From 2e47ad73aead135ef9d14a17b1d522f9de0ff41d Mon Sep 17 00:00:00 2001
From: Konstantin Nazarov <mail@knazarov.com>
Date: Fri, 6 Dec 2024 21:39:01 +0000
Subject: [PATCH] Implement branches

---
 src/vm.cpp | 44 +++++++++++++++++++++++++++++---------------
 1 file changed, 29 insertions(+), 15 deletions(-)

diff --git a/src/vm.cpp b/src/vm.cpp
index ca6ca54..da7c793 100644
--- a/src/vm.cpp
+++ b/src/vm.cpp
@@ -136,22 +136,36 @@ void eval(uint8_t* memory, size_t memory_size) {
                 }
                 break;
             }
-            case 0x63: { // B-type (BEQ, BNE)
-                imm = ((instr >> 7) & 0x1E) | ((instr >> 20) & 0x7E0) |
-                      ((instr >> 19) & 0x800) | ((instr >> 31) << 12);
-                imm = sign_extend(imm, 13); // Sign-extend 13-bit immediate
-                if (funct3 == 0x0) { // BEQ
-                    if (registers[rs1] == registers[rs2]) {
-                        pc += imm - 4; // Offset PC (adjust for pre-increment)
-                    }
-                } else if (funct3 == 0x1) { // BNE
-                    if (registers[rs1] != registers[rs2]) {
-                        pc += imm - 4; // Offset PC
-                    }
-                } else {
-                    throw std::runtime_error("Unknown B-type instruction");
+            case 0x63: { // B-type (branches)
+              imm = ((instr >> 7) & 0x1E) | ((instr >> 20) & 0x7E0) |
+                ((instr >> 19) & 0x800) | ((instr >> 31) << 12);
+              imm = sign_extend(imm, 13); // Sign-extend 13-bit immediate
+              if (funct3 == 0x0) { // BEQ
+                if (registers[rs1] == registers[rs2]) {
+                  pc += imm - 4; // Offset PC (adjust for pre-increment)
                 }
-                break;
+              } else if (funct3 == 0x1) { // BNE
+                if (registers[rs1] != registers[rs2]) {
+                  pc += imm - 4; // Offset PC
+                }
+              } else if (funct3 == 0x4) { // BLT
+                if (static_cast<int32_t>(registers[rs1]) <
+                    static_cast<int32_t>(registers[rs2])) {
+                  pc += imm - 4;
+                }
+              } else if (funct3 == 0x5) { // BGE
+                if (static_cast<int32_t>(registers[rs1]) >=
+                    static_cast<int32_t>(registers[rs2])) {
+                  pc += imm - 4;
+                }
+              } else if (funct3 == 0x6) { // BLTU
+                if (registers[rs1] < registers[rs2]) pc += imm - 4;
+              } else if (funct3 == 0x7) { // BGEU
+                if (registers[rs1] >= registers[rs2]) pc += imm - 4;
+              } else {
+                throw std::runtime_error("Unknown B-type instruction");
+              }
+              break;
             }
             case 0x03: { // I-type (loads)
                 imm = sign_extend(instr >> 20, 12); // Extract 12-bit immediate