Separate Apple Clang from LLVM Clang (#17110)

* Separate Apple Clang from LLVM Clang

Apple Clang is a compiler of its own. All places
referring to "-apple" suffix have been updated.

* Hack to use a dash in 'apple-clang'

To be able to use autodoc from Sphinx we need
a valid Python name for the module that contains
Apple's Clang code.

* Updated packages to account for the existence of apple-clang

Co-authored-by: Adam J. Stewart <ajstewart426@gmail.com>

* Added unit test for XCode related functions

Co-authored-by: Gregory Becker <becker33@llnl.gov>
Co-authored-by: Adam J. Stewart <ajstewart426@gmail.com>

62 files changed, 136 insertions, 94 deletions

diff --git a/var/spack/repos/builtin/packages/allpaths-lg/package.py b/var/spack/repos/builtin/packages/allpaths-lg/package.py
index 6ebca2eee6..b0bb49b3a1 100644
--- a/var/spack/repos/builtin/packages/allpaths-lg/package.py
+++ b/var/spack/repos/builtin/packages/allpaths-lg/package.py
@@ -18,6 +18,7 @@ class AllpathsLg(AutotoolsPackage):
     # compiles with gcc 4.7.0 to 4.9.4)
     conflicts('%gcc@:4.6.4,5.1.0:')
     conflicts('%cce')
+    conflicts('%apple-clang')
     conflicts('%clang')
     conflicts('%intel')
     conflicts('%nag')
diff --git a/var/spack/repos/builtin/packages/aluminum/package.py b/var/spack/repos/builtin/packages/aluminum/package.py
index 5edc4c3792..c5d6a45ed8 100644
--- a/var/spack/repos/builtin/packages/aluminum/package.py
+++ b/var/spack/repos/builtin/packages/aluminum/package.py
@@ -47,8 +47,8 @@ class Aluminum(CMakePackage):
             '-DALUMINUM_ENABLE_MPI_CUDA:BOOL=%s' % ('+mpi_cuda' in spec),
             '-DALUMINUM_ENABLE_NCCL:BOOL=%s' % ('+nccl' in spec)]
 
-        # Add support for OS X to find OpenMP
-        if (self.spec.satisfies('%clang platform=darwin')):
+        # Add support for OS X to find OpenMP (LLVM installed via brew)
+        if self.spec.satisfies('%clang platform=darwin'):
             clang = self.compiler.cc
             clang_bin = os.path.dirname(clang)
             clang_root = os.path.dirname(clang_bin)
diff --git a/var/spack/repos/builtin/packages/amber/package.py b/var/spack/repos/builtin/packages/amber/package.py
index d2ec13fb3e..481377047c 100644
--- a/var/spack/repos/builtin/packages/amber/package.py
+++ b/var/spack/repos/builtin/packages/amber/package.py
@@ -100,12 +100,10 @@ class Amber(Package, CudaPackage):
     depends_on('cuda@7.5.18', when='@:16+cuda')
 
     # conflicts
-    conflicts('+x11', when='platform=cray',
-              msg='x11 amber applications not available for cray')
-    conflicts('+openmp', when='%clang',
-              msg='openmp optimizations not available for the clang compiler')
-    conflicts('+openmp', when='%pgi',
-              msg='openmp optimizations not available for the pgi compiler')
+    conflicts('+x11', when='platform=cray', msg='x11 amber applications not available for cray')
+    conflicts('+openmp', when='%clang', msg='OpenMP optimizations not available for the clang compiler')
+    conflicts('+openmp', when='%apple-clang', msg='OpenMP optimizations not available for the Apple clang compiler')
+    conflicts('+openmp', when='%pgi', msg='OpenMP optimizations not available for the pgi compiler')
 
     def setup_build_environment(self, env):
         amber_src = self.stage.source_path
diff --git a/var/spack/repos/builtin/packages/amrex/package.py b/var/spack/repos/builtin/packages/amrex/package.py
index 32da808f1d..f6cb778f4b 100644
--- a/var/spack/repos/builtin/packages/amrex/package.py
+++ b/var/spack/repos/builtin/packages/amrex/package.py
@@ -65,6 +65,7 @@ class Amrex(CMakePackage):
     depends_on('cmake@3.5:',  type='build', when='@:18.10.99')
     depends_on('cmake@3.13:', type='build', when='@18.11:')
     depends_on('cmake@3.14:', type='build', when='@19.04:')
+    conflicts('%apple-clang')
     conflicts('%clang')
 
     def url_for_version(self, version):
diff --git a/var/spack/repos/builtin/packages/ape/package.py b/var/spack/repos/builtin/packages/ape/package.py
index 114185aaa4..bf9f895e68 100644
--- a/var/spack/repos/builtin/packages/ape/package.py
+++ b/var/spack/repos/builtin/packages/ape/package.py
@@ -29,11 +29,13 @@ class Ape(Package):
         # When preprocessor expands macros (i.e. CFLAGS) defined as quoted
         # strings the result may be > 132 chars and is terminated.
         # This will look to a compiler as an Unterminated character constant
-        # and produce Line truncated errors. To vercome this, add flags to
+        # and produce Line truncated errors. To overcome this, add flags to
         # let compiler know that the entire line is meaningful.
         # TODO: For the lack of better approach, assume that clang is mixed
-        # with GNU fortran.
-        if spec.satisfies('%clang') or spec.satisfies('%gcc'):
+        # TODO: with GNU fortran.
+        if (spec.satisfies('%apple-clang') or
+                spec.satisfies('%clang') or
+                spec.satisfies('%gcc')):
             args.extend([
                 'FCFLAGS=-O2 -ffree-line-length-none'
             ])
diff --git a/var/spack/repos/builtin/packages/atlas/package.py b/var/spack/repos/builtin/packages/atlas/package.py
index 4d56d0016d..2a355dfca7 100644
--- a/var/spack/repos/builtin/packages/atlas/package.py
+++ b/var/spack/repos/builtin/packages/atlas/package.py
@@ -102,7 +102,7 @@ class Atlas(Package):
 
         # Workaround for macOS Clang:
         # http://math-atlas.sourceforge.net/atlas_install/node66.html
-        if spec.satisfies('@3.10.3: %clang platform=darwin'):
+        if spec.satisfies('@3.10.3: %apple-clang'):
             options.append('--force-clang=' + spack_cc)
 
