8372097: C2: PhasePrintLevel requires setting PrintPhaseLevel explicitly to be active

Reviewed-by: mhaessig, chagedorn

src/hotspot/share/opto/c2_globals.hpp

@@ -428,7 +428,7 @@
           "0=print nothing except PhasePrintLevel directives, "             \
           "6=all details printed. "                                         \
           "Level of detail of printouts can be set on a per-method level "  \
-          "as well by using CompileCommand=PrintPhaseLevel.")                        \
+          "as well by using CompileCommand=PhasePrintLevel.")               \
           range(-1, 6)                                                      \
                                                                             \
   develop(bool, PrintIdealGraph, false,                                     \

src/hotspot/share/opto/compile.cpp

@@ -5233,7 +5233,7 @@ void Compile::end_method() {
 
 #ifndef PRODUCT
 bool Compile::should_print_phase(const int level) const {
-  return PrintPhaseLevel > 0 && directive()->PhasePrintLevelOption >= level &&
+  return PrintPhaseLevel >= 0 && directive()->PhasePrintLevelOption >= level &&
          _method != nullptr; // Do not print phases for stubs.
 }
 

test/hotspot/jtreg/compiler/oracle/TestPhasePrintLevel.java

@@ -0,0 +1,110 @@
+/*
+ * Copyright (c) 2025, 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
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+package compiler.oracle;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import jdk.test.lib.process.OutputAnalyzer;
+import jdk.test.lib.process.ProcessTools;
+
+import compiler.lib.ir_framework.CompilePhase;
+
+/**
+ * @test
+ * @bug 8372097
+ * @summary Checks that -XX:CompileCommand=PhasePrintLevel,... interacts with
+ *          -XX:PrintPhaseLevel as expected.
+ * @library /test/lib /
+ * @requires vm.debug & vm.compiler2.enabled & vm.flagless
+ * @run driver compiler.oracle.TestPhasePrintLevel
+ */
+
+public class TestPhasePrintLevel {
+
+    static final String level1Phase = CompilePhase.FINAL_CODE.getName();
+    static final String level2Phase = CompilePhase.GLOBAL_CODE_MOTION.getName();
+
+    public static void main(String[] args) throws Exception {
+        // Test flag level < 0: nothing should be printed regardless of the compile command level.
+        test(-1, -1, null,        level1Phase);
+        test(-1,  0, null,        level1Phase);
+        test(-1,  1, null,        level1Phase);
+
+        // Test flag level = 0: the compile command level should determine what is printed.
+        test(0,  -1, null,        level1Phase);
+        test(0,   0, null,        level1Phase);
+        test(0,   1, level1Phase, null);
+        test(0,   2, level2Phase, null);
+
+        // Test flag level > 0: the compile command level should take precedence.
+        test(1,  -1, null,        level1Phase);
+        test(1,   0, null,        level1Phase);
+        test(1,   1, level1Phase, null);
+        test(2,   1, level1Phase, level2Phase);
+        test(1,   2, level2Phase, null);
+    }
+
+    static void test(int flagLevel, int compileCommandLevel, String expectedPhase, String unexpectedPhase) throws Exception {
+        List<String> options = new ArrayList<String>();
+        options.add("-Xbatch");
+        options.add("-XX:CompileOnly=" + getTestName());
+        options.add("-XX:PrintPhaseLevel=" + flagLevel);
+        options.add("-XX:CompileCommand=PhasePrintLevel," + getTestName() + "," + compileCommandLevel);
+        options.add(getTestClass());
+        OutputAnalyzer oa = ProcessTools.executeTestJava(options);
+        oa.shouldHaveExitValue(0)
+            .shouldContain("CompileCommand: PhasePrintLevel compiler/oracle/TestPhasePrintLevel$TestMain.test intx PhasePrintLevel = " + compileCommandLevel)
+            .shouldNotContain("CompileCommand: An error occurred during parsing")
+            .shouldNotContain("# A fatal error has been detected by the Java Runtime Environment");
+        if (expectedPhase != null) {
+            oa.shouldContain(expectedPhase);
+        }
+        if (unexpectedPhase != null) {
+            oa.shouldNotContain(unexpectedPhase);
+        }
+    }
+
+    static String getTestClass() {
+        return TestMain.class.getName();
+    }
+
+    static String getTestName() {
+        return getTestClass() + "::test";
+    }
+
+    static class TestMain {
+        public static void main(String[] args) {
+            for (int i = 0; i < 10_000; i++) {
+                test(i);
+            }
+        }
+
+        static void test(int i) {
+            if ((i % 1000) == 0) {
+                System.out.println("Hello World!");
+            }
+        }
+    }
+}