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