RISC-V M extension :定点乘法和除法。直接使用整数寄存器,不增加其他寄存器(减少硬件开销,指令数目,寄存器之间的拷贝延迟和线程的上下文,同时有利于编译调度)
The instructions in the A extension realize the RCsc memory model with a memory ordering annotation(注释), which comprises two bits on the static instruction: aq and rl.
A split organization provides a natural register file banking strategy, simplifying the provision of register file ports for superscalar implementations.
浮点乘加指令(FMA):accelerate the implementation of some floating-point library routines, and in general can improve the performance and accuracy of many algorithms.