From ad8c598e84bd1e5469e2487cc3e4d0ea784d0ff3 Mon Sep 17 00:00:00 2001
From: Bad Diode <bd@badd10de.dev>
Date: Mon, 25 Oct 2021 14:32:18 +0200
Subject: Add callframe support for the VM

---
 src/bytecode/vm.h | 70 ++++++++++++++++++++++++++++++++-----------------------
 1 file changed, 41 insertions(+), 29 deletions(-)

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

diff --git a/src/bytecode/vm.h b/src/bytecode/vm.h
index b6f9848..23c3d89 100755
--- a/src/bytecode/vm.h
+++ b/src/bytecode/vm.h
@@ -8,13 +8,20 @@
 #include "debug.h"
 #include "hashtable.h"
 
+#define VM_FRAMES_CAP 64
 #define VM_STACK_CAP 1024
 
-typedef struct VM {
-    // Program code.
-    Chunk *chunk;
-    // Program counter.
+typedef struct CallFrame {
+    // Current code being run.
+    Object procedure;
+    // Current program counter for this call.
     u8 *pc;
+    // Ref to stack. Is this really needed?
+    // Object *stack;
+} CallFrame;
+
+typedef struct VM {
+    CallFrame *frames;
     // Stack.
     Object *stack;
     // Global variables.
@@ -24,17 +31,22 @@ typedef struct VM {
 void vm_init(VM *vm);
 void vm_free(VM *vm);
 void vm_reset(VM *vm);
-void vm_interpret(VM *vm, Chunk *chunk);
+void vm_interpret(VM *vm);
 
 void
 vm_init(VM *vm) {
     *vm = (VM){0};
+    array_init(vm->frames, VM_FRAMES_CAP);
+    for (size_t i = 0; i < array_cap(vm->frames); i++) {
+        vm->frames[i] = (CallFrame){0};
+    }
     array_init(vm->stack, VM_STACK_CAP);
     vm->globals = ht_init();
 }
 
 void
 vm_free(VM *vm) {
+    array_free(vm->frames);
     array_free(vm->stack);
     ht_free(vm->globals);
 }
@@ -50,16 +62,16 @@ vm_reset(VM *vm) {
     error_push((Error){ \
         .type = ERR_TYPE_RUNTIME, \
         .value = ERR_WRONG_ARG_TYPE, \
-        .line = vm->chunk->lines[vm->pc - vm->chunk->code - 1].line, \
-        .col = vm->chunk->lines[vm->pc - vm->chunk->code - 1].col, \
+        .line = chunk->lines[frame->pc - chunk->code - 1].line, \
+        .col = chunk->lines[frame->pc - chunk->code - 1].col, \
     })
 
 #define SYMBOL_NOT_FOUND_ERR() \
     error_push((Error){ \
         .type = ERR_TYPE_RUNTIME, \
         .value = ERR_SYMBOL_NOT_FOUND, \
-        .line = vm->chunk->lines[vm->pc - vm->chunk->code - 1].line, \
-        .col = vm->chunk->lines[vm->pc - vm->chunk->code - 1].col, \
+        .line = chunk->lines[frame->pc - chunk->code - 1].line, \
+        .col = chunk->lines[frame->pc - chunk->code - 1].col, \
     })
 
 #define FIXNUM_ARITHMETIC_OP(OP) \
@@ -123,11 +135,11 @@ vm_reset(VM *vm) {
     } while (false)
 
 void
-vm_interpret(VM *vm, Chunk *chunk) {
-    vm->chunk = chunk;
-    vm->pc = vm->chunk->code;
+vm_interpret(VM *vm) {
+    CallFrame *frame = &vm->frames[array_size(vm->frames) - 1];
+    Chunk *chunk = frame->procedure.chunk;
 
-    if (vm->chunk->code == NULL || array_size(vm->chunk->code) == 0) {
+    if (chunk->code == NULL || array_size(chunk->code) == 0) {
         error_push((Error){
             .type = ERR_TYPE_RUNTIME,
             .value = ERR_EMPTY_CHUNK,
@@ -135,8 +147,8 @@ vm_interpret(VM *vm, Chunk *chunk) {
         return;
     }
 
-    u8 *last = vm->chunk->code + array_size(vm->chunk->code);
-    while (vm->pc < last) {
+    u8 *last = chunk->code + array_size(chunk->code);
+    while (frame->pc < last) {
 #ifdef DEBUG_TRACE_EXECUTION
         printf("stack:  [ ");
         for (size_t i = 0; i < array_size(vm->stack); i++) {
@@ -146,13 +158,13 @@ vm_interpret(VM *vm, Chunk *chunk) {
             }
         }
         printf(" ]\nop: ");
-        disassemble_instruction(vm->chunk, (vm->pc - vm->chunk->code));
+        disassemble_instruction(chunk, (frame->pc - chunk->code));
 #endif
-        u8 instruction = *vm->pc++;
+        u8 instruction = *frame->pc++;
         switch (instruction) {
             case OP_CONSTANT: {
-                u8 constant = *vm->pc++;
-                Object obj = vm->chunk->constants[constant];
+                u8 constant = *frame->pc++;
+                Object obj = chunk->constants[constant];
                 array_push(vm->stack, obj);
             } break;
             case OP_DEF: {
@@ -197,17 +209,17 @@ vm_interpret(VM *vm, Chunk *chunk) {
             case OP_LESS_EQUAL: { FIXNUM_COMPARE_OP(<=); } break;
             case OP_GREATER_EQUAL: { FIXNUM_COMPARE_OP(>=); } break;
             case OP_JUMP: {
-                u16 a = *vm->pc++;
-                u16 b = *vm->pc++;
+                u16 a = *frame->pc++;
+                u16 b = *frame->pc++;
                 s16 offset = (a << 8) | b;
-                vm->pc += offset;
+                frame->pc += offset;
             } break;
             case OP_JUMP_IF_FALSE: {
-                u16 a = *vm->pc++;
-                u16 b = *vm->pc++;
+                u16 a = *frame->pc++;
+                u16 b = *frame->pc++;
                 s16 offset = (a << 8) | b;
                 if (IS_FALSE(array_pop(vm->stack))) {
-                    vm->pc += offset;
+                    frame->pc += offset;
                 }
             } break;
             case OP_DISPLAY: {
@@ -248,8 +260,8 @@ vm_interpret(VM *vm, Chunk *chunk) {
                 error_push((Error){
                     .type = ERR_TYPE_RUNTIME,
                     .value = ERR_NOT_IMPLEMENTED,
-                    .line = vm->chunk->lines[vm->pc - vm->chunk->code - 1].line,
-                    .col = vm->chunk->lines[vm->pc - vm->chunk->code - 1].col,
+                    .line = chunk->lines[frame->pc - chunk->code - 1].line,
+                    .col = chunk->lines[frame->pc - chunk->code - 1].col,
                 });
                 return;
             } break;
@@ -259,8 +271,8 @@ vm_interpret(VM *vm, Chunk *chunk) {
     error_push((Error){
         .type = ERR_TYPE_RUNTIME,
         .value = ERR_PC_OOB,
-        .line = vm->chunk->lines[0].line,
-        .col = vm->chunk->lines[0].col,
+        .line = chunk->lines[0].line,
+        .col = chunk->lines[0].col,
     });
 }
 
-- 
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