From e8a30ba744982f1f00db6a962bd849ef53514bff Mon Sep 17 00:00:00 2001
From: Bad Diode <bd@badd10de.dev>
Date: Thu, 30 Dec 2021 14:33:11 +0100
Subject: Add `def` builtin and local var load/store ops

---
 src/ir.h | 44 ++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 40 insertions(+), 4 deletions(-)

diff --git a/src/ir.h b/src/ir.h
index 8518adb..d9706ee 100644
--- a/src/ir.h
+++ b/src/ir.h
@@ -49,6 +49,13 @@ typedef enum Op {
     OP_JUMP_IF_LT,
     OP_JUMP_IF_GE,
     OP_JUMP_IF_LE,
+    // Variable access.
+    // - Require an index corresponding to the local variable to store.
+    // - Consume the last item in the stack.
+    OP_STORE_LOCAL,
+    // - Require an index corresponding to the local variable to load.
+    // - The loaded value is pushed into the stack.
+    OP_LOAD_LOCAL,
     // Primitive complex commands.
     // - Prints the last object in the stack.
     OP_PRINT,
@@ -83,6 +90,8 @@ static const char* ops_str[] = {
     [OP_JUMP_IF_LT]    = "OP_JUMP_IF_LT",
     [OP_JUMP_IF_GE]    = "OP_JUMP_IF_GE",
     [OP_JUMP_IF_LE]    = "OP_JUMP_IF_LE",
+    [OP_STORE_LOCAL]   = "OP_STORE_LOCAL",
+    [OP_LOAD_LOCAL]    = "OP_LOAD_LOCAL",
     [OP_PRINT]         = "OP_PRINT",
     [OP_CALL]          = "OP_CALL",
     [OP_RETURN]        = "OP_RETURN",
@@ -100,6 +109,10 @@ typedef struct Instruction {
         // OP_JUMP
         // OP_JUMP_IF_xxx
         size_t label_id;
+
+        // OP_STORE_LOCAL
+        // OP_LOAD_LOCAL
+        size_t index;
     };
 
     // Original line/column for debugging purposes.
@@ -114,6 +127,9 @@ typedef struct Procedure {
     // Program code.
     Instruction *instructions;
 
+    // Locals code.
+    Object **locals;
+
     // Number of locals and parameters.
     size_t n_params;
     size_t n_locals;
@@ -142,6 +158,12 @@ typedef struct ProgramIr {
         array_push((PROC)->instructions, inst); \
     } while(false);
 
+#define INST_VAR(PROC, OP, ARG, LINE, COL) \
+    do { \
+        Instruction inst = (Instruction){(OP), .index = (ARG), (LINE), (COL)}; \
+        array_push((PROC)->instructions, inst); \
+    } while(false);
+
 void
 print_instruction(Instruction *instruction) {
     printf("%4ld:%-4ld ", instruction->line, instruction->col);
@@ -163,6 +185,10 @@ print_instruction(Instruction *instruction) {
         case OP_LABEL: {
             printf("%-16s -> %zu\n", ops_str[op], instruction->label_id);
         } break;
+        case OP_STORE_LOCAL:
+        case OP_LOAD_LOCAL: {
+            printf("%-16s -> %zu\n", ops_str[op], instruction->index);
+        } break;
         default: {
             printf("%s\n", ops_str[op]);
         } break;
@@ -184,6 +210,7 @@ proc_alloc(ProgramIr *program, StringView name) {
     array_init(proc->name, name.n);
     array_insert(proc->name, name.start, name.n);
     array_init(proc->instructions, 0);
+    array_init(proc->locals, 0);
     array_push(program->procedures, proc);
     return proc;
 }
@@ -351,6 +378,17 @@ compile_if(ProgramIr *program, Procedure *proc, Object *obj) {
     }
 }
 
+void
+compile_def(ProgramIr *program, Procedure *proc, Object *obj) {
+    ssize_t idx = find_var_index(proc->locals, obj->var_name);
+    if (idx == -1) {
+        array_push(proc->locals, obj->var_name);
+        idx = array_size(proc->locals) - 1;
+    }
+    compile_object(program, proc, obj->var_expr);
+    INST_VAR(proc, OP_STORE_LOCAL, idx, obj->line, obj->col);
+}
+
 void
 compile_object(ProgramIr *program, Procedure *proc, Object *obj) {
     switch (obj->type) {
@@ -358,13 +396,11 @@ compile_object(ProgramIr *program, Procedure *proc, Object *obj) {
         case OBJ_TYPE_TRUE:
         case OBJ_TYPE_FALSE:
         case OBJ_TYPE_STRING:
-        case OBJ_TYPE_FIXNUM: {
-            INST_ARG(proc, OP_PUSH, obj, obj->line, obj->col);
-        } break;
+        case OBJ_TYPE_FIXNUM: { INST_ARG(proc, OP_PUSH, obj, obj->line, obj->col); } break;
         case OBJ_TYPE_PAIR: { compile_proc_call(program, proc, obj); } break;
         case OBJ_TYPE_IF: { compile_if(program, proc, obj); } break;
         // case OBJ_TYPE_LAMBDA: { compile_lambda(obj); } break;
-        // case OBJ_TYPE_DEF: { compile_def(obj); } break;
+        case OBJ_TYPE_DEF: { compile_def(program, proc, obj); } break;
         // case OBJ_TYPE_SYMBOL: { compile_symbol(obj); } break;
         default: {
             // TODO: assert?
-- 
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