From 583e0b431a6581206368968d56287a858d53b10a Mon Sep 17 00:00:00 2001
From: Bad Diode <bd@badd10de.dev>
Date: Tue, 26 Oct 2021 13:34:44 +0200
Subject: Add initial parameter support for function calls

---
 src/bytecode/vm.h | 18 +++++++++++++++---
 1 file changed, 15 insertions(+), 3 deletions(-)

(limited to 'src/bytecode/vm.h')

diff --git a/src/bytecode/vm.h b/src/bytecode/vm.h
index 0ce6dec..98c94fa 100755
--- a/src/bytecode/vm.h
+++ b/src/bytecode/vm.h
@@ -19,6 +19,8 @@ typedef struct CallFrame {
     // Object *locals;
     // Return counter.
     u8 *rp;
+    // Starting point of the locals for this procedure.
+    size_t stack_offset;
 } CallFrame;
 
 typedef struct VM {
@@ -149,8 +151,7 @@ vm_interpret(VM *vm) {
         return;
     }
 
-    u8 *last = frame->chunk->code + array_size(frame->chunk->code);
-    while (vm->pc < last) {
+    while (true) {
 #ifdef DEBUG_TRACE_EXECUTION
         printf("stack:  [ ");
         for (size_t i = 0; i < array_size(vm->stack); i++) {
@@ -164,6 +165,10 @@ vm_interpret(VM *vm) {
 #endif
         u8 instruction = *vm->pc++;
         switch (instruction) {
+            case OP_LOCAL: {
+                u8 local = *vm->pc++;
+                array_push(vm->stack, vm->stack[frame->stack_offset + local]);
+            } break;
             case OP_CONSTANT: {
                 u8 constant = *vm->pc++;
                 Object obj = frame->chunk->constants[constant];
@@ -256,7 +261,11 @@ vm_interpret(VM *vm) {
             } break;
             case OP_CALL: {
                 Object proc = array_pop(vm->stack);
-                CallFrame new_frame = (CallFrame){proc.chunk, vm->pc};
+                CallFrame new_frame = (CallFrame){
+                    .chunk = proc.chunk,
+                    .rp = vm->pc,
+                    .stack_offset = array_size(vm->stack) - array_size(proc.chunk->params),
+                };
                 array_push(vm->frames, new_frame);
                 frame = &vm->frames[array_size(vm->frames) - 1];
                 vm->pc = frame->chunk->code;
@@ -272,6 +281,9 @@ vm_interpret(VM *vm) {
                 }
                 vm->pc = frame->rp;
                 array_head(vm->frames)->size--;
+                Object ret = array_pop(vm->stack);
+                array_head(vm->stack)->size = frame->stack_offset;
+                array_push(vm->stack, ret);
                 frame = &vm->frames[array_size(vm->frames) - 1];
             } break;
             case OP_DROP: {
-- 
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