implemented instructions beq, bne, blt, bge, bltu, bgeu, improved unsigned number handling

riscemu/CPU.py

@@ -178,10 +178,20 @@ class CPU:
         INS_NOT_IMPLEMENTED(ins)
 
     def instruction_beq(self, ins: 'LoadedInstruction'):
-        INS_NOT_IMPLEMENTED(ins)
+        ASSERT_LEN(ins.args, 3)
+        reg1 = ins.get_reg(0)
+        reg2 = ins.get_reg(1)
+        dest = ins.get_imm(2)
+        if self.regs.get(reg1) == self.regs.get(reg2):
+            self.pc = dest
 
     def instruction_bne(self, ins: 'LoadedInstruction'):
-        INS_NOT_IMPLEMENTED(ins)
+        ASSERT_LEN(ins.args, 3)
+        reg1 = ins.get_reg(0)
+        reg2 = ins.get_reg(1)
+        dest = ins.get_imm(2)
+        if self.regs.get(reg1) != self.regs.get(reg2):
+            self.pc = dest
 
     def instruction_blt(self, ins: 'LoadedInstruction'):
         ASSERT_LEN(ins.args, 3)
@@ -192,13 +202,28 @@ class CPU:
             self.pc = dest
 
     def instruction_bge(self, ins: 'LoadedInstruction'):
-        INS_NOT_IMPLEMENTED(ins)
+        ASSERT_LEN(ins.args, 3)
+        reg1 = ins.get_reg(0)
+        reg2 = ins.get_reg(1)
+        dest = ins.get_imm(2)
+        if self.regs.get(reg1) >= self.regs.get(reg2):
+            self.pc = dest
 
     def instruction_bltu(self, ins: 'LoadedInstruction'):
-        INS_NOT_IMPLEMENTED(ins)
+        ASSERT_LEN(ins.args, 3)
+        reg1 = to_unsigned(ins.get_reg(0))
+        reg2 = to_unsigned(ins.get_reg(1))
+        dest = ins.get_imm(2)
+        if self.regs.get(reg1) < self.regs.get(reg2):
+            self.pc = dest
 
     def instruction_bgeu(self, ins: 'LoadedInstruction'):
-        INS_NOT_IMPLEMENTED(ins)
+        ASSERT_LEN(ins.args, 3)
+        reg1 = to_unsigned(ins.get_reg(0))
+        reg2 = to_unsigned(ins.get_reg(1))
+        dest = ins.get_imm(2)
+        if self.regs.get(reg1) >= self.regs.get(reg2):
+            self.pc = dest
 
     def instruction_j(self, ins: 'LoadedInstruction'):
         INS_NOT_IMPLEMENTED(ins)

riscemu/helpers.py

@@ -35,10 +35,21 @@ def int_from_bytes(bytes, unsigned=False):
     for b in bytes:
         num = num << 8
         num += b
-    sign = num >> (len(bytes) * 8 - 1)
-    if sign and not unsigned:
-        return num - 2 ** (8 * len(bytes))
-    return num
+
+    if unsigned:
+        return num
+
+    return to_signed(num)
+
+
+def to_unsigned(num: int, bytes=4):
+    if num < 0:
+        return 2**(bytes * 8) - num
+
+
+def to_signed(num: int, bytes=4):
+    if num >> (bytes * 8 - 1):
+        return num - 2 ** (8 * bytes)
 
 
 # Colors