Add aarch64 midr_el1 implementation

BUILD.bazel

@@ -244,7 +244,10 @@ cc_library(
             "include/internal/windows_utils.h",
         ],
         PLATFORM_CPU_ARM: ["include/cpuinfo_arm.h"],
-        PLATFORM_CPU_ARM64: ["include/cpuinfo_aarch64.h"],
+        PLATFORM_CPU_ARM64: [
+            "include/cpuinfo_aarch64.h",
+            "include/internal/cpuid_aarch64.h",
+        ],
         PLATFORM_CPU_MIPS: ["include/cpuinfo_mips.h"],
         PLATFORM_CPU_PPC: ["include/cpuinfo_ppc.h"],
         PLATFORM_CPU_RISCV32: ["include/cpuinfo_riscv.h"],
@@ -288,6 +291,7 @@ cc_library(
         ],
         PLATFORM_CPU_ARM: ["src/impl_arm_linux_or_android.c"],
         PLATFORM_CPU_ARM64: [
+            "src/impl_aarch64_cpuid.c",
             "src/impl_aarch64_linux_or_android.c",
             "src/impl_aarch64_macos_or_iphone.c",
             "src/impl_aarch64_windows.c",

CMakeLists.txt

@@ -106,6 +106,7 @@ macro(add_cpu_features_headers_and_sources HDRS_LIST_NAME SRCS_LIST_NAME)
       list(APPEND ${HDRS_LIST_NAME} ${PROJECT_SOURCE_DIR}/include/cpuinfo_arm.h)
   elseif(PROCESSOR_IS_AARCH64)
       list(APPEND ${HDRS_LIST_NAME} ${PROJECT_SOURCE_DIR}/include/cpuinfo_aarch64.h)
+      list(APPEND ${SRCS_LIST_NAME} ${PROJECT_SOURCE_DIR}/include/internal/cpuid_aarch64.h)
       list(APPEND ${SRCS_LIST_NAME} ${PROJECT_SOURCE_DIR}/include/internal/windows_utils.h)
   elseif(PROCESSOR_IS_X86)
       list(APPEND ${HDRS_LIST_NAME} ${PROJECT_SOURCE_DIR}/include/cpuinfo_x86.h)

include/internal/cpuid_aarch64.h

@@ -0,0 +1,28 @@
+// Copyright 2023 Google LLC
+//
+// 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.
+
+#ifndef CPU_FEATURES_INCLUDE_CPUID_AARCH64_H_
+#define CPU_FEATURES_INCLUDE_CPUID_AARCH64_H_
+
+#include <stdint.h>
+
+#include "cpu_features_macros.h"
+
+CPU_FEATURES_START_CPP_NAMESPACE
+
+uint64_t GetMidrEl1();
+
+CPU_FEATURES_END_CPP_NAMESPACE
+
+#endif  // CPU_FEATURES_INCLUDE_CPUID_AARCH64_H_

src/impl_aarch64_cpuid.c

@@ -0,0 +1,39 @@
+// Copyright 2023 Google LLC
+//
+// 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 "cpu_features_macros.h"
+
+#ifdef CPU_FEATURES_ARCH_AARCH64
+#ifdef CPU_FEATURES_OS_FREEBSD
+#if (defined(CPU_FEATURES_COMPILER_GCC) || defined(CPU_FEATURES_COMPILER_CLANG))
+
+#include "internal/cpuid_aarch64.h"
+
+#ifdef CPU_FEATURES_MOCK_CPUID_AARCH64
+// Implementation will be provided by test/cpuinfo_aarch64_test.cc.
+#else
+
+uint64_t GetMidrEl1() {
+  uint64_t midr_el1;
+  __asm("mrs %0, MIDR_EL1" : "=r"(midr_el1));
+  return midr_el1;
+}
+#endif  // CPU_FEATURES_MOCK_CPUID_AARCH64
+
+#else
+#error "Unsupported compiler, aarch64 cpuid requires either GCC or Clang."
+#endif  // (defined(CPU_FEATURES_COMPILER_GCC) ||
+        // defined(CPU_FEATURES_COMPILER_CLANG))
+#endif  // CPU_FEATURES_OS_FREEBSD
+#endif  // CPU_FEATURES_ARCH_AARCH64

src/impl_aarch64_freebsd.c

@@ -12,12 +12,15 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+#include <printf.h>
+
 #include "cpu_features_macros.h"
 
 #ifdef CPU_FEATURES_ARCH_AARCH64
 #ifdef CPU_FEATURES_OS_FREEBSD
 
 #include "cpuinfo_aarch64.h"
+#include "internal/cpuid_aarch64.h"
 #include "impl_aarch64__base_implementation.inl"
 
 static const Aarch64Info kEmptyAarch64Info;
@@ -30,6 +33,14 @@ Aarch64Info GetAarch64Info(void) {
       kSetters[i](&info.features, true);
     }
   }
+  printf("cpuid is supported: %d", info.features.cpuid);
+  if (info.features.cpuid) {
+    const uint64_t midr_el1 = GetMidrEl1();
+    info.implementer = ExtractBitRange(midr_el1, 31, 24);
+    info.variant = ExtractBitRange(midr_el1, 23, 20);
+    info.part = ExtractBitRange(midr_el1, 15, 4);
+    info.revision = ExtractBitRange(midr_el1, 3, 0);
+  }
   return info;
 }