charm: provide MPI (#8647)

* Charm: provide MPI
* add mpicc wrappers
* clarify MPI comment

var/spack/repos/builtin/packages/charm/package.py

@@ -92,6 +92,25 @@ class Charm(Package):
     variant("production", default=True, description="Build charm++ with all optimizations")
     variant("tracing", default=False, description="Enable tracing modules")
 
+    # FIXME: backend=mpi also provides mpi, but spack does not support
+    # depends_on("mpi") and provides("mpi") in the same package currently.
+    for b in ['multicore', 'netlrts', 'verbs', 'gni', 'ofi', 'pami',
+              'pamilrts']:
+        provides('mpi@2', when='@6.7.1: build-target=AMPI backend={0}'.format(b))
+        provides('mpi@2', when='@6.7.1: build-target=LIBS backend={0}'.format(b))
+
+    def setup_dependent_environment(self, spack_env, run_env, dependent_spec):
+        spack_env.set('MPICC',  join_path(self.prefix.bin, 'ampicc'))
+        spack_env.set('MPICXX', join_path(self.prefix.bin, 'ampicxx'))
+        spack_env.set('MPIF77', join_path(self.prefix.bin, 'ampif77'))
+        spack_env.set('MPIF90', join_path(self.prefix.bin, 'ampif90'))
+
+    def setup_dependent_package(self, module, dependent_spec):
+        self.spec.mpicc = join_path(self.prefix.bin, 'ampicc')
+        self.spec.mpicxx = join_path(self.prefix.bin, 'ampicxx')
+        self.spec.mpifc = join_path(self.prefix.bin, 'ampif90')
+        self.spec.mpif77 = join_path(self.prefix.bin, 'ampif77')
+
     depends_on("mpi", when="backend=mpi")
     depends_on("papi", when="+papi")
     depends_on("cuda", when="+cuda")