         # Lapack resource to provide full lapack build. Note that
diff --git a/var/spack/repos/builtin/packages/binutils/package.py b/var/spack/repos/builtin/packages/binutils/package.py
index 791606f564..96fdcc067b 100644
--- a/var/spack/repos/builtin/packages/binutils/package.py
+++ b/var/spack/repos/builtin/packages/binutils/package.py
@@ -120,9 +120,10 @@ class Binutils(AutotoolsPackage, GNUMirrorPackage):
     def flag_handler(self, name, flags):
         # To ignore the errors of narrowing conversions for
         # the Fujitsu compiler
-        if name == 'cxxflags'\
-           and (self.compiler.name == 'fj' or self.compiler.name == 'clang')\
-           and self.version <= ver('2.31.1'):
+        if name == 'cxxflags' and (
+            self.spec.satisfies('@:2.31.1') and
+            self.compiler.name in ('fj', 'clang', 'apple-clang')
+        ):
             flags.append('-Wno-narrowing')
         elif name == 'cflags':
             if self.spec.satisfies('@:2.34 %gcc@10:'):
diff --git a/var/spack/repos/builtin/packages/boost/package.py b/var/spack/repos/builtin/packages/boost/package.py
index 1e5bd00c2b..d0d8691c33 100644
--- a/var/spack/repos/builtin/packages/boost/package.py
+++ b/var/spack/repos/builtin/packages/boost/package.py
@@ -398,7 +398,9 @@ class Boost(Package):
         # and at least in clang 3.9 still fails to build
         #   http://www.boost.org/build/doc/html/bbv2/reference/precompiled_headers.html
         #   https://svn.boost.org/trac/boost/ticket/12496
-        if spec.satisfies('%clang') or spec.satisfies('%fj'):
+        if (spec.satisfies('%apple-clang') or
+                spec.satisfies('%clang') or
+                spec.satisfies('%fj')):
             options.extend(['pch=off'])
             if '+clanglibcpp' in spec:
                 cxxflags.append('-stdlib=libc++')
diff --git a/var/spack/repos/builtin/packages/bucky/package.py b/var/spack/repos/builtin/packages/bucky/package.py
index 859fabde34..41337e7e84 100644
--- a/var/spack/repos/builtin/packages/bucky/package.py
+++ b/var/spack/repos/builtin/packages/bucky/package.py
@@ -19,6 +19,7 @@ class Bucky(MakefilePackage):
 
     # Compilation requires gcc
     conflicts('%cce')
+    conflicts('%apple-clang')
     conflicts('%clang')
     conflicts('%intel')
     conflicts('%nag')
diff --git a/var/spack/repos/builtin/packages/cbench/package.py b/var/spack/repos/builtin/packages/cbench/package.py
index ceeec3b468..8a24a54d6e 100644
--- a/var/spack/repos/builtin/packages/cbench/package.py
+++ b/var/spack/repos/builtin/packages/cbench/package.py
@@ -26,6 +26,7 @@ class Cbench(MakefilePackage):
 
     # The following compilers are not supported by Cbench:
     conflicts('%cce')
+    conflicts('%apple-clang')
     conflicts('%clang')
     conflicts('%nag')
     conflicts('%xl')
diff --git a/var/spack/repos/builtin/packages/cp2k/package.py b/var/spack/repos/builtin/packages/cp2k/package.py
index 0a172d025f..1fba619ffc 100644
--- a/var/spack/repos/builtin/packages/cp2k/package.py
+++ b/var/spack/repos/builtin/packages/cp2k/package.py
@@ -141,6 +141,7 @@ class Cp2k(MakefilePackage, CudaPackage):
     depends_on('wannier90', when='@3.0+mpi', type='build')
 
     # CP2K needs compiler specific compilation flags, e.g. optflags
+    conflicts('%apple-clang')
     conflicts('%clang')
     conflicts('%nag')
 
diff --git a/var/spack/repos/builtin/packages/dealii/package.py b/var/spack/repos/builtin/packages/dealii/package.py
index 0f46c318f6..8d7bd2be81 100644
--- a/var/spack/repos/builtin/packages/dealii/package.py
+++ b/var/spack/repos/builtin/packages/dealii/package.py
@@ -301,7 +301,7 @@ class Dealii(CMakePackage, CudaPackage):
             cxx_flags_release.extend(['-O3'])
         elif spec.satisfies('%intel'):
             cxx_flags_release.extend(['-O3'])
-        elif spec.satisfies('%clang'):
+        elif spec.satisfies('%clang') or spec.satisfies('%apple-clang'):
             cxx_flags_release.extend(['-O3', '-ffp-contract=fast'])
 
         # Python bindings
diff --git a/var/spack/repos/builtin/packages/elfutils/package.py b/var/spack/repos/builtin/packages/elfutils/package.py
index 651caf3d76..cd6b961227 100644
--- a/var/spack/repos/builtin/packages/elfutils/package.py
+++ b/var/spack/repos/builtin/packages/elfutils/package.py
@@ -56,6 +56,7 @@ class Elfutils(AutotoolsPackage, SourcewarePackage):
     # in gcc, but not in clang. C code compiled with gcc is
     # binary-compatible with clang, so it should be possible to build
     # elfutils with gcc, and then link it to clang-built libraries.
+    conflicts('%apple-clang')
     conflicts('%clang')
 
     # Elfutils uses -Wall and we don't want to fail the build over a
diff --git a/var/spack/repos/builtin/packages/f18/package.py b/var/spack/repos/builtin/packages/f18/package.py
index 699cfde6c6..235210c142 100644
--- a/var/spack/repos/builtin/packages/f18/package.py
+++ b/var/spack/repos/builtin/packages/f18/package.py
@@ -30,6 +30,9 @@ class F18(CMakePackage):
 
     # Conflicts
     compiler_warning = 'F18 requires a compiler with support for C++17'
+    # See https://en.wikipedia.org/wiki/Xcode#Latest_versions for a
+    # conversion table from LLVM versions to Apple's Clang
+    conflicts('%apple-clang@:10.1', msg=compiler_warning)
     conflicts('%clang@:6', msg=compiler_warning)
     conflicts('%gcc@:7.1', msg=compiler_warning)
     conflicts('%intel', msg=compiler_warning)
diff --git a/var/spack/repos/builtin/packages/fftw/package.py b/var/spack/repos/builtin/packages/fftw/package.py
index 961c4cfc66..b644677fd1 100644
--- a/var/spack/repos/builtin/packages/fftw/package.py
+++ b/var/spack/repos/builtin/packages/fftw/package.py
@@ -57,6 +57,7 @@ class Fftw(AutotoolsPackage):
               msg='Long double precision is not supported in FFTW 2')
     conflicts('precision=quad', when='@2.1.5',
               msg='Quad precision is not supported in FFTW 2')
+    conflicts('+openmp', when='%apple-clang', msg="Apple's clang does not support OpenMP")
 
     provides('fftw-api@2', when='@2.1.5')
     provides('fftw-api@3', when='@3:')
@@ -124,11 +125,6 @@ class Fftw(AutotoolsPackage):
 
         # Variants that affect every precision
         if '+openmp' in spec:
-            # Note: Apple's Clang does not support OpenMP.
-            if spec.satisfies('%clang'):
-                ver = str(self.compiler.version)
-                if ver.endswith('-apple'):
-                    raise InstallError("Apple's clang does not support OpenMP")
             options.append('--enable-openmp')
             if spec.satisfies('@:2'):
                 # TODO: libtool strips CFLAGS, so 2.x libxfftw_threads
diff --git a/var/spack/repos/builtin/packages/fujitsu-mpi/package.py b/var/spack/repos/builtin/packages/fujitsu-mpi/package.py
index c0a882ec4c..fcf4dc8e94 100644
--- a/var/spack/repos/builtin/packages/fujitsu-mpi/package.py
+++ b/var/spack/repos/builtin/packages/fujitsu-mpi/package.py
@@ -13,6 +13,7 @@ class FujitsuMpi(Package):
 
     conflicts('%arm')
     conflicts('%cce')
+    conflicts('%apple-clang')
     conflicts('%clang')
     conflicts('%gcc')
     conflicts('%intel')
diff --git a/var/spack/repos/builtin/packages/gitconddb/package.py b/var/spack/repos/builtin/packages/gitconddb/package.py
index 9400ea549c..e2808e91c0 100644
--- a/var/spack/repos/builtin/packages/gitconddb/package.py
+++ b/var/spack/repos/builtin/packages/gitconddb/package.py
@@ -40,4 +40,5 @@ class Gitconddb(CMakePackage):
 
