relative jumps can now jump 16 insns in both directions

ASM-SYNTAX.md

@@ -65,8 +65,10 @@ mov
 	'MOV' register ',' register
 
 jmp
-	'JMP' digit(-3, 7)
-	'JMPC' digit(-3, 7)
+	'JMP' digit(-16, -1)
+	'JMP' digit(1, 16)
+	'JMPC' digit(-16, -1)
+	'JMPC' digit(1, 16)
 	'AJMP' register
 	'AJMPC' register
 

DESIGN.md

@@ -31,7 +31,7 @@ ALU operations.
 
 ```
 +—+—+—+—+—+—+—+—+
-|0|0|M|0|0|0|0|0|
+|1|0|0|0|1|0|0|M|
 +—+—+—+—+—+—+—+—+
 ```
 
@@ -41,46 +41,36 @@ pointed to by lower half or `R1`. Data is written to / read from `R0`.
 `M` — `0` for load (read byte from memory and put in ALU register),
 `1` for store (read byte from ALU register and put in memory).
 
-### LOAD IMMEDIATE
+### NEAR JUMP
 
 ```
 +—+—+—+—+———————+
-|0|1|H|R|I I I I|
+|0|0|D|C|O O O O|
 +—+—+—+—+———————+
 ```
 
-`H` — `0` to use 4 least significant bits, `1` to use 4 most
-significant bits.
-
-`R` — `0` to use `R0` register, `1` to use `R1` register.
-
-`IIII` — 4-bit immediate value.
-
-### NEAR JUMP BACKWARD
-
-```
-+—+—+—+—+—+—+———+
-|1|0|0|0|1|C|O O|
-+—+—+—+—+—+—+———+
-```
+`D` — jump direction. `0` to jump forward and `1` to jump backward.
 
 `C` — `0` to ignore carry flag and jump unconditionally,
 `1` to only jump if carry flag is set.
 
-`OO` — jump offset.
+`OOOO` — jump offset. Actual jump offset is higher than encoded
+offset by 1, since offset of 0 doesn't make any sense.
 
-### NEAR JUMP FORWARD
+### LOAD IMMEDIATE
 
 ```
-+—+—+—+—+—+—————+
-|1|0|0|1|C|O O O|
-+—+—+—+—+—+—————+
++—+—+—+—+———————+
+|0|1|H|R|I I I I|
++—+—+—+—+———————+
 ```
 
-`C` — `0` to ignore carry flag and jump unconditionally,
-`1` to only jump if carry flag is set.
+`H` — `0` to use 4 least significant bits, `1` to use 4 most
+significant bits.
 
-`OOO` — jump offset.
+`R` — `0` to use `R0` register, `1` to use `R1` register.
+
+`IIII` — 4-bit immediate value.
 
 ### FAR JUMP
 

acceptance-tests/add_four_ints.pgm

@@ -11,5 +11,5 @@ P2
 117 # MOV R1.h, 5
 228 # ADD
 95  # MOV R1.l, 0xf
-32  # STORE
+137 # STORE
 245 # HALT

toy_cpu_4bit/src/assembler.rs

@@ -9,7 +9,7 @@ use std::{
     num,
     ops::RangeInclusive,
 };
-use ux::{u2, u3, u4};
+use ux::{u3, u4};
 
 type InstructionDecoder = fn(&str, &Regex) -> Result<Instruction, AssemblerErrorKind>;
 
