主要是确定指令的opcode,RISC-V标准指令都是32位的,于是把指令的最低两位固定设置为11,来识别指令长度,于是opcode剩余的编码空间只有[6:2],在RISC-V通用指令集中,大部分编码空间已被占用,剩余四个编码空间可支持自定义指令拓展。 其中custom-2与custom-3是给未来的RV128保留的,将来的标准指令拓展会规避custom-0与...
那么问题就来了,既然 picorv32 自定义的指令也是 R-type 的,为什么 opcode 没有用 RISC-V 标准规定的 R-type: 0110011,而是用了自定义的 0001011 呢?我只能大胆猜测,这么做是为了提醒自己这部分 R-type 不是 RISC-V 的标准,在其他 RISC-V CPU 上执行这些指令就会报错:非法指令,所以找了一个还没有被用...
The acc instruction, identified by the operation code (opcode) 0001011, performs a multivariable sum-of-products operation using the eight values stored in the predefined registers as ACC inputs. The result of the operation is stored in the destination register specified by rd. When ACC is used...
0000011 --- XXXXX --- XXXXX 0001011 f7 rs2 rs f3 rd opcode Example:maskirq x1, x2 The processor starts with all interrupts disabled.An illegal instruction or bus error while the illegal instruction or bus error interrupt is disabled will cause the processor to halt.wait...
0000101 --- XXXXX --- XXXXX 0001011 f7 rs2 rs f3 rd opcode Example: timer x1, x2 Building a pure RV32I Toolchain TL;DR: Run the following commands to build the complete toolchain: make download-tools make -j$(nproc) build-tools The default settings in the riscv-tools build...
注:RISC-V ISA在32位指令集中提供了四组custom指令:custom0、custom1、custom2、custom3,它们的opcode分别为:0001011、1101011、1011011、1111011。 三、接口定义 注:Direction是针对E203 core的。 四、指令处理 指令的处理主要有以下几步: 1、E203内核先取指,译码,如果识别到是一条NICE指令,则通过request channel...
0000000 --- 000XX --- XXXXX 0001011 f7 rs2 qs f3 rd opcode Example: getq x5, q2 setq qd, rs This instruction copies the value from a general-purpose register to a q-register. 0000001 --- XXXXX --- 000XX 0001011 f7 rs2 rs f3 qd opcode Example...
void _builtin_riscv_acc(int *data); 测试函数: void test(int *data){ _builtin_riscv_acc(data); } Costom-0指令格式: |---| | 31~25 |24~20|19~15|14~12| 11~7 | 6~0 | |---| | 0000100|00000| rs1 | 010 |00000 |0001011| ...
0000100 --- 00000 --- XXXXX 0001011 f7 rs2 rs f3 rd opcode Example: waitirq x1 timer Reset the timer counter to a new value. The counter counts down clock cycles and triggers the timer interrupt when transitioning from 1 to 0. Setting the counter to zero disables the timer. The old...
0000010 --- 00000 --- 00000 0001011 f7 rs2 rs f3 rd opcode Example: retirq maskirq The "IRQ Mask" register contains a bitmask of masked (disabled) interrupts. This instruction writes a new value to the irq mask register and reads the old value. 0000011...