XHOST detection fails

[susilehtola]

Running CMake on my laptop with Fedora 32 results in

-- Performing Test CMAKE_CXX_FLAGS [-xHost] - Failed
-- Performing Test CMAKE_CXX_FLAGS [-march=native] - Failed
-- Performing Test CMAKE_CXX_FLAGS [/arch:AVX2] - Failed
CMake Warning at cmake/psi4OptionsTools.cmake:108 (message):
  Option unfulfilled as none of -xHost;-march=native;/arch:AVX2 valid
Call Stack (most recent call first):
  cmake/psi4OptionsTools.cmake:162 (add_C_or_CXX_flags)
  cmake/psi4OptionsTools.cmake:187 (add_CXX_flags)
  cmake/psi4OptionsTools.cmake:202 (add_flags)
  CMakeLists.txt:134 (option_with_flags)

CMakeError.log is

Performing C SOURCE FILE Test test_option failed with the following output:
Change Dir: /home/work/psi4/objdir/CMakeFiles/CMakeTmp

Run Build Command(s):/usr/bin/gmake cmTC_686f3/fast && /usr/bin/gmake  -f CMakeFiles/cmTC_686f3.dir/build.make CMakeFiles/cmTC_686f3.dir/build
gmake[1]: Entering directory '/home/work/psi4/objdir/CMakeFiles/CMakeTmp'
Building C object CMakeFiles/cmTC_686f3.dir/src.c.o
/usr/lib64/ccache/cc   -Dtest_option -xHost   -xHost -o CMakeFiles/cmTC_686f3.dir/src.c.o   -c /home/work/psi4/objdir/CMakeFiles/CMakeTmp/src.c
cc: error: language Host not recognized
cc: error: language Host not recognized
gmake[1]: *** [CMakeFiles/cmTC_686f3.dir/build.make:86: CMakeFiles/cmTC_686f3.dir/src.c.o] Error 1
gmake[1]: Leaving directory '/home/work/psi4/objdir/CMakeFiles/CMakeTmp'
gmake: *** [Makefile:141: cmTC_686f3/fast] Error 2


Source file was:
int main(void) { return 0; }

making it seem that the CMake files aren't even testing the flags.

If I change the order in CMakeLists.txt so that -march=native comes first, the output is correct:

-- Setting option ENABLE_XHOST: ON
-- Performing Test CMAKE_C_FLAGS [-march=native] - Success, Appending
-- Performing Test CMAKE_CXX_FLAGS [-march=native] - Success, Appending

[susilehtola]

Since the problem is that CMake is not detecting the proper flags, this issue also affects all the other options

option_with_flags(ENABLE_XHOST "Enables processor-specific optimization (with MSVC, it enables AVX2 instructions)" ON
                  "-xHost" "-march=native" "/arch:AVX2")
option_with_flags(ENABLE_CODE_COVERAGE "Enables details on code coverage" OFF
                  "-ftest-coverage")
option_with_flags(ENABLE_BOUNDS_CHECK "Enables bounds check in Fortran" OFF
                  "-ftrapuv -check all -fpstkchk" "-fcheck=all" "-fbounds-check -fcheck-array-temporaries")
option_with_flags(ENABLE_ASAN "Enables address sanitizer (requires similarly compiled Python and Numpy)" OFF
                  "-fsanitize=address -fno-omit-frame-pointer")
option_with_flags(ENABLE_TSAN "Enables thread sanitizer (requires similarly compiled Python and Numpy)" OFF
                  "-fsanitize=thread -fPIE -pie -fno-omit-frame-pointer")
option_with_flags(ENABLE_UBSAN "Enables undefined behavior sanitizer (requires similarly compiled Python and Numpy)" OFF
                  "-fsanitize=undefined -fno-omit-frame-pointer")
option_with_flags(ENABLE_MSAN "Enables memory sanitizer (requires similarly compiled Python and Numpy)" OFF
                  "-fsanitize=memory -fPIE -pie -fno-omit-frame-pointer")

[loriab]

What compiler is this? Perhaps it has an option -x<language>?

[susilehtola]

$ gcc --version
gcc (GCC) 10.2.1 20201005 (Red Hat 10.2.1-5)
Copyright (C) 2020 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

From the man page

       You can specify the input language explicitly with the -x option:

       -x language
           Specify explicitly the language for the following input files (rather than letting the compiler choose a default based on the file name
           suffix).  This option applies to all following input files until the next -x option.  Possible values for language are:

                   c  c-header  cpp-output
                   c++  c++-header  c++-cpp-output
                   objective-c  objective-c-header  objective-c-cpp-output
                   objective-c++ objective-c++-header objective-c++-cpp-output
                   assembler  assembler-with-cpp
                   ada
                   d
                   f77  f77-cpp-input f95  f95-cpp-input
                   go
                   brig

       -x none
           Turn off any specification of a language, so that subsequent files are handled according to their file name suffixes (as they are if -x has not
           been used at all).

so yes, looks like -xHost gets parsed as a language override.

[loriab]

That's annoying of GCC. xHost (for Intel) is before march (for Gnu) b/c the former also has a march.

The other flags (enable_code_coverage through enable_msan) aren't necessarily affected, right?

[susilehtola]

Yes, that's true. However, the test program failed to build with -xHost so it is odd that the CMake scripts would not proceed to test the further alternatives.

[loriab]

The underlying cmake cmd is checking for a compiler error code, not compilation failure.

I'm confused as to why this is appearing now, as the -x<lang> has been in GCC for many years (at least since 4.8.5).

[loriab]

Ok, the only non-invasive way I see around this is the below in the main CM file (change primary language as needed):

if(CMAKE_CXX_COMPILER_ID MATCHES Intel)
option_with_flags(ENABLE_XHOST "Enables processor-specific optimization (with MSVC, it enables AVX2 instructions)" ON
                  "-xHost" "-march=native" "/arch:AVX2")
else()
option_with_flags(ENABLE_XHOST "Enables processor-specific optimization (with MSVC, it enables AVX2 instructions)" ON
                  "-march=native" "-xHost" "/arch:AVX2")
endif()

For Intel, -march=native might be a near approximation to -xHost, but I'd rather use the latter official flag.
Do you want to try this out for Libxc, @susilehtola?

I observed another problem that when conda compilers are present and -DCMAKE_CXX_COMPILER=icpc passed, that the -fno-plt set in the envvar CXXFLAGS by conda env activation was unsupported by Intel and so triggered all three ENABLE_XHOST options to fail unless CXXFLAGS= explicitly cleared/set beforehand. I had deliberately not made psi4 CMake dependent on envvars, but it looks like CMake started doing that in 3.10, hmpf. https://cmake.org/cmake/help/v3.10/manual/cmake-env-variables.7.html#manual:cmake-env-variables(7)