dnl -*- shell-script -*-
dnl
dnl Copyright (c) 2004-2005 The Trustees of Indiana University and Indiana
dnl                         University Research and Technology
dnl                         Corporation.  All rights reserved.
dnl Copyright (c) 2004-2006 The University of Tennessee and The University
dnl                         of Tennessee Research Foundation.  All rights
dnl                         reserved.
dnl Copyright (c) 2004-2008 High Performance Computing Center Stuttgart,
dnl                         University of Stuttgart.  All rights reserved.
dnl Copyright (c) 2004-2006 The Regents of the University of California.
dnl                         All rights reserved.
dnl Copyright (c) 2007-2009 Sun Microsystems, Inc.  All rights reserved.
dnl Copyright (c) 2008-2021 Cisco Systems, Inc.  All rights reserved.
dnl Copyright (c) 2012-2017 Los Alamos National Security, LLC. All rights
dnl                         reserved.
dnl Copyright (c) 2015-2019 Research Organization for Information Science
dnl                         and Technology (RIST).  All rights reserved.
dnl Copyright (c) 2020      Triad National Security, LLC. All rights
dnl                         reserved.
dnl Copyright (c) 2021      IBM Corporation.  All rights reserved.
dnl
dnl $COPYRIGHT$
dnl
dnl Additional copyrights may follow
dnl
dnl $HEADER$
dnl

AC_DEFUN([OPAL_CC_HELPER],[
    OPAL_VAR_SCOPE_PUSH([opal_cc_helper_result])
    AC_MSG_CHECKING([$1])

    AC_LINK_IFELSE([AC_LANG_PROGRAM([$3],[$4])],
                   [$2=1
                    opal_cc_helper_result=yes],
                   [$2=0
                    opal_cc_helper_result=no])

    AC_MSG_RESULT([$opal_cc_helper_result])
    OPAL_VAR_SCOPE_POP
])


AC_DEFUN([OPAL_PROG_CC_C11_HELPER],[
    OPAL_VAR_SCOPE_PUSH([opal_prog_cc_c11_helper_CFLAGS_save])

    opal_prog_cc_c11_helper_CFLAGS_save=$CFLAGS
    CFLAGS="$CFLAGS $1"

    OPAL_CC_HELPER([if $CC $1 supports C11 _Thread_local], [opal_prog_cc_c11_helper__Thread_local_available],
                   [],[[static _Thread_local int  foo = 1;++foo;]])

    OPAL_CC_HELPER([if $CC $1 supports C11 atomic variables], [opal_prog_cc_c11_helper_atomic_var_available],
                   [[#include <stdatomic.h>]], [[static atomic_long foo = 1;++foo;]])

    OPAL_CC_HELPER([if $CC $1 supports C11 _Atomic keyword], [opal_prog_cc_c11_helper__Atomic_available],
                   [[#include <stdatomic.h>]],[[static _Atomic long foo = 1;++foo;]])

    OPAL_CC_HELPER([if $CC $1 supports C11 _Generic keyword], [opal_prog_cc_c11_helper__Generic_available],
                   [[#define FOO(x) (_Generic (x, int: 1))]], [[static int x, y; y = FOO(x);]])

    OPAL_CC_HELPER([if $CC $1 supports C11 _Static_assert], [opal_prog_cc_c11_helper__static_assert_available],
                   [[#include <stdint.h>]],[[_Static_assert(sizeof(int64_t) == 8, "WTH");]])

    OPAL_CC_HELPER([if $CC $1 supports C11 atomic_fetch_xor_explicit], [opal_prog_cc_c11_helper_atomic_fetch_xor_explicit_available],
                   [[#include <stdatomic.h>
#include <stdint.h>]],[[_Atomic uint32_t a; uint32_t b; atomic_fetch_xor_explicit(&a, b, memory_order_relaxed);]])

    AS_IF([test $opal_prog_cc_c11_helper__Thread_local_available -eq 1 && test $opal_prog_cc_c11_helper_atomic_var_available -eq 1 && test $opal_prog_cc_c11_helper_atomic_fetch_xor_explicit_available -eq 1],
          [$2],
          [$3])

    CFLAGS=$opal_prog_cc_c11_helper_CFLAGS_save

    OPAL_VAR_SCOPE_POP
])

AC_DEFUN([OPAL_PROG_CC_C11],[
    OPAL_VAR_SCOPE_PUSH([opal_prog_cc_c11_flags])
    if test -z "$opal_cv_c11_supported" ; then
        opal_cv_c11_supported=no
        opal_cv_c11_flag_required=yes

        AC_MSG_CHECKING([if $CC requires a flag for C11])

        AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[
#if __STDC_VERSION__ < 201112L
#error "Without any CLI flags, this compiler does not support C11"
#endif
                                           ]],[])],
                          [opal_cv_c11_flag_required=no])

        AC_MSG_RESULT([$opal_cv_c11_flag_required])

        if test "x$opal_cv_c11_flag_required" = "xno" ; then
            AC_MSG_NOTICE([verifying $CC supports C11 without a flag])
            OPAL_PROG_CC_C11_HELPER([], [], [opal_cv_c11_flag_required=yes])
        fi

        if test "x$opal_cv_c11_flag_required" = "xyes" ; then
            opal_prog_cc_c11_flags="-std=gnu11 -std=c11 -c11"

            AC_MSG_NOTICE([checking if $CC supports C11 with a flag])
            opal_cv_c11_flag=
            for flag in $(echo $opal_prog_cc_c11_flags | tr ' ' '\n') ; do
                OPAL_PROG_CC_C11_HELPER([$flag],[opal_cv_c11_flag=$flag],[])
                if test "x$opal_cv_c11_flag" != "x" ; then
                    OPAL_FLAGS_APPEND_UNIQ([CFLAGS], ["$opal_cv_c11_flag"])
                    AC_MSG_NOTICE([using $flag to enable C11 support])
                    opal_cv_c11_supported=yes
                    break
                fi
            done
        else
            AC_MSG_NOTICE([no flag required for C11 support])
            opal_cv_c11_supported=yes
        fi
    fi

    OPAL_VAR_SCOPE_POP
])

# OPAL_CHECK_CC_IQUOTE()
# ----------------------
# Check if the compiler supports the -iquote option. This options
# removes the specified directory from the search path when using
# #include <>. This check works around an issue caused by C++20
# which added a <version> header. This conflicts with the
# VERSION file at the base of our source directory on case-
# insensitive filesystems.
AC_DEFUN([OPAL_CHECK_CC_IQUOTE],[
    OPAL_VAR_SCOPE_PUSH([opal_check_cc_iquote_CFLAGS_save])
    opal_check_cc_iquote_CFLAGS_save=${CFLAGS}
    CFLAGS="${CFLAGS} -iquote ."
    AC_MSG_CHECKING([for $CC option to add a directory only to the search path for the quote form of include])
    AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[]],[])],
                      [opal_cc_iquote="-iquote"],
                      [opal_cc_iquote="-I"])
    CFLAGS=${opal_check_cc_iquote_CFLAGS_save}
    OPAL_VAR_SCOPE_POP
    AC_MSG_RESULT([$opal_cc_iquote])
])

# OPAL_SETUP_CC()
# ---------------
# Do everything required to setup the C compiler.  Safe to AC_REQUIRE
# this macro.
AC_DEFUN([OPAL_SETUP_CC],[
    # AM_PROG_CC_C_O AC_REQUIREs AC_PROG_CC, so we have to be a little
    # careful about ordering here, and AC_REQUIRE these things so that
    # they get stamped out in the right order.

    AC_REQUIRE([_OPAL_START_SETUP_CC])
    AC_REQUIRE([_OPAL_PROG_CC])
    AC_REQUIRE([AM_PROG_CC_C_O])

    OPAL_VAR_SCOPE_PUSH([opal_prog_cc_c11_helper__Thread_local_available opal_prog_cc_c11_helper_atomic_var_available opal_prog_cc_c11_helper__Atomic_available opal_prog_cc_c11_helper__static_assert_available opal_prog_cc_c11_helper__Generic_available opal_prog_cc__thread_available opal_prog_cc_c11_helper_atomic_fetch_xor_explicit_available opal_prog_cc_c11_helper_proper__Atomic_support_in_atomics])

    OPAL_PROG_CC_C11

    OPAL_CHECK_CC_IQUOTE

    OPAL_C_COMPILER_VENDOR([opal_c_vendor])

    if test $opal_cv_c11_supported = no ; then
        # It is not currently an error if C11 support is not available. Uncomment the
        # following lines and update the warning when we require a C11 compiler.
        # AC_MSG_WARNING([Open MPI requires a C11 (or newer) compiler])
        # AC_MSG_ERROR([Aborting.])
        # From Open MPI 1.7 on we require a C99 compliant compiler
        dnl with autoconf 2.70 AC_PROG_CC makes AC_PROG_CC_C99 obsolete
        m4_version_prereq([2.70],
            [],
            [AC_PROG_CC_C99])
        # The result of AC_PROG_CC_C99 is stored in ac_cv_prog_cc_c99
        if test "x$ac_cv_prog_cc_c99" = xno ; then
            AC_MSG_WARN([Open MPI requires a C99 (or newer) compiler. C11 is recommended.])
            AC_MSG_ERROR([Aborting.])
        fi

        # Get the correct result for C11 support flags now that the compiler flags have
        # changed
        OPAL_PROG_CC_C11_HELPER([], [], [])
    fi

    # Check if compiler support __thread
    OPAL_CC_HELPER([if $CC $1 supports __thread], [opal_prog_cc__thread_available],
               [],[[static __thread int  foo = 1;++foo;]])

    OPAL_CC_HELPER([if $CC $1 supports C11 _Thread_local], [opal_prog_cc_c11_helper__Thread_local_available],
                   [],[[static _Thread_local int  foo = 1;++foo;]])

    dnl At this time Open MPI only needs thread local and the atomic convenience types for C11 support. These
    dnl will likely be required in the future.
    AC_DEFINE_UNQUOTED([OPAL_C_HAVE__THREAD_LOCAL], [$opal_prog_cc_c11_helper__Thread_local_available],
                       [Whether C compiler supports __Thread_local])

    AC_DEFINE_UNQUOTED([OPAL_C_HAVE_ATOMIC_CONV_VAR], [$opal_prog_cc_c11_helper_atomic_var_available],
                       [Whether C compiler support atomic convenience variables in stdatomic.h])

    AC_DEFINE_UNQUOTED([OPAL_C_HAVE__ATOMIC], [$opal_prog_cc_c11_helper__Atomic_available],
                       [Whether C compiler supports __Atomic keyword])

    AC_DEFINE_UNQUOTED([OPAL_C_HAVE__GENERIC], [$opal_prog_cc_c11_helper__Generic_available],
                       [Whether C compiler supports __Generic keyword])

    AC_DEFINE_UNQUOTED([OPAL_C_HAVE__STATIC_ASSERT], [$opal_prog_cc_c11_helper__static_assert_available],
                       [Whether C compiler support _Static_assert keyword])

    AC_DEFINE_UNQUOTED([OPAL_C_HAVE___THREAD], [$opal_prog_cc__thread_available],
                       [Whether C compiler supports __thread])

    # Check for standard headers, needed here because needed before
    # the types checks.  This is only necessary for Autoconf < v2.70.
    m4_version_prereq([2.70],
                      [],
                      [AC_HEADER_STDC])

    # GNU C and autotools are inconsistent about whether this is
    # defined so let's make it true everywhere for now...  However, IBM
    # XL compilers on PPC Linux behave really badly when compiled with
    # _GNU_SOURCE defined, so don't define it in that situation.
    #
    # Don't use AC_GNU_SOURCE because it requires that no compiler
    # tests are done before setting it, and we need to at least do
    # enough tests to figure out if we're using XL or not.
    AS_IF([test "$opal_cv_c_compiler_vendor" != "ibm"],
          [AH_VERBATIM([_GNU_SOURCE],
                       [/* Enable GNU extensions on systems that have them.  */
#ifndef _GNU_SOURCE
# undef _GNU_SOURCE
#endif])
           AC_DEFINE([_GNU_SOURCE])])

    AS_IF([test "$opal_cv_c_compiler_vendor" = "intel"],
          [OPAL_CC_HELPER([if $CC is Intel < 20200310 (lacks proper support for atomic operations on _Atomic variables)], [opal_prog_cc_c11_helper_proper__Atomic_support_in_atomics],
                          [],[[
                   #ifdef __INTEL_COMPILER
                   #if __INTEL_COMPILER_BUILD_DATE <= 20200310
                   #error Lacks support for proper atomic operations on _Atomic variables.
                   #endif  /* __INTEL_COMPILER_BUILD_DATE <= 20200310 */
                   #endif  /* __INTEL_COMPILER */
                             ]])],
          [opal_prog_cc_c11_helper_proper__Atomic_support_in_atomics=1])

    AC_DEFINE_UNQUOTED([OPAL_C_HAVE_ATOMIC_SUPPORT_FOR__ATOMIC], [$opal_prog_cc_c11_helper_proper__Atomic_support_in_atomics],
                       [Whether C compiler supports atomic operations on _Atomic variables without warnings])

    # Do we want code coverage
    if test "$WANT_COVERAGE" = "1"; then
        # For compilers > gcc-4.x, use --coverage for
        # compiling and linking to circumvent trouble with
        # libgcov.
        LDFLAGS_orig="$LDFLAGS"
        OPAL_FLAGS_APPEND_UNIQ([LDFLAGS], ["--coverage"])
        OPAL_COVERAGE_FLAGS=

        _OPAL_CHECK_SPECIFIC_CFLAGS(--coverage, coverage)
        if test "$opal_cv_cc_coverage" = "1" ; then
            OPAL_COVERAGE_FLAGS="--coverage"
            CLEANFILES="*.gcno ${CLEANFILES}"
            CONFIG_CLEAN_FILES="*.gcda *.gcov ${CONFIG_CLEAN_FILES}"
            AC_MSG_WARN([$OPAL_COVERAGE_FLAGS has been added to CFLAGS (--enable-coverage)])
        else
            _OPAL_CHECK_SPECIFIC_CFLAGS(-ftest-coverage, ftest_coverage)
            _OPAL_CHECK_SPECIFIC_CFLAGS(-fprofile-arcs, fprofile_arcs)
            if test "$opal_cv_cc_ftest_coverage" = "0" || test "opal_cv_cc_fprofile_arcs" = "0" ; then
                AC_MSG_WARN([Code coverage functionality is not currently available with $CC])
                AC_MSG_ERROR([Configure: Cannot continue])
            fi
            CLEANFILES="*.bb *.bbg ${CLEANFILES}"
            OPAL_COVERAGE_FLAGS="-ftest-coverage -fprofile-arcs"
        fi
        WANT_DEBUG=1
   fi

    # These flags are generally gcc-specific; even the
    # gcc-impersonating compilers won't accept them.
    OPAL_CFLAGS_BEFORE_PICKY="$CFLAGS"

    if test $WANT_PICKY_COMPILER -eq 1; then
        _OPAL_CHECK_SPECIFIC_CFLAGS(-Wundef, Wundef)
        _OPAL_CHECK_SPECIFIC_CFLAGS(-Wno-long-long, Wno_long_long, int main() { long long x; })
        _OPAL_CHECK_SPECIFIC_CFLAGS(-Wsign-compare, Wsign_compare)
        _OPAL_CHECK_SPECIFIC_CFLAGS(-Wmissing-prototypes, Wmissing_prototypes)
        _OPAL_CHECK_SPECIFIC_CFLAGS(-Wstrict-prototypes, Wstrict_prototypes)
        _OPAL_CHECK_SPECIFIC_CFLAGS(-Wcomment, Wcomment)
        _OPAL_CHECK_SPECIFIC_CFLAGS(-Wshadow, Wshadow)
        _OPAL_CHECK_SPECIFIC_CFLAGS(-Werror-implicit-function-declaration, Werror_implicit_function_declaration)
        _OPAL_CHECK_SPECIFIC_CFLAGS(-Wno-long-double, Wno_long_double, int main() { long double x; })
        _OPAL_CHECK_SPECIFIC_CFLAGS(-fno-strict-aliasing, fno_strict_aliasing, int main() { long double x; })
        _OPAL_CHECK_SPECIFIC_CFLAGS(-pedantic, pedantic)
        _OPAL_CHECK_SPECIFIC_CFLAGS(-Wall, Wall)

        # There are some warnings that we specifically do not care
        # about / do not agree that gcc emits warnings about them.  So
        # we turn them off.
        _OPAL_CHECK_SPECIFIC_CFLAGS(-Wformat-truncation=0, format_truncation)
    fi

    # Note: Some versions of clang (at least >= 3.5 -- perhaps
    # older versions, too?) and xlc with -g (v16.1, perhaps older)
    # will *warn* about -finline-functions, but still allow it.
    # This is very annoying, so check for that warning, too.
    # The clang warning looks like this:
    # clang: warning: optimization flag '-finline-functions' is not supported
    # clang: warning: argument unused during compilation: '-finline-functions'
    # the xlc warning looks like this:
    # warning: "-qinline" is not compatible with "-g". "-qnoinline" is being set.
    _OPAL_CHECK_SPECIFIC_CFLAGS(-finline-functions, finline_functions)

    # Try to enable restrict keyword
    RESTRICT_CFLAGS=
    case "$opal_c_vendor" in
        intel)
            RESTRICT_CFLAGS="-restrict"
        ;;
        sgi)
            RESTRICT_CFLAGS="-LANG:restrict=ON"
        ;;
    esac
    if test ! -z "$RESTRICT_CFLAGS" ; then
        _OPAL_CHECK_SPECIFIC_CFLAGS($RESTRICT_CFLAGS, restrict)
    fi

    # see if the C compiler supports __builtin_expect
    AC_CACHE_CHECK([if $CC supports __builtin_expect],
        [opal_cv_cc_supports___builtin_expect],
        [AC_LINK_IFELSE([AC_LANG_PROGRAM([],
          [void *ptr = (void*) 0;
           if (__builtin_expect (ptr != (void*) 0, 1)) return 0;])],
          [opal_cv_cc_supports___builtin_expect="yes"],
          [opal_cv_cc_supports___builtin_expect="no"])])
    if test "$opal_cv_cc_supports___builtin_expect" = "yes" ; then
        have_cc_builtin_expect=1
    else
        have_cc_builtin_expect=0
    fi
    AC_DEFINE_UNQUOTED([OPAL_C_HAVE_BUILTIN_EXPECT], [$have_cc_builtin_expect],
        [Whether C compiler supports __builtin_expect])

