v12: Support for Flang 22

[mathomp4]

With the release of Flang 22.1.0, we can now build MAPL and pass all unit tests. So next up is GEOSgcm.

I'm currently testing this now. At a minimum we need FMS 2025 so I am starting from #933

OS Support

Linux

I can build working flang 22 with my build-llvm-flang script

macOS

I have not been able to get a working flang with build-llvm-flang. macOS is just weird enough. Luckily @cho-m is on the case in Homebrew land (see Homebrew/homebrew-core#269143). I already use their gfortran-15 so I hope they can provide us a nice easy flang in the future! → It's on homebrew!

Performance

I have been able to run. Current performance:

Compiler	Model Throughput (d/d)	Walltime
ifort	336.261	04:53
GNU	415.782	04:16
Flang 0	348.372	04:52
Flang 1	352.001	04:49
Flang 2	363.181	04:49

Key:

• Flang 0: -O3 -g
• Flang 1: -O3 -march=znver2 -g
• Flang 2: -O3 -march=znver2 -funroll-loops -fstack-arrays -g

Latest flags on GEOS-ESM/ESMA_cmake#517

Changes Needed

At present it is:

> mepo status
Checking status...
GEOSgcm                | (b) feature/v12-remove-mom5
env                    | (t) v6.1.0 (DH)
   | g5_modules: modified, not staged
cmake                  | (b) feature/flang-flags
ecbuild                | (t) geos/v3.13.1 (DH)
NCEP_Shared            | (t) v1.4.0 (DH)
   | NCEP_sp/imax_verify.h: modified, not staged
   |       NCEP_sp/splat.f: modified, not staged
   |     NCEP_w3/errexit.f: modified, not staged
GMAO_Shared            | (t) GCMv12-rc22 (DH)
   | GMAO_mpeu/m_random.F: modified, not staged
GEOS_Util              | (t) GCMv12-rc22 (DH)
   |                                  post/rs_numtiles.F90: modified, not staged
   | pre/prepare_ocnExtData/daily_clim_SST_FRACI_eight.F90: modified, not staged
GMAO_perllib           | (t) v1.1.0 (DH)
MAPL                   | (t) v2.65.0 (DH)
GEOSgcm_GridComp       | (b) feature/v12-remove-mom5
   |                              GEOSagcm_GridComp/GEOSphysics_GridComp/GEOSgwd_GridComp/ncar_gwd/gw_convect.F90: modified, not staged
   |                                     GEOSagcm_GridComp/GEOSphysics_GridComp/GEOSmoist_GridComp/CMakeLists.txt: modified, not staged
   |         GEOSagcm_GridComp/GEOSphysics_GridComp/GEOSsurface_GridComp/Utils/Raster/makebcs/mkMITAquaRaster.F90: modified, not staged
   |             GEOSagcm_GridComp/GEOSphysics_GridComp/GEOSsurface_GridComp/Utils/mk_restarts/CatchmentCNRst.F90: modified, not staged
   |               GEOSagcm_GridComp/GEOSphysics_GridComp/GEOSsurface_GridComp/Utils/mk_restarts/CatchmentRst.F90: modified, not staged
   |           GEOSagcm_GridComp/GEOSphysics_GridComp/GEOSsurface_GridComp/Utils/mk_restarts/SaltImpConverter.F90: modified, not staged
   |            GEOSagcm_GridComp/GEOSphysics_GridComp/GEOSsurface_GridComp/Utils/mk_restarts/SaltIntSplitter.F90: modified, not staged
   |                GEOSagcm_GridComp/GEOSphysics_GridComp/GEOSsurface_GridComp/Utils/mk_restarts/Scale_Catch.F90: modified, not staged
   |              GEOSagcm_GridComp/GEOSphysics_GridComp/GEOSsurface_GridComp/Utils/mk_restarts/Scale_CatchCN.F90: modified, not staged
   |             GEOSagcm_GridComp/GEOSphysics_GridComp/GEOSsurface_GridComp/Utils/mk_restarts/cv_SaltRestart.F90: modified, not staged
   |         GEOSagcm_GridComp/GEOSphysics_GridComp/GEOSsurface_GridComp/Utils/mk_restarts/mk_CatchCNRestarts.F90: modified, not staged
   |        GEOSagcm_GridComp/GEOSphysics_GridComp/GEOSsurface_GridComp/Utils/mk_restarts/mk_GEOSldasRestarts.F90: modified, not staged
   | GEOSagcm_GridComp/GEOSphysics_GridComp/GEOSsurface_GridComp/Utils/mk_restarts/mk_LakeLandiceSaltRestarts.F90: modified, not staged
   |                   GEOSagcm_GridComp/GEOSphysics_GridComp/GEOSturbulence_GridComp/GEOS_TurbulenceGridComp.F90: modified, not staged
geos_state_bias        | (t) geos/v1.0.0 (DH)
GigaTraj               | (t) geos/v1.0.0 (DH)
FVdycoreCubed_GridComp | (b) feature/v12-fms2025-useifdef
   | c2c.F90: modified, not staged
fvdycore               | (b) feature/v12-fms2025-useifdef
   | tools/fv_eta.F90: modified, not staged
GEOSchem_GridComp      | (t) GCMv12-rc22 (DH)
HEMCO                  | (t) geos/v2.3.0 (DH)
geos-chem              | (t) geos/v13.0.0-rc1 (DH)
GOCART                 | (b) develop
QuickChem              | (t) v1.0.0 (DH)
RRG                    | (t) v1.1.0 (DH)
TR                     | (t) v1.2.0 (DH)
GMI                    | (t) v1.3.0 (DH)
StratChem              | (t) v1.0.0 (DH)
   | SC_GridComp/SC_GridCompMod.F90: modified, not staged
MAM                    | (t) v1.1.0 (DH)
MATRIX                 | (t) v1.0.0 (DH)
CARMA                  | (t) v1.1.0 (DH)
GAAS                   | (t) v1.0.0 (DH)
   | LDE_Mod.F90: modified, not staged
ACHEM                  | (t) v1.0.1 (DH)
GEOS_OceanGridComp     | (b) feature/v12-remove-mom5
mom6                   | (t) geos/v3.7 (DH)
   | src/ALE/MOM_remapping.F90: modified, not staged
mit                    | (t) checkpoint68o (DH)
cice6                  | (t) geos/v0.2.0 (DH)
icepack                | (t) geos/v0.3.0 (DH)
sis2                   | (t) geos/v0.0.1 (DH)
GEOSradiation_GridComp | (t) GCMv12-rc20 (DH)
RRTMGP                 | (t) geos/v1.8+1.0.0 (DH)
ww3                    | (t) v7.14-geos-r1 (DH)
umwm                   | (t) v2.0.0-geos-r1 (DH)
GEOSgcm_App            | (b) feature/v12-remove-mom5
UMD_Etc                | (t) v1.4.0 (DH)
   |  UMD_oletkf/common_mom4.f90: modified, not staged
   |    UMD_oletkf/letkf_obs.f90: modified, not staged
   |    UMD_utils/anaice2rst.f90: modified, not staged
   |     UMD_utils/ocean_iau.f90: modified, not staged
   | UMD_utils/ocean_moments.f90: modified, not staged
CPLFCST_Etc            | (t) v1.0.1 (DH)
Topo                   | (t) geos/v2.1.0 (DH)
GenCast_GEOS-FP        | (t) geos/v0.3.1 (DH)

A bit of everywhere, almost always because Flang is pretty strict on Fortran.