xref: /llvm-project/utils/bazel/llvm-project-overlay/llvm/enum_targets_gen.bzl (revision d016712b2cbeecf13c0d558c7c8932fd66e14847) 
1# This file is licensed under the Apache License v2.0 with LLVM Exceptions.
2# See https://llvm.org/LICENSE.txt for license information.
3# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
4
5"""A rule to expand LLVM target enumerations.
6
7Replaces in a text file a single variable of the style `@LLVM_ENUM_FOOS@` with a
8list of macro invocations, one for each target on its own line:
9
10```
11LLVM_FOO(TARGET1)
12LLVM_FOO(TARGET2)
13// ...
14```
15
16Example:
17load(":enum_targets_gen.bzl", "enum_targets_gen")
18
19enum_targets_gen(
20    name = "disassemblers_def_gen",
21    src = "include/llvm/Config/Disassemblers.def.in",
22    out = "include/llvm/Config/Disassemblers.def",
23    macro_name = "DISASSEMBLER",
24    targets = llvm_target_disassemblers,
25)
26
27This rule provides a slightly more semantic API than template_rule, but the main
28reason it exists is to permit a list with selects to be passed for `targets` as
29a select is not allowed to be passed to a rule within another data structure.
30"""
31
32def enum_targets_gen_impl(ctx):
33    to_replace = ctx.attr.placeholder_name
34    if not to_replace:
35        to_replace = "@LLVM_ENUM_{}S@".format(ctx.attr.macro_name)
36    replacement = "\n".join([
37        "LLVM_{}({})\n".format(ctx.attr.macro_name, t)
38        for t in ctx.attr.targets
39    ])
40
41    ctx.actions.expand_template(
42        template = ctx.file.src,
43        output = ctx.outputs.out,
44        substitutions = {to_replace: replacement},
45    )
46
47enum_targets_gen = rule(
48    attrs = {
49        "src": attr.label(
50            mandatory = True,
51            allow_single_file = True,
52        ),
53        "out": attr.output(mandatory = True),
54        "targets": attr.string_list(mandatory = True),
55        "macro_name": attr.string(
56            mandatory = True,
57            doc = "The name of the enumeration. This is the suffix of the" +
58                  " placeholder being replaced `@LLVM_ENUM_{}S@` and of the" +
59                  " macro invocations generated `LLVM_{}(TARGET)`. Should be" +
60                  " all caps and singular, e.g. 'DISASSEMBLER'",
61        ),
62        "placeholder_name": attr.string(
63            doc = "The name of the placeholder. If unset, this defaults to" +
64                  " `@LLVM_ENUM_{macro_name}S@`",
65        ),
66    },
67    implementation = enum_targets_gen_impl,
68)
69