Use inlined representation for class initializer, loop initialization…

… too costly
liachmodded · Sep 4, 2024 · 3b92745 · 3b92745
1 parent ceb3db0
commit 3b92745
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Showing 2 changed files with 65 additions and 26 deletions.
diff --git a/src/java.base/share/classes/jdk/internal/classfile/impl/RawBytecodeHelper.java b/src/java.base/share/classes/jdk/internal/classfile/impl/RawBytecodeHelper.java
@@ -24,8 +24,6 @@
  */
 package jdk.internal.classfile.impl;
 
-import java.lang.classfile.Opcode;
-import java.util.Arrays;
 import java.util.List;
 import java.util.function.BiFunction;
 import java.util.function.Function;
@@ -34,11 +32,7 @@
 import jdk.internal.util.Preconditions;
 import jdk.internal.vm.annotation.Stable;
 
-import static java.lang.classfile.ClassFile.ASTORE_3;
-import static java.lang.classfile.ClassFile.ISTORE;
-import static java.lang.classfile.ClassFile.LOOKUPSWITCH;
-import static java.lang.classfile.ClassFile.TABLESWITCH;
-import static java.lang.classfile.ClassFile.WIDE;
+import static java.lang.classfile.ClassFile.*;
 
 public final class RawBytecodeHelper {
 
@@ -58,22 +52,42 @@ public RawBytecodeHelper start() {
 
     public static final int ILLEGAL = -1;
 
-    private static final @Stable byte[] LENGTHS;
-
-    static {
-        var lengths = new byte[0x100];
-        Arrays.fill(lengths, (byte) -1);
-        for (var op : Opcode.values()) {
-            if (!op.isWide()) {
-                lengths[op.bytecode()] = (byte) op.sizeIfFixed();
-            } else {
-                // Wide pseudo-opcodes have double the length as normal variants
-                // Must match logic in checkSpecialInstruction()
-                assert lengths[op.bytecode() & 0xFF] * 2 == op.sizeIfFixed();
-            }
-        }
-        LENGTHS = lengths;
-    }
+    /**
+     * The length of opcodes, 0 for
+     * This is generated as if:
+     * {@snippet lang=java :
+     * var lengths = new byte[0x100];
+     * Arrays.fill(lengths, (byte) -1);
+     * for (var op : Opcode.values()) {
+     *     if (!op.isWide()) {
+     *         lengths[op.bytecode()] = (byte) op.sizeIfFixed();
+     *     } else {
+     *         // Wide pseudo-opcodes have double the length as normal variants
+     *         // Must match logic in checkSpecialInstruction()
+     *         assert lengths[op.bytecode() & 0xFF] * 2 == op.sizeIfFixed();
+     *     }
+     * }
+     * }
+     * Tested in UtilTest.
+     */
+    public static final @Stable byte[] LENGTHS = new byte[] {
+            1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
+            2, 3, 2, 3, 3, 2, 2, 2, 2, 2, 1, 1, 1, 1, 1, 1,
+            1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
+            1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 1, 1, 1, 1, 1,
+            1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
+            1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
+            1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
+            1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
+            1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
+            1, 1, 1, 1, 1, 1, 1, 1, 1, 3, 3, 3, 3, 3, 3, 3,
+            3, 3, 3, 3, 3, 3, 3, 3, 3, 2, -1, -1, 1, 1, 1, 1,
+            1, 1, 3, 3, 3, 3, 3, 3, 3, 5, 5, 3, 2, 3, 1, 1,
+            3, 3, 1, 1, -1, 4, 3, 3, 5, 5, -1, -1, -1, -1, -1, -1,
+            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+    };
 
     public static boolean isStoreIntoLocal(int code) {
         return (ISTORE <= code && code <= ASTORE_3);
@@ -232,11 +246,12 @@ public void next() {
         int len = LENGTHS[code];
         opcode = code;
         isWide = false;
-        if (len < 0) {
+        // Consider using 0 vs -1 to represent invalid vs special
+        if (len <= 0) {
             len = checkSpecialInstruction(code);
         }
 
-        if (len < 0 || (nextBci += len) > endBci()) {
+        if (len <= 0 || (nextBci += len) > endBci()) {
             opcode = ILLEGAL;
         }
     }

diff --git a/test/jdk/jdk/classfile/UtilTest.java b/test/jdk/jdk/classfile/UtilTest.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2022, 2023, 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
@@ -26,7 +26,14 @@
  * @summary Testing ClassFile Util.
  * @run junit UtilTest
  */
+import java.lang.classfile.ClassFile;
+import java.lang.classfile.Opcode;
 import java.lang.constant.MethodTypeDesc;
+import java.lang.invoke.MethodHandles;
+import java.util.Arrays;
+import java.util.BitSet;
+
+import jdk.internal.classfile.impl.RawBytecodeHelper;
 import jdk.internal.classfile.impl.Util;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.params.ParameterizedTest;
@@ -76,4 +83,21 @@ void testParameterSlots() {
     private void assertSlots(String methodDesc, int slots) {
         assertEquals(Util.parameterSlots(MethodTypeDesc.ofDescriptor(methodDesc)), slots);
     }
+
+    @Test
+    void testOpcodeLengthTable() {
+        var lengths = new byte[0x100];
+        Arrays.fill(lengths, (byte) -1);
+        for (var op : Opcode.values()) {
+            if (!op.isWide()) {
+                lengths[op.bytecode()] = (byte) op.sizeIfFixed();
+            } else {
+                // Wide pseudo-opcodes have double the length as normal variants
+                // Must match logic in checkSpecialInstruction()
+                assertEquals(op.sizeIfFixed(), lengths[op.bytecode() & 0xFF] * 2, op + " size");
+            }
+        }
+
+        assertArrayEquals(lengths, RawBytecodeHelper.LENGTHS);
+    }
 }