feat: Add JALR

pattonkan · Feb 13, 2024 · 4ad2bc4 · 4ad2bc4
1 parent 570ea7a
commit 4ad2bc4
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Showing 2 changed files with 21 additions and 7 deletions.
diff --git a/src/cpu.rs b/src/cpu.rs
@@ -127,9 +127,10 @@ pub fn exec_jal(cpu: &mut CPU, instr: u32) {
     cpu.pc = (cpu.pc as i32 + imm) as u32;
 }
 pub fn exec_jalr(cpu: &mut CPU, instr: u32) {
-    let imm = imm_j(instr) as i32;
+    let imm = imm_i(instr) as i32;
     cpu.xregs.regs[rd(instr) as usize] = cpu.pc + 4;
-    cpu.pc = (cpu.pc as i32 + imm) as u32;
+    // ignore the last 1 bit with 0xfffffffe
+    cpu.pc = (cpu.xregs.regs[rs1(instr) as usize] as i32).wrapping_add(imm) as u32 & 0xfffffffe;
 }
 pub fn exec_beq(cpu: &mut CPU, instr: u32) {}
 pub fn exec_bne(cpu: &mut CPU, instr: u32) {}

diff --git a/tests/cpu_test.rs b/tests/cpu_test.rs
@@ -9,12 +9,12 @@ mod tests {
     fn test_exec_lui() {
         let mut cpu_test = cpu::CPU::new();
 
-        // lui x5, 4
+        // lui x5, (4<<12)
         let instr: u32 = helper::set_u_type_instruction(4 << 12, 5, LUI as u8);
         cpu::exec_lui(&mut cpu_test, instr);
         assert_eq!(cpu_test.xregs.regs[5], 4 << 12);
 
-        // lui x5, -4
+        // lui x5, (-4<<12)
         let instr: u32 = helper::set_u_type_instruction(-4 << 12, 5, LUI as u8);
         cpu::exec_lui(&mut cpu_test, instr);
         assert_eq!(cpu_test.xregs.regs[5], (-4 << 12) as u32);
@@ -24,12 +24,12 @@ mod tests {
         let mut cpu_test = cpu::CPU::new();
 
         let ori_pc = cpu_test.pc;
-        // auipc x5, 4
+        // auipc x5, (4<<12)
         let instr: u32 = helper::set_u_type_instruction(4 << 12, 5, AUIPC as u8);
         cpu::exec_auipc(&mut cpu_test, instr);
         assert_eq!(cpu_test.xregs.regs[5], ori_pc + (4 << 12));
 
-        // auipc x5, -4
+        // auipc x5, (-4<<12)
         let instr: u32 = helper::set_u_type_instruction(-4 << 12, 5, AUIPC as u8);
         cpu::exec_auipc(&mut cpu_test, instr);
         assert_eq!(
@@ -39,6 +39,7 @@ mod tests {
     }
     #[test]
     fn test_exec_jal() {
+        // TODO add test case for imm is a negative number
         let mut cpu_test = cpu::CPU::new();
 
         let ori_pc = cpu_test.pc;
@@ -49,7 +50,19 @@ mod tests {
         assert_eq!(cpu_test.pc, ori_pc + 12);
     }
     #[test]
-    fn test_exec_jalr() {}
+    fn test_exec_jalr() {
+        // TODO add test case for imm is a negative number
+        let mut cpu_test = cpu::CPU::new();
+
+        let ori_pc = cpu_test.pc;
+        // set x1=3
+        helper::set_register_val(&mut cpu_test, 1, 3);
+        // jalr x5, 12
+        let instr: u32 = helper::set_i_type_instruction(12, 1, JALR as u8, 5);
+        cpu::exec_jalr(&mut cpu_test, instr);
+        assert_eq!(cpu_test.xregs.regs[5], ori_pc + 4);
+        assert_eq!(cpu_test.pc, (3 + 12) & 0xfffffffe);
+    }
     #[test]
     fn test_exec_beq() {}
     #[test]