     # Known conflicts on C++17 compatibility (aggressive for now)
     conflicts('%gcc@:7.9.999', msg="GitCondDB requires GCC 8 or newer for C++17 support")
+    conflicts('%apple-clang', when="@:0.1.99", msg="No Darwin support for clang in older versions")
     conflicts('%clang platform=darwin', when="@:0.1.99", msg="No Darwin support for clang in older versions")
diff --git a/var/spack/repos/builtin/packages/graphviz/package.py b/var/spack/repos/builtin/packages/graphviz/package.py
index 4f8e772f19..34b2d8dd2e 100644
--- a/var/spack/repos/builtin/packages/graphviz/package.py
+++ b/var/spack/repos/builtin/packages/graphviz/package.py
@@ -137,6 +137,13 @@ class Graphviz(AutotoolsPackage):
         filter_file(r'-lstdc\+\+', '-lc++', 'configure.ac',
                     *(d + '/Makefile.am' for d in mkdirs))
 
+    @when('%apple-clang')
+    def patch(self):
+        # When using Clang, replace GCC's libstdc++ with LLVM's libc++
+        mkdirs = ['cmd/dot', 'cmd/edgepaint', 'cmd/mingle', 'plugin/gdiplus']
+        filter_file(r'-lstdc\+\+', '-lc++', 'configure.ac',
+                    *(d + '/Makefile.am' for d in mkdirs))
+
     def configure_args(self):
         spec = self.spec
         args = ['--disable-silent-rules']
diff --git a/var/spack/repos/builtin/packages/hpgmg/package.py b/var/spack/repos/builtin/packages/hpgmg/package.py
index e701d1c212..f5567ba2c9 100644
--- a/var/spack/repos/builtin/packages/hpgmg/package.py
+++ b/var/spack/repos/builtin/packages/hpgmg/package.py
@@ -59,13 +59,11 @@ class Hpgmg(Package):
             args.append('--no-fv')
         else:
             # Apple's Clang doesn't support OpenMP
-            if not (self.spec.satisfies('%clang') and self.compiler.is_apple):
+            if not self.spec.satisfies('%apple-clang'):
                 cflags.append(self.compiler.openmp_flag)
 
         if '+debug' in self.spec:
             cflags.append('-g')
-        elif any(map(self.spec.satisfies, ['%gcc', '%clang', '%intel'])):
-            cflags.append('-O3')
         else:
             cflags.append('-O3')
 
diff --git a/var/spack/repos/builtin/packages/hydrogen/package.py b/var/spack/repos/builtin/packages/hydrogen/package.py
index 449fe046dc..9d12235d72 100644
--- a/var/spack/repos/builtin/packages/hydrogen/package.py
+++ b/var/spack/repos/builtin/packages/hydrogen/package.py
@@ -131,8 +131,8 @@ class Hydrogen(CMakePackage):
             '-DHydrogen_ENABLE_HALF=%s' % ('+half' in spec),
         ]
 
-        # Add support for OS X to find OpenMP
-        if (self.spec.satisfies('%clang platform=darwin')):
+        # Add support for OS X to find OpenMP (LLVM installed via brew)
+        if self.spec.satisfies('%clang platform=darwin'):
             clang = self.compiler.cc
             clang_bin = os.path.dirname(clang)
             clang_root = os.path.dirname(clang_bin)
diff --git a/var/spack/repos/builtin/packages/intel-tbb/package.py b/var/spack/repos/builtin/packages/intel-tbb/package.py
index c470e8933b..4c652f6fce 100644
--- a/var/spack/repos/builtin/packages/intel-tbb/package.py
+++ b/var/spack/repos/builtin/packages/intel-tbb/package.py
@@ -69,6 +69,8 @@ class IntelTbb(Package):
     #
     #    See https://github.com/intel/tbb/pull/147 for details.
     #
+    conflicts('%apple-clang', when='@:2019.6',
+              msg='2019.7 or later required for clang')
     conflicts('%clang', when='@:2019.6',
               msg='2019.7 or later required for clang')
 
@@ -163,7 +165,7 @@ class IntelTbb(Package):
         #
         self.coerce_to_spack("build")
 
-        if spec.satisfies('%clang'):
+        if spec.satisfies('%clang') or spec.satisfies('%apple-clang'):
             tbb_compiler = "clang"
         elif spec.satisfies('%intel'):
             tbb_compiler = "icc"
diff --git a/var/spack/repos/builtin/packages/kahip/package.py b/var/spack/repos/builtin/packages/kahip/package.py
index 7d12d36bc2..e2ca1aeaa1 100644
--- a/var/spack/repos/builtin/packages/kahip/package.py
+++ b/var/spack/repos/builtin/packages/kahip/package.py
@@ -32,6 +32,7 @@ class Kahip(SConsPackage):
     depends_on('argtable')
     depends_on('mpi')  # Note: upstream package only tested on openmpi
 
+    conflicts('%apple-clang')
     conflicts('%clang')
 
     def patch(self):
diff --git a/var/spack/repos/builtin/packages/kentutils/package.py b/var/spack/repos/builtin/packages/kentutils/package.py
index 379d3486c0..f0b4ee8322 100644
--- a/var/spack/repos/builtin/packages/kentutils/package.py
+++ b/var/spack/repos/builtin/packages/kentutils/package.py
@@ -22,6 +22,7 @@ class Kentutils(MakefilePackage):
     depends_on('mariadb')
 
     conflicts('%cce')
+    conflicts('%apple-clang')
     conflicts('%clang')
     conflicts('%intel')
     conflicts('%nag')
diff --git a/var/spack/repos/builtin/packages/lbann/package.py b/var/spack/repos/builtin/packages/lbann/package.py
index 04b044610f..bc0da109ec 100644
--- a/var/spack/repos/builtin/packages/lbann/package.py
+++ b/var/spack/repos/builtin/packages/lbann/package.py
@@ -164,16 +164,16 @@ class Lbann(CMakePackage):
             # protobuf is included by py-protobuf+cpp
             '-DProtobuf_DIR={0}'.format(spec['protobuf'].prefix)])
 
-        if self.spec.satisfies('@:0.90') or self.spec.satisfies('@0.95:'):
+        if spec.satisfies('@:0.90') or spec.satisfies('@0.95:'):
             args.extend([
                 '-DHydrogen_DIR={0}/CMake/hydrogen'.format(
                     spec['hydrogen'].prefix)])
-        elif self.spec.satisfies('@0.94'):
+        elif spec.satisfies('@0.94'):
             args.extend([
                 '-DElemental_DIR={0}/CMake/elemental'.format(
                     spec['elemental'].prefix)])
 
-        if self.spec.satisfies('@0.94:0.98.2'):
+        if spec.satisfies('@0.94:0.98.2'):
             args.extend(['-DLBANN_WITH_NCCL:BOOL=%s' % ('+gpu +nccl' in spec)])
 
         if '+vtune' in spec:
@@ -188,8 +188,8 @@ class Lbann(CMakePackage):
                 '-DConduit_DIR={0}'.format(spec['conduit'].prefix)])
 
