"""Experimental Skylark rules for Apple's Metal.
This creates a .metallib file containing compiled Metal shaders.
Note that the default behavior in Xcode is to put all metal shaders into a
single "default.metallib", which can be loaded using the method
newDefaultLibrary in MTLDevice. Meanwhile, the metal_library rule creates a
named .metallib, which can be loaded using newLibraryWithFile:error:.
Example:
metal_library(
name = "my_shaders",
srcs = ["my_shaders.metal"],
hdrs = ["my_shaders.h"],
)
This produces a "my_shaders.metallib".
The metal_library target can be added to the deps attribute of an objc_library.
The dependent objc_library can then access the headers declared by the
metal_library, if any.
The metal_library target can also be added to the resources attribute as a
simple data file, but in that case any declared headers are not visible to
dependent objc_library rules.
"""
load("@bazel_skylib//lib:dicts.bzl", "dicts")
load("@build_bazel_apple_support//lib:apple_support.bzl", "apple_support")
# This load statement is overriding the visibility of the internal implementation of rules_apple.
# This rule will be migrated to rules_apple in the future, hence the override. Please do not use
# this import anywhere else.
load(
"@build_bazel_rules_apple//apple/internal:resources.bzl",
"resources",
)
def _metal_compiler_args(ctx, src, obj, minimum_os_version, copts, diagnostics, deps_dump):
"""Returns arguments for metal compiler."""
apple_fragment = ctx.fragments.apple
platform = apple_fragment.single_arch_platform
if not minimum_os_version:
minimum_os_version = ctx.attr._xcode_config[apple_common.XcodeVersionConfig].minimum_os_for_platform_type(
platform.platform_type,
)
args = copts + [
"-arch",
"air64", # TODO: choose based on target device/cpu/platform?
"-emit-llvm",
"-c",
"-gline-tables-only",
"-isysroot",
apple_support.path_placeholders.sdkroot(),
"-ffast-math",
"-serialize-diagnostics",
diagnostics.path,
"-o",
obj.path,
"-mios-version-min=%s" % minimum_os_version,
"",
src.path,
"-MMD",
"-MT",
"dependencies",
"-MF",
deps_dump.path,
]
return args
def _metal_compiler_inputs(srcs, hdrs, deps = []):
"""Determines the list of inputs required for a compile action."""
cc_infos = [dep[CcInfo] for dep in deps if CcInfo in dep]
dep_headers = depset(transitive = [
cc_info.compilation_context.headers
for cc_info in cc_infos
])
return depset(srcs + hdrs, transitive = [dep_headers])
def _metal_library_impl(ctx):
"""Implementation for metal_library Skylark rule."""
# A unique path for rule's outputs.
objs_outputs_path = "{}.objs/".format(ctx.label.name)
output_objs = []
for src in ctx.files.srcs:
basename = src.basename
obj = ctx.actions.declare_file(objs_outputs_path + basename + ".air")
output_objs.append(obj)
diagnostics = ctx.actions.declare_file(objs_outputs_path + basename + ".dia")
deps_dump = ctx.actions.declare_file(objs_outputs_path + basename + ".dat")
args = (["metal"] +
_metal_compiler_args(ctx, src, obj, ctx.attr.minimum_os_version, ctx.attr.copts, diagnostics, deps_dump))
apple_support.run(
ctx,
xcode_path_resolve_level = apple_support.xcode_path_resolve_level.args,
inputs = _metal_compiler_inputs(ctx.files.srcs, ctx.files.hdrs, ctx.attr.deps),
outputs = [obj, diagnostics, deps_dump],
mnemonic = "MetalCompile",
executable = "/usr/bin/xcrun",
toolchain = None,
arguments = args,
use_default_shell_env = False,
progress_message = ("Compiling Metal shader %s" %
(basename)),
)
output_lib = ctx.actions.declare_file(ctx.label.name + ".metallib")
args = [
"metallib",
"-split-module",
"-o",
output_lib.path,
] + [x.path for x in output_objs]
apple_support.run(
ctx,
xcode_path_resolve_level = apple_support.xcode_path_resolve_level.args,
inputs = output_objs,
outputs = (output_lib,),
mnemonic = "MetalLink",
executable = "/usr/bin/xcrun",
toolchain = None,
arguments = args,
progress_message = (
"Linking Metal library %s" % ctx.label.name
),
)
objc_provider = apple_common.new_objc_provider(
providers = [x[apple_common.Objc] for x in ctx.attr.deps if apple_common.Objc in x],
)
cc_infos = [dep[CcInfo] for dep in ctx.attr.deps if CcInfo in dep]
if ctx.files.hdrs:
cc_infos.append(
CcInfo(
compilation_context = cc_common.create_compilation_context(
headers = depset([f for f in ctx.files.hdrs]),
),
),
)
return [
DefaultInfo(
files = depset([output_lib]),
),
objc_provider,
cc_common.merge_cc_infos(cc_infos = cc_infos),
# Return the provider for the new bundling logic of rules_apple.
resources.bucketize_typed(
bucket_type = "unprocessed",
expect_files = True,
resources = [output_lib],
),
]
METAL_LIBRARY_ATTRS = dicts.add(apple_support.action_required_attrs(), {
"srcs": attr.label_list(allow_files = [".metal"], allow_empty = False),
"hdrs": attr.label_list(allow_files = [".h"]),
"deps": attr.label_list(providers = [["objc", CcInfo], [apple_common.Objc, CcInfo]]),
"copts": attr.string_list(),
"minimum_os_version": attr.string(),
})
metal_library = rule(
implementation = _metal_library_impl,
attrs = METAL_LIBRARY_ATTRS,
fragments = ["apple", "objc"],
)
"""
Builds a Metal library.
Args:
srcs: Metal shader sources.
hdrs: Header files used by the shader sources.
deps: objc_library targets whose headers should be visible to the shaders.
The header files declared in this rule are also visible to any objc_library
rules that have it as a dependency, so that constants and typedefs can be
shared between Metal and Objective-C code.
"""
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