diff --git a/compiler/arch.ts b/compiler/arch.ts
index 203a1f1..851e67a 100644
--- a/compiler/arch.ts
+++ b/compiler/arch.ts
@@ -1,18 +1,6 @@
-import { Pos } from "./Token.ts";
-
-export type Output = {
-    program: Program;
-    sourceMap: SourceMapping[];
-};
-
 export type Program = Ins[];
 export type Ins = Ops | number;
 
-export type SourceMapping = {
-    bytecodeOffset: number;
-    pos: Pos;
-};
-
 // NOTICE: keep up to date with runtime/arch.hpp
 
 export type Ops = typeof Ops;
@@ -41,4 +29,5 @@ export const Ops = {
     Or: 21,
     Xor: 22,
     Not: 23,
+    SourceMap: 24,
 } as const;
diff --git a/runtime/arch.hpp b/runtime/arch.hpp
index 317ed5b..5443a62 100644
--- a/runtime/arch.hpp
+++ b/runtime/arch.hpp
@@ -31,6 +31,7 @@ enum class Op : uint32_t {
     Or = 21,
     Xor = 22,
     Not = 23,
+    SourceMap = 24,
 };
 
 }
diff --git a/runtime/vm.cpp b/runtime/vm.cpp
index 9dca2ad..e67d579 100644
--- a/runtime/vm.cpp
+++ b/runtime/vm.cpp
@@ -195,11 +195,20 @@ void VM::run()
                 stack_push(Bool { .value = value });
                 break;
             }
-            case Op::Not:
+            case Op::Not: {
                 assert_stack_has(1);
                 auto value = !stack_pop().as_bool().value;
                 stack_push(Bool { .value = value });
                 break;
+            }
+            case Op::SourceMap: {
+                assert_program_has(3);
+                auto index = eat_int32();
+                auto line = eat_int32();
+                auto col = eat_int32();
+                this->current_pos = { index, line, col };
+                break;
+            }
         }
     }
 }
diff --git a/runtime/vm.hpp b/runtime/vm.hpp
index 20758fb..87314ad 100644
--- a/runtime/vm.hpp
+++ b/runtime/vm.hpp
@@ -10,10 +10,40 @@
 
 namespace sliger {
 
+struct SourcePos {
+    int index;
+    int line;
+    int col;
+};
+
+struct FGNode {
+    uint32_t fn;
+    int64_t acc;
+    int64_t ic_start;
+    size_t parent;
+    std::vector<size_t> children;
+};
+
+class FlameGraphBuilder {
+public:
+    inline auto report_call(size_t fn, int64_t ic_start) { }
+
+    inline auto report_return(int64_t ic_end) { }
+
+private:
+    std::vector<FGNode> nodes;
+};
+
+struct VMOpts {
+    bool flameGraph;
+    bool codeCoverage;
+};
+
 class VM {
 public:
-    VM(const std::vector<uint32_t>& program)
-        : program(program.data())
+    VM(const std::vector<uint32_t>& program, VMOpts opts)
+        : opts(opts)
+        , program(program.data())
         , program_size(program.size())
     {
     }
@@ -92,11 +122,14 @@ public:
     }
 
 private:
+    VMOpts opts;
     uint32_t pc = 0;
     uint32_t bp = 0;
     const uint32_t* program;
     size_t program_size;
     std::vector<Value> stack;
     std::vector<Value> pool_heap;
+    SourcePos current_pos = { 0, 1, 1 };
 };
+
 }