Add clang toolchain config and some other minor related changes

cuda/BUILD.bazel

@@ -21,7 +21,6 @@ cuda_archs_flag(
     build_setting_default = "",
 )
 
-#TODO:
 # Command line flag to select compiler for cuda_library() code.
 string_flag(
     name = "compiler",
@@ -32,6 +31,16 @@ string_flag(
     ],
 )
 
+config_setting(
+    name = "compiler_is_nvcc",
+    flag_values = {":compiler": "nvcc"},
+)
+
+config_setting(
+    name = "compiler_is_clang",
+    flag_values = {":compiler": "clang"},
+)
+
 #TODO:
 # Command line flag for copts to add to cuda_library() compile command.
 string_list_flag(

cuda/defs.bzl

@@ -8,13 +8,15 @@ load(
     _find_cuda_toolchain = "find_cuda_toolchain",
     _use_cuda_toolchain = "use_cuda_toolchain",
 )
+load("//cuda/private:toolchain_configs/clang.bzl", _cuda_toolchain_config_clang = "cuda_toolchain_config")
 load("//cuda/private:toolchain_configs/nvcc.bzl", _cuda_toolchain_config_nvcc = "cuda_toolchain_config")
 load("//cuda/private:toolchain_configs/nvcc_msvc.bzl", _cuda_toolchain_config_nvcc_msvc = "cuda_toolchain_config")
 
 cuda_toolkit = _cuda_toolkit
 cuda_toolchain = _cuda_toolchain
 find_cuda_toolchain = _find_cuda_toolchain
 use_cuda_toolchain = _use_cuda_toolchain
+cuda_toolchain_config_clang = _cuda_toolchain_config_clang
 cuda_toolchain_config_nvcc_msvc = _cuda_toolchain_config_nvcc_msvc
 cuda_toolchain_config_nvcc = _cuda_toolchain_config_nvcc
 

cuda/private/cuda_toolkit.bzl

@@ -1,4 +1,5 @@
 def register_detected_cuda_toolchains():
     native.register_toolchains(
         "@local_cuda//toolchain:nvcc-local-toolchain",
+        "@local_cuda//toolchain/clang:clang-local-toolchain",
     )

cuda/private/repositories.bzl

@@ -126,9 +126,43 @@ def config_cuda_toolkit_and_nvcc(repository_ctx, cuda):
         substitutions["%{env_tmp}"] = _to_forward_slash(env_tmp)
     repository_ctx.template("toolchain/BUILD", tpl_label, substitutions = substitutions, executable = False)
 
+def detect_clang(repository_ctx):
+    ## Detect clang executable
+    # Path to clang is
+    # - taken from CUDA_CLANG_PATH environment variable or
+    # - taken from BAZEL_LLVM environment variable as <BAZEL_LLVM>/bin/clang or
+    # - determined through 'which clang' or
+    # - treated as being not detected and not configured
+    bin_ext = ".exe" if _is_windows(repository_ctx) else ""
+    clang_path = repository_ctx.os.environ.get("CUDA_CLANG_PATH", None)
+    if clang_path == None:
+        bazel_llvm = repository_ctx.os.environ.get("BAZEL_LLVM", None)
+        if bazel_llvm != None and repository_ctx.path(bazel_llvm + "/bin/clang" + bin_ext).exists:
+            clang_path = bazel_llvm + "/bin/clang" + bin_ext
+    if clang_path == None:
+        clang_path = str(repository_ctx.which("clang"))
+    return clang_path
+
+def config_clang(repository_ctx, cuda, clang_path):
+    # Generate @local_cuda//toolchain/clang/BUILD
+    tpl_label = Label("//cuda:templates/BUILD.local_toolchain_clang")
+    substitutions = {
+        "%{clang_path}": _to_forward_slash(clang_path),
+        "%{cuda_path}": _to_forward_slash(cuda.path),
+        "%{cuda_version}": "{}.{}".format(cuda.version_major, cuda.version_minor),
+        "%{nvlink_label}": cuda.nvlink_label,
+        "%{link_stub_label}": cuda.link_stub_label,
+        "%{bin2c_label}": cuda.bin2c_label,
+        "%{fatbinary_label}": cuda.fatbinary_label,
+    }
+    repository_ctx.template("toolchain/clang/BUILD", tpl_label, substitutions = substitutions, executable = False)
+
 def _local_cuda_impl(repository_ctx):
     cuda = detect_cuda_toolkit(repository_ctx)
     config_cuda_toolkit_and_nvcc(repository_ctx, cuda)
+    clang_path = detect_clang(repository_ctx)
+    if clang_path != None:
+        config_clang(repository_ctx, cuda, clang_path)
 
 _local_cuda = repository_rule(
     implementation = _local_cuda_impl,