@@ -429,13 +429,15 @@ fn parse_jmp_impl(
     use_carry: bool,
 ) -> Result<Instruction, AssemblerErrorKind> {
     match parse_i8(regex.captures(line).unwrap().get(1).unwrap().as_str())? {
-        x @ -3..=-1 => Ok(Instruction::NearJumpBackward {
+        x @ -16..=-1 => Ok(Instruction::NearJump {
             use_carry,
-            offset: u2::new(-x as u8),
+            offset: u4::new(-(x + 1) as u8),
+            forward: false,
         }),
-        x @ 0..=7 => Ok(Instruction::NearJumpForward {
+        x @ 1..=16 => Ok(Instruction::NearJump {
             use_carry,
-            offset: u3::new(x as u8),
+            offset: u4::new((x - 1) as u8),
+            forward: true,
         }),
         x => Err(AssemblerErrorKind::invalid_relative_jump_offset(x)),
     }
@@ -537,7 +539,7 @@ mod tests {
     };
     use lazy_static::lazy_static;
     use std::fmt::{Binary, Display, LowerHex, Octal};
-    use ux::{u2, u3, u4};
+    use ux::{u3, u4};
 
     lazy_static! {
         static ref ASM: Assembler = Assembler::new();
@@ -684,53 +686,25 @@ mod tests {
     }
 
     #[test]
-    fn asm_line_jmp() {
-        for i in 0..=7u8 {
-            for j in PrintIntegers::new(i) {
-                assert_eq!(
-                    ASM.line_to_insn(&format!("JMP {}", j)).unwrap(),
-                    Instruction::NearJumpForward {
-                        use_carry: false,
-                        offset: u3::new(i)
-                    }
-                )
-            }
-        }
-        for i in 1..=3u8 {
-            for j in PrintIntegers::new(i) {
-                assert_eq!(
-                    ASM.line_to_insn(&format!("JMP -{}", j)).unwrap(),
-                    Instruction::NearJumpBackward {
-                        use_carry: false,
-                        offset: u2::new(i)
-                    }
-                )
-            }
-        }
-    }
-
-    #[test]
-    fn asm_line_jmpc() {
-        for i in 0..=7u8 {
-            for j in PrintIntegers::new(i) {
-                assert_eq!(
-                    ASM.line_to_insn(&format!("JMPC {}", j)).unwrap(),
-                    Instruction::NearJumpForward {
-                        use_carry: true,
-                        offset: u3::new(i)
-                    }
-                )
-            }
-        }
-        for i in 1..=3u8 {
-            for j in PrintIntegers::new(i) {
-                assert_eq!(
-                    ASM.line_to_insn(&format!("JMPC -{}", j)).unwrap(),
-                    Instruction::NearJumpBackward {
-                        use_carry: true,
-                        offset: u2::new(i)
-                    }
-                )
+    fn asm_line_jmp_jmpc() {
+        for (insn, use_carry, sign, forward) in [
+            ("JMP", false, "", true),
+            ("JMP", false, "-", false),
+            ("JMPC", true, "", true),
+            ("JMPC", true, "-", false),
+        ] {
+            for i in 0..=15u8 {
+                for j in PrintIntegers::new(i + 1) {
+                    assert_eq!(
+                        ASM.line_to_insn(&format!("{} {}{}", insn, sign, j))
+                            .unwrap(),
+                        Instruction::NearJump {
+                            use_carry,
+                            offset: u4::new(i),
+                            forward,
+                        }
+                    )
+                }
             }
         }
     }

toy_cpu_4bit/src/cpu.rs

@@ -69,15 +69,15 @@ impl Cpu {
         self.IP += Wrapping(1);
     }
 
-    fn near_jump(&mut self, use_carry: bool, forward: bool, offset: u8) {
+    fn near_jump(&mut self, forward: bool, use_carry: bool, offset: u4) {
         if use_carry && !self.C {
             self.IP += Wrapping(1);
             return;
         }
         if forward {
-            self.IP += Wrapping(offset);
+            self.IP += Wrapping(u8::from(offset) + 1);
         } else {
-            self.IP -= Wrapping(offset);
+            self.IP -= Wrapping(u8::from(offset) + 1);
         }
     }
 