         # Add support for OpenMP
-        if (self.spec.satisfies('%clang')):
-            if (sys.platform == 'darwin'):
+        if spec.satisfies('%clang') or spec.satisfies('%apple-clang'):
+            if sys.platform == 'darwin':
                 clang = self.compiler.cc
                 clang_bin = os.path.dirname(clang)
                 clang_root = os.path.dirname(clang_bin)
@@ -210,7 +210,7 @@ class Lbann(CMakePackage):
             args.extend([
                 '-DcuDNN_DIR={0}'.format(
                     spec['cudnn'].prefix)])
-            if self.spec.satisfies('@0.94:0.98.2'):
+            if spec.satisfies('@0.94:0.98.2'):
                 args.extend(['-DCUB_DIR={0}'.format(
                     spec['cub'].prefix)])
                 if '+nccl' in spec:
diff --git a/var/spack/repos/builtin/packages/libceed/package.py b/var/spack/repos/builtin/packages/libceed/package.py
index 36d46dae0b..a7ae5b21f8 100644
--- a/var/spack/repos/builtin/packages/libceed/package.py
+++ b/var/spack/repos/builtin/packages/libceed/package.py
@@ -71,14 +71,14 @@ class Libceed(Package):
                 opt = '-O3 -g -ffp-contract=fast'
                 if compiler.version >= ver(4.9):
                     opt += ' -fopenmp-simd'
+            elif compiler.name == 'apple-clang':
+                opt = '-O3 -g -march=native -ffp-contract=fast'
+                if compiler.version >= ver(10):
+                    opt += ' -fopenmp-simd'
             elif compiler.name == 'clang':
                 opt = '-O3 -g -march=native -ffp-contract=fast'
-                if compiler.version.string.endswith('-apple'):
-                    if compiler.version >= ver(10):
-                        opt += ' -fopenmp-simd'
-                else:  # not apple clang
-                    if compiler.version >= ver(6):
-                        opt += ' -fopenmp-simd'
+                if compiler.version >= ver(6):
+                    opt += ' -fopenmp-simd'
             elif compiler.name in ['xl', 'xl_r']:
                 opt = '-O -g -qsimd=auto'
             else:
diff --git a/var/spack/repos/builtin/packages/libcerf/package.py b/var/spack/repos/builtin/packages/libcerf/package.py
index e37e7f6339..a5c00dabaf 100644
--- a/var/spack/repos/builtin/packages/libcerf/package.py
+++ b/var/spack/repos/builtin/packages/libcerf/package.py
@@ -23,7 +23,7 @@ class Libcerf(AutotoolsPackage, SourceforgePackage):
         options = []
         # Clang reports unused functions as errors, see
         # http://clang.debian.net/status.php?version=3.8.1&key=UNUSED_FUNCTION
-        if spec.satisfies('%clang'):
+        if spec.satisfies('%clang') or spec.satisfies('%apple-clang'):
             options.append('CFLAGS=-Wno-unused-function')
         # fujitsu compiler has a error about unused functions too.
         if spec.satisfies('%fj'):
diff --git a/var/spack/repos/builtin/packages/librsb/package.py b/var/spack/repos/builtin/packages/librsb/package.py
index 90cc5b67a8..2a292b9479 100644
--- a/var/spack/repos/builtin/packages/librsb/package.py
+++ b/var/spack/repos/builtin/packages/librsb/package.py
@@ -17,6 +17,7 @@ class Librsb(AutotoolsPackage):
     version('1.2.0.8',   '8bebd19a1866d80ade13eabfdd0f07ae7e8a485c0b975b5d15f531ac204d80cb')
 
     depends_on('zlib')
+    conflicts('%apple-clang')
     conflicts('%clang')
 
     def configure_args(self):
diff --git a/var/spack/repos/builtin/packages/likwid/package.py b/var/spack/repos/builtin/packages/likwid/package.py
index 8e89693ce1..a104b67003 100644
--- a/var/spack/repos/builtin/packages/likwid/package.py
+++ b/var/spack/repos/builtin/packages/likwid/package.py
@@ -60,9 +60,15 @@ class Likwid(Package):
                     *files)
 
     def install(self, spec, prefix):
-        supported_compilers = {'clang': 'CLANG', 'gcc': 'GCC', 'intel': 'ICC'}
+        supported_compilers = {
+            'apple-clang': 'CLANG',
+            'clang': 'CLANG',
+            'gcc': 'GCC',
+            'intel': 'ICC'
+        }
         if spec.target.family == 'aarch64':
-            supported_compilers = {'gcc': 'GCCARMv8', 'clang': 'ARMCLANG'}
+            supported_compilers = {
+                'gcc': 'GCCARMv8', 'clang': 'ARMCLANG', 'arm': 'ARMCLANG'}
         elif spec.target.family == 'ppc64' or spec.target.family == 'ppc64le':
             supported_compilers = {'gcc': 'GCCPOWER'}
         if self.compiler.name not in supported_compilers:
diff --git a/var/spack/repos/builtin/packages/maverick/package.py b/var/spack/repos/builtin/packages/maverick/package.py
index 6c560bb202..60909c551b 100644
--- a/var/spack/repos/builtin/packages/maverick/package.py
+++ b/var/spack/repos/builtin/packages/maverick/package.py
@@ -17,6 +17,7 @@ class Maverick(MakefilePackage):
 
     conflicts('%gcc@:6.0')
     conflicts('%cce')
+    conflicts('%apple-clang')
     conflicts('%clang')
     conflicts('%intel')
     conflicts('%nag')
diff --git a/var/spack/repos/builtin/packages/mpich/package.py b/var/spack/repos/builtin/packages/mpich/package.py
index c9c7886a08..d862f12522 100644
--- a/var/spack/repos/builtin/packages/mpich/package.py
+++ b/var/spack/repos/builtin/packages/mpich/package.py
@@ -79,6 +79,7 @@ spack package at this time.''',
     # see https://lists.mpich.org/pipermail/discuss/2016-May/004764.html
     # and https://lists.mpich.org/pipermail/discuss/2016-June/004768.html
     patch('mpich32_clang.patch', when='@3.2:3.2.0%clang')
+    patch('mpich32_clang.patch', when='@3.2:3.2.0%apple-clang')
 
     # Fix SLURM node list parsing
     # See https://github.com/pmodels/mpich/issues/3572
diff --git a/var/spack/repos/builtin/packages/mpilander/package.py b/var/spack/repos/builtin/packages/mpilander/package.py
index 276f380a86..9b72915180 100644
--- a/var/spack/repos/builtin/packages/mpilander/package.py
+++ b/var/spack/repos/builtin/packages/mpilander/package.py
@@ -31,6 +31,7 @@ class Mpilander(CMakePackage):
     # compiler support
     conflicts('%gcc@:4.7')
     conflicts('%clang@:3.8')
+    conflicts('%apple-clang@:7.4')
     conflicts('%intel@:16')
 
     def cmake_args(self):
diff --git a/var/spack/repos/builtin/packages/musl/package.py b/var/spack/repos/builtin/packages/musl/package.py
index 7c68735c20..05ec4eb5ff 100644
--- a/var/spack/repos/builtin/packages/musl/package.py
+++ b/var/spack/repos/builtin/packages/musl/package.py
@@ -38,7 +38,7 @@ class Musl(Package):
         if self.compiler.name == 'gcc':
             config.filter("WRAPCC_GCC = .*'", "WRAPCC_GCC = {0}'".
                           format(self.compiler.cc))
-        elif self.compiler.name == 'clang':
+        elif self.compiler.name in ('clang', 'apple-clang'):
             config.filter("WRAPCC_CLANG = .*'", "WRAPCC_CLANG = {0}'".
                           format(self.compiler.cc))
 
