如何在 MPLAB X 中使用 mips 汇编为每个宏调用创建唯一标签 [英] How can one create a unique label for each macro call using mips assembly in MPLAB X

问题描述

我有一个执行比较的宏，如果比较不正确，则跳转到宏的末尾.这是一个简化的例子:

I have a macro which performs a comparison, and jumps to the end of the macro if that comparison isn't true. Here is a simplified example:

.macro do_work_if_value_not_zero value
    li s0, value
    bne s0, zero, exit_label
    nop   

    // Do work

    exit_label:
.endm

然而，问题是我多次调用这个宏:

The issue however is that I call this macro several times like so:

do_work_if_value_not_zero 5
do_work_if_value_not_zero 3
do_work_if_value_not_zero 12

结果我收到以下错误:

错误:符号`exit_label'已经定义

Error: symbol `exit_label' is already defined

因为我从不多次使用相同的参数调用宏，所以我尝试使用参数名称与:"连接来创建一个唯一的标签，如下所示:

Because I never call the macro with the same parameter multiple times, I attempted to use the parameter name concatenated with a ':' to create a unique label like so:

.macro do_work_if_value_not_zero value
    li s0, value
    bne s0, zero, \value
    nop   

    // Do work

    \value:
.endm

但是这似乎不起作用，而且我收到了更多错误.

However this did not seem to work, and I received more errors.

因此我的问题是，如何为每个宏调用创建唯一的退出标签以避免此问题?

Thus my question is, how can one create a unique exit label for each macro call to avoid this issue?

推荐答案

大多数汇编器允许这样的局部标签:

Most assemblers allow local labels like this:

.macro do_work_if_value_not_zero 
    li s0, value
    bne s0, zero, 1f     # 1f means branch forward to the next label '1:'
    nop   

    // Do work

    1:
.endm

来自 MIPS 汇编器手册 此处:

From the MIPS assembler manual here:

生成的标签是单个数值 (1...255).参考一个生成的标签，立即放入 f(向前)或 a b(向后)在数字之后.该引用告诉汇编器查找最近生成的标签，对应于中的数字词汇向前或向后.

A generated label is a single numeric value (1...255). To reference a generated label, put an f (forward) or a b (backward) immediately after the digit. The reference tells the assembler to look for the nearest generated label that corresponds to the number in the lexically forward or backward direction.

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