Add cpu-target-features binary

This is a very small executable which is used to determine what CPU
target features are enabled for a given compiler toolchain. These
features are only provided through internal compiler defines, and thus
we have to do a lot of macro shenaningans to get them to display
correctly.

Bug: 354747380
Test: Built for x86_64 cuttlefish, not tested installation
Change-Id: Ic68cd365c41ddd278a856a21796e1645a82fd760

Author: ajordanr-google

cpu_target_features/Android.bp

@@ -0,0 +1,18 @@
+package {
+    default_applicable_licenses: ["Android-Apache-2.0"],
+}
+
+cc_binary {
+    name: "cpu-target-features",
+    srcs: [
+        "main.cpp",
+    ],
+    generated_headers: ["print_target_features.inc"],
+}
+
+genrule {
+    name: "print_target_features.inc",
+    out: ["print_target_features.inc"],
+    tool_files: ["generate_printer.py"],
+    cmd: "$(location generate_printer.py) $(out)",
+}

cpu_target_features/generate_printer.py

@@ -0,0 +1,107 @@
+#!/usr/bin/env python3
+
+"""Generate the compilation target feature printing source code.
+
+The source code for detecting target features is heavily redundant and
+copy-pasted, and is easier to maintain using a generative script.
+
+This script creates the source and the include files in its current
+directory.
+"""
+
+import argparse
+from pathlib import Path
+from typing import Dict, List, Iterable
+
+_CPP_BOILERPLATE: str = """\
+#include <stdio.h>
+
+#define TO_STRING_EXP(DEF) #DEF
+#define TO_STRING(DEF) TO_STRING_EXP(DEF)
+"""
+
+_FEATURES = {
+    "Aarch64": [
+        "__ARM_FEATURE_AES",
+        "__ARM_FEATURE_BTI",
+        "__ARM_FEATURE_CRC32",
+        "__ARM_FEATURE_CRYPTO",
+        "__ARM_FEATURE_PAC_DEFAULT",
+        "__ARM_FEATURE_SHA2",
+        "__ARM_FEATURE_SHA3",
+        "__ARM_FEATURE_SHA512",
+    ],
+    "Arm32": [
+        "__ARM_ARCH_ISA_THUMB",
+        "__ARM_FEATURE_AES",
+        "__ARM_FEATURE_BTI",
+        "__ARM_FEATURE_CRC32",
+        "__ARM_FEATURE_CRYPTO",
+        "__ARM_FEATURE_PAC_DEFAULT",
+        "__ARM_FEATURE_SHA2",
+    ],
+    "X86": [
+        "__AES__",
+        "__AVX__",
+        "__CRC32__",
+        "__POPCNT__",
+        "__SHA512__",
+        "__SHA__",
+    ],
+    "Riscv": [
+        "__riscv_vector",
+    ],
+}
+
+
+def _make_function_sig(name: str) -> str:
+    return f"void print{name}TargetFeatures()"
+
+
+def check_template(define: str) -> List[str]:
+    return [
+        f"#if defined({define})",
+        f'  printf("%s=%s\\n", TO_STRING_EXP({define}), TO_STRING({define}));',
+        "#else",
+        f'  printf("%s not defined\\n", TO_STRING_EXP({define}));',
+        "#endif",
+    ]
+
+
+def generate_cpp_file(define_mapping: Dict[str, List[str]]) -> List[str]:
+    out: List[str] = _CPP_BOILERPLATE.split("\n")
+    for target, defines in define_mapping.items():
+        out.append("")
+        out.extend(generate_print_function(target, defines))
+    return out
+
+
+def generate_print_function(name: str, defines: List[str]) -> List[str]:
+    """Generate a print<DEFINE>TargetFeatures function."""
+    function_body = [_make_function_sig(name) + " {"]
+    for d in defines:
+        function_body.extend(check_template(d))
+    function_body.append("}")
+    return function_body
+
+
+def parse_args() -> argparse.Namespace:
+    parser = argparse.ArgumentParser(description=__doc__)
+    parser.add_argument(
+        "cpp_in",
+        type=Path,
+        help="Output path to generate the cpp file.",
+    )
+    return parser.parse_args()
+
+
+def main() -> None:
+    args = parse_args()
+    printer_cpp_filepath = args.cpp_in
+    printer_cpp_filepath.write_text(
+        "\n".join(generate_cpp_file(_FEATURES)), encoding="utf-8"
+    )
+
+
+if __name__ == "__main__":
+    main()

cpu_target_features/main.cpp

@@ -0,0 +1,37 @@
+/*
+ * Copyright (C) 2024 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <stdio.h>
+
+#include "print_target_features.inc"
+
+int main() {
+#if defined(__aarch64__)
+  printAarch64TargetFeatures();
+  return 0;
+#elif defined(__arm__)
+  printArm32TargetFeatures();
+  return 0;
+#elif defined(__x86_64__) || defined(__i386__)
+  printX86TargetFeatures();
+  return 0;
+#elif defined(__riscv)
+  printRiscvTargetFeatures();
+  return 0;
+#else
+#error Unsupported arch. This binary only supports aarch64, arm, x86, x86-64, and risc-v
+#endif
+}