s, i1 undef, i1 %t
%b = xor i1 %s, 1
%c = and i1 %a, %b

In D82702#2146195, @phosek wrote:

I spent some time debugging this, and to be honest, I don't know what's going on. The problem is that in the multilib variant case, the header includes are missing. So normally, the generated Ninja entries would look like this:

build libcxx/src/CMakeFiles/cxx_static.dir/filesystem/operations.cpp.obj: CXX_COMPILER__cxx_static /src/clang-llvm/llvm-project/libcxx/src/filesystem/operations.cpp || cmake_object_order_depends_target_cxx_static
  DEFINES = -DNDEBUG -D_LIBCPP_BUILDING_LIBRARY -D_LIBCPP_DISABLE_VISIBILITY_ANNOTATIONS -D_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS
  DEP_FILE = libcxx/src/CMakeFiles/cxx_static.dir/filesystem/operations.cpp.obj.d
  FLAGS = --target=x86_64-unknown-fuchsia -I/usr/local/google/home/phosek/clang-llvm/sdk/pkg/fdio/include -fPIC -fvisibility-inlines-hidden -Werror=date-time -Werror=unguarded-availability-new -Wall -Wextra -Wno-unused-parameter -Wwrite-strings -Wcast-qual -Wmissing-field-initializers -Wimplicit-fallthrough -Wcovered-switch-default -Wno-noexcept-type -Wnon-virtual-dtor -Wdelete-non-virtual-dtor -Wstring-conversion -ffunction-sections -fdata-sections -ffile-prefix-map=/src/clang-llvm/llvm-build/fuchsia/runtimes/runtimes-x86_64-unknown-fuchsia-bins=../llvm-build/fuchsia/runtimes/runtimes-x86_64-unknown-fuchsia-bins -ffile-prefix-map=/src/clang-llvm/llvm-project/= -no-canonical-prefixes -O2 -g -DNDEBUG   -DLIBCXX_BUILDING_LIBCXXABI -nostdinc++ -fvisibility-inlines-hidden -fvisibility=hidden -Wall -Wextra -W -Wwrite-strings -Wno-unused-parameter -Wno-long-long -Werror=return-type -Wextra-semi -Wno-user-defined-literals -Wno-covered-switch-default -Wno-ignored-attributes -Wno-error -fvisibility-global-new-delete-hidden -include /src/clang-llvm/llvm-build/fuchsia/runtimes/runtimes-x86_64-unknown-fuchsia-bins/libcxx/__config_site -std=c++14
  INCLUDES = -Ilibcxx/include/c++build -I/src/clang-llvm/llvm-build/fuchsia/include/c++/v1
  OBJECT_DIR = libcxx/src/CMakeFiles/cxx_static.dir
  OBJECT_FILE_DIR = libcxx/src/CMakeFiles/cxx_static.dir/filesystem

but with this patch, we would end up with this:

build libcxx/src/CMakeFiles/cxx_static.dir/filesystem/operations.cpp.obj: CXX_COMPILER__cxx_static /src/clang-llvm/llvm-project/libcxx/src/filesystem/operations.cpp || cmake_object_order_depends_target_cxx_static
  DEFINES = -DNDEBUG -D_LIBCPP_BUILDING_LIBRARY -D_LIBCPP_DISABLE_NEW_DELETE_DEFINITIONS -D_LIBCPP_DISABLE_VISIBILITY_ANNOTATIONS -D_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS
  DEP_FILE = libcxx/src/CMakeFiles/cxx_static.dir/filesystem/operations.cpp.obj.d
  FLAGS = --target=x86_64-unknown-fuchsia -I/usr/local/google/home/phosek/clang-llvm/sdk/pkg/fdio/include -fPIC -fvisibility-inlines-hidden -Werror=date-time -Werror=unguarded-availability-new -Wall -Wextra -Wno-unused-parameter -Wwrite-strings -Wcast-qual -Wmissing-field-initializers -Wimplicit-fallthrough -Wcovered-switch-default -Wno-noexcept-type -Wnon-virtual-dtor -Wdelete-non-virtual-dtor -Wstring-conversion -fno-omit-frame-pointer -fsanitize=address -fsanitize-address-use-after-scope -ffunction-sections -fdata-sections -ffile-prefix-map=/src/clang-llvm/llvm-build/fuchsia/runtimes/runtimes-x86_64-unknown-fuchsia+asan+noexcept-bins=../llvm-build/fuchsia/runtimes/runtimes-x86_64-unknown-fuchsia+asan+noexcept-bins -ffile-prefix-map=/src/clang-llvm/llvm-project/= -no-canonical-prefixes -O2 -g -DNDEBUG   -DLIBCXX_BUILDING_LIBCXXABI -fno-omit-frame-pointer -gline-tables-only -fsanitize=address -fsanitize=address -nostdinc++ -fvisibility-inlines-hidden -fvisibility=hidden -Wall -Wextra -W -Wwrite-strings -Wno-unused-parameter -Wno-long-long -Werror=return-type -Wextra-semi -Wno-user-defined-literals -Wno-covered-switch-default -Wno-ignored-attributes -Wno-error -fno-exceptions -include /src/clang-llvm/llvm-build/fuchsia/runtimes/runtimes-x86_64-unknown-fuchsia+asan+noexcept-bins/libcxx/__config_site -std=c++14
  INCLUDES = -Ilibcxx/include/c++build
  OBJECT_DIR = libcxx/src/CMakeFiles/cxx_static.dir
  OBJECT_FILE_DIR = libcxx/src/CMakeFiles/cxx_static.dir/filesystem

See the INCLUDES variable, in the latter case, -I/src/clang-llvm/llvm-build/fuchsia/include/c++/v1 is missing so compiler fails to find libc++ headers.

I have no idea why that happens. I inserted debugging prints into various places and I haven't seen any obvious issue. The only difference between the two runtime builds is (aside from ASan instrumentation) that in the latter case, compiler-rt isn't being built as part of runtimes, but I still don't see why that would should matter here.

I agree that I'd like to have more info inline and this is going in the right direction, but what seems missing is still the check line itself.

Formatting changes

Here are a few other places to contemplate similar changes: