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lang: Document bytecode.c

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This commit is contained in:
Jookia 2023-08-06 22:22:08 +10:00
parent 2799d9832e
commit 29657417b0
1 changed files with 21 additions and 1 deletions
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22
lang/bytecode.c
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@ -7,15 +7,19 @@
#include "object.h"
#include "vm.h"
// Opcode definitions, see bytecode_run for further documentation
enum opcodes {
// 0x00 is reserved for inline strings
OP_NUM = 0x01,
OP_RET = 0x03,
// 0x02 was an earlier variant of OP_DROP
OP_CALL = 0x04,
OP_NULL = 0x05,
OP_GET = 0x06,
OP_SET = 0x07,
OP_DROP = 0x08,
OP_DEPTH_CHECK = 0x09,
// 0x60 onwards are reserved for inline strings
};
// clang-format off
@ -34,6 +38,8 @@ void bytecode_run(VmState state) {
unsigned char op = OP_RET;
while ((op = *pos_code++) != OP_RET) {
switch (op) {
// OP_NUM pushes a number on to the stack
// First argument is a 4-byte little endian number
case OP_NUM: {
int num = 0;
num |= *pos_code++ << 0;
@ -43,6 +49,9 @@ void bytecode_run(VmState state) {
vm_stack_push(state, number_create(num));
break;
}
// OP_CALL dispatches a call to the top of stack object
// First argument is a 1-byte argument count
// Second argument is the call string
case OP_CALL: {
int arg_count = *pos_code++;
const char *dispatch = (const char *)pos_code;
@ -51,32 +60,43 @@ void bytecode_run(VmState state) {
object_drop(&obj);
break;
}
// OP_NULL pushes object_none on to the stack
case OP_NULL: {
vm_stack_push(state, object_none());
break;
}
// OP_GET duplicates an element from the stack and stores
// the result at the top
// First argument is the stack index
case OP_GET: {
Object obj = vm_stack_get(state, *pos_code++);
vm_stack_push(state, obj);
break;
}
// OP_SET stores the stack top element at a stack index
// The stack top element is dropped in the process
// First argument is the stack index
case OP_SET: {
Object obj = vm_stack_pop(state);
vm_stack_set(state, *pos_code++, obj);
break;
}
// OP_DROP drops multiple stack elements starting at the top
// First argument is the number of elements to drop
case OP_DROP: {
vm_stack_drop(state, *pos_code++);
break;
}
// OP_DEPTH_CHECK checks that the stack is a certain size
// First argument is the expected depth
case OP_DEPTH_CHECK: {
int depth = *pos_code++;
abort_if(vm_stack_depth(state) != depth,
"stack depth mismatch");
break;
}
// Skip over strings and unknown OPs
default:
// Skip over ASCII and unknown OPs
break;
}
}