Use a cache when generating the map header to minimize stack wastage

src/llvm_backend.cpp

@@ -502,10 +502,16 @@ lbValue lb_generate_anonymous_proc_lit(lbModule *m, String const &prefix_name, A
 
 lbValue lb_gen_map_header(lbProcedure *p, lbValue map_val_ptr, Type *map_type) {
 	GB_ASSERT_MSG(is_type_pointer(map_val_ptr.type), "%s", type_to_string(map_val_ptr.type));
-	lbAddr h = lb_add_local_generated(p, t_map_header, false); // all the values will be initialzed later
 	map_type = base_type(map_type);
 	GB_ASSERT(map_type->kind == Type_Map);
 
+	lbAddr h = {};
+	lbAddr *found = map_get(&p->map_header_cache, map_val_ptr.value);
+	if (found != nullptr) {
+		h = *found;
+	} else {
+		h = lb_add_local_generated(p, t_map_header, false); // all the values will be initialzed later
+
 		Type *key_type = map_type->Map.key;
 		Type *val_type = map_type->Map.value;
 		gb_unused(val_type);
@@ -545,6 +551,10 @@ lbValue lb_gen_map_header(lbProcedure *p, lbValue map_val_ptr, Type *map_type) {
 		lbValue m = lb_emit_conv(p, map_val_ptr, type_deref(gep0.type));
 		lb_emit_store(p, gep0, m);
 
+
+		map_set(&p->map_header_cache, map_val_ptr.value, h);
+	}
+
 	return lb_addr_load(p, h);
 }
 

src/llvm_backend.hpp

@@ -308,6 +308,7 @@ struct lbProcedure {
 
 	PtrMap<Ast *, lbValue> selector_values;
 	PtrMap<Ast *, lbAddr>  selector_addr;
+	PtrMap<LLVMValueRef, lbAddr> map_header_cache;
 };
 
 

src/llvm_backend_proc.cpp

@@ -123,6 +123,7 @@ lbProcedure *lb_create_procedure(lbModule *m, Entity *entity, bool ignore_body)
 	p->scope_stack.allocator   = a;
 	map_init(&p->selector_values,  a, 0);
 	map_init(&p->selector_addr,    a, 0);
+	map_init(&p->map_header_cache, a, 0);
 
 	if (p->is_foreign) {
 		lb_add_foreign_library_path(p->module, entity->Procedure.foreign_library);