    # see if the C compiler supports __builtin_prefetch
    AC_CACHE_CHECK([if $CC supports __builtin_prefetch],
        [opal_cv_cc_supports___builtin_prefetch],
        [AC_LINK_IFELSE([AC_LANG_PROGRAM([],
          [int ptr;
           __builtin_prefetch(&ptr,0,0);])],
          [opal_cv_cc_supports___builtin_prefetch="yes"],
          [opal_cv_cc_supports___builtin_prefetch="no"])])
    if test "$opal_cv_cc_supports___builtin_prefetch" = "yes" ; then
        have_cc_builtin_prefetch=1
    else
        have_cc_builtin_prefetch=0
    fi
    AC_DEFINE_UNQUOTED([OPAL_C_HAVE_BUILTIN_PREFETCH], [$have_cc_builtin_prefetch],
        [Whether C compiler supports __builtin_prefetch])

    # see if the C compiler supports __builtin_clz
    AC_CACHE_CHECK([if $CC supports __builtin_clz],
        [opal_cv_cc_supports___builtin_clz],
        [AC_LINK_IFELSE([AC_LANG_PROGRAM([],
            [int value = 0xffff; /* we know we have 16 bits set */
             if ((8*sizeof(int)-16) != __builtin_clz(value)) return 0;])],
            [opal_cv_cc_supports___builtin_clz="yes"],
            [opal_cv_cc_supports___builtin_clz="no"])])
    if test "$opal_cv_cc_supports___builtin_clz" = "yes" ; then
        have_cc_builtin_clz=1
    else
        have_cc_builtin_clz=0
    fi
    AC_DEFINE_UNQUOTED([OPAL_C_HAVE_BUILTIN_CLZ], [$have_cc_builtin_clz],
        [Whether C compiler supports __builtin_clz])

    # Preload the optflags for the case where the user didn't specify
    # any.  If we're using GNU compilers, use -O3 (since it GNU
    # doesn't require all compilation units to be compiled with the
    # same level of optimization -- selecting a high level of
    # optimization is not prohibitive).  If we're using anything else,
    # be conservative and just use -O.
    #
    # Note: gcc-impersonating compilers accept -O3
    if test "$WANT_DEBUG" = "1"; then
        OPTFLAGS=
    else
        if test "$GCC" = yes; then
            OPTFLAGS="-O3"
        else
            OPTFLAGS="-O"
        fi
    fi

    OPAL_ENSURE_CONTAINS_OPTFLAGS("$OPAL_CFLAGS_BEFORE_PICKY")
    OPAL_CFLAGS_BEFORE_PICKY="$co_result"

    AC_MSG_CHECKING([for C optimization flags])
    OPAL_ENSURE_CONTAINS_OPTFLAGS(["$CFLAGS"])
    AC_MSG_RESULT([$co_result])
    CFLAGS="$co_result"
    AC_MSG_RESULT(CFLAGS result: $CFLAGS)
    OPAL_VAR_SCOPE_POP
])


AC_DEFUN([_OPAL_START_SETUP_CC],[
    opal_show_subtitle "C compiler and preprocessor"
])


AC_DEFUN([_OPAL_PROG_CC],[
    dnl It is really easy to accidentally call AC_PROG_CC implicitly through
    dnl some other test run before OPAL_SETUP_CC.  Try to make that harder.
    m4_provide_if([AC_PROG_CC],
                  [m4_fatal([AC_PROG_CC called before OPAL_SETUP_CC])])

    #
    # Check for the compiler
    #
    OPAL_VAR_SCOPE_PUSH([dummy opal_cc_arvgv0])

    AC_USE_SYSTEM_EXTENSIONS

    AC_PROG_CC
    BASECC="`basename $CC`"
    OPAL_CC="$CC"
    AC_DEFINE_UNQUOTED(OPAL_CC, "$OPAL_CC", [OMPI underlying C compiler])
    set dummy $CC
    opal_cc_argv0=[$]2
    OPAL_WHICH([$opal_cc_argv0], [OPAL_CC_ABSOLUTE])
    AC_SUBST(OPAL_CC_ABSOLUTE)

    OPAL_VAR_SCOPE_POP
])