BEQ get wrong adrress because we may ignore the priority between "<<" and "+"

[XuDongZe]

For inst.s, just the first one inst our teacher gave us.
The PC of beq is 0x20,and the ins is 0x12320001,so we will get a imm32 = 0x01 after decode and extend;
Next if beq is ok, we will get a new PC = PC + 4  + imm32<<2. So there is a trap in the priority between "<< " and "+":    the priority of "+" is higher than "<<".
If we write our code like this,we will get a wrong adress 0x94.( Now the PC is 0x20,io.pc_imm_32 is 0x01)
pc_b 		:= pc + 4  + io.pc_imm32 << 2
This is because the priority of "+" is higher than "<<",so we first get pc+4+io.pc_imm32, which is 0x20+0x04+0x01 = 0x25 ( for the demical is 37 ) ;then we let 0x25<<2,so we get a  wrong address 0x94(for the demical is 37*4=148).

But that's not we want. we just want imm32<<2 first, so we can just do , add a bracket like this:
pc_b := pc + 4 + (io.pc_imm32 << 2)

[zavs]

pc_b := pc + 4  + io.pc_imm32 << 2

equals

pc_b := (pc + 4 + io.pc_imm32) << 2

ADD operation has higher priority than SHIFT