@@ -46,7 +46,7 @@ class Musl(Package):
         args = ['--prefix={0}'.format(self.prefix)]
         if self.compiler.name == 'gcc':
             args.append('--enable-wrapper=gcc')
-        elif self.compiler.name == 'clang':
+        elif self.compiler.name in ('clang', 'apple-clang'):
             args.append('--enable-wrapper=clang')
         else:
             args.append('--enable-wrapper=no')
diff --git a/var/spack/repos/builtin/packages/octopus/package.py b/var/spack/repos/builtin/packages/octopus/package.py
index 1073965e81..bed1c1a256 100644
--- a/var/spack/repos/builtin/packages/octopus/package.py
+++ b/var/spack/repos/builtin/packages/octopus/package.py
@@ -97,11 +97,13 @@ class Octopus(Package):
         # When preprocessor expands macros (i.e. CFLAGS) defined as quoted
         # strings the result may be > 132 chars and is terminated.
         # This will look to a compiler as an Unterminated character constant
-        # and produce Line truncated errors. To vercome this, add flags to
+        # and produce Line truncated errors. To overcome this, add flags to
         # let compiler know that the entire line is meaningful.
         # TODO: For the lack of better approach, assume that clang is mixed
         # with GNU fortran.
-        if spec.satisfies('%clang') or spec.satisfies('%gcc'):
+        if (spec.satisfies('%apple-clang') or
+                spec.satisfies('%clang') or
+                spec.satisfies('%gcc')):
             args.extend([
                 'FCFLAGS=-O2 -ffree-line-length-none'
             ])
diff --git a/var/spack/repos/builtin/packages/onednn/package.py b/var/spack/repos/builtin/packages/onednn/package.py
index b723fabd9c..82d22296f9 100644
--- a/var/spack/repos/builtin/packages/onednn/package.py
+++ b/var/spack/repos/builtin/packages/onednn/package.py
@@ -64,7 +64,7 @@ class Onednn(CMakePackage):
     # https://github.com/oneapi-src/oneDNN#requirements-for-building-from-source
     depends_on('cmake@2.8.11:', type='build')
     depends_on('tbb@2017:', when='cpu_runtime=tbb')
-    depends_on('llvm-openmp', when='%clang platform=darwin cpu_runtime=omp')
+    depends_on('llvm-openmp', when='%apple-clang cpu_runtime=omp')
     depends_on('opencl@1.2:', when='gpu_runtime=ocl')
 
     def cmake_args(self):
@@ -81,7 +81,7 @@ class Onednn(CMakePackage):
             args.append('-DDNNL_BUILD_TESTS=OFF')
 
         # https://github.com/oneapi-src/oneDNN/issues/591
-        if self.spec.satisfies('%clang platform=darwin cpu_runtime=omp'):
+        if self.spec.satisfies('%apple-clang cpu_runtime=omp'):
             args.extend([
                 '-DOpenMP_CXX_FLAGS={0}'.format(self.compiler.openmp_flag),
                 '-DOpenMP_C_FLAGS={0}'.format(self.compiler.openmp_flag),
diff --git a/var/spack/repos/builtin/packages/openblas/package.py b/var/spack/repos/builtin/packages/openblas/package.py
index c1a0c1e01b..61a530b37f 100644
--- a/var/spack/repos/builtin/packages/openblas/package.py
+++ b/var/spack/repos/builtin/packages/openblas/package.py
@@ -95,7 +95,7 @@ class Openblas(MakefilePackage):
     patch('openblas-0.3.8-darwin.patch', when='@0.3.8 platform=darwin')
     # Fix ICE in LLVM 9.0.0 https://github.com/xianyi/OpenBLAS/pull/2329
     # Patch as in https://github.com/xianyi/OpenBLAS/pull/2597
-    patch('openblas_appleclang11.patch', when='@0.3.8:0.3.9 %clang@11.0.3-apple')
+    patch('openblas_appleclang11.patch', when='@0.3.8:0.3.9 %apple-clang@11.0.3')
 
     # Add conditions to f_check to determine the Fujitsu compiler
     patch('openblas_fujitsu.patch', when='%fj')
@@ -105,6 +105,9 @@ class Openblas(MakefilePackage):
     conflicts('+consistent_fpcsr', when='threads=none',
               msg='FPCSR consistency only applies to multithreading')
 
+    conflicts('threads=openmp', when='%apple-clang', msg="Apple's clang does not support OpenMP")
+    conflicts('threads=openmp @:0.2.19', when='%clang', msg='OpenBLAS @:0.2.19 does not support OpenMP with clang!')
+
     @property
     def parallel(self):
         # unclear whether setting `-j N` externally was supported before 0.3
@@ -120,18 +123,6 @@ class Openblas(MakefilePackage):
                 'OpenBLAS requires both C and Fortran compilers!'
             )
 
-        # Add support for OpenMP
-        if (self.spec.satisfies('threads=openmp') and
-            self.spec.satisfies('%clang')):
-            if str(self.spec.compiler.version).endswith('-apple'):
-                raise InstallError("Apple's clang does not support OpenMP")
-            if '@:0.2.19' in self.spec:
-                # Openblas (as of 0.2.19) hardcoded that OpenMP cannot
-                # be used with any (!) compiler named clang, bummer.
-                raise InstallError(
-                    'OpenBLAS @:0.2.19 does not support OpenMP with clang!'
-                )
-
     @staticmethod
     def _read_targets(target_file):
         """Parse a list of available targets from the OpenBLAS/TargetList.txt
diff --git a/var/spack/repos/builtin/packages/pdt/package.py b/var/spack/repos/builtin/packages/pdt/package.py
index 35164db1c5..bf3f954982 100644
--- a/var/spack/repos/builtin/packages/pdt/package.py
+++ b/var/spack/repos/builtin/packages/pdt/package.py
@@ -33,7 +33,8 @@ class Pdt(AutotoolsPackage):
     variant('pic', default=False, description="Builds with pic")
 
     def patch(self):
-        if self.spec.satisfies('%clang'):
+        spec = self.spec
+        if spec.satisfies('%clang') or spec.satisfies('%apple-clang'):
             filter_file(r'PDT_GXX=g\+\+ ',
                         r'PDT_GXX=clang++ ', 'ductape/Makefile')
 
diff --git a/var/spack/repos/builtin/packages/petsc/package.py b/var/spack/repos/builtin/packages/petsc/package.py
index f328171072..9da9740674 100644
--- a/var/spack/repos/builtin/packages/petsc/package.py
+++ b/var/spack/repos/builtin/packages/petsc/package.py
@@ -2,11 +2,7 @@
 # Spack Project Developers. See the top-level COPYRIGHT file for details.
 #
 # SPDX-License-Identifier: (Apache-2.0 OR MIT)
-
-
 import os
-import sys
-from spack import *
 
 
 class Petsc(Package):
@@ -116,9 +112,7 @@ class Petsc(Package):
     # temporary workaround Clang 8.1.0 with XCode 8.3 on macOS, see
     # https://bitbucket.org/petsc/petsc/commits/4f290403fdd060d09d5cb07345cbfd52670e3cbc
     # the patch is an adaptation of the original commit to 3.7.5
-    if sys.platform == "darwin":
-        patch('macos-clang-8.1.0.diff',
-              when='@3.7.5%clang@8.1.0:')
+    patch('macos-clang-8.1.0.diff', when='@3.7.5%apple-clang@8.1.0:')
     patch('pkg-config-3.7.6-3.8.4.diff', when='@3.7.6:3.8.4')
 
     patch('xcode_stub_out_of_sync.patch', when='@:3.10.4')
diff --git a/var/spack/repos/builtin/packages/pixman/package.py b/var/spack/repos/builtin/packages/pixman/package.py
index 1087dabbbf..a145edc638 100644
--- a/var/spack/repos/builtin/packages/pixman/package.py
+++ b/var/spack/repos/builtin/packages/pixman/package.py
@@ -29,7 +29,8 @@ class Pixman(AutotoolsPackage):
     # __builtin_shuffle was removed in clang 5.0.
     # From version 9.1 apple-clang is based on clang 5.0.
     # Patch is obtained from above link.
-    patch('clang.patch', when='@0.34%clang@9.1.0-apple:')
+    patch('clang.patch', when='@0.34%apple-clang@9.1.0:')
+    patch('clang.patch', when='@0.34%clang@5.0.0:')
 
