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8241071: Generation of classes.jsa with -Xshare:dump is not deterministic

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Reviewed-by: dholmes, stuefe
This commit is contained in:
Ioi Lam 2020-05-05 11:10:02 -07:00
parent 957eb270f0
commit eadcb08c3c
20 changed files with 369 additions and 92 deletions
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12
src/java.base/share/classes/java/util/ImmutableCollections.java
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@ -64,14 +64,22 @@ class ImmutableCollections {
private static final boolean REVERSE;
static {
// to generate a reasonably random and well-mixed SALT, use an arbitrary
// value (a slice of pi), multiply with the System.nanoTime, then pick
// value (a slice of pi), multiply with a random seed, then pick
// the mid 32-bits from the product. By picking a SALT value in the
// [0 ... 0xFFFF_FFFFL == 2^32-1] range, we ensure that for any positive
// int N, (SALT32L * N) >> 32 is a number in the [0 ... N-1] range. This
// property will be used to avoid more expensive modulo-based
// calculations.
long color = 0x243F_6A88_85A3_08D3L; // slice of pi
long seed = System.nanoTime();
// When running with -Xshare:dump, the VM will supply a "random" seed that's
// derived from the JVM build/version, so can we generate the exact same
// CDS archive for the same JDK build. This makes it possible to verify the
// consistency of the JDK build.
long seed = VM.getRandomSeedForCDSDump();
if (seed == 0) {
seed = System.nanoTime();
}
SALT32L = (int)((color * seed) >> 16) & 0xFFFF_FFFFL;
// use the lowest bit to determine if we should reverse iteration
REVERSE = (SALT32L & 1) == 0;

4
src/java.base/share/classes/jdk/internal/misc/VM.java
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@ -1,5 +1,5 @@
/*
* Copyright (c) 1996, 2018, Oracle and/or its affiliates. All rights reserved.
* Copyright (c) 1996, 2020, 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
@ -421,6 +421,8 @@ public class VM {
*/
public static native void initializeFromArchive(Class<?> c);
public static native long getRandomSeedForCDSDump();
/**
* Provides access to information on buffer usage.
*/