8359126: [AIX] new test TestImplicitNullChecks.java fails

Author: TheRealMDoerr

test/hotspot/jtreg/compiler/gcbarriers/TestImplicitNullChecks.java

@@ -67,7 +67,10 @@ public static void main(String[] args) {
     }
 
     @Test
-    @IR(applyIfOr = {"UseZGC", "true", "UseG1GC", "true"},
+    // On AIX, implicit null checks are limited because the zero page is
+    // readable (but not writable). See os::zero_page_read_protected().
+    @IR(applyIfPlatform = {"aix", "false"},
+        applyIfOr = {"UseZGC", "true", "UseG1GC", "true"},
         counts = {IRNode.NULL_CHECK, "1"},
         phase = CompilePhase.FINAL_CODE)
     static Object testLoad(Outer o) {

test/hotspot/jtreg/compiler/lib/ir_framework/test/IREncodingPrinter.java

@@ -62,6 +62,7 @@ public class IREncodingPrinter {
     // as adding non-existent platforms can lead to skipped tests.
     private static final List<String> irTestingPlatforms = new ArrayList<String>(Arrays.asList(
         // os.family
+        "aix",
         "linux",
         "mac",
         "windows",
@@ -346,7 +347,9 @@ private boolean checkPlatform(String platform, String value) {
         }
 
         String os = "";
-        if (Platform.isLinux()) {
+        if (Platform.isAix()) {
+            os = "aix";
+        } else if (Platform.isLinux()) {
             os = "linux";
         } else if (Platform.isOSX()) {
             os = "mac";