1 files changed, 90 insertions, 0 deletions
diff --git a/usr.bin/oemu/cpu.c b/usr.bin/oemu/cpu.c
index 9b8c622..5689953 100644
--- a/usr.bin/oemu/cpu.c
+++ b/usr.bin/oemu/cpu.c
@@ -123,6 +123,81 @@ cpu_add(struct oemu_cpu *cpu, inst_t *inst)
 }
 
 /*
+ * Decode the INST_SUB instruction
+ *
+ * @cpu: CPU that is executing
+ * @inst: Instruction dword
+ */
+static void
+cpu_sub(struct oemu_cpu *cpu, inst_t *inst)
+{
+    struct cpu_regs *regs = &cpu->regs;
+    imm_t imm;
+
+    if (inst->rd > NELEM(regs->xreg)) {
+        printf("bad register operand for 'sub'\n");
+        return;
+    }
+
+    imm = regs->xreg[inst->rd];
+    regs->xreg[inst->rd] -= inst->imm;
+    printf("%d - %d -> X%d, new=%d\n",
+        imm, inst->imm, inst->rd, regs->xreg[inst->rd]);
+}
+
+/*
+ * Decode the INST_MUL instruction
+ *
+ * @cpu: CPU that is executing
+ * @inst: Instruction dword
+ */
+static void
+cpu_mul(struct oemu_cpu *cpu, inst_t *inst)
+{
+    struct cpu_regs *regs = &cpu->regs;
+    imm_t imm;
+
+    if (inst->rd > NELEM(regs->xreg)) {
+        printf("bad register operand for 'mul'\n");
+        return;
+    }
+
+    imm = regs->xreg[inst->rd];
+    regs->xreg[inst->rd] *= inst->imm;
+    printf("%d * %d -> X%d, new=%d\n",
+        imm, inst->imm, inst->rd, regs->xreg[inst->rd]);
+}
+
+/*
+ * Decode the INST_DIV instruction
+ *
+ * @cpu: CPU that is executing
+ * @inst: Instruction dword
+ */
+static void
+cpu_div(struct oemu_cpu *cpu, inst_t *inst)
+{
+    struct cpu_regs *regs = &cpu->regs;
+    imm_t imm;
+
+    if (inst->rd > NELEM(regs->xreg)) {
+        printf("bad register operand for 'div'\n");
+        return;
+    }
+
+    imm = regs->xreg[inst->rd];
+    if (imm == 0) {
+        /* TODO: Some sort of interrupt */
+        printf("** DIVIDE BY ZERO **\n");
+        return;
+    }
+
+    regs->xreg[inst->rd] /= inst->imm;
+    printf("%d / %d -> X%d, new=%d\n",
+        imm, inst->imm, inst->rd, regs->xreg[inst->rd]);
+}
+
+/*
  * Reset a CPU to a default state
  */
 void
@@ -161,6 +236,21 @@ cpu_kick(struct oemu_cpu *cpu, struct sysmem *mem)
         case INST_ADD:
             cpu_add(cpu, inst);
             break;
+        case INST_SUB:
+            cpu_sub(cpu, inst);
+            break;
+        case INST_MUL:
+            cpu_mul(cpu, inst);
+            break;
+        case INST_DIV:
+            cpu_div(cpu, inst);
+            break;
+        }
+
+        /* Is this a halt instruction? */
+        if (inst->opcode == INST_HLT) {
+            printf("HALTED\n");
+            break;
         }
 
         if (regs->ip >= MEMORY_SIZE) {