@@ -331,13 +331,12 @@ impl Cpu {
         match insn {
             Instruction::Load => self.load(),
             Instruction::Store => self.store(),
+            Instruction::NearJump {
+                forward,
+                use_carry,
+                offset,
+            } => self.near_jump(forward, use_carry, offset),
             Instruction::LoadImmediate { low, reg, val } => self.load_imm(low, reg, val),
-            Instruction::NearJumpBackward { use_carry, offset } => {
-                self.near_jump(use_carry, false, u8::from(offset))
-            }
-            Instruction::NearJumpForward { use_carry, offset } => {
-                self.near_jump(use_carry, true, u8::from(offset))
-            }
             Instruction::FarJump { reg, use_carry } => self.far_jump(use_carry, reg),
             Instruction::CmpEqual => self.cmp_equal(),
             Instruction::CmpGreater => self.cmp_gt(),
@@ -408,8 +407,74 @@ mod tests {
     use std::num::Wrapping;
 
     #[test]
+    fn insn_near_jump_backward_unconditional() {
+        let mut cpu = Cpu::new(&[]);
+        cpu.code[20] = 0b00100010;
+        cpu.IP = Wrapping(20);
+        {
+            assert!(!cpu.step()); // CPU has not halted
+            assert_eq!(cpu.IP.0, 17); // instruction pointer has advanced
+            assert!(!cpu.C); // carry is not affected
+        }
+    }
+
+    #[test]
+    fn insn_near_jump_backward_conditional_must() {
+        let mut cpu = Cpu::new(&[]);
+        cpu.code[40] = 0b00110010;
+        cpu.IP = Wrapping(40);
+        cpu.C = true;
+        {
+            assert!(!cpu.step()); // CPU has not halted
+            assert_eq!(cpu.IP.0, 37); // instruction pointer had advanced
+            assert!(cpu.C); // carry is not affected
+        }
+    }
+
+    #[test]
+    fn insn_near_jump_backward_conditional_must_not() {
+        let mut cpu = Cpu::new(&[]);
+        cpu.code[40] = 0b00110010;
+        cpu.IP = Wrapping(40);
+        {
+            assert!(!cpu.step()); // CPU has not halted
+            assert_eq!(cpu.IP.0, 41); // instruction pointer had advanced
+            assert!(!cpu.C); // carry is not affected
+        }
+    }
+
+    #[test]
+    fn insn_near_jump_forward_unconditional() {
+        let mut cpu = Cpu::new(&[0b00000010]);
+        {
+            assert!(!cpu.step()); // CPU has not halted
+            assert_eq!(cpu.IP.0, 0b11); // instruction pointer had advanced
+            assert!(!cpu.C); // carry is not affected
+        }
+    }
+    #[test]
+    fn insn_near_jump_forward_conditional_must() {
+        let mut cpu = Cpu::new(&[0b00010010]);
+        cpu.C = true;
+        {
+            assert!(!cpu.step()); // CPU has not halted
+            assert_eq!(cpu.IP.0, 0b11); // instruction pointer had advanced
+            assert!(cpu.C); // carry is not affected
+        }
+    }
+    #[test]
+    fn insn_near_jump_forward_conditional_must_not() {
+        let mut cpu = Cpu::new(&[0b00010010]);
+        {
+            assert!(!cpu.step()); // CPU has not halted
+            assert_eq!(cpu.IP.0, 1); // instruction pointer had advanced
+            assert!(!cpu.C); // carry is not affected
+        }
+    }
+
+    #[test]
     fn insn_load() {
-        let mut cpu = Cpu::new(&[0b00000000]);
+        let mut cpu = Cpu::new(&[0b10001000]);
         cpu.R1 = Wrapping(0x2);
         cpu.data[0x2] = 0x77;
         {
@@ -422,7 +487,7 @@ mod tests {
 
     #[test]
     fn insn_load_ignores_high_order_bytes_in_address() {
-        let mut cpu = Cpu::new(&[0b00000000]);
+        let mut cpu = Cpu::new(&[0b10001000]);
         cpu.R1 = Wrapping(0x72);
         cpu.data[0x2] = 0x77;
         {
@@ -435,7 +500,7 @@ mod tests {
 
