在Java方法中使用dup进行计算 [英] Using dup for calculations in a Java method

问题描述

我目前有一种方法可以执行以下操作:给定:value，offset，stride，它会向value增加offset，将其保持在一组size stride中.
例子:

I currently have a method that does the follow: given: value, offset, stride, it adds offset to value keeping it within a group of size stride.
Examples:

20、5、30 => 25
29，5，30 => 4
42，5，30 => 47

20, 5, 30 => 25
29, 5, 30 => 4
42, 5, 30 => 47

我当前的代码是:

int cycle(int value, int offset, int stride) {
    final int rem = value % stride;
    return ((rem + offset) % stride - rem + value);
}

编译为以下内容:

int cycle(int, int, int);
  Code:
     0: iload_1
     1: iload_3
     2: irem
     3: istore        4
     5: iload         4
     7: iload_2
     8: iadd
     9: iload_3
    10: irem
    11: iload         4
    13: isub
    14: iload_1
    15: iadd
    16: ireturn

是否有任何代码更改和/或编译器选项的组合可以使它生成类似这样的内容? (该示例是手工编写的):

Is there any combination of code changes and / or compiler options that can make it produce something like this instead? (The example was written by hand):

int cycle(int, int, int);
  Code:
     0: iload_1
     1: iload_3
     2: irem
     3: dup
     4: iload_2
     5: iadd
     6: iload_3
     7: irem
     8: isub
     9: iload_1
    10: iadd
    11: ireturn

推荐答案

最优化的JVM(尤其是最常用的HotSpot JVM)会将代码转换为

Most optimizing JVMs, most notably the commonly using HotSpot JVM, will transform the code into the SSA form before applying any other optimization. For this representation, it is entirely irrelevant whether the original code used temporary local variables or dup on the operand stack, the in­ter­me­di­ate representation will be the same.

因此javac没有提供任何选项来控制这种结构的字节码表示，但是无论如何都没关系.

So javac doesn’t offer any option to control the byte code representation of such a construct, but it doesn’t matter anyway.

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