在 ARM C 调用约定中保存哪些寄存器? [英] What registers to save in the ARM C calling convention?
问题描述
自从我上次编写 arm 汇编程序以来已经有一段时间了，我对细节有点生疏了.如果我从 arm 调用一个 C 函数，我只需要担心保存 r0-r3 和 lr，对吗?
It's been a while since I last coded arm assembler and I'm a little rusty on the details. If I call a C function from arm, I only have to worry about saving r0-r3 and lr, right?
如果 C 函数使用任何其他寄存器，它是否负责将这些寄存器保存在堆栈中并恢复它们?换句话说，编译器将生成代码来为 C 函数执行此操作.
If the C function uses any other registers, is it responsible for saving those on the stack and restoring them? In other words, the compiler would generate code to do this for C functions.
例如，如果我在汇编函数中使用 r10，我不必将其值压入堆栈或内存，并在 C 调用后弹出/恢复它，对吗?
For example if I use r10 in an assembler function, I don't have to push its value on the stack, or to memory, and pop/restore it after a C call, do I?
这是针对 arm-eabi-gcc 4.3.0.
This is for arm-eabi-gcc 4.3.0.
推荐答案
这取决于 ABI 针对您正在编译的平台.在 Linux 上，有两个 ARM ABI；旧的和新的.AFAIK，新的(EABI)实际上是ARM的AAPCS.完整的 EABI 定义目前位于 这里在 ARM 上信息中心.
It depends on the ABI for the platform you are compiling for. On Linux, there are two ARM ABIs; the old one and the new one. AFAIK, the new one (EABI) is in fact ARM's AAPCS. The complete EABI definitions currently live here on ARM's infocenter.
- r0-r3 是参数和暂存寄存器；r0-r1 也是结果寄存器
- r4-r8 是被调用者保存寄存器
- r9 可能是一个被调用者保存寄存器(在 AAPCS 的某些变体上它是一个特殊寄存器)
- r10-r11 是被调用者保存寄存器
- r12-r15 是特殊寄存器
- r0-r3 are the argument and scratch registers; r0-r1 are also the result registers
- r4-r8 are callee-save registers
- r9 might be a callee-save register or not (on some variants of AAPCS it is a special register)
- r10-r11 are callee-save registers
- r12-r15 are special registers
被调用者必须保存被调用者保存的寄存器(与调用者保存寄存器相反，调用者保存寄存器)；所以，如果这是你正在使用的 ABI，你不必在调用另一个函数之前保存 r10(另一个函数负责保存它).
A callee-save register must be saved by the callee (in opposition to a caller-save register, where the caller saves the register); so, if this is the ABI you are using, you do not have to save r10 before calling another function (the other function is responsible for saving it).
您使用的编译器没有区别；特别是 gcc 可以为几个不同的 ABI 配置，甚至可以在命令行上进行更改.查看它生成的序言/结尾代码并不是那么有用，因为它是为每个函数量身定制的，编译器可以使用其他方式来保存寄存器(例如，将它保存在函数).
Which compiler you are using makes no difference; gcc in particular can be configured for several different ABIs, and it can even be changed on the command line. Looking at the prologue/epilogue code it generates is not that useful, since it is tailored for each function and the compiler can use other ways of saving a register (for instance, saving it in the middle of a function).
术语:callee-save"是non-volatile"或call-preserved"的同义词:什么是被调用者和调用者保存的寄存器?
进行函数调用时，您可以假设 r4-r11(可能除了 r9)中的值在(调用保留)之后仍然存在，但不适用于 r0-r3(调用破坏/易失性).
Terminology: "callee-save" is a synonym for "non-volatile" or "call-preserved": What are callee and caller saved registers?
When making a function call, you can assume that the values in r4-r11 (except maybe r9) are still there after (call-preserved), but not for r0-r3 (call-clobbered / volatile).
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