     @run_before('build')
     def patch_config_h_for_intel(self):
diff --git a/var/spack/repos/builtin/packages/plasma/package.py b/var/spack/repos/builtin/packages/plasma/package.py
index bf4d8c68ee..efeb980bd8 100644
--- a/var/spack/repos/builtin/packages/plasma/package.py
+++ b/var/spack/repos/builtin/packages/plasma/package.py
@@ -58,6 +58,7 @@ class Plasma(CMakePackage):
     conflicts("%gcc@:5.99", when='@17.2:')
 
     conflicts("%cce")
+    conflicts('%apple-clang')
     conflicts("%clang")
     conflicts("%intel")
     conflicts("%nag")
diff --git a/var/spack/repos/builtin/packages/precice/package.py b/var/spack/repos/builtin/packages/precice/package.py
index 11250f60bd..45548275c8 100644
--- a/var/spack/repos/builtin/packages/precice/package.py
+++ b/var/spack/repos/builtin/packages/precice/package.py
@@ -60,6 +60,7 @@ class Precice(CMakePackage):
     # We require C++11 compiler support as well as
     # library support for time manipulators (N2071, N2072)
     conflicts('%gcc@:4')
+    conflicts('%apple-clang@:4')
     conflicts('%clang@:3.7')
     conflicts('%intel@:14')
     conflicts('%pgi@:14')
diff --git a/var/spack/repos/builtin/packages/py-dgl/package.py b/var/spack/repos/builtin/packages/py-dgl/package.py
index 544b527f69..9ef1bd9ed8 100644
--- a/var/spack/repos/builtin/packages/py-dgl/package.py
+++ b/var/spack/repos/builtin/packages/py-dgl/package.py
@@ -29,7 +29,7 @@ class PyDgl(CMakePackage):
 
     depends_on('cmake@3.5:', type='build')
     depends_on('cuda', when='+cuda')
-    depends_on('llvm-openmp', when='%clang platform=darwin +openmp')
+    depends_on('llvm-openmp', when='%apple-clang +openmp')
 
     # Python dependencies
     # See python/setup.py
@@ -66,7 +66,7 @@ class PyDgl(CMakePackage):
         if '+openmp' in self.spec:
             args.append('-DUSE_OPENMP=ON')
 
-            if self.spec.satisfies('%clang platform=darwin'):
+            if self.spec.satisfies('%apple-clang'):
                 args.extend([
                     '-DOpenMP_CXX_FLAGS=' +
                     self.spec['llvm-openmp'].headers.include_flags,
diff --git a/var/spack/repos/builtin/packages/py-exodus-bundler/package.py b/var/spack/repos/builtin/packages/py-exodus-bundler/package.py
index c13f30eb46..eddb3da88f 100644
--- a/var/spack/repos/builtin/packages/py-exodus-bundler/package.py
+++ b/var/spack/repos/builtin/packages/py-exodus-bundler/package.py
@@ -15,6 +15,7 @@ class PyExodusBundler(PythonPackage):
 
     version('2.0.2', sha256='4e896a2034b94cf7b4fb33d86a68e29a7d3b08e57541e444db34dddc6ac1ef68')
 
+    depends_on('musl', type='run', when='%apple-clang')
     depends_on('musl', type='run', when='%clang')
     depends_on('musl', type='run', when='%gcc')
     depends_on('py-setuptools', type=('build', 'run'))
diff --git a/var/spack/repos/builtin/packages/py-flye/package.py b/var/spack/repos/builtin/packages/py-flye/package.py
index db3804e11d..090d36cdb9 100644
--- a/var/spack/repos/builtin/packages/py-flye/package.py
+++ b/var/spack/repos/builtin/packages/py-flye/package.py
@@ -26,7 +26,7 @@ class PyFlye(PythonPackage):
     msg = 'C++ compiler with C++11 support required'
     conflicts('%gcc@:4.7',   msg=msg)
     conflicts('%clang@:3.2', msg=msg)
-    # Requires Apple Clang 5.0+ but no way to specify that right now
+    conflicts('apple-clang@:4.9', msg=msg)
 
     def setup_build_environment(self, env):
         if self.spec.target.family == 'aarch64':
diff --git a/var/spack/repos/builtin/packages/py-scikit-learn/package.py b/var/spack/repos/builtin/packages/py-scikit-learn/package.py
index 52c9beae43..d73d3f7576 100644
--- a/var/spack/repos/builtin/packages/py-scikit-learn/package.py
+++ b/var/spack/repos/builtin/packages/py-scikit-learn/package.py
@@ -69,9 +69,7 @@ class PyScikitLearn(PythonPackage):
     depends_on('py-pytest@3.3.0:', type='test')
     depends_on('py-pandas', type='test')
     depends_on('py-setuptools', type='build')
-    # Technically not correct, but currently no way to check if we
-    # are using Apple Clang or not.
-    depends_on('llvm-openmp', when='@0.21: %clang platform=darwin +openmp')
+    depends_on('llvm-openmp', when='@0.21: %apple-clang +openmp')
 
     # Release tarballs are already cythonized. If you wanted to build a release
     # version without OpenMP support, you would need to delete all .c files
@@ -84,7 +82,7 @@ class PyScikitLearn(PythonPackage):
         if self.spec.satisfies('~openmp'):
             env.set('SKLEARN_NO_OPENMP', 'True')
         # https://scikit-learn.org/stable/developers/advanced_installation.html#mac-osx
-        elif self.spec.satisfies('@0.21: %clang platform=darwin +openmp'):
+        elif self.spec.satisfies('@0.21: %apple-clang +openmp'):
             env.append_flags(
                 'CPPFLAGS', self.compiler.openmp_flag)
             env.append_flags(
diff --git a/var/spack/repos/builtin/packages/py-torch/package.py b/var/spack/repos/builtin/packages/py-torch/package.py
index c240144f11..1ffeb81b23 100644
--- a/var/spack/repos/builtin/packages/py-torch/package.py
+++ b/var/spack/repos/builtin/packages/py-torch/package.py
@@ -155,7 +155,7 @@ class PyTorch(PythonPackage, CudaPackage):
     depends_on('nccl', when='+nccl')
     depends_on('gloo', when='+gloo')
     depends_on('opencv', when='+opencv')
-    depends_on('llvm-openmp', when='%clang platform=darwin +openmp')
+    depends_on('llvm-openmp', when='%apple-clang +openmp')
     depends_on('ffmpeg', when='+ffmpeg')
     depends_on('leveldb', when='+leveldb')
     depends_on('lmdb', when='+lmdb')
diff --git a/var/spack/repos/builtin/packages/qmcpack/package.py b/var/spack/repos/builtin/packages/qmcpack/package.py
index 5307b3d2d5..07724f63fe 100644
--- a/var/spack/repos/builtin/packages/qmcpack/package.py
+++ b/var/spack/repos/builtin/packages/qmcpack/package.py
@@ -102,6 +102,7 @@ class Qmcpack(CMakePackage, CudaPackage):
     conflicts('+afqmc', when='@:3.6.0', msg='AFQMC not recommended before v3.7')
     conflicts('+afqmc', when='~mpi', msg='AFQMC requires building with +mpi')
     conflicts('+afqmc', when='%gcc@:6.0', msg='AFQMC code requires gcc@6.1 or greater')
+    conflicts('+afqmc', when='%apple-clang@:9.2', msg='AFQMC code requires clang 4.1 or greater')
     conflicts('+afqmc', when='%clang@:4.0', msg='AFQMC code requires clang 4.1 or greater')
     conflicts('+afqmc', when='%intel@:18', msg='AFQMC code requires intel19 or greater')
 
