Add libxc 5.0.0 (#17807)

With experimental CUDA support and some patches to make it compile.

Currently +shared and +cuda conflict, this has to be fixed upstream.

var/spack/repos/builtin/packages/libxc/0001-Bugfix-avoid-implicit-pointer-cast-to-make-libxc-com.patch

+From 205a08a30ee0d057d173f9eaa6fc6414f6960c22 Mon Sep 17 00:00:00 2001
+From: Xavier Andrade <xavier@tddft.org>
+Date: Wed, 27 May 2020 15:42:32 -0700
+Subject: [PATCH] Bugfix: avoid implicit pointer cast to make libxc compile
+ with a C++ compiler.
+
+---
+ src/functionals.c | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git a/src/functionals.c b/src/functionals.c
+index 3f668292..293f7f9b 100644
+--- a/src/functionals.c
++++ b/src/functionals.c
+@@ -324,7 +324,7 @@ xc_func_set_ext_params_name(xc_func_type *p, const char *name, double par)
+ 
+   assert(p != NULL && p->info->ext_params.n > 0);
+   
+-  ext_params = libxc_malloc(p->info->ext_params.n*sizeof(double));
++  ext_params = (double *) libxc_malloc(p->info->ext_params.n*sizeof(double));
+   for(ii=0; ii<p->info->ext_params.n; ii++){
+     if(strcmp(p->info->ext_params.names[ii], name) == 0)
+       ext_params[ii] = par;
+-- 
+2.25.1
+

var/spack/repos/builtin/packages/libxc/0002-Mark-xc_erfcx-a-GPU_FUNCTION.patch

+From 11b90a0a477925f19dfeb7e1f672058f25d83387 Mon Sep 17 00:00:00 2001
+From: Harmen Stoppels <harmenstoppels@gmail.com>
+Date: Fri, 31 Jul 2020 13:54:39 +0200
+Subject: [PATCH] Mark xc_erfcx a GPU_FUNCTION
+
+---
+ src/faddeeva.c | 3 +++
+ 1 file changed, 3 insertions(+)
+
+diff --git a/src/faddeeva.c b/src/faddeeva.c
+index ceec4736..03484713 100644
+--- a/src/faddeeva.c
++++ b/src/faddeeva.c
+@@ -29,6 +29,8 @@
+ 
+ #include "config.h"
+ 
++#include "util.h"
++
+ #include <math.h>
+ 
+ /* erfcx(x) = exp(x^2) erfc(x) function, for real x, written by
+@@ -477,6 +479,7 @@ return 0.97771701335885035464e0 + (0.22000938572830479551e-1 + (0.27951610702682
+   return 1.0;
+ }
+ 
++GPU_FUNCTION
+ double xc_erfcx(double x)
+ {
+   if (x >= 0) {
+-- 
+2.25.1
+

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

@@ -6,13 +6,14 @@
 from spack import *
 
 
-class Libxc(AutotoolsPackage):
+class Libxc(AutotoolsPackage, CudaPackage):
     """Libxc is a library of exchange-correlation functionals for
     density-functional theory."""
 
     homepage = "https://tddft.org/programs/libxc/"
     url      = "https://www.tddft.org/programs/libxc/down.php?file=2.2.2/libxc-2.2.2.tar.gz"
 
+    version('5.0.0', sha256='1cdc57930f7b57da4eb9b2c55a50ba1c2c385936ddaf5582fee830994461a892')
     version('4.3.4', sha256='a8ee37ddc5079339854bd313272856c9d41a27802472ee9ae44b58ee9a298337')
     version('4.3.2', sha256='bc159aea2537521998c7fb1199789e1be71e04c4b7758d58282622e347603a6f')
     version('4.2.3', sha256='02e49e9ba7d21d18df17e9e57eae861e6ce05e65e966e1e832475aa09e344256')
@@ -20,6 +21,14 @@ class Libxc(AutotoolsPackage):
     version('2.2.2', sha256='6ca1d0bb5fdc341d59960707bc67f23ad54de8a6018e19e02eee2b16ea7cc642')
     version('2.2.1', sha256='ade61c1fa4ed238edd56408fd8ee6c2e305a3d5753e160017e2a71817c98fd00')
 
+    variant('shared', default=True, description='Build shared libraries')
+
+    conflicts('+shared +cuda', msg='Only ~shared supported with +cuda')
+    conflicts('+cuda', when='@:4', msg='CUDA support only in libxc 5.0.0 and above')
+
+    patch('0001-Bugfix-avoid-implicit-pointer-cast-to-make-libxc-com.patch', when='@5.0.0')
+    patch('0002-Mark-xc_erfcx-a-GPU_FUNCTION.patch', when='@5.0.0')
+
     @property
     def libs(self):
         """Libxc can be queried for the following parameters:
@@ -36,7 +45,8 @@ def libs(self):
         # Libxc installs both shared and static libraries.
         # If a client ask for static explicitly then return
         # the static libraries
-        shared = ('static' not in query_parameters)
+        shared = (self.spec.variants['shared'].value and
+                  'static' not in query_parameters)
 
         # Libxc has a fortran90 interface: give clients the
         # possibility to query for it
@@ -82,8 +92,24 @@ def setup_build_environment(self, env):
         env.append_flags('CFLAGS',  optflags)
         env.append_flags('FCFLAGS', optflags)
 
+        if '+cuda' in self.spec:
+            nvcc = self.spec['cuda'].prefix.bin.nvcc
+            env.set('CCLD', '{0} -ccbin {1}'.format(nvcc, spack_cc))
+            env.set('CC', '{0} -x cu -ccbin {1}'.format(nvcc, spack_cc))
+
+            cuda_arch = self.spec.variants['cuda_arch'].value[0]
+
+            if cuda_arch != 'none':
+                env.append_flags('CFLAGS', '-arch=sm_{0}'.format(cuda_arch))
+
     def configure_args(self):
-        args = ['--enable-shared']
+        spec = self.spec
+
+        args = [
+            '--enable-shared' if '+shared' in spec else '--disable-shared',
+            '--enable-cuda' if '+cuda' in spec else '--disable-cuda'
+        ]
+
         return args
 
     def check(self):