[GR-60081] Update aarch64 to use the 8.1-a instruction set by default.

substratevm/CHANGELOG.md

@@ -16,6 +16,7 @@ At runtime, premain runtime options are set along with main class' arguments in
 * (GR-58383) The length of the printed stack trace when using `-XX:MissingRegistrationReportingMode=Warn` can now be set with `-XX:MissingRegistrationWarnContextLines=` and its default length is now 8.
 * (GR-58914) `ActiveProcessorCount` must be set at isolate or VM creation time.
 * (GR-59326) Ensure builder ForkJoin commonPool parallelism always respects NativeImageOptions.NumberOfThreads.
+* (GR-60081) Native Image now targets `armv8.1-a` by default on AArch64. Use `-march=compatibility` for best compatibility or `-march=native` for best performance if the native executable is deployed on the same machine or on a machine with the same CPU features. To list all available machine types, use `-march=list`.
 
 ## GraalVM for JDK 23 (Internal Version 24.1.0)
 * (GR-51520) The old class initialization strategy, which was deprecated in GraalVM for JDK 22, is removed. The option `StrictImageHeap` no longer has any effect.

substratevm/src/com.oracle.svm.hosted/src/com/oracle/svm/hosted/NativeImageOptions.java

@@ -86,7 +86,7 @@ public class NativeImageOptions {
     public static final String MICRO_ARCHITECTURE_LIST = "list";
 
     @APIOption(name = "-march")//
-    @Option(help = "Generate instructions for a specific machine type. Defaults to 'x86-64-v3' on AMD64 and 'armv8-a' on AArch64. " +
+    @Option(help = "Generate instructions for a specific machine type. Defaults to 'x86-64-v3' on AMD64 and 'armv8.1-a' on AArch64. " +
                     "Use -march=" + MICRO_ARCHITECTURE_COMPATIBILITY + " for best compatibility, or -march=" + MICRO_ARCHITECTURE_NATIVE +
                     " for best performance if the native executable is deployed on the same machine or on a machine with the same CPU features. " +
                     "To list all available machine types, use -march=" + MICRO_ARCHITECTURE_LIST + ".", type = User)//

substratevm/src/com.oracle.svm.hosted/src/com/oracle/svm/hosted/util/CPUType.java

@@ -80,7 +80,7 @@ static String getSelectedOrDefaultMArch() {
         } else if (Platform.includedIn(Platform.AMD64.class)) {
             return CPUTypeAMD64.getDefaultName(false);
         } else if (Platform.includedIn(Platform.AARCH64.class)) {
-            return CPUTypeAArch64.getDefaultName();
+            return CPUTypeAArch64.getDefaultName(false);
         } else if (Platform.includedIn(Platform.RISCV64.class)) {
             return CPUTypeRISCV64.getDefaultName();
         } else {

substratevm/src/com.oracle.svm.hosted/src/com/oracle/svm/hosted/util/CPUTypeAArch64.java

@@ -45,6 +45,7 @@
 import com.oracle.svm.core.option.SubstrateOptionsParser;
 import com.oracle.svm.core.util.UserError;
 import com.oracle.svm.hosted.NativeImageOptions;
+import com.oracle.svm.util.LogUtils;
 import com.oracle.svm.util.StringUtil;
 
 import jdk.vm.ci.aarch64.AArch64;
@@ -113,15 +114,23 @@ public EnumSet<CPUFeature> getFeatures() {
         }
     }
 
-    public static String getDefaultName() {
-        return ARMV8_A.getName();
+    public static String getDefaultName(boolean printFallbackWarning) {
+        if (NATIVE.getFeatures().containsAll(ARMV8_1_A.getFeatures())) {
+            return ARMV8_1_A.getName();
+        } else {
+            if (printFallbackWarning) {
+                LogUtils.warning("The host machine does not support all features of '%s'. Falling back to '%s' for best compatibility.",
+                                ARMV8_1_A.getName(), SubstrateOptionsParser.commandArgument(NativeImageOptions.MicroArchitecture, COMPATIBILITY.getName()));
+            }
+            return COMPATIBILITY.getName();
+        }
     }
 
     @Platforms(Platform.HOSTED_ONLY.class)
     public static EnumSet<CPUFeature> getSelectedFeatures() {
         String value = NativeImageOptions.MicroArchitecture.getValue();
         if (value == null) {
-            value = getDefaultName();
+            value = getDefaultName(true);
         }
         return getCPUFeaturesForArch(value);
     }