diff --git a/var/spack/repos/builtin/packages/qt/package.py b/var/spack/repos/builtin/packages/qt/package.py
index ba28042fa3..7e016846ab 100644
--- a/var/spack/repos/builtin/packages/qt/package.py
+++ b/var/spack/repos/builtin/packages/qt/package.py
@@ -286,7 +286,7 @@ class Qt(Package):
             "qmake/qmake.pri",
             "src/tools/bootstrap/bootstrap.pro"
         ]
-        if '%clang' in self.spec:
+        if '%clang' in self.spec or '%apple-clang' in self.spec:
             files_to_filter += [
                 "mkspecs/unsupported/macx-clang-libc++/qmake.conf",
                 "mkspecs/common/clang.conf"
diff --git a/var/spack/repos/builtin/packages/raxml/package.py b/var/spack/repos/builtin/packages/raxml/package.py
index 08d99e6b16..7eb477dfc6 100644
--- a/var/spack/repos/builtin/packages/raxml/package.py
+++ b/var/spack/repos/builtin/packages/raxml/package.py
@@ -25,6 +25,7 @@ class Raxml(Package):
 
     # Compiles with either GCC or ICC.
     conflicts('%cce')
+    conflicts('%apple-clang')
     conflicts('%clang')
     conflicts('%nag')
     conflicts('%pgi')
diff --git a/var/spack/repos/builtin/packages/sgpp/package.py b/var/spack/repos/builtin/packages/sgpp/package.py
index 7e5b907374..728638500f 100644
--- a/var/spack/repos/builtin/packages/sgpp/package.py
+++ b/var/spack/repos/builtin/packages/sgpp/package.py
@@ -97,6 +97,7 @@ class Sgpp(SConsPackage):
 
     # Compiler with C++11 support is required
     conflicts('%gcc@:4.8.4', msg='Compiler with c++11 support is required!')
+    conflicts('%apple-clang@:3.9', msg='Compiler with c++11 support is required!')
     conflicts('%clang@:3.2', msg='Compiler with c++11 support is required!')
     conflicts('%intel@:14', msg='Compiler with c++11 support is required!')
     # Solver python bindings are actually using the pde module at one point:
diff --git a/var/spack/repos/builtin/packages/silo/package.py b/var/spack/repos/builtin/packages/silo/package.py
index 9192937393..3d9ef4e16c 100644
--- a/var/spack/repos/builtin/packages/silo/package.py
+++ b/var/spack/repos/builtin/packages/silo/package.py
@@ -57,6 +57,13 @@ class Silo(AutotoolsPackage):
 
     @when('%clang@9:')
     def patch(self):
+        self.clang_9_patch()
+
+    @when('%apple-clang@11.0.3:')
+    def patch(self):
+        self.clang_9_patch()
+
+    def clang_9_patch(self):
         # Clang 9 and later include macro definitions in <math.h> that conflict
         # with typedefs DOMAIN and RANGE used in Silo plugins.
         # It looks like the upstream fpzip repo has been fixed, but that change
diff --git a/var/spack/repos/builtin/packages/snap-berkeley/package.py b/var/spack/repos/builtin/packages/snap-berkeley/package.py
index 90d970e277..de9928e0c3 100644
--- a/var/spack/repos/builtin/packages/snap-berkeley/package.py
+++ b/var/spack/repos/builtin/packages/snap-berkeley/package.py
@@ -22,6 +22,7 @@ class SnapBerkeley(MakefilePackage):
 
     conflicts('%gcc@6:')
     conflicts('%cce')
+    conflicts('%apple-clang')
     conflicts('%clang')
     conflicts('%intel')
     conflicts('%nag')
diff --git a/var/spack/repos/builtin/packages/sqlitebrowser/package.py b/var/spack/repos/builtin/packages/sqlitebrowser/package.py
index 6cd8eeb9b8..b92d65348e 100644
--- a/var/spack/repos/builtin/packages/sqlitebrowser/package.py
+++ b/var/spack/repos/builtin/packages/sqlitebrowser/package.py
@@ -18,6 +18,7 @@ class Sqlitebrowser(CMakePackage):
 
     msg = 'sqlitebrowser requires C++11 support'
     conflicts('%gcc@:4.8.0', msg=msg)
+    conflicts('%apple-clang@:3.9', msg=msg)
     conflicts('%clang@:3.2', msg=msg)
     conflicts('%intel@:12',  msg=msg)
     conflicts('%xl@:13.0',   msg=msg)
diff --git a/var/spack/repos/builtin/packages/suite-sparse/package.py b/var/spack/repos/builtin/packages/suite-sparse/package.py
index eef38fefae..703fbcf670 100644
--- a/var/spack/repos/builtin/packages/suite-sparse/package.py
+++ b/var/spack/repos/builtin/packages/suite-sparse/package.py
@@ -115,7 +115,7 @@ class SuiteSparse(Package):
         # CFLAGS, but not all compilers use the same flags for these
         # optimizations
         if any([x in spec
-                for x in ('%clang', '%gcc', '%intel')]):
+                for x in ('%apple-clang', '%clang', '%gcc', '%intel')]):
             make_args += ['CFLAGS+=-fno-common -fexceptions']
         elif '%pgi' in spec:
             make_args += ['CFLAGS+=--exceptions']
diff --git a/var/spack/repos/builtin/packages/sundials/package.py b/var/spack/repos/builtin/packages/sundials/package.py
index e374a4bbca..50832e6e5a 100644
--- a/var/spack/repos/builtin/packages/sundials/package.py
+++ b/var/spack/repos/builtin/packages/sundials/package.py
@@ -214,7 +214,7 @@ class Sundials(CMakePackage):
             return 'ON' if varstr in self.spec else 'OFF'
 
         fortran_flag = self.compiler.f77_pic_flag
-        if (spec.satisfies('%clang platform=darwin')) and ('+fcmix' in spec):
+        if (spec.satisfies('%apple-clang')) and ('+fcmix' in spec):
             f77 = Executable(self.compiler.f77)
             libgfortran = LibraryList(f77('--print-file-name',
                                           'libgfortran.a', output=str))
diff --git a/var/spack/repos/builtin/packages/trilinos/package.py b/var/spack/repos/builtin/packages/trilinos/package.py
index 16f916849c..7896d809f2 100644
--- a/var/spack/repos/builtin/packages/trilinos/package.py
+++ b/var/spack/repos/builtin/packages/trilinos/package.py
@@ -683,7 +683,9 @@ class Trilinos(CMakePackage):
 
