compile optimization

docs/spec/mcode.md

@@ -10,12 +10,11 @@ Mcode is a JSON-based intermediate representation that can be interpreted direct
 ## Pipeline
 
 ```
-Source → Tokenize → Parse (AST) → Mcode (JSON) → Interpret
-                                                → Compile to Mach (planned)
-                                                → Compile to native (planned)
+Source → Tokenize → Parse (AST) → Fold → Mcode (JSON) → Streamline → Interpret
+                                                                    → QBE → Native
 ```
 
-Mcode is produced by the `JS_Mcode` compiler pass, which emits a cJSON tree. The mcode interpreter walks this tree directly, dispatching on instruction name strings.
+Mcode is produced by `mcode.cm`, which lowers the folded AST to JSON instruction arrays. The streamline optimizer (`streamline.cm`) then eliminates redundant operations. The result can be interpreted by `mcode.c`, or lowered to QBE IL by `qbe_emit.cm` for native compilation. See [Compilation Pipeline](pipeline.md) for the full overview.
 
 ## JSMCode Structure
 
@@ -44,16 +43,37 @@ struct JSMCode {
 
 ## Instruction Format
 
-Each instruction is a JSON array. The first element is the instruction name (string), followed by operands:
+Each instruction is a JSON array. The first element is the instruction name (string), followed by operands (typically `[op, dest, ...args, line, col]`):
 
 ```json
-["LOADK", 0, 42]
-["ADD", 2, 0, 1]
-["JMPFALSE", 3, "else_label"]
-["CALL", 0, 2, 1]
+["access", 3, 5, 1, 9]
+["load_index", 10, 4, 9, 5, 11]
+["store_dynamic", 4, 11, 12, 6, 3]
+["frame", 15, 14, 1, 7, 7]
+["setarg", 15, 0, 16, 7, 7]
+["invoke", 15, 13, 7, 7]
 ```
 
-The instruction set mirrors the Mach VM opcodes — same operations, same register semantics, but with string dispatch instead of numeric opcodes.
+### Typed Load/Store
+
+Memory operations come in typed variants for optimization:
+
+- `load_index dest, obj, idx` — array element by integer index
+- `load_field dest, obj, key` — record property by string key
+- `load_dynamic dest, obj, key` — unknown; dispatches at runtime
+- `store_index obj, val, idx` — array element store
+- `store_field obj, val, key` — record property store
+- `store_dynamic obj, val, key` — unknown; dispatches at runtime
+
+The compiler selects the appropriate variant based on `type_tag` and `access_kind` annotations from parse and fold.
+
+### Decomposed Calls
+
+Function calls are split into separate instructions:
+
+- `frame dest, fn, argc` — allocate call frame
+- `setarg frame, idx, val` — set argument
+- `invoke frame, result` — execute the call
 
 ## Labels