llvm: make targets a multivalued variant (#27735)

* llvm: make targets a multivalued variant

* Fix the targets variant values

1. Make them lowercase and add a mapping to cmake equivalent
2. auto -> all
2. Restore composability by using a multivalued variant, so that
   `targets=all` and `targets=x86` is combined to `targets=all,x86`
   which is then transformed into LLVM_TARGETS_TO_BUILD=all.

* use targets=x86 in iwyu

* Default to nvptx/amdgpu/host arch targets

* default to none

* Update var/spack/repos/builtin/packages/zig/package.py

share/spack/gitlab/cloud_pipelines/stacks/e4s-on-power/spack.yaml

@@ -128,7 +128,7 @@ spack:
     - libnrm
     - libquo
     - libunwind
-    - llvm +all_targets +clang +compiler-rt +libcxx +lld +lldb +llvm_dylib +flang ~cuda
+    - llvm targets=amdgpu,nvptx +clang +compiler-rt +libcxx +lld +lldb +llvm_dylib +flang ~cuda
     - loki
     - mercury
     - metall

share/spack/gitlab/cloud_pipelines/stacks/e4s/spack.yaml

@@ -139,7 +139,7 @@ spack:
     - libnrm
     - libquo
     - libunwind
-    - llvm +all_targets +clang +compiler-rt +libcxx +lld +lldb +llvm_dylib +flang ~cuda
+    - llvm targets=amdgpu,nvptx +clang +compiler-rt +libcxx +lld +lldb +llvm_dylib +flang ~cuda
     - loki
     - mercury
     - metall

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

@@ -32,15 +32,8 @@ class Iwyu(CMakePackage):
     depends_on('llvm+clang@8.0:8', when='@0.12')
     depends_on('llvm+clang@7.0:7', when='@0.11')
 
-    # Non-X86 CPU use all_targets variants because iwyu use X86AsmParser
+    # iwyu uses X86AsmParser
-    depends_on('llvm+all_targets', when='target=aarch64:')
+    depends_on('llvm targets=x86')
-    depends_on('llvm+all_targets', when='target=arm:')
-    depends_on('llvm+all_targets', when='target=ppc:')
-    depends_on('llvm+all_targets', when='target=ppcle:')
-    depends_on('llvm+all_targets', when='target=ppc64:')
-    depends_on('llvm+all_targets', when='target=ppc64le:')
-    depends_on('llvm+all_targets', when='target=sparc:')
-    depends_on('llvm+all_targets', when='target=sparc64:')
 
     @when('@0.14:')
     def cmake_args(self):

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

@@ -138,10 +138,14 @@ class Llvm(CMakePackage, CudaPackage):
         description="Link LLVM tools against the LLVM shared library",
     )
     variant(
-        "all_targets",
+        "targets",
-        default=False,
+        default="none",
-        description="Build all supported targets, default targets "
+        description=("What targets to build. Spack's target family is always added "
-        "<current arch>,NVPTX,AMDGPU,CppBackend",
+                     "(e.g. X86 is automatically enabled when targeting znver2)."),
+        values=("all", "none", "aarch64", "amdgpu", "arm", "avr", "bpf", "cppbackend",
+                "hexagon", "lanai", "mips", "msp430", "nvptx", "powerpc", "riscv",
+                "sparc", "systemz", "webassembly", "x86", "xcore"),
+        multi=True
     )
     variant(
         "build_type",
@@ -271,6 +275,11 @@ class Llvm(CMakePackage, CudaPackage):
     # Fixed in upstream versions of both
     conflicts('^cmake@3.19.0', when='@6.0.0:11.0.0')
 
+    # Starting in 3.9.0 CppBackend is no longer a target (see
+    # LLVM_ALL_TARGETS in llvm's top-level CMakeLists.txt for
+    # the complete list of targets)
+    conflicts("targets=cppbackend", when='@3.9.0:')
+
     # Github issue #4986
     patch("llvm_gcc7.patch", when="@4.0.0:4.0.1+lldb %gcc@7.0:")
 
@@ -618,27 +627,9 @@ def cmake_args(self):
             define('LIBCXX_ENABLE_STATIC_ABI_LIBRARY', True)
         ])
 
-        if "+all_targets" not in spec:  # all is default on cmake
+        cmake_args.append(define(
-
+            "LLVM_TARGETS_TO_BUILD",
-            targets = ["NVPTX", "AMDGPU"]
+            get_llvm_targets_to_build(spec)))
-            if spec.version < Version("3.9.0"):
-                # Starting in 3.9.0 CppBackend is no longer a target (see
-                # LLVM_ALL_TARGETS in llvm's top-level CMakeLists.txt for
-                # the complete list of targets)
-                targets.append("CppBackend")
-
-            if spec.target.family in ("x86", "x86_64"):
-                targets.append("X86")
-            elif spec.target.family == "arm":
-                targets.append("ARM")
-            elif spec.target.family == "aarch64":
-                targets.append("AArch64")
-            elif spec.target.family in ("sparc", "sparc64"):
-                targets.append("Sparc")
-            elif spec.target.family in ("ppc64", "ppc64le", "ppc", "ppcle"):
-                targets.append("PowerPC")
-
-            cmake_args.append(define("LLVM_TARGETS_TO_BUILD", targets))
 
         cmake_args.append(from_variant("LIBOMP_TSAN_SUPPORT", "omp_tsan"))
 
@@ -706,3 +697,51 @@ def post_install(self):
 
         with working_dir(self.build_directory):
             install_tree("bin", join_path(self.prefix, "libexec", "llvm"))
+
+
+def get_llvm_targets_to_build(spec):
+    targets = spec.variants['targets'].value
+
+    # Build everything?
+    if 'all' in targets:
+        return 'all'
+
+    # Convert targets variant values to CMake LLVM_TARGETS_TO_BUILD array.
+    spack_to_cmake = {
+        "aarch64": "AArch64",
+        "amdgpu": "AMDGPU",
+        "arm": "ARM",
+        "avr": "AVR",
+        "bpf": "BPF",
+        "cppbackend": "CppBackend",
+        "hexagon": "Hexagon",
+        "lanai": "Lanai",
+        "mips": "Mips",
+        "msp430": "MSP430",
+        "nvptx": "NVPTX",
+        "powerpc": "PowerPC",
+        "riscv": "RISCV",
+        "sparc": "Sparc",
+        "systemz": "SystemZ",
+        "webassembly": "WebAssembly",
+        "x86": "X86",
+        "xcore": "XCore"
+    }
+
+    if 'none' in targets:
+        llvm_targets = set()
+    else:
+        llvm_targets = set(spack_to_cmake[target] for target in targets)
+
+    if spec.target.family in ("x86", "x86_64"):
+        llvm_targets.add("X86")
+    elif spec.target.family == "arm":
+        llvm_targets.add("ARM")
+    elif spec.target.family == "aarch64":
+        llvm_targets.add("AArch64")
+    elif spec.target.family in ("sparc", "sparc64"):
+        llvm_targets.add("Sparc")
+    elif spec.target.family in ("ppc64", "ppc64le", "ppc", "ppcle"):
+        llvm_targets.add("PowerPC")
+
+    return list(llvm_targets)

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

@@ -17,6 +17,6 @@ class Zig(CMakePackage):
         default='Release', description='CMake build type'
     )
 
-    depends_on('llvm@11.0.0: +all_targets')
+    depends_on('llvm@11.0.0: targets=all')
 
     provides('ziglang')