update comments

git-svn-id: https://svn.r-project.org/R/trunk@84716 00db46b3-68df-0310-9c12-caf00c1e9a41

m4/openmp.m4

@@ -32,7 +32,7 @@
 # [Change for Intel preferring -fiopenmp and deprecating -fopenmp in 2023.]
 
 # _AC_LANG_OPENMP is a language-dependent program defined in c.m4 in
-# the autoconf library.
+# the autoconf library. And this is a modification of its AC_OPENMP
 
 # R_OPENMP
 # --------
@@ -57,12 +57,12 @@ AC_DEFUN([R_OPENMP],
  [ac_cv_prog_[]_AC_LANG_ABBREV[]_openmp='none needed'],
  [ac_cv_prog_[]_AC_LANG_ABBREV[]_openmp='unsupported'
  dnl Try these flags:
- dnl GCC >= 4.2, clang >= 3.8 -fopenmp
+ dnl GCC >= 4.2, clang >= 3.8, flang-new -fopenmp
  dnl clang 3.7.x -fopenmp=libomp
- dnl (-fopenmp is accepted but does not work)
+ dnl (-fopenmp was accepted but does not work)
  dnl Oracle C, Fortran -xopenmp
  dnl (also accepts -fopenmp as from 12.4, but does not work in 12.5)
- dnl Intel C, Fortran -qopenmp
+ dnl 'Classic' Intel C, Fortran -qopenmp
  dnl Intel -openmp (deprecated)
  dnl (https://software.intel.com/en-us/node/581863,
  dnl https://software.intel.com/en-us/node/525020)
@@ -73,13 +73,13 @@ AC_DEFUN([R_OPENMP],
  dnl Cray CCE -homp
  dnl NEC SX -Popenmp
  dnl Lahey Fortran (Linux) --openmp
- dnl flang  -mp, also -fopenmp
+ dnl Classic flang -mp, also -fopenmp
  dnl If in this loop a compiler is passed an option that it doesn't
  dnl understand or that it misinterprets, the AC_LINK_IFELSE test
  dnl will fail (since we know that it failed without the option),
  dnl therefore the loop will continue searching for an option, and
  dnl no output file called 'penmp' or 'mp' is created.
- dnl Sept 2017: Solaris needs -xopenmp before -fopenmp
+ dnl Sept 2017: Solaris needs -xopenmp tested before -fopenmp
  for ac_option in -xopenmp -fiopenmp -fopenmp -qopenmp \
  -openmp -mp -omp -qsmp=omp -homp \
  -fopenmp=libomp \