GCC ARM的-mfloat-abi选项

Question

GCC的ARM编译选项-mfloat-abi=name，其中soft和softfp有什么区别？

下面是GCC ARM的解释，我的理解是：

hard表示编译成浮点运算指令，一般是CPU内带有支持浮点运算的FPU

soft表示软件实现浮点运算，一般是在glibc里有软件的方法实现浮点运算（以前好像有种FPE的方法，在内核里面实现浮点运算，因为性能低下，现在很少使用）

softfp按照他的翻译是，虽然生成了浮点指定，但是仍然使用软浮点运算的调用规则？ 什么意思。。

-mfloat-abi=name
Specifies which floating-point ABI to use. Permissible values are: `soft', `softfp' and `hard'.
Specifying `soft' causes GCC to generate output containing library calls for floating-point operations. `softfp' allows the generation of code using hardware floating-point instructions, but still uses the soft-float calling conventions. `hard' allows generation of floating-point instructions and uses FPU-specific calling conventions.

The default depends on the specific target configuration. Note that the hard-float and soft-float ABIs are not link-compatible; you must compile your entire program with the same ABI, and link with a compatible set of libraries.

Answer 1

> Permissible values are: `soft', `softfp' and `hard'.

Answer 2

GCC的ARM编译选项-mfloat-abi=name，其中哪有soft和softfp

Answer 3

> FPU-specific calling conventions

不熟悉arm，但看起来arm的FPU有特定的调用约定。