[Bazel] Condition Exegesis target-specific sources

[GMNGeoffrey]

Summary

Not everything is X86 :-P

[chandlerc]

utils/bazel/llvm-project-overlay/llvm/BUILD.bazel

2356–2359

I'm confused why we need to condition on whether the *host* is x86?

This may be obvious from the error you're fixing, but I think it would need some kind of comment here. We don't condition the x86 assembler or disassembler on the host architecture...

[GMNGeoffrey]

utils/bazel/llvm-project-overlay/llvm/BUILD.bazel

2356–2359

Ah you're totally right. This select was present in our internal config and I thought it was there for good reason, but apparently not. I've removed it there. Thanks for catching this :-)

utils/bazel/llvm-project-overlay/llvm/BUILD.bazel

 # This file is licensed under the Apache License v2.0 with LLVM Exceptions.
 # See https://llvm.org/LICENSE.txt for license information.
 # SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
+load("@bazel_skylib//lib:selects.bzl", "selects")
 load(":template_rule.bzl", "template_rule")
 load(":tblgen.bzl", "gentbl")
 load(":config.bzl", "llvm_config_defines")
 load(":targets.bzl", "llvm_targets")
 load(":enum_targets_gen.bzl", "enum_targets_gen")
 load(":binary_alias.bzl", "binary_alias")
 
 package(
     default_visibility = ["//visibility:public"],
     licenses = ["notice"],
 )
 
 exports_files(["LICENSE.TXT"])
 
 # It may be tempting to add compiler flags here, but that should be avoided.
 # The necessary warnings and other compile flags should be provided by the
 # toolchain or the `.bazelrc` file. This is just a workaround until we have a
 # widely available feature to enable unlimited stack frame instead of using
 # this `Make` variable.
 llvm_copts = [
     "$(STACK_FRAME_UNLIMITED)",
 ]
 
+config_setting(
+    name = "x86_32",
+    constraint_values = ["@platforms//cpu/cpu:x86_32"],
+)
+
+config_setting(
+    name = "x86_64",
+    constraint_values = ["@platforms//cpu/cpu:x86_64"],
+)
+
+selects.config_setting_group(
+    name = "any_x86",
+    match_any = [
+        ":x86_32",
+        ":x86_64",
+    ],
+)
+
 enum_targets_gen(
     name = "targets_def_gen",
     src = "include/llvm/Config/Targets.def.in",
     out = "include/llvm/Config/Targets.def",
     macro_name = "TARGET",
     targets = llvm_targets,
 )
 
deps = [
         ":Support",
     ],
 )
 
 cc_library(
     name = "Exegesis",
     srcs = glob([
         "tools/llvm-exegesis/lib/*.cpp",
-        "tools/llvm-exegesis/lib/X86/*.cpp",
-        "tools/llvm-exegesis/lib/X86/*.h",
 
         # We have to include these headers here as well as in the `hdrs` below
         # to allow the `.cpp` files to use file-relative-inclusion to find
         # them, even though consumers of this library use inclusion relative to
         # `tools/llvm-exegesis/lib` with the `strip_includes_prefix` of this
         # library. This mixture appears to be incompatible with header modules.
         "tools/llvm-exegesis/lib/*.h",
+    ]) + select({
+        ":any_x86": glob([
+            "tools/llvm-exegesis/lib/X86/*.cpp",
+            "tools/llvm-exegesis/lib/X86/*.h",
         ]),
+        "//conditions:default": [],
+    }),
     hdrs = glob(["tools/llvm-exegesis/lib/*.h"]),
     copts = llvm_copts + ["-DHAVE_LIBPFM=1"],
     defines = ["LLVM_EXEGESIS_INITIALIZE_NATIVE_TARGET=InitializeX86ExegesisTarget"],
     features = ["-header_modules"],
     strip_include_prefix = "tools/llvm-exegesis/lib",
     tags = [
         "manual",  # External dependency (libpfm4)
         "nobuildkite",  # TODO(chandlerc): Add support for fetching and building libpfm4 and enable this.