         # Fortran lib (assumes clang is built with gfortran!)
         if '+fortran' in spec and (
-                spec.satisfies('%gcc') or spec.satisfies('%clang')):
+                spec.satisfies('%gcc') or spec.satisfies('%clang') or
+                spec.satisfies('%apple-clang')
+        ):
             options.append(define('Trilinos_ENABLE_Fortran', True))
             if '+mpi' in spec:
                 libgfortran = os.path.dirname(os.popen(
diff --git a/var/spack/repos/builtin/packages/unblur/package.py b/var/spack/repos/builtin/packages/unblur/package.py
index 428f44c08e..7366ad836a 100644
--- a/var/spack/repos/builtin/packages/unblur/package.py
+++ b/var/spack/repos/builtin/packages/unblur/package.py
@@ -27,6 +27,7 @@ class Unblur(AutotoolsPackage):
     # Requires Intel Fortran compiler
     conflicts('%gcc')
     conflicts('%pgi')
+    conflicts('%apple-clang')
     conflicts('%clang')
     conflicts('%cce')
     conflicts('%xl')
diff --git a/var/spack/repos/builtin/packages/valgrind/package.py b/var/spack/repos/builtin/packages/valgrind/package.py
index 4555b0b886..20d8791f4e 100644
--- a/var/spack/repos/builtin/packages/valgrind/package.py
+++ b/var/spack/repos/builtin/packages/valgrind/package.py
@@ -40,7 +40,7 @@ class Valgrind(AutotoolsPackage, SourcewarePackage):
     variant('ubsan', default=sys.platform != 'darwin',
             description='Activates ubsan support for valgrind')
 
-    conflicts('+ubsan', when='platform=darwin %clang',
+    conflicts('+ubsan', when='%apple-clang',
               msg="""
 Cannot build libubsan with clang on macOS.
 Otherwise with (Apple's) clang there is a linker error:
diff --git a/var/spack/repos/builtin/packages/vtk/package.py b/var/spack/repos/builtin/packages/vtk/package.py
index 0df4c4a5fc..2a334cb1fb 100644
--- a/var/spack/repos/builtin/packages/vtk/package.py
+++ b/var/spack/repos/builtin/packages/vtk/package.py
@@ -285,9 +285,7 @@ class Vtk(CMakePackage):
             # string. This fix was recommended on the VTK mailing list
             # in March 2014 (see
             # https://public.kitware.com/pipermail/vtkusers/2014-March/083368.html)
-            if (self.spec.satisfies('%clang') and
-                    self.compiler.is_apple and
-                    self.compiler.version >= Version('5.1.0')):
+            if self.spec.satisfies('%apple-clang@5.1.0:'):
                 cmake_args.extend(['-DVTK_REQUIRED_OBJCXX_FLAGS='])
 
             # A bug in tao pegtl causes build failures with intel compilers
diff --git a/var/spack/repos/builtin/packages/warpx/package.py b/var/spack/repos/builtin/packages/warpx/package.py
index dc19f916fe..c564528b40 100644
--- a/var/spack/repos/builtin/packages/warpx/package.py
+++ b/var/spack/repos/builtin/packages/warpx/package.py
@@ -68,7 +68,8 @@ class Warpx(MakefilePackage):
 
     def edit(self, spec, prefix):
         comp = 'gcc'
-        vendors = {'%gcc': 'gcc', '%intel': 'intel', '%clang': 'llvm'}
+        vendors = {'%gcc': 'gcc', '%intel': 'intel',
+                   '%apple-clang': 'llvm', '%clang': 'llvm'}
         for key, value in vendors.items():
             if self.spec.satisfies(key):
                 comp = value
diff --git a/var/spack/repos/builtin/packages/xios/package.py b/var/spack/repos/builtin/packages/xios/package.py
index 54eca9fead..2b5c6f9dae 100644
--- a/var/spack/repos/builtin/packages/xios/package.py
+++ b/var/spack/repos/builtin/packages/xios/package.py
@@ -31,6 +31,7 @@ class Xios(Package):
 
     # Workaround bug #17782 in llvm, where reading a double
     # followed by a character is broken (e.g. duration '1d'):
+    patch('llvm_bug_17782.patch', when='@1.1: %apple-clang')
     patch('llvm_bug_17782.patch', when='@1.1: %clang')
 
     depends_on('netcdf-c+mpi')
@@ -45,6 +46,13 @@ class Xios(Package):
 
     @when('%clang')
     def patch(self):
+        self.patch_llvm()
+
+    @when('%apple-clang')
+    def patch(self):
+        self.patch_llvm()
+
+    def patch_llvm(self):
         """Fix type references that are ambiguous for clang."""
         for dirpath, dirnames, filenames in os.walk('src'):
             for filename in filenames:
@@ -99,12 +107,13 @@ OASIS_LIB=""
         param['BOOST_LIB_DIR'] = spec['boost'].prefix.lib
         param['BLITZ_INC_DIR'] = spec['blitz'].prefix.include
         param['BLITZ_LIB_DIR'] = spec['blitz'].prefix.lib
-        if spec.satisfies('%clang platform=darwin'):
+        if spec.satisfies('%apple-clang'):
             param['LIBCXX'] = '-lc++'
         else:
             param['LIBCXX'] = '-lstdc++'
 
-        if any(map(spec.satisfies, ('%gcc', '%intel', '%clang'))):
+        if any(map(spec.satisfies,
+                   ('%gcc', '%intel', '%apple-clang', '%clang'))):
             text = r"""
 %CCOMPILER      {MPICXX}
 %FCOMPILER      {MPIFC}
diff --git a/var/spack/repos/builtin/packages/xsdktrilinos/package.py b/var/spack/repos/builtin/packages/xsdktrilinos/package.py
index b679ee7277..effb4404b0 100644
--- a/var/spack/repos/builtin/packages/xsdktrilinos/package.py
+++ b/var/spack/repos/builtin/packages/xsdktrilinos/package.py
@@ -65,7 +65,9 @@ class Xsdktrilinos(CMakePackage):
         ])
 
         # Fortran lib
-        if spec.satisfies('%gcc') or spec.satisfies('%clang'):
+        if (spec.satisfies('%gcc') or
+                spec.satisfies('%clang') or
+                spec.satisfies('%apple-clang')):
             libgfortran = os.path.dirname(os.popen(
                 '%s --print-file-name libgfortran.a' %
                 join_path(mpi_bin, 'mpif90')).read())
diff --git a/var/spack/repos/builtin/packages/yaml-cpp/package.py b/var/spack/repos/builtin/packages/yaml-cpp/package.py
index 11f1f9fbef..a83471f23a 100644
--- a/var/spack/repos/builtin/packages/yaml-cpp/package.py
+++ b/var/spack/repos/builtin/packages/yaml-cpp/package.py
@@ -35,9 +35,7 @@ class YamlCpp(CMakePackage):
 
     conflicts('%gcc@:4.7', when='@0.6.0:', msg="versions 0.6.0: require c++11 support")
     conflicts('%clang@:3.3.0', when='@0.6.0:', msg="versions 0.6.0: require c++11 support")
-    # currently we can't check for apple-clang's version
-    # conflicts('%clang@:4.0.0-apple', when='@0.6.0:',
-    # msg="versions 0.6.0: require c++11 support")
+    conflicts('%apple-clang@:4.0.0', when='@0.6.0:', msg="versions 0.6.0: require c++11 support")
     conflicts('%intel@:11.1', when='@0.6.0:', msg="versions 0.6.0: require c++11 support")
     conflicts('%xl@:13.1', when='@0.6.0:', msg="versions 0.6.0: require c++11 support")
     conflicts('%xl_r@:13.1', when='@0.6.0:', msg="versions 0.6.0: require c++11 support")