     #[test]
     fn insn_store() {
-        let mut cpu = Cpu::new(&[0b00100000]);
+        let mut cpu = Cpu::new(&[0b10001001]);
         cpu.R0 = Wrapping(0x12);
         cpu.R1 = Wrapping(0x3);
         {
@@ -448,7 +513,7 @@ mod tests {
 
     #[test]
     fn insn_store_ignores_high_order_bytes_in_address() {
-        let mut cpu = Cpu::new(&[0b00100000]);
+        let mut cpu = Cpu::new(&[0b10001001]);
         cpu.R0 = Wrapping(0x12);
         cpu.R1 = Wrapping(0xD3);
         {
@@ -461,7 +526,7 @@ mod tests {
 
     #[test]
     fn insn_store_load() {
-        let mut cpu = Cpu::new(&[0b00100000, 0b00000000]);
+        let mut cpu = Cpu::new(&[0b10001001, 0b10001000]);
         {
             cpu.R0 = Wrapping(0x44);
             cpu.R1 = Wrapping(0x1);
@@ -514,74 +579,6 @@ mod tests {
     }
 
     #[test]
-    fn insn_near_jump_backward_unconditional() {
-        let mut cpu = Cpu::new(&[]);
-        cpu.code[20] = 0b10001010;
-        cpu.IP = Wrapping(20);
-        {
-            assert!(!cpu.step()); // CPU has not halted
-            assert_eq!(cpu.IP.0, 18); // instruction pointer had advanced
-            assert!(!cpu.C); // carry is not affected
-        }
-    }
-
-    #[test]
-    fn insn_near_jump_backward_conditional_must() {
-        let mut cpu = Cpu::new(&[]);
-        cpu.code[40] = 0b10001110;
-        cpu.IP = Wrapping(40);
-        cpu.C = true;
-        {
-            assert!(!cpu.step()); // CPU has not halted
-            assert_eq!(cpu.IP.0, 38); // instruction pointer had advanced
-            assert!(cpu.C); // carry is not affected
-        }
-    }
-
-    #[test]
-    fn insn_near_jump_backward_conditional_must_not() {
-        let mut cpu = Cpu::new(&[]);
-        cpu.code[40] = 0b10001110;
-        cpu.IP = Wrapping(40);
-        {
-            assert!(!cpu.step()); // CPU has not halted
-            assert_eq!(cpu.IP.0, 41); // instruction pointer had advanced
-            assert!(!cpu.C); // carry is not affected
-        }
-    }
-
-    #[test]
-    fn insn_near_jump_forward_unconditional() {
-        let mut cpu = Cpu::new(&[0b10010101]);
-        {
-            assert!(!cpu.step()); // CPU has not halted
-            assert_eq!(cpu.IP.0, 0b101); // instruction pointer had advanced
-            assert!(!cpu.C); // carry is not affected
-        }
-    }
-
-    #[test]
-    fn insn_near_jump_forward_conditional_must() {
-        let mut cpu = Cpu::new(&[0b10011011]);
-        cpu.C = true;
-        {
-            assert!(!cpu.step()); // CPU has not halted
-            assert_eq!(cpu.IP.0, 0b011); // instruction pointer had advanced
-            assert!(cpu.C); // carry is not affected
-        }
-    }
-
-    #[test]
-    fn insn_near_jump_forward_conditional_must_not() {
-        let mut cpu = Cpu::new(&[0b10011011]);
-        {
-            assert!(!cpu.step()); // CPU has not halted
-            assert_eq!(cpu.IP.0, 1); // instruction pointer had advanced
-            assert!(!cpu.C); // carry is not affected
-        }
-    }
-
-    #[test]
     fn insn_far_jump_unconditional_r0() {
         let mut cpu = Cpu::new(&[0b10000000]);
         cpu.R0 = Wrapping(0xA0);

toy_cpu_4bit/src/instruction.rs

@@ -1,7 +1,7 @@
 // SPDX-License-Identifier: MIT
 // Copyright Murad Karammaev, Nikita Kuzmin
 
