To learn how addressing modes work for load and store instructions on PowerPC processors, you must first understand a little bit about the PowerPC instruction format.

为了解寻址模式对于PowerPC处理器上的加载和存储指令是如何工作的，我们必须先要对PowerPC指令格式有点了解。

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The PowerPC uses a load/store (also called RISC) instruction set, which means that the only time it accesses main memory is for loading into registers or copying a register to memory.

PowerPC 使用了加载/存储（也成为 RISC）指令集，这意味着访问主存的惟一 时机就是将内存加载到寄存器或将寄存器中的内容复制到内存中时。

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Note that test1 must load and store the global errs value each time it is incremented, whereas test2 stores localerrs in a register and needs only a single instruction.

可以看到test1()中每次加法都需要读取和存储全局变量errs，而在test2()中，localerrs分配在寄存器上，只需要一条指令。

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