Date: 2018.9.7
1、参考：
https://community.arm.com/processors/f/discussions/3330/how-aarch32-bit-applications-will-be-supported-on-aarch64
https://community.arm.com/processors/f/discussions/7521/what-is-the-equivalent-instruction-for-qsub-in-armv8
https://community.arm.com/iot/embedded/f/discussions/124/how-to-implement-saturation-instructions-in-armv8-architecture?ReplySortBy=Votes&ReplySortOrder=Descending
2、armv8与aarch32指令集的重要差异
In AArch64, there are no SIMD or saturating arithmetic instructions which operate on general-purpose registers.Such operations use the NEON registers.
QADD,QSUB,SSAT，USAT等饱和指令在ARMv8中不支持，即没有通用寄存器的饱和指令。
ARM32中的SWP指令在ARMv8中也不支持。
THE END!