[llvm-branch-commits] [compiler-rt] [llvm] [clang] [builtins][arm64] Build __init_cpu_features_resolver on Apple platforms (PR #73685)

[Fangrui Song via llvm-branch-commits]

================
@@ -1259,6 +1270,64 @@ struct {
   // As features grows new fields could be added
 } __aarch64_cpu_features __attribute__((visibility("hidden"), nocommon));
 
+#if defined(__APPLE__)
+#include <TargetConditionals.h>
+#if TARGET_OS_OSX || TARGET_OS_IPHONE
+#include <dispatch/dispatch.h>
+#include <sys/sysctl.h>
+
+static bool isKnownAndSupported(const char *name) {
+  int32_t val = 0;
+  size_t size = sizeof(val);
+  if (sysctlbyname(name, &val, &size, NULL, 0))
+    return false;
+  return val;
+}
+
+void __init_cpu_features_resolver(void) {
+  static dispatch_once_t onceToken = 0;
+  dispatch_once(&onceToken, ^{
+    // https://developer.apple.com/documentation/kernel/1387446-sysctlbyname/determining_instruction_set_characteristics
+    static struct {
+      const char *sysctl_name;
+      enum CPUFeatures feature;
+    } Features[] = {
+        {"hw.optional.arm.FEAT_FlagM", FEAT_FLAGM},
+        {"hw.optional.arm.FEAT_FlagM2", FEAT_FLAGM2},
+        {"hw.optional.arm.FEAT_FHM", FEAT_FP16FML},
+        {"hw.optional.arm.FEAT_DotProd", FEAT_DOTPROD},
+        {"hw.optional.arm.FEAT_RDM", FEAT_RDM},
+        {"hw.optional.arm.FEAT_LSE", FEAT_LSE},
+        {"hw.optional.floatingpoint", FEAT_FP},
+        {"hw.optional.AdvSIMD", FEAT_SIMD},
+        {"hw.optional.armv8_crc32", FEAT_CRC},
+        {"hw.optional.arm.FEAT_SHA1", FEAT_SHA1},
+        {"hw.optional.arm.FEAT_SHA256", FEAT_SHA2},
+        {"hw.optional.armv8_2_sha3", FEAT_SHA3},
+        {"hw.optional.arm.FEAT_AES", FEAT_AES},
+        {"hw.optional.arm.FEAT_PMULL", FEAT_PMULL},
+        {"hw.optional.arm.FEAT_FP16", FEAT_FP16},
+        {"hw.optional.arm.FEAT_JSCVT", FEAT_JSCVT},
+        {"hw.optional.arm.FEAT_FCMA", FEAT_FCMA},
+        {"hw.optional.arm.FEAT_LRCPC", FEAT_RCPC},
+        {"hw.optional.arm.FEAT_LRCPC2", FEAT_RCPC2},
+        {"hw.optional.arm.FEAT_FRINTTS", FEAT_FRINTTS},
+        {"hw.optional.arm.FEAT_I8MM", FEAT_I8MM},
+        {"hw.optional.arm.FEAT_BF16", FEAT_BF16},
+        {"hw.optional.arm.FEAT_SB", FEAT_SB},
+        {"hw.optional.arm.FEAT_SSBS", FEAT_SSBS2},
+        {"hw.optional.arm.FEAT_BTI", FEAT_BTI},
+    };
+
+    for (size_t I = 0, E = sizeof(Features) / sizeof(Features[0]); I != E; ++I)
----------------
MaskRay wrote:

compiler-rt generally uses lower-case variable names.

https://github.com/llvm/llvm-project/pull/73685