2 files changed, 21 insertions, 8 deletions

diff --git a/src/fvm.c b/src/fvm.c
index 858bd4a..6326dc8 100644
--- a/src/fvm.c
+++ b/src/fvm.c
@@ -10,6 +10,7 @@ int fvm_init(struct fvm *vm, void *code, int64_t stack_size) {
   vm->sp = (fvm_word_t)(stack_vm + stack_size);
   vm->bp = vm->sp;
   vm->pc = (fvm_word_t)code;
+  vm->rv = 0;
   return 1;
 }
 
@@ -74,14 +75,15 @@ void fvm_store8(struct fvm *vm, fvm_word_t addr, int8_t value) {
 }
 
 
-int fvm_execute(struct fvm *vm) {
+int64_t fvm_execute(struct fvm *vm) {
   fvm_word_t a, b, c;
   fvm_float_t x, y, z;
   while (1) {
     enum fvm_op op = (enum fvm_op)(uint8_t)fvm_load8(vm, vm->pc);
     switch (op) {
     case FVM_OP_SP:
-      fvm_push(vm, vm->sp);
+      a = vm->sp;
+      fvm_push(vm, a);
       vm->pc++;
       break;
     case FVM_OP_SSP:
@@ -96,6 +98,15 @@ int fvm_execute(struct fvm *vm) {
       vm->bp = fvm_pop(vm);
       vm->pc++;
       break;
+    case FVM_OP_RV:
+      a = vm->rv;
+      fvm_push(vm, a);
+      vm->pc++;
+      break;
+    case FVM_OP_SRV:
+      vm->rv = fvm_pop(vm);
+      vm->pc++;
+      break;
     case FVM_OP_PC:
       fvm_push(vm, vm->pc);
       vm->pc++;
@@ -410,8 +421,7 @@ int fvm_execute(struct fvm *vm) {
       vm->pc++;
       break;
     case FVM_OP_EXIT:
-      a = fvm_pop(vm);
-      return a;
+      return vm->rv;
     default:
       fprintf(stderr, "unknown opcode.\n");
       break; 
diff --git a/src/fvm.h b/src/fvm.h
index bfa5888..8d8cb87 100644
--- a/src/fvm.h
+++ b/src/fvm.h
@@ -12,9 +12,10 @@ struct fvm;
 typedef int64_t (*fvm_syscall_fn_t)(struct fvm* vm);
 
 struct fvm {
-  fvm_word_t sp;
-  fvm_word_t bp;
-  fvm_word_t pc;
+  fvm_word_t sp;  // stack pointer
+  fvm_word_t bp;  // base pointer
+  fvm_word_t pc;  // programm counter
+  fvm_word_t rv;  // return value
   fvm_syscall_fn_t *syscall_table;
 };
 
@@ -24,6 +25,8 @@ enum fvm_op {
   FVM_OP_BP,
   FVM_OP_SBP,
   FVM_OP_PC,
+  FVM_OP_RV,
+  FVM_OP_SRV,
   
   FVM_OP_IMM,
   
@@ -95,7 +98,7 @@ enum fvm_op {
 };
 
 int fvm_init(struct fvm *vm, void *code, int64_t stack_size);
-int fvm_execute(struct fvm *vm);
+int64_t fvm_execute(struct fvm *vm);
 
 void fvm_push(struct fvm *vm, fvm_word_t value);
 int64_t fvm_pop(struct fvm *vm);