我写了一个riscv 64模拟器，但是在分支指令的偏移量计算上有一个问题（尤其是bge）。
对我来说，当条件满足时，计算要添加到PC的偏移量的公式是：PC = PC+IMM;立即数摘自指令：这是我的C代码：

void BNE(unsigned long instr) {

unsigned long IMM1 = instr >>7 & 0b11111;
unsigned long IMM2 = instr >> 25 & 0b1111111;

unsigned long first = IMM1 & 0b1; // 11 eme bits IMM\[11\]  
unsigned long second = IMM1 >> 1 & 0b1111; // IMM\[4:1\]
unsigned long third = IMM2 & 0b111111;  //imm\[10:5\]   
unsigned long fourth = IMM2 >> 6 & 0b1; // IMM\[12\]

// after extract assemble :
unsigned long imm = second | third << 5 |  first <<7 | fourth << 9; // \<- I think here is the problem

}

当程序得到这个简单的程序代码：

// I have simplified the code :
00000000000100e8 \<init\>:

10130:  fd843783            ld  a5,-40(s0)

1018c:  fae7d2e3            bge a5,a4,10130 \<init+0x48\> # note that the condition is always met on my code

我得到了：0x 7a 2。
PC地址为：0x1018c
当我添加0x 1018 c到0x 7a 2，我得到：0x 1092 E有一个问题，但我不知道在哪里。我认为imm变量的提取有一些问题。
我试过修改imm变量的位移位和掩码。但是我没有任何运气。
我已经试过了：

unsigned long imm = second | third << 4 |  first << 5 | fourth << 6; // output wrong data
unsigned long imm = second | third << 6 |  first << 11 | fourth << 12; // output the same data as imm 
unsigned long imm = second | third << 5 |  first << 7 | fourth << 9; // actual version
unsigned long   imm = second | third <<  6 |  first << 7 | fourth <<8; // output the same data as imm