8332032: C2: Remove ExpandSubTypeCheckAtParseTime flag

Reviewed-by: thartmann, rcastanedalo

src/hotspot/share/opto/c2_globals.hpp

@@ -767,9 +767,6 @@
   product(bool, UseProfiledLoopPredicate, true,                             \
           "Move predicates out of loops based on profiling data")           \
                                                                             \
-  product(bool, ExpandSubTypeCheckAtParseTime, false, DIAGNOSTIC,           \
-          "Do not use subtype check macro node")                            \
-                                                                            \
   develop(uintx, StressLongCountedLoop, 0,                                  \
           "if > 0, convert int counted loops to long counted loops"         \
           "to stress handling of long counted loops: run inner loop"        \

src/hotspot/share/opto/graphKit.cpp

@@ -2713,17 +2713,12 @@ Node* Phase::gen_subtype_check(Node* subklass, Node* superklass, Node** ctrl, No
     // Here, the type of 'fa' is often exact, so the store check
     // of fa[1]=x will fold up, without testing the nullness of x.
     //
-    // Do not skip the static sub type check with StressReflectiveCode during
-    // parsing (i.e. with ExpandSubTypeCheckAtParseTime) because the
-    // associated CheckCastNodePP could already be folded when the type
-    // system can prove it's an impossible type. Therefore, we should also
-    // do the static sub type check here to ensure control is folded as well.
-    // Otherwise, the graph is left in a broken state.
     // At macro expansion, we would have already folded the SubTypeCheckNode
     // being expanded here because we always perform the static sub type
     // check in SubTypeCheckNode::sub() regardless of whether
-    // StressReflectiveCode is set or not.
-    switch (C->static_subtype_check(superk, subk, !ExpandSubTypeCheckAtParseTime)) {
+    // StressReflectiveCode is set or not. We can therefore skip this
+    // static check when StressReflectiveCode is on.
+    switch (C->static_subtype_check(superk, subk)) {
     case Compile::SSC_always_false:
       {
         Node* always_fail = *ctrl;
@@ -2904,8 +2899,7 @@ Node* Phase::gen_subtype_check(Node* subklass, Node* superklass, Node** ctrl, No
 }
 
 Node* GraphKit::gen_subtype_check(Node* obj_or_subklass, Node* superklass) {
-  bool expand_subtype_check = C->post_loop_opts_phase() ||   // macro node expansion is over
-                              ExpandSubTypeCheckAtParseTime; // forced expansion
+  bool expand_subtype_check = C->post_loop_opts_phase(); // macro node expansion is over
   if (expand_subtype_check) {
     MergeMemNode* mem = merged_memory();
     Node* ctrl = control();

test/hotspot/jtreg/compiler/types/TestSubTypeCheckMacroTrichotomy.java

@@ -1,6 +1,6 @@
 /*
  * Copyright (c) 2020, Red Hat, Inc. All rights reserved.
- * Copyright (c) 2022, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2022, 2024, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -32,7 +32,6 @@
  * @run main/othervm -XX:-BackgroundCompilation TestSubTypeCheckMacroTrichotomy
  * @run main/othervm -XX:-BackgroundCompilation
  *     -XX:+IgnoreUnrecognizedVMOptions -XX:+StressReflectiveCode
- *     -XX:+UnlockDiagnosticVMOptions -XX:+ExpandSubTypeCheckAtParseTime
  *     -XX:-TieredCompilation -XX:CompileThreshold=100 TestSubTypeCheckMacroTrichotomy
  *
  */

test/hotspot/jtreg/compiler/types/TestSubTypeCheckWithBottomArray.java

@@ -50,12 +50,10 @@
  *          either against an interface or an unrelated non-sub-class.
  *
  * @run main/othervm -Xcomp -XX:CompileCommand=compileonly,compiler.types.TestSubTypeCheckWithBottomArray::test*
- *                   -XX:+UnlockDiagnosticVMOptions -XX:+ExpandSubTypeCheckAtParseTime
  *                   -XX:+IgnoreUnrecognizedVMOptions -XX:+StressReflectiveCode
  *                   -XX:CompileCommand=inline,compiler.types.TestSubTypeCheckWithBottomArray::check*
  *                   compiler.types.TestSubTypeCheckWithBottomArray
  * @run main/othervm -Xbatch -XX:CompileCommand=compileonly,compiler.types.TestSubTypeCheckWithBottomArray::test*
- *                   -XX:+UnlockDiagnosticVMOptions -XX:+ExpandSubTypeCheckAtParseTime
  *                   -XX:+IgnoreUnrecognizedVMOptions -XX:+StressReflectiveCode
  *                   -XX:CompileCommand=inline,compiler.types.TestSubTypeCheckWithBottomArray::check*
  *                   compiler.types.TestSubTypeCheckWithBottomArray