-use ux::{u2, u3, u4};
+use ux::{u3, u4};
 
 #[derive(Debug, PartialEq, Clone)]
 pub enum Register {
@@ -19,19 +19,16 @@ pub enum ShiftMode {
 pub enum Instruction {
     Load,
     Store,
+    NearJump {
+        forward: bool,
+        use_carry: bool,
+        offset: u4,
+    },
     LoadImmediate {
         low: bool,
         reg: Register,
         val: u4,
     },
-    NearJumpBackward {
-        use_carry: bool,
-        offset: u2,
-    },
-    NearJumpForward {
-        use_carry: bool,
-        offset: u3,
-    },
     FarJump {
         reg: Register,
         use_carry: bool,
@@ -90,8 +87,13 @@ pub enum Instruction {
 
 pub fn decode(insn: u8) -> Instruction {
     match insn {
-        0b00000000 => Instruction::Load,
-        0b00100000 => Instruction::Store,
+        0b00000000..=0b00111111 => Instruction::NearJump {
+            forward: insn & 0b00100000 == 0,
+            use_carry: insn & 0b00010000 != 0,
+            offset: u4::new(insn & 0b00001111),
+        },
+        0b10001000 => Instruction::Load,
+        0b10001001 => Instruction::Store,
         0b01000000..=0b01111111 => Instruction::LoadImmediate {
             low: insn & 0b00100000 == 0,
             reg: if insn & 0b00010000 == 0 {
@@ -101,14 +103,6 @@ pub fn decode(insn: u8) -> Instruction {
             },
             val: u4::new(insn & 0b00001111),
         },
-        0b10001000..=0b10001111 => Instruction::NearJumpBackward {
-            use_carry: insn & 0b00000100 != 0,
-            offset: u2::new(insn & 0b00000011),
-        },
-        0b10010000..=0b10011111 => Instruction::NearJumpForward {
-            use_carry: insn & 0b00001000 != 0,
-            offset: u3::new(insn & 0b00000111),
-        },
         0b10000000..=0b10000011 => Instruction::FarJump {
             reg: if insn & 0b00000010 == 0 {
                 Register::R0
@@ -222,8 +216,24 @@ pub fn decode(insn: u8) -> Instruction {
 
 pub fn encode(insn: Instruction) -> u8 {
     match insn {
-        Instruction::Load => 0b00000000,
-        Instruction::Store => 0b00100000,
+        Instruction::Load => 0b10001000,
+        Instruction::Store => 0b10001001,
+        Instruction::NearJump {
+            forward,
+            use_carry,
+            offset,
+        } => {
+            let mut ret = 0u8;
+            ret |= match forward {
+                true => 0,
+                false => 0b00100000,
+            };
+            ret |= match use_carry {
+                true => 0b00010000,
+                false => 0,
+            };
+            ret | u8::from(offset)
+        }
         Instruction::LoadImmediate { low, reg, val } => {
             let mut ret = 0b01000000u8;
             ret |= match low {
@@ -236,14 +246,6 @@ pub fn encode(insn: Instruction) -> u8 {
             };
             ret | u8::from(val)
         }
-        Instruction::NearJumpBackward { use_carry, offset } => match use_carry {
-            false => 0b10001000 | u8::from(offset),
-            true => 0b10001100 | u8::from(offset),
-        },
-        Instruction::NearJumpForward { use_carry, offset } => match use_carry {
-            false => 0b10010000 | u8::from(offset),
-            true => 0b10011000 | u8::from(offset),
-        },
         Instruction::FarJump { reg, use_carry } => match reg {
             Register::R0 => 0b10000000 | if use_carry { 1 } else { 0 },
             Register::R1 => 0b10000010 | if use_carry